Abdominal Wall Abscess Due to Mycobacterium neworleansense: A Case Report

Abdominal Wall Abscess Due to Mycobacterium neworleansense: A Case Report | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Case Report Abdominal Wall Abscess Due to Mycobacterium neworleansense: A Case Report Yupei Xiang, Bing Fan, Bo Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7980994/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Introduction Nontuberculous mycobacteria are widely distributed in the natural environment and can cause cutaneous infections through traumatic injuries or invasive procedures, leading to nontuberculous mycobacterial skin diseases. However, skin infections caused by Mycobacterium neworleansense are exceedingly rare. This article reports a case of an abdominal wall abscess resulting from this uncommon pathogen, with the aim of enhancing clinical recognition and improving the diagnosis and management of infections associated with Mycobacterium neworleansense. Case presentation A 74-year-old male with diabetes was hospitalized due to an abscess on the left abdominal wall at a site of long-term insulin administration. After admission, surgical incision and drainage of the abscess were performed. Microbiological culture of the intraoperative pus specimen revealed growth of non-tuberculous mycobacteria, which was subsequently identified as Mycobacterium neworleansense using a combination of 16S rRNA gene sequencing and biochemical profiling. Antimicrobial susceptibility testing demonstrated resistance to macrolides and tetracyclines, but susceptibility to trimethoprim-sulfamethoxazole, aminoglycosides, moxifloxacin, and imipenem. Following surgical intervention, the patient received a combined antibiotic regimen of trimethoprim-sulfamethoxazole and moxifloxacin, which led to successful clinical resolution of the infection. Conclusion Mycobacterium neworleansense has the potential to cause subcutaneous abscesses following injection-related procedures. Successful management of such infections relies on accurate pathogen identification through molecular and biochemical methods, coupled with targeted antimicrobial therapy guided by susceptibility testing, and supported by appropriate surgical intervention. Nontuberculous mycobacteria Mycobacterium neworleansense Abdominal Wall Abscess infections Figures Figure 1 Figure 2 Figure 3 Introduction Mycolicibacterium neworleansense is a rapidly growing non-tuberculous mycobacterium (NTM) and a newly identified species within the Mycobacterium fortuitum complex. This bacterium has only been detected in a scalp wound and a cerebrospinal fluid specimen. However, reports of human infections caused by Mycolicibacterium neworleansense are extremely rare. This article presents a case of an abdominal wall abscess caused by Mycolicibacterium neworleansense , aiming to improve the clinical diagnosis and treatment of infections associated with this pathogen. Case presentation A 74-year-old male was admitted to the hospital for left abdominal mass for 10 days, with redness, swelling and pain for 4 days .10 days ago, the patient found a small mass on the left abdominal wall without special treatment. After 6 days, the size of the mass increased significantly, accompanied by redness, swelling and tenderness of the surrounding skin, and the patient went to the general surgery department. He had a history of hypertension and diabetes for more than 10 years.Levamlodipine besylate tablets and valsartan tablets were used to maintain blood pressure.Insulin injection was used to treat diabetes, and the mass was localized at his long-term abdominal insulin injection site. On admission, physical examination revealed a mass approximately 2.0 cm × 1.5 cm in the left abdominal wall above the umbilical plane, with ill-defined borders, overlying skin erythema, and mild tenderness, but no significant fluctuation. Below the umbilical plane, another protruding mass measuring about 5 cm × 7 cm was observed, with intact skin and no ulceration or exudate. It was soft in texture, poorly demarcated, and accompanied by localized erythema, elevated skin temperature, marked tenderness, and significant fluctuation. CT imaging demonstrated thickening of the skin in the left lower abdominal pelvic wall (below the umbilical level) with a nodular appearance, smooth surface, and ill-defined margins toward the adipose tissue, measuring approximately 39 mm × 21 mm × 37 mm (Fig .1A).Localized skin thickening was also observed in the left mid-abdominal wall, with a moderately dense nodular shadow seen in the subcutaneous fat layer, demonstrating ill-defined margins and measuring approximately 15 mm × 11 mm × 12 mm ( Fig. 1 B ). laboratory data revealed the following values: glycated hemoglobin 8.2%, white blood cell count 8.34×10⁹/L, red blood cell count 4.65×10¹²/L, hemoglobin 143 g/L, platelet count 249×10⁹/L.The initial diagnosis was multiple left abdominal wall infections with abscess, stage 2 hypertension, and type 2 diabetes mellitus. On the day of admission, surgical incision and drainage of the abscess were performed. Intraoperative examination revealed inflammatory changes in the surrounding tissue, with the abscess base extending into the intermuscular septum. Subsequent debridement of pus and necrotic tissue was carried out, and a pus specimen was sent for microbiological analysis. Postoperative therapeutic regimen included piperacillin-tazobactam for anti-infective treatment, supplemented with sodium aescinate to reduce edema and insulin for glycemic control. Microscopic examination of the pus specimen following Gram staining revealed slender, pleomorphic gram-positive bacilli that were also positive for acid-fast staining. Culture of the specimen on Columbia blood agar and chocolate agar yielded small, white colonies at 24 hours. By 48 hours, these colonies had enlarged into medium-sized, white colonies with irregular margins and rough, wrinkled surfaces ( Fig. 2 A ). Staining of the purified isolate confirmed the presence of gram-positive, acid-fast–positive bacilli (Fig .2B).Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) initially identified the isolate as Mycobacterium smegmatis, with an identification score of 1.34 (species-level threshold: 2.000). For further characterization, 16S rRNA gene sequencing was performed on the pure culture. BLAST analysis against the NCBI database demonstrated 100% sequence identity with the 16S rRNA gene of Mycolicibacterium neworleansense strain ATCC 49404 (Accession No. NR_042914.1). A series of biochemical assays were performed, with results as follows: negative for sorbitol fermentation, and positive for nitrate reduction, catalase activity, and xylose fermentation—a profile consistent with M. neworleansense. The combination of 16S rRNA gene sequencing data and biochemical characteristics, the isolate was definitively identified as Mycolicibacterium neworleansense. Antimicrobial susceptibility testing was performed using the broth microdilution method, with results interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines (M100-ED32). The isolate was resistant to rifampin (MIC > 16 µg/mL), clarithromycin (MIC > 64 µg/mL), doxycycline (MIC > 32 µg/mL), minocycline (MIC > 128 µg/mL), and azithromycin (MIC > 32 µg/mL). It was susceptible to cefoxitin (MIC ≤ 4 µg/mL), moxifloxacin (MIC ≤ 0.125 µg/mL), trimethoprim-sulfamethoxazole (MIC ≤ 8 µg/mL), amikacin (MIC ≤ 1 µg/mL), ethambutol (MIC ≤ 5 µg/mL), imipenem-cilastatin (MIC ≤ 0.5 µg/mL), and linezolid (MIC ≤ 8 µg/mL). An intermediate susceptibility was observed for tobramycin (MIC = 16 µg/mL). The anti-infective regimen was transitioned to oral clarithromycin (500 mg twice daily) on postoperative day 3. Based on the susceptibility profile, therapy was escalated on day 9 to a combination of trimethoprim-sulfamethoxazole (960 mg twice daily) and moxifloxacin (400 mg daily). The patient was discharged 12 days post-operatively following notable clinical improvement and continued on combined antibiotic therapy with trimethoprim-sulfamethoxazole and moxifloxacin. Following two months of treatment, the surgical site exhibited complete healing without any evidence of local recurrence or distant infection. The treatment was deemed successful( Fig. 3 ). Discussion This case report describes the first identification of Mycobacterium neworleansense causing a cutaneous infection in China, a species that remains exceptionally rare globally. Successful management was achieved through the timely pathogen identification via smear and culture, which guided a combination of surgical intervention and susceptibility-directed antimicrobial therapy, highlighting the importance of this integrated approach. Mycolicibacterium neworleansense was first classified in 1991 as the third biovariant complex member of Mycobacterium fortuitum [ 1 ] . In 2004, through multigene sequence analysis and phenotypic characterization, Schinsky MF et al. established it as a distinct species and named it Mycolicibacterium neworleansense [ 2 ] . Subsequently, Asmar et al. performed whole-genome sequencing of the reference strain ATCC 49404, further confirming it at the genomic level as a novel species within the M. fortuitum complex [ 3 ] . Similar to most nontuberculous mycobacteria (NTM), conventional identification of M. neworleansense remains challenging.Expert Consensus on the Molecular Diagnosis of Nontuberculous Mycobacterial Diseases, recommend the use of multiple molecular methods for NTM identification, including sequencing of the 16S rRNA, 16S–23S rRNA internal transcribed spacer (ITS), rpoB, and hsp65 genes; PCR-restriction fragment length polymorphism analysis (PRA); metagenomic next-generation sequencing (mNGS); whole-genome sequencing (WGS); and matrix-assisted laser desorption/ionization–time of flight mass spectrometry (MALDI-TOF MS) [ 4 , 5 ] . According to Schinsky MF et al. [ 2 ] , Mycolicibacterium neworleansense exhibits overlapping hsp65 gene sequences and PRA profiles with other members of the third Mycobacterium fortuitum complex, complicating accurate discrimination. MALDI-TOF MS also demonstrates limitations in practical identification; here, the isolate was initially misidentified as Mycobacterium smegmatis. Moreover, methods based on ITS or rpoB gene regions remain inadequately validated for identifying M. neworleansense, and their discriminatory power requires further confirmation. Although mNGS and WGS allow precise species-level identification, their high cost precludes routine use [ 6 ] . Thus, with currently available techniques, 16S rRNA gene sequencing remains the most practical and reliable approach. It should be noted, however, that M. neworleansense exhibits high 16S rRNA sequence homology with Mycolicibacterium bonickei, which can lead to misidentification. Fortunately, these two species display distinct phenotypic characteristics: M. neworleansense is positive for xylose and erythritol fermentation tests, whereas M. bonickei is negative for both, providing a useful criterion for differentiation. Here, although the 16S rRNA sequence showed 100% homology with M. neworleansense ATCC 49404, it also displayed high homology with M. bonickei. Ultimately, the isolate was confirmed as M. neworleansense based on the positive results of xylose and erythritol fermentation tests. Human infection caused by Mycolicibacterium neworleansense is clinically exceedingly rare. A systematic search of both Chinese and English literature databases, including Wanfang, CNKI, and PubMed, revealed no confirmed case reports of human infection by this organism. According to existing records, the type strain ATCC 49404 was isolated from a scalp wound sample in New Orleans, USA; another study from China reported its isolation from a cerebrospinal fluid specimen [ 7 ] . In the present case, the patient presented with clear local infectious symptoms and developed an abscess. The smear microscopy and culture results of the abscess specimen were consistent, and the patient responded well to targeted antimicrobial therapy. Therefore, M. neworleansense was identified as the causative pathogen of this abdominal wall abscess. This case represents a subcutaneous injection‑associated cutaneous infection due to M. neworleansense. It is noteworthy that injection procedures are one of the common routes of skin and soft tissue infections caused by nontuberculous mycobacteria (NTM) [ 8 , 9 ]. The patient, who required long‑term insulin injections for diabetes, was exposed to increased skin microbial load during the hot summer, and inadequate skin disinfection might have facilitated pathogen entry. Thus, strict adherence to skin aseptic techniques and ensuring the sterility of medical devices during any invasive procedure are crucial measures for preventing cutaneous infections caused by M. neworleansense and other NTM. Clinically, the infection in this case had a relatively acute onset, with rapid enlargement of the mass within six days, which may be related to the rapid growth rate of this bacterium. In vitro culture showed that M. neworleansense formed visible colonies on solid media within 24 hours, with typical morphology apparent by 48 hours—a characteristic that offers an advantage for early etiological diagnosis. There are no established guidelines or consensus recommendations for antimicrobial therapy targeting Mycolicibacterium neworleansense.Although treatment regimens for Mycobacterium fortuitum have been suggested as a reference, studies have shown that species within the M. fortuitum complex may exhibit distinct drug resistance profiles [ 10 – 12 ]. In our case, antimicrobial susceptibility testing revealed that the isolate was resistant to macrolides—such as clarithromycin and azithromycin—which are commonly used in the treatment of M. fortuitum infections. This underscores the importance of species-level identification of nontuberculous mycobacteria (NTM), along with drug susceptibility testing, for