Comparative Study between SmeDEF Multidrug Efflux Pump and CTX-M ESBL as Resistance Determinants in Nosocomial Isolates of Stenotrophomonas Maltophilia

Abstract

Background: Stenotrophomonas maltophilia (S. maltophilia) is an important opportunistic pathogen that is usually associated with hospital acquired infections. Increased antibiotic resistance among those isolates is a real life threatening problem. Efflux pump and ESBL are two main causes of resistance in S. maltophilia. Objectives: The aims of this study were to isolate S. maltophilia from different sites of nosocomial infections among patients in Mansoura University Hospitals (MUHs), to determine multidrug resistant (MDR) isolates, to characterize those isolates as regarding presence of SmeDEF efflux pump and CTX-M ESBL and to compare the prevalence of both determinants as a cause of resistance in those isolates. Methodology: The study was conducted on 220 S. maltophilia isolates from nosocomialy infected patients which were subjected to antimicrobial susceptibility testing to determine the MDR isolates that were phenotypically tested for presence of efflux pump mediated antibiotic resistance and ESBL production by microdilution test and double disk synergy test respectively followed by detection of SmeDEF and CTX-M genes by PCR in the phenotypically positive isolates. Results: Antibiotic susceptibility testing of the 220 S. maltophilia isolates revealed that 179 (81.4%) of them were MDR, of which 43 (24%) were positive for efflux pump system and 147 (82.1%) were positive for ESBL production by phenotypic tests. PCR revealed that SmeDEF gene was detected in 38 (21.2%) of the MDR S. maltophilia isolates, where as CTX-M gene was found to be harbored by only 12 (6.7%) of those isolates. Conclusion: SmeDEF efflux pump was found to be a more prevalent cause of multiple antibiotic resistance in S. maltophilia nosocomial isolates than CTX-M ESBL; this may be helpful in improving the patient outcome if the exact cause of resistance is kept in mind during designation of the patient treatment regimen.