Distribution of blaTEM, blaCTX-M and blaSHV genes and biofilm-forming capacity among Stenotrophomonas maltophilia clinical isolates

Background and Aim : Stenotrophomonas maltophilia known as one of the major contributor to nosocomial infections. Extended-spectrum ßlactamase (ESBL)-producing S. maltophilia is spreading worldwide particularly in the immunocompromised patients. We aimed to determine the frequency of ESBL encoding genes, blaTEM, blaCTX-M and blaSHV among clinical isolates of S. maltophilia.Methods : In this descriptive cross-sectional study, a total of ۹۷ S. maltophilia isolates were collected from five tertiary-care hospitals affiliated to Tehran and Qazvin University of Medical Sciences between September ۲۰۱۹ and March ۲۰۲۰ and were identified through standard biochemical tests and PCR amplification of the ۲۳S rRNA gene. Antibiotic susceptibility was investigated by disk diffusion test. Biofilm formation was determined by microtiter plate assay. The blaTEM, blaCTX-M and blaSHV were detected by PCR and sequencing Results : All isolates were resistant to imipenem and meropenem. Levofloxacin, minocycline and trimethoprim/sulfamethoxazole exhibited the highest susceptibility of ۹۷.۹ %, ۸۸.۷% and ۸۵.۶ %, respectively. The resistance rates to other antibiotics were as follow: ceftazidime (۷۶.۳ %); ticarcillin/clavulanate (۶۰.۹%); chloramphenicol (۳۹.۲%); tigecycline (۱۳.۴%). Among the isolates examined, ۹۳ (۹۵.۹%) were able to produce biofilm, of which ۴۵ (۴۶.۴%) were strong biofilm-producers, whereas ۴۱ (۴۲.۳%) and ۷ (۷.۲%) were moderate and weak biofilm-producers, respectively. The existence of blaTEM and blaCTX-M was detected in ۱۰ (۱۰.۳%) and ۴ (۴.۱ %) isolates respectively, whereas none of the isolates carried blaSHV gene. One of the isolates harbored both the blaTEM and blaCTX-M genes.Conclusion : The prevalence of β-lactamase-producing genes in S. maltophilia detected by our study is of great concern and highlights the need of appropriate infection control protocols including screening isolates with beta-lactamase-producing genes to prevent further infection.

کلیدواژه ها:

Stenotrophomonas maltophili ، ESBL ، Biofilm