formulating effective anti-infective regimens. The Diagnosis and Treatment Guidelines for Nontuberculous Mycobacterial Diseases (2020 Edition) emphasize that, in addition to selecting active antimicrobial agents, ensuring an adequate treatment duration is essential. A course of at least four months is generally recommended to minimize the risk of relapse. Beyond pharmacological therapy, surgical debridement represents a key intervention in managing M. neworleansense infections, particularly in cases with extensive involvement, abscess formation, or poor response to antimicrobial therapy [ 13 – 15 ] . Active surgical intervention can significantly improve clinical outcomes. In this patient, who had developed a well-defined abscess, a combination of surgical drainage and debridement, together with targeted antimicrobial therapy, led to marked clinical improvement. Conclusion We herein report a case of abdominal wall abscess caused by the rare pathogen Mycolicibacterium neworleansense, which was successfully managed with surgical debridement combined with targeted antimicrobial therapy. This case highlights that nontuberculous mycobacterial (NTM) infection should be considered in patients with skin and soft tissue infections, particularly when predisposing factors such as a history of injections are present. The accurate identification of M. neworleansense remains challenging in microbiological diagnosis. Although 16S rRNA gene sequencing remains the most reliable method currently available, its high sequence homology with closely related species such as M. bonickei must be considered, and phenotypic tests such as xylose fermentation are recommended for differentiation. Antimicrobial susceptibility testing revealed resistance to certain commonly used macrolides, indicating that empiric regimens for the M. fortuitum complex should not be empirically adopted and that therapy should be guided by actual susceptibility results. Based on the experience from this case, we recommend early smear and culture of pus to guide initial clinical management in M. neworleansense-related skin and soft tissue infections. Achieving precise anti-infective therapy relies on species-level identification using molecular techniques combined with drug susceptibility testing. Furthermore, in cases where an abscess has formed, proactive surgical intervention is essential for infection control and optimizing treatment outcomes. Abbreviations CT Computed tomography MIC Minimum Inhibitory Concentration Declarations Ethics approval and consent to participate Obtain the patient's informed consent and agreement. Authors’ contributions Yupei Xiang identified the suitability of this case for publication, and was the major contributor to writing the manuscript, the literature review, data analysis and interpretation, and editing of the manuscript. Bing Fan assisted with the literature review, writing and editing of the manuscript, and interpretation of the results. Bo Liu assisted with conceptualization of the case study, interpretation of the results, and writing and editing of the manuscript. Consent for publication All authors critically reviewed and approved the final manuscript. Competing interests The authors declare no competing interests. Funding No external sources of funding were received for this case report. Data availability The datasets supporting the conclusions of this article are fully presented within the manuscript and its supplementary files. Consent to participate Written informed consent was obtained from the participant for the use of his protected health information and identifiable medical images in this research publication. Acknowledgements We are grateful to the patient and his family for their consent to the use of clinical data for research and explicit permission to publish this case report. References Brown-Elliott BA, Wallace RJ Jr. Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria. Clin Microbiol Rev. 2002;15(4):716-746. Schinsky MF, Morey RE, Steigerwalt AG, et al. Taxonomic variation in the Mycobacterium fortuitum third biovariant complex: description of Mycobacterium boenickei sp. nov., Mycobacterium houstonense sp. nov., Mycobacterium neworleansense sp. nov. and Mycobacterium brisbanense sp. nov. and recognition of Mycobacterium porcinum from human clinical isolates. Int J Syst Evol Microbiol. 2004;54(Pt 5):1653-1667. Asmar S, Robert C, Croce O, Caputo A, Drancourt M. Draft genome sequence of Mycobacterium neworleansense strain ATCC 49404T. Genome Announc. 2015;3(6):e01314-15. Nontuberculous Mycobacterial Disease Branch of Chinese Antituberculosis Association, Sun Q. Expert consensus on molecular diagnosis of nontuberculous mycobacterial diseases [in Chinese]. Chin J Antituberc. 2025;47(8):961-975. Tortoli E, Fedrizzi T, Meehan CJ, et al. The new phylogeny of the genus Mycobacterium: The old and the news. Infect Genet Evol. 2017;56:19-25. "Belt and Road" Dermatology Alliance Mycobacterial Disease Research Alliance, Chinese Leprosy Association Branch of Dermatology Laboratory and Diagnosis. Chinese expert consensus on diagnosis and treatment of cutaneous nontuberculous mycobacterial diseases (2024 edition) [in Chinese]. Chin J Dermatol. 2024;57(2):109-118. Wu YF, Li QC, Jia QJ, et al. Identification and drug resistance analysis of pathogens causing nontuberculous mycobacterial pulmonary disease in suburban areas of Hangzhou [in Chinese]. J Tuberc Lung Dis. 2025;6(4):420-425. Wentworth AB, Drage LA, Wengenack NL, Wilson JW, Lohse CM. Increased incidence of cutaneous nontuberculous mycobacterial infection, 1980 to 2009: a population-based study. Mayo Clin Proc. 2013;88(1):38-45. Yacisin K, Hsieh JL, Weiss D, et al. Outbreak of non-tuberculous mycobacteria skin or soft tissue infections associated with handling fish - New York City, 2013-2014. Epidemiol Infect. 2017;145(11):2269-2279. Gong N, Tan Y, Li M, et al. ALA-PDT combined with antibiotics for the treatment of multiple skin abscesses caused by Mycobacterium fortuitum. Photodiagnosis Photodyn Ther. 2016;15:70-72. Tuberculosis Branch of Chinese Medical Association, Editorial Board of Chinese Journal of Tuberculosis and Respiratory Diseases. Expert consensus on diagnosis and treatment of nontuberculous mycobacterial diseases [in Chinese]. Chin J Tuberc Respir Dis. 2012;35(8):572-580. Tuberculosis Branch of Chinese Medical Association. Guidelines for diagnosis and treatment of nontuberculous mycobacterial diseases (2020 edition) [in Chinese]. Chin J Tuberc Respir Dis. 2020;43(11):918-946. Conyers LE, Saunders BM. Treatment for non-tuberculous mycobacteria: challenges and prospects. Front Microbiol. 2024;15:1394220. Sreekumar A, Kumar A, Biswas R, Biswas L. Emerging and alternative strategies for the treatment of nontuberculous mycobacterial infections. Expert Rev Anti Infect Ther. 2024;22(10):835-853. Gerasimova EN, Ismatullin DD, Lyamin AV, Zhestkov AV. General characteristics, features of cultivation and antibiotic resistance representatives of Mycobacterium fortuitum group representatives (review of literature). Klin Lab Diagn. 