A study on the active efflux system in methicillin-resistant Staphylococcus aureus

Abstract

Objective To explore the status of methicillin-resistant Staphylococcus aureus (MRSA) infection in an intensive care unit (ICU), and investigate the active efflux mechanism of MRSA. Methods Eighty isolates were identified as MRSA among 102 strains of Staphylococcus aureus collected, and then the minimal inhibitory concentration (MIC) were determined. The 4 primers of active efflux gene were designed to amplify the 80 clinical isolates respectively by polymerase chain reaction (PCR). The PCR products were analyzed by electrophoresis in order to grasp the situation of the existence of the four genes (norA, qacA, qacB and qacJ). Omeprazole inhibition test was used to observe the changes in the susceptibility of MRSA to antibiotics. Results The detection rate of MRSA was 78.4%. The sensitivity rate of MRSA to both vancomycin and teicoplanin was 100.0%, while to other antibiotics (oxacillin, benzylpenicillin, cefuroxime, cefotaxime, ceftazidime, ceftiaxone, cefepime, cefoxitin, imipenem, piperacillin and tazobactam, azithromycin, erythromycin, chloramphenicol, clindamycin, amikacin, gentamicin, levofloxacin, gatifloxacin, ciprofloxacin) MRSA was multi-drug resistant. The detection rates of norA, qacA, qacB and qacJ were 67.5% (54/80), 15.0% (12/80), 21.2% (17/80) and 11.2% (9/80), respectively. Combined use of omeprazole and levofloxacin could lower MIC value. Conclusion The infection of MRSA in ICU is serious. MRSA is multi-drug resistant and possesses active efflux genes norA, qacA, qacB and qacJ. Omeprazole can inhibit the activity of the active efflux genes. Key words: Methicillin-resistant Staphylococcus aureus ; Minimal inhibitory concentration ; Multi-drug resistant ; Active efflux gene ; Omeprazole ;