Relationship between antibiotic resistance with class 1 integron and SmeDEF efflux pump encoding genes in clinical isolates of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an emerging multidrug-resistant organism with an increasing frequency of hospital-acquired infections predominantly in developing countries. The purpose of this study was to determine the antibiotic resistance and frequency of the smeD , class1 integron, and sul1 genes in clinical isolates of S. maltophilia in two Iranian provinces. From January 2020 to September 2021, 38 clinical isolates of S. maltophila were collected from patients in hospitals in Tabriz and Sanandaj provinces of Iran. S. maltophilia isolates were confirmed by standard bacteriological tests and 16S rRNA gene PCR. Disc diffusion and E-test methods were used to determine the antibiotic resistance pattern. PCR was performed to investigate the presence of smeD , class1 integron, and sul1 genes. The antimicrobial test for the isolated S. maltophilia showed a high level of sensitivity against most of the antibiotics used. Maximum sensitivity was recorded for ciprofloxacin [100% (38/38)] and levofloxacin 100% (38/38), followed by ceftazidim [97.36% (37/38)], trimethoprim-sulfamethoxazole [94.73% (36/38)], ticarcillin-clavulanate [60.52% (23/38)] and piperacillin-tazobactam [55.26% (21/38)]. We observed a high prevalence of smeD [100% (38/38)] and class1 integron [94.73% (36/38)] genes in the isolates, and none of the isolates carried the sul1 gene. The findings from this study indicate that resistance to trimethoprim-sulfamethoxazole was not observed and still, trimethoprim-sulfamethoxazole is the best drug with desirable antimicrobial effect in the treatment of nosocomial infections caused by S. maltophilia strains. Despite the observation of a high number of class1 integron, the sul1 gene was not observed, which indicates the role of this gene in high-level trimethoprim-sulfamethoxazole resistance and not having a role in low-level resistance. Based on our results clinical microbiology laboratories need continuous surveillance of resistance rates to trimethoprim-sulfamethoxazole, because of the possibility of S. maltophilia acquiring trimethoprim-sulfamethoxazole-resistance by mobile gen elements.