2021;66(4):223-228. Additional Declarations No competing interests reported. Supplementary Files CARECHECKLIST.pdf Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 27 Jan, 2026 Reviews received at journal 22 Jan, 2026 Reviewers agreed at journal 10 Jan, 2026 Reviews received at journal 10 Jan, 2026 Reviewers agreed at journal 06 Jan, 2026 Reviewers agreed at journal 03 Dec, 2025 Reviewers invited by journal 03 Dec, 2025 Editor invited by journal 24 Nov, 2025 Editor assigned by journal 06 Nov, 2025 Submission checks completed at journal 04 Nov, 2025 First submitted to journal 04 Nov, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7980994","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":554999560,"identity":"520187db-89bf-4cb5-8548-a9f6841f377a","order_by":0,"name":"Yupei Xiang","email":"","orcid":"","institution":"jiulongpo district science city people's hospital","correspondingAuthor":false,"prefix":"","firstName":"Yupei","middleName":"","lastName":"Xiang","suffix":""},{"id":554999562,"identity":"93372d0f-c987-4250-9d87-51260927895f","order_by":1,"name":"Bing Fan","email":"","orcid":"","institution":"jiulongpo district science city people's hospital","correspondingAuthor":false,"prefix":"","firstName":"Bing","middleName":"","lastName":"Fan","suffix":""},{"id":554999568,"identity":"17a39c6b-814c-442f-ae80-18f457f43b92","order_by":2,"name":"Bo Liu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYBACNvaG5Md/KmyYgQwitfDxHHhmwHMmjZ2f5wCRWuQkHB9I8LYc5peckUCswySYEwwkG9KkDW4+3niDocYmmrAW6baEB4Y7bIwNbqcVWzAcS8ttIKhF5kyCQeKZtGSD2zlmEowNh4nQIpH/QeJg2+H6DTfPEK0lIUGyse0ws+QMHmK18BxIM2Y4k8bMzwP0SwIxfpFvB0YlAzgqD2+88aHGhrAWZGAgkUCKcogWUnWMglEwCkbByAAAEOQ/cHXMSn0AAAAASUVORK5CYII=","orcid":"","institution":"jiulongpo district science city people's hospital","correspondingAuthor":true,"prefix":"","firstName":"Bo","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2025-10-29 14:38:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7980994/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7980994/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":97692897,"identity":"bedeb77b-2c6f-4406-be12-38d19708f266","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"json","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5788,"visible":true,"origin":"","legend":"","description":"","filename":"7e051a04ad564014be8240dd2581de8e.json","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/b8c0d0ec167e3689aa2940a8.json"},{"id":97892945,"identity":"ddedd012-019e-4fce-8192-7845c884fca9","added_by":"auto","created_at":"2025-12-10 15:24:23","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":764646,"visible":true,"origin":"","legend":"","description":"","filename":"CARECHECKLIST.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/2fe2320de77d05f240a2f1ef.pdf"},{"id":97692903,"identity":"488e4b68-f28d-473b-aaa2-42e8e7a7983a","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":603744,"visible":true,"origin":"","legend":"","description":"","filename":"InformedConsentforPublicationofCaseReport.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/3067a709d9a0a34e3179dc61.pdf"},{"id":97692907,"identity":"9527ac3d-86e4-475b-8e4d-7767390e2520","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":51850,"visible":true,"origin":"","legend":"","description":"","filename":"7e051a04ad564014be8240dd2581de8e1enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/3e82a85b0c9fbae1f9f70a46.xml"},{"id":97692905,"identity":"587b0771-2096-4094-bfc8-850177c49610","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":4,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1534075,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/3713d9fd68e288a3706ca869.png"},{"id":97692909,"identity":"0ac43c8f-3f13-4625-aaf8-f1b1463b026c","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":4179308,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/ca64a316ea1266639b804fbe.png"},{"id":97894139,"identity":"be7bcded-c93b-4c97-810f-1a5dafff40d8","added_by":"auto","created_at":"2025-12-10 15:31:58","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":21259,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/3772d4aa13178337c7189c99.png"},{"id":97894065,"identity":"db86fa41-fe54-4e0a-b605-da1000bc18a8","added_by":"auto","created_at":"2025-12-10 15:31:54","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":79086,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/3d9a9fe156a129a4173ec433.png"},{"id":97892793,"identity":"f58e1af2-ded3-4902-9e38-84adcfefb183","added_by":"auto","created_at":"2025-12-10 15:21:50","extension":"png","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":133301,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/352e18c5d8774edbba430b97.png"},{"id":97692901,"identity":"8c17383a-6b86-4591-b97e-2e09b74ab480","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":12818,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/509737328b7ebb632066df7d.png"},{"id":97692910,"identity":"54911f66-eb89-4c2c-aaa1-9ece3567f95d","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"xml","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":48348,"visible":true,"origin":"","legend":"","description":"","filename":"7e051a04ad564014be8240dd2581de8e1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/d4250955c77fc33a02e9fd48.xml"},{"id":97893556,"identity":"7ccc52a4-2d9a-41cc-8050-57056398f8b1","added_by":"auto","created_at":"2025-12-10 15:30:42","extension":"html","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":57128,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/715faf1e354b070e389e20c1.html"},{"id":97692895,"identity":"f2b78566-72d9-48ec-bc73-260706da8912","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":253825,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAbdominal CT scan of the patient. (A) The left lower abdominal pelvic wall shows skin thickening with a nodular configuration. The skin surface is smooth, with ill-defined margins toward the adipose tissue. The lesion measures approximately 39 mm × 21 mm × 37 mm and exhibits heterogeneous density. (B) The left mid-abdominal wall demonstrates localized skin thickening with a smooth surface. A moderately dense nodular shadow with indistinct borders is seen within the subcutaneous fat layer, measuring approximately 15 mm × 11 mm × 12 mm and showing heterogeneous density.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/32010360ca9749c8e38d2456.png"},{"id":97692896,"identity":"ad279ab5-808e-4382-bd1c-a590f25bba98","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":282961,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCharacteristics of the isolated bacterium. (A) After 48 hours of culture on Columbia blood agar, the pus specimen developed medium-sized, white colonies with irregular margins and rough, wrinkled surfaces. (B) Acid-fast staining of the purified colonies confirmed the presence of acid-fast–positive bacilli.