An Uncommon Infection due to an Unusual Pathogen. Report of a Pubic Symphisis Septic Arthritis after Caesarean Delivery due to Cutibacterium Acnes

Pubic symphysis septic arthritis is a rare condition mainly associated with pregnancy. Fewer than 35 cases have been reported. We report a case that occurred after delivery by caesarean section, and which was due to Cutibacterium acnes. Management involved three lines of antibiotic therapy and surgical debridement. The combination of this rare pathology and a germ often considered commensal led to an erratic diagnosis for almost six years. One of the consequences, in addition to chronic pain, was destabilization of the pelvic girdle, necessitating surgery. After more than 18 months of follow-up, there was no relapse.

Pubic symphysis, Arthritis, Pregnancy, Caesarean delivery, Cutibacterium acnes

Diagnosis can be difficult especially when the pathology is rare, but when the diagnosis is the combination of two rare entities, it becomes very complex. Infections of the pubic symphysis are relatively rare and classically reported after urological surgery or in athletes [1]. This pathology has been rarely reported during pregnancy or in the aftermath of childbirth. Consequences can be significant, with potential repercussions on pelvic stability [2]. Cutibacterium acnes has long been considered a commensal germ with little to no involvement in infections [3]. We now know that it is a genuine pathogenic germ, mainly found in shoulder and clavicle infections. Since, this germ does not provoke inflammatory phenomena, symptoms can be long-lasting, delaying investigations and its detection. To the best of our knowledge, we report here the first case of infection of a pubic symphysis solely due to C. acnes in a woman who had given birth by caesarean section. Case report A 31 year-old woman complained of pain when walking. Pain was mechanical and localized in both adductor muscles. It had started five months after a Caesarean delivery which had been carried out without any complications. An X-ray taken at the time showed demineralization of the symphysis margins. An MRI confirmed the diagnosis of symphysitis without intra- or extra-articular collection. However, the diagnosis was not retained and neither surgical exploration nor biopsy was performed. The following period was marked by diagnostic erraticism, with an escalating number of radiological examinations including CT scan and bone scan (Fig. 1). Several diagnoses were suggested over a 6 year period, such as inflammatory rheumatism, fibromyalgia or endometriosis. The patient was finally examined by a surgeon who supported the infectious hypothesis. Six years after the onset of clinical signs, a biopsy of the pubic symphysis and the small collection located behind the joint was performed. Bacteriological analysis revealed the presence of C. acnes. The patient was then treated with a combination of Amoxicillin (2 g qid) and clindamycin (600 tid) for three months. The pain improved but at the end of the treatment the patient complained of persistent pain in the adductors and when pressing on the symphysis. Given the clinical signs and the recurrent collection shown on MRI, a further surgical biopsy was performed which again revealed C. acnes. Histopathology examination was consistent with chronic osteoarthritis. A combination of ceftriaxone (2 g qd) and rifampicin (600 mg bid) was prescribed for six weeks, followed by a combination of rifampicin (600 mg bid) and levofloxacin (500 mg bid) for a further six weeks. After a period of improvement, pain recurred. Despite improved MRI images, a small collection remained. It was therefore decided to proceed with surgery to debride the site and edges of the symphysis to promote healing. Two out of the three intraoperative samples were positive for C. acnes. A new course of antibiotics was initiated, again combining Amoxicillin at a higher dose (3 g tid) and clindamycin (600 tid) for six weeks. The patient's local and general condition finally improved, with a reduction and then a resolution of pain and the ability of walking properly again. After more than 18 months of follow-up, there has been no relapse. Surgery to stabilize the symphysis is currently considered as the stability of the lumbar spine is beginning to be affected.

Arthritis of the pubis symphysis is a rare condition, little known to physicians. Ross et al. reported the biggest series with a mere 100 cases from a 30 year review of the literature. More recently Hansen et al. reported 26 patients from a single center over a period of 11 years. The occurrence of this condition in conjunction with pregnancy is mainly reported as clinical case. In Ross’s series, only two cases were associated with pregnancy. The largest series (19 patients) reports the consequences of this infection, such as lumbopelvic pain [2]. Taken altogether, less than 35 cases have been reported in association with pregnancy. Symptoms can arise during pregnancy or after delivery. Patient’s main complaint is pain on walking. This is because adductor muscles are attached to the pubic symphysis, so inflammation of the symphysis is transmitted to the muscles, resulting in pain. In the literature, infection began during pregnancy for six patients, between the 12th and 37th week of amenorrhea. For the others, pain began shortly after delivery, in the vast majority of cases (n = 24) within the first two days. In two patients, symptoms appeared later (five days and eight weeks). We found no patient like ours, in whom symphysis was diagnosed following caesarean section. Microbiologically, when a germ is detected, it is mainly Staphylococcus aureus or Coagulase negative Staphylococcus, Streptococcus spp.. Cutibacterium acnes was only detected once, in association with Staphylococcus capitis. In contrast to the case of our patient, this involved a vaginal delivery and the patient presented clinical signs at twelve weeks’ amenorrhea. As with our patient, microbiological diagnosis was made by puncture. However, given the association of the two commensal germs in a single sample, it is unclear whether one or both germs are involved, all the more so as the antibiotic treatment used (Clindamycin) is effective against both germs. In fact, Cutibacterium acnes is an integral part of the skin microbiota. However, although it can be found all over the skin using biomolecular technics, it is mainly found on the upper part of the body. Its implication in the infection in the pubic area is therefore uncommon. It has long been considered a commensal bacterium. Thus, interpreting a single positive sample is difficult. This is what happened with the patient’s first sample, which was considered as noncontributory by several physicians. However, subsequent concordant bacteriological samples confirmed the involvement of this bacterium. Treatment can be challenging. In the series of Hansen, relapses requiring revision surgery were observed in five out of 26 patients [1]. In the series of Ross et al., more than half the patients underwent surgical debridements and/or abscess drainage. It therefore appears that aggressive treatment of the infected sites such as debridement or achievement of the symphysis edges is necessary to maximize the chances of cure. The duration of antibiotic treatment is not clearly defined, but varies in the literature from six to 12 weeks.

Although this seems to be a very rare pathology, we believe it is important to report it, as it could prevent other patients from having the same kind of experience. Funding There is no funding source. Declarations Conflict of interest There is no conflict of interest. Ethical Approval Not necessary. Informed Consent A written consent was obtained from the patient. Footnotes Eric Denes is a Infectiologie Specialist, M.D; Rachid Saddiki is a Orthopaedic and Spinal Surgeon, M.D. Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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