Clonal spread of trimethoprim-sulfamethoxazole–resistant Stenotrophomonas maltophilia isolates in a tertiary hospital

Abstract

Aim: The aims of this study were to: (i) determine antibiotic susceptibility of clinical isolates, (ii) investigate the presence of different classes of integrons and genes responsible for sulphonamide resistance, (iii) assess the molecular epidemiology of the isolates by determining their clonal relatedness, and (iv) investigate the potential sources of infection by collecting environmental samples when necessary.Methods: 99 isolates from clinical specimens of hospitalized patients were screened by PCR for , , genes, and integron-associated integrase genes: , , and . PFGE was used to determine the clonal relatedness of the isolates. Results: Susceptibility rates for trimethoprim-sulfamethoxazole, levofloxacin, and ceftazidime were 90.9%, 91.9%, and 53.5% respectively. All trimethoprim-sulfamethoxazole–resistant isolates were positive for and . PFGE analysis revealed that 24 of the isolates were clonally related, clustering in seven different clones. Five of the nine trimethoprim-sulfamethoxazole–resistant isolates were clonally related. The first isolate in this clone was from a wound sample of a patient in the infectious diseases clinic, and the other four were isolated from the bronchoalveolar lavage samples of patients in the thoracic surgery unit. The patient with the first isolate neither underwent bronchoscopy nor stayed in the thoracic surgery unit. Although clustering was observed in bronchoalveolar lavage samples, no growth was detected in environmental samples. Conclusion: The findings demonstrated that the gene carried by class 1 integrons plays an important role in trimethoprim-sulfamethoxazole resistance in isolates. PFGE analysis revealed a high degree of genetic diversity. However, detection of clonally related isolates suggests the acquisition from a common source and/or cross-transmission of this microorganism between the patients.

Keywords

• stenotrophomonas maltophilia
• trimethoprim-sulfamethoxazole resistance
• pfge
• sul
• integron