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/c6de4cf9af6fe6a16866be25.png"},{"id":97692898,"identity":"9283e2e8-a4ed-4502-a7b2-a02d76cb5a10","added_by":"auto","created_at":"2025-12-08 11:15:09","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":51146,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTreatment course.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/67c78ce44daf00ea73bb1c2e.png"},{"id":97902409,"identity":"e4e557b8-951b-41be-be69-b26310c0537b","added_by":"auto","created_at":"2025-12-10 15:52:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7234708,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/94ce99f5-9975-417f-823f-b2e6c7595cec.pdf"},{"id":97892962,"identity":"518db8d5-1877-4591-b620-999276659762","added_by":"auto","created_at":"2025-12-10 15:24:45","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":764646,"visible":true,"origin":"","legend":"","description":"","filename":"CARECHECKLIST.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7980994/v1/d5f0427155c646c22d2b3c2f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Abdominal Wall Abscess Due to Mycobacterium neworleansense: A Case Report","fulltext":[{"header":"Introduction","content":"\u003cp\u003e\u003cb\u003eMycolicibacterium neworleansense\u003c/b\u003e \u003cb\u003eis a rapidly growing non-tuberculous mycobacterium (NTM) and a newly identified species within the\u003c/b\u003e \u003cb\u003eMycobacterium fortuitum\u003c/b\u003e \u003cb\u003ecomplex. This bacterium has only been detected in a scalp wound and a cerebrospinal fluid specimen. However, reports of human infections caused by\u003c/b\u003e \u003cb\u003eMycolicibacterium neworleansense\u003c/b\u003e \u003cb\u003eare extremely rare. This article presents a case of an abdominal wall abscess caused by\u003c/b\u003e \u003cb\u003eMycolicibacterium neworleansense\u003c/b\u003e, \u003cb\u003eaiming to improve the clinical diagnosis and treatment of infections associated with this pathogen.\u003c/b\u003e\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003e\u003cb\u003eA 74-year-old male was admitted to the hospital for left abdominal mass for 10 days, with redness, swelling and pain for 4 days .10 days ago, the patient found a small mass on the left abdominal wall without special treatment. After 6 days, the size of the mass increased significantly, accompanied by redness, swelling and tenderness of the surrounding skin, and the patient went to the general surgery department. He had a history of hypertension and diabetes for more than 10 years.Levamlodipine besylate tablets and valsartan tablets were used to maintain blood pressure.Insulin injection was used to treat diabetes, and the mass was localized at his long-term abdominal insulin injection site.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eOn admission, physical examination revealed a mass approximately 2.0 cm \u0026times; 1.5 cm in the left abdominal wall above the umbilical plane, with ill-defined borders, overlying skin erythema, and mild tenderness, but no significant fluctuation. Below the umbilical plane, another protruding mass measuring about 5 cm \u0026times; 7 cm was observed, with intact skin and no ulceration or exudate. It was soft in texture, poorly demarcated, and accompanied by localized erythema, elevated skin temperature, marked tenderness, and significant fluctuation. CT imaging demonstrated thickening of the skin in the left lower abdominal pelvic wall (below the umbilical level) with a nodular appearance, smooth surface, and ill-defined margins toward the adipose tissue, measuring approximately 39 mm \u0026times; 21 mm \u0026times; 37 mm (Fig .1A).Localized skin thickening was also observed in the left mid-abdominal wall, with a moderately dense nodular shadow seen in the subcutaneous fat layer, demonstrating ill-defined margins and measuring approximately 15 mm \u0026times; 11 mm \u0026times; 12 mm (\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB\u003cb\u003e). laboratory data revealed the following values: glycated hemoglobin 8.2%, white blood cell count 8.34\u0026times;10⁹/L, red blood cell count 4.65\u0026times;10\u0026sup1;\u0026sup2;/L, hemoglobin 143 g/L, platelet count 249\u0026times;10⁹/L.The initial diagnosis was multiple left abdominal wall infections with abscess, stage 2 hypertension, and type 2 diabetes mellitus.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eOn the day of admission, surgical incision and drainage of the abscess were performed. Intraoperative examination revealed inflammatory changes in the surrounding tissue, with the abscess base extending into the intermuscular septum. Subsequent debridement of pus and necrotic tissue was carried out, and a pus specimen was sent for microbiological analysis. Postoperative therapeutic regimen included piperacillin-tazobactam for anti-infective treatment, supplemented with sodium aescinate to reduce edema and insulin for glycemic control.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eMicroscopic examination of the pus specimen following Gram staining revealed slender, pleomorphic gram-positive bacilli that were also positive for acid-fast staining. Culture of the specimen on Columbia blood agar and chocolate agar yielded small, white colonies at 24 hours. By 48 hours, these colonies had enlarged into medium-sized, white colonies with irregular margins and rough, wrinkled surfaces (\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA\u003cb\u003e). Staining of the purified isolate confirmed the presence of gram-positive, acid-fast\u0026ndash;positive bacilli (Fig .2B).Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) initially identified the isolate as Mycobacterium smegmatis, with an identification score of 1.34 (species-level threshold: 2.000). For further characterization, 16S rRNA gene sequencing was performed on the pure culture. BLAST analysis against the NCBI database demonstrated 100% sequence identity with the 16S rRNA gene of Mycolicibacterium neworleansense strain ATCC 49404 (Accession No. NR_042914.1).\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eA series of biochemical assays were performed, with results as follows: negative for sorbitol fermentation, and positive for nitrate reduction, catalase activity, and xylose fermentation\u0026mdash;a profile consistent with M. neworleansense. The combination of 16S rRNA gene sequencing data and biochemical characteristics, the isolate was definitively identified as Mycolicibacterium neworleansense.