Retrospective analysis of antibiotic resistance profiles and frequency of resistance genes of clinical Stenotrophomonas maltophilia isolates

Stenotrophomonas maltophilia is an opportunistic pathogen that can cause infections, especially in hospital environments and in immunocompromised individuals. Due to its resistance to many broad-spectrum antibiotics, treatment options that can be used in clinical practice are limited. The reported increase in resistance to trimethoprim-sulfamethoxazole, which is recommended as the first line of treatment, complicates the treatment of S. maltophilia induced infections. Although the association of integrons, which are genetic elements involved in the transmission of antibiotic resistance genes, and sul genes, which are responsible for sulfonamide resistance, with antibiotic resistance has been investigated in other gram negative bacteria, data for S. maltophilia in our country are very limited. This study aims to evaluate the susceptibility profiles of S. maltophilia isolates to antimicrobial agents commonly used in treatment and to investigate the presence of different classes of integrons and sul genes responsible for resistance. The study included 100 S. maltophilia isolates from various clinical specimens sent to Balıkesir University Health Practice and Research Hospital Medical Microbiology Laboratory between 2017 and 2023. Bacterial identification and antibiotic susceptibility testing were performed using the BD Phoenix™ M50 Automated System (Becton Dickinson, USA). The susceptibility of the isolates to trimethoprim-sulfamethoxazole was also tested by disk diffusion method. All isolates were investigated for sul1, sul2 genes and integron-related integrase genes (intI1, intI2) by polymerase chain reaction. Susceptibility rates of the isolates to trimethoprim-sulfamethoxazole, levofloxacin and ceftazidime were 96%, 66% and 38%, respectively. As a result of polymerase chain reaction, intI1 and sul1 gene regions were found positive together in two isolates resistant to trimethoprim-sulfamethoxazole, while sul1 and sul2 gene regions were found in two seperate isolates sensitive to trimethoprim-sulfamethoxazole. IntI2 gene was not detected in any isolate. In conclusion, determination of the antimicrobial susceptibility status and the presence of resistance genes in S. maltophilia isolates in our hospital will contribute to the national data and will guide the control of the spread of resistant strains and the establishment of rational antibiotic use policies.