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eAntimicrobial susceptibility testing was performed using the broth microdilution method, with results interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines (M100-ED32). The isolate was resistant to rifampin (MIC\u0026thinsp;\u0026gt;\u0026thinsp;16 \u0026micro;g/mL), clarithromycin (MIC\u0026thinsp;\u0026gt;\u0026thinsp;64 \u0026micro;g/mL), doxycycline (MIC\u0026thinsp;\u0026gt;\u0026thinsp;32 \u0026micro;g/mL), minocycline (MIC\u0026thinsp;\u0026gt;\u0026thinsp;128 \u0026micro;g/mL), and azithromycin (MIC\u0026thinsp;\u0026gt;\u0026thinsp;32 \u0026micro;g/mL). It was susceptible to cefoxitin (MIC\u0026thinsp;\u0026le;\u0026thinsp;4 \u0026micro;g/mL), moxifloxacin (MIC\u0026thinsp;\u0026le;\u0026thinsp;0.125 \u0026micro;g/mL), trimethoprim-sulfamethoxazole (MIC\u0026thinsp;\u0026le;\u0026thinsp;8 \u0026micro;g/mL), amikacin (MIC\u0026thinsp;\u0026le;\u0026thinsp;1 \u0026micro;g/mL), ethambutol (MIC\u0026thinsp;\u0026le;\u0026thinsp;5 \u0026micro;g/mL), imipenem-cilastatin (MIC\u0026thinsp;\u0026le;\u0026thinsp;0.5 \u0026micro;g/mL), and linezolid (MIC\u0026thinsp;\u0026le;\u0026thinsp;8 \u0026micro;g/mL). An intermediate susceptibility was observed for tobramycin (MIC\u0026thinsp;=\u0026thinsp;16 \u0026micro;g/mL).\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe anti-infective regimen was transitioned to oral clarithromycin (500 mg twice daily) on postoperative day 3. Based on the susceptibility profile, therapy was escalated on day 9 to a combination of trimethoprim-sulfamethoxazole (960 mg twice daily) and moxifloxacin (400 mg daily). The patient was discharged 12 days post-operatively following notable clinical improvement and continued on combined antibiotic therapy with trimethoprim-sulfamethoxazole and moxifloxacin. Following two months of treatment, the surgical site exhibited complete healing without any evidence of local recurrence or distant infection. The treatment was deemed successful(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e).\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cb\u003eThis case report describes the first identification of Mycobacterium neworleansense causing a cutaneous infection in China, a species that remains exceptionally rare globally. Successful management was achieved through the timely pathogen identification via smear and culture, which guided a combination of surgical intervention and susceptibility-directed antimicrobial therapy, highlighting the importance of this integrated approach.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eMycolicibacterium neworleansense was first classified in 1991 as the third biovariant complex member of Mycobacterium fortuitum\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eIn 2004, through multigene sequence analysis and phenotypic characterization, Schinsky MF et al. established it as a distinct species and named it Mycolicibacterium neworleansense\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eSubsequently, Asmar et al. performed whole-genome sequencing of the reference strain ATCC 49404, further confirming it at the genomic level as a novel species within the M. fortuitum complex\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eSimilar to most nontuberculous mycobacteria (NTM), conventional identification of M. neworleansense remains challenging.Expert Consensus on the Molecular Diagnosis of Nontuberculous Mycobacterial Diseases, recommend the use of multiple molecular methods for NTM identification, including sequencing of the 16S rRNA, 16S\u0026ndash;23S rRNA internal transcribed spacer (ITS), rpoB, and hsp65 genes; PCR-restriction fragment length polymorphism analysis (PRA); metagenomic next-generation sequencing (mNGS); whole-genome sequencing (WGS); and matrix-assisted laser desorption/ionization\u0026ndash;time of flight mass spectrometry (MALDI-TOF MS)\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAccording to Schinsky MF et al.\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e, \u003cb\u003eMycolicibacterium neworleansense exhibits overlapping hsp65 gene sequences and PRA profiles with other members of the third Mycobacterium fortuitum complex, complicating accurate discrimination. MALDI-TOF MS also demonstrates limitations in practical identification; here, the isolate was initially misidentified as Mycobacterium smegmatis. Moreover, methods based on ITS or rpoB gene regions remain inadequately validated for identifying M. neworleansense, and their discriminatory power requires further confirmation. Although mNGS and WGS allow precise species-level identification, their high cost precludes routine use\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eThus, with currently available techniques, 16S rRNA gene sequencing remains the most practical and reliable approach. It should be noted, however, that M. neworleansense exhibits high 16S rRNA sequence homology with Mycolicibacterium bonickei, which can lead to misidentification. Fortunately, these two species display distinct phenotypic characteristics: M. neworleansense is positive for xylose and erythritol fermentation tests, whereas M. bonickei is negative for both, providing a useful criterion for differentiation. Here, although the 16S rRNA sequence showed 100% homology with M. neworleansense ATCC 49404, it also displayed high homology with M. bonickei. Ultimately, the isolate was confirmed as M. neworleansense based on the positive results of xylose and erythritol fermentation tests.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eHuman infection caused by Mycolicibacterium neworleansense is clinically exceedingly rare. A systematic search of both Chinese and English literature databases, including Wanfang, CNKI, and PubMed, revealed no confirmed case reports of human infection by this organism. According to existing records, the type strain ATCC 49404 was isolated from a scalp wound sample in New Orleans, USA; another study from China reported its isolation from a cerebrospinal fluid specimen\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eIn the present case, the patient presented with clear local infectious symptoms and developed an abscess. The smear microscopy and culture results of the abscess specimen were consistent, and the patient responded well to targeted antimicrobial therapy. Therefore, M. neworleansense was identified as the causative pathogen of this abdominal wall abscess. This case represents a subcutaneous injection‑associated cutaneous infection due to M. neworleansense. It is noteworthy that injection procedures are one of the common routes of skin and soft tissue infections caused by nontuberculous mycobacteria (NTM)\u003c/b\u003e \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/sup\u003e \u003cb\u003eThe patient, who required long‑term insulin injections for diabetes, was exposed to increased skin microbial load during the hot summer, and inadequate skin disinfection might have facilitated pathogen entry. Thus, strict adherence to skin aseptic techniques and ensuring the sterility of medical devices during any invasive procedure are crucial measures for preventing cutaneous infections caused by M. neworleansense and other NTM. Clinically, the infection in this case had a relatively acute onset, with rapid enlargement of the mass within six days, which may be related to the rapid growth rate of this bacterium. In vitro culture showed that M. neworleansense formed visible colonies on solid media within 24 hours, with typical morphology apparent by 48 hours\u0026mdash;a characteristic that offers an advantage for early etiological diagnosis.\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eThere are no established guidelines or consensus recommendations for antimicrobial therapy targeting Mycolicibacterium neworleansense.Although treatment regimens for Mycobacterium fortuitum have been suggested as a reference, studies have shown that species within the M. fortuitum complex may exhibit distinct drug resistance profiles\u003c/b\u003e \u003csup\u003e[\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/sup\u003e \u003cb\u003eIn our case, antimicrobial susceptibility testing revealed that the isolate was resistant to macrolides\u0026mdash;such as clarithromycin and azithromycin\u0026mdash;which are commonly used in the treatment of M. fortuitum infections. This underscores the importance of species-level identification of nontuberculous mycobacteria (NTM), along with drug susceptibility testing, for formulating effective anti-infective regimens. The Diagnosis and Treatment Guidelines for Nontuberculous Mycobacterial Diseases (2020 Edition) emphasize that, in addition to selecting active antimicrobial agents, ensuring an adequate treatment duration is essential. A course of at least four months is generally recommended to minimize the risk of relapse. Beyond pharmacological therapy, surgical debridement represents a key intervention in managing M. neworleansense infections, particularly in cases with extensive involvement, abscess formation, or poor response to antimicrobial therapy\u003c/b\u003e \u003csup\u003e[\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. \u003cb\u003eActive surgical intervention can significantly improve clinical outcomes. In this patient, who had developed a well-defined abscess, a combination of surgical drainage and debridement, together with targeted antimicrobial therapy, led to marked clinical improvement.\u003c/b\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003e\u003cb\u003eWe herein report a case of abdominal wall abscess caused by the rare pathogen Mycolicibacterium neworleansense, which was successfully managed with surgical debridement combined with targeted antimicrobial therapy. This case highlights that nontuberculous mycobacterial (NTM) infection should be considered in patients with skin and soft tissue infections, particularly when predisposing factors such as a history of injections are present. The accurate identification of M. neworleansense remains challenging in microbiological diagnosis. Although 16S rRNA gene sequencing remains the most reliable method currently available, its high sequence homology with closely related species such as M. bonickei must be considered, and phenotypic tests such as xylose fermentation are recommended for differentiation. Antimicrobial susceptibility testing revealed resistance to certain commonly used macrolides, indicating that empiric regimens for the M. fortuitum complex should not be empirically adopted and that therapy should be guided by actual susceptibility results. Based on the experience from this case, we recommend early smear and culture of pus to guide initial clinical management in M. neworleansense-related skin and soft tissue infections. Achieving precise anti-infective therapy relies on species-level identification using molecular techniques combined with drug susceptibility testing. Furthermore, in cases where an abscess has formed, proactive surgical intervention is essential for infection control and optimizing treatment outcomes.\u003c/b\u003e\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u003cb\u003eCT\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eComputed tomography\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u003cb\u003eMIC\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003e\u003cb\u003eMinimum Inhibitory Concentration\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics\u0026nbsp;approval\u0026nbsp;and\u0026nbsp;consent\u0026nbsp;to\u0026nbsp;participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObtain the patient's informed consent and agreement.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eYupei Xiang identified the suitability of this case for publication, and was the major contributor to writing the manuscript, the literature review, data analysis and interpretation, and editing of the manuscript. Bing Fan assisted with the literature review, writing and editing of the manuscript, and interpretation of the results. Bo Liu assisted with conceptualization of the case study, interpretation of the results, and writing and editing of the manuscript.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent\u0026nbsp;for\u0026nbsp;publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;All authors critically reviewed and approved the final manuscript.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe authors declare no competing interests.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNo external sources of funding were received for this case report.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe datasets supporting the conclusions of this article are fully presented within the manuscript and its supplementary files.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWritten informed consent was obtained from the participant for the use of his protected health information and identifiable medical images in this research publication.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWe are grateful to the patient and his family for their consent to the use of clinical data for research and explicit permission to publish this case report.\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBrown-Elliott BA, Wallace RJ Jr. Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria. Clin Microbiol Rev. 2002;15(4):716-746.\u003c/li\u003e\n\u003cli\u003eSchinsky MF, Morey RE, Steigerwalt AG, et al. Taxonomic variation in the Mycobacterium fortuitum third biovariant complex: description of Mycobacterium boenickei sp. nov., Mycobacterium houstonense sp. nov., Mycobacterium neworleansense sp. nov. and Mycobacterium brisbanense sp. nov. and recognition of Mycobacterium porcinum from human clinical isolates. Int J Syst Evol Microbiol. 2004;54(Pt 5):1653-1667.\u003c/li\u003e\n\u003cli\u003eAsmar S, Robert C, Croce O, Caputo A, Drancourt M. Draft genome sequence of Mycobacterium neworleansense strain ATCC 49404T. Genome Announc. 2015;3(6):e01314-15.\u003c/li\u003e\n\u003cli\u003eNontuberculous Mycobacterial Disease Branch of Chinese Antituberculosis Association, Sun Q. Expert consensus on molecular diagnosis of nontuberculous mycobacterial diseases [in Chinese]. Chin J Antituberc. 2025;47(8):961-975.\u003c/li\u003e\n\u003cli\u003eTortoli E, Fedrizzi T, Meehan CJ, et al. The new phylogeny of the genus Mycobacterium: The old and the news. Infect Genet Evol. 2017;56:19-25.\u003c/li\u003e\n\u003cli\u003e\u0026quot;Belt and Road\u0026quot; Dermatology Alliance Mycobacterial Disease Research Alliance, Chinese Leprosy Association Branch of Dermatology Laboratory and Diagnosis. Chinese expert consensus on diagnosis and treatment of cutaneous nontuberculous mycobacterial diseases (2024 edition) [in Chinese]. Chin J Dermatol. 2024;57(2):109-118.\u003c/li\u003e\n\u003cli\u003eWu YF, Li QC, Jia QJ, et al. Identification and drug resistance analysis of pathogens causing nontuberculous mycobacterial pulmonary disease in suburban areas of Hangzhou [in Chinese]. J Tuberc Lung Dis. 2025;6(4):420-425.\u003c/li\u003e\n\u003cli\u003eWentworth AB, Drage LA, Wengenack NL, Wilson JW, Lohse CM. Increased incidence of cutaneous nontuberculous mycobacterial infection, 1980 to 2009: a population-based study. Mayo Clin Proc. 2013;88(1):38-45.\u003c/li\u003e\n\u003cli\u003eYacisin K, Hsieh JL, Weiss D, et al. Outbreak of non-tuberculous mycobacteria skin or soft tissue infections associated with handling fish - New York City, 2013-2014. Epidemiol Infect. 2017;145(11):2269-2279.\u003c/li\u003e\n\u003cli\u003eGong N, Tan Y, Li M, et al. ALA-PDT combined with antibiotics for the treatment of multiple skin abscesses caused by Mycobacterium fortuitum. Photodiagnosis Photodyn Ther. 2016;15:70-72.\u003c/li\u003e\n\u003cli\u003eTuberculosis Branch of Chinese Medical Association, Editorial Board of Chinese Journal of Tuberculosis and Respiratory Diseases. Expert consensus on diagnosis and treatment of nontuberculous mycobacterial diseases [in Chinese]. Chin J Tuberc Respir Dis. 2012;35(8):572-580.\u003c/li\u003e\n\u003cli\u003eTuberculosis Branch of Chinese Medical Association. Guidelines for diagnosis and treatment of nontuberculous mycobacterial diseases (2020 edition) [in Chinese]. Chin J Tuberc Respir Dis. 2020;43(11):918-946.\u003c/li\u003e\n\u003cli\u003eConyers LE, Saunders BM. Treatment for non-tuberculous mycobacteria: challenges and prospects. Front Microbiol. 2024;15:1394220.\u003c/li\u003e\n\u003cli\u003eSreekumar A, Kumar A, Biswas R, Biswas L. Emerging and alternative strategies for the treatment of nontuberculous mycobacterial infections. Expert Rev Anti Infect Ther. 2024;22(10):835-853.\u003c/li\u003e\n\u003cli\u003eGerasimova EN, Ismatullin DD, Lyamin AV, Zhestkov AV. General characteristics, features of cultivation and antibiotic resistance representatives of Mycobacterium fortuitum group representatives (review of literature). Klin Lab Diagn. 2021;66(4):223-228.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-infectious-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"infd","sideBox":"Learn more about [BMC Infectious Diseases](http://bmcinfectdis.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/infd","title":"BMC Infectious Diseases","twitterHandle":"#bmcinfectdis","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Nontuberculous mycobacteria, Mycobacterium neworleansense, Abdominal Wall Abscess, infections","lastPublishedDoi":"10.21203/rs.3.rs-7980994/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7980994/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIntroduction\u003c/p\u003e\u003cp\u003eNontuberculous mycobacteria are widely distributed in the natural environment and can cause cutaneous infections through traumatic injuries or invasive procedures, leading to nontuberculous mycobacterial skin diseases. However, skin infections caused by Mycobacterium neworleansense are exceedingly rare. This article reports a case of an abdominal wall abscess resulting from this uncommon pathogen, with the aim of enhancing clinical recognition and improving the diagnosis and management of infections associated with Mycobacterium neworleansense.\u003c/p\u003e\u003cp\u003eCase presentation\u003c/p\u003e\u003cp\u003eA 74-year-old male with diabetes was hospitalized due to an abscess on the left abdominal wall at a site of long-term insulin administration. After admission, surgical incision and drainage of the abscess were performed. Microbiological culture of the intraoperative pus specimen revealed growth of non-tuberculous mycobacteria, which was subsequently identified as Mycobacterium neworleansense using a combination of 16S rRNA gene sequencing and biochemical profiling. Antimicrobial susceptibility testing demonstrated resistance to macrolides and tetracyclines, but susceptibility to trimethoprim-sulfamethoxazole, aminoglycosides, moxifloxacin, and imipenem. Following surgical intervention, the patient received a combined antibiotic regimen of trimethoprim-sulfamethoxazole and moxifloxacin, which led to successful clinical resolution of the infection.\u003c/p\u003e\u003cp\u003eConclusion\u003c/p\u003e\u003cp\u003eMycobacterium neworleansense has the potential to cause subcutaneous abscesses following injection-related procedures. Successful management of such infections relies on accurate pathogen identification through molecular and biochemical methods, coupled with targeted antimicrobial therapy guided by susceptibility testing, and supported by appropriate surgical intervention.\u003c/p\u003e","manuscriptTitle":"Abdominal Wall Abscess Due to Mycobacterium neworleansense: A Case Report","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-08 11:15:04","doi":"10.21203/rs.3.rs-7980994/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-27T09:18:58+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-23T01:59:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"266554000026714919200336600124741422005","date":"2026-01-10T20:27:16+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-10T09:58:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"198293437698048058602209703093932420215","date":"2026-01-07T02:29:06+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"281134747141808262821744327003187909117","date":"2025-12-04T03:50:36+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-04T01:28:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-24T10:31:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-11-06T09:55:29+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-11-04T16:50:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Infectious Diseases","date":"2025-11-04T16:02:39+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-infectious-diseases","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"infd","sideBox":"Learn more about [BMC Infectious Diseases](http://bmcinfectdis.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/infd","title":"BMC Infectious Diseases","twitterHandle":"#bmcinfectdis","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8f6a2c2b-590b-4bb2-99b0-0eccb205ba78","owner":[],"postedDate":"December 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-12T11:25:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-08 11:15:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7980994","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7980994","identity":"rs-7980994","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}