[The action of active efflux system on multi-drug resistance in methicillin resistant Staphylococcus aureus]

To study the active efflux gene qacB, qacJ and smr in methicillin resistant Staphylococcus aureus (MRSA) and to investigate their effect on the multi-drug resistance (MDR) of MRSA.

The three pairs of ideal primers of active efflux gene qacB, qacJ and smr were designed by computer with Primer Premier 5.0 software. A total of 124 clinical isolates of MRSA were amplified respectively by polymerase chain reaction (PCR) with above mentioned primers. The PCR products were separated by electrophoresis on an 1.5% agarose gel with 0.5 microg/ml ethidium bromide. Reserpine inhibition test was used to observe the changes of the susceptibility to antibiotics of MRSA which had qacB, qacJ and smr genes separately.

Of the 124 strains of MRSA, 86 strains had qacB, 45 strains had qacJ and 32 strains had smr gene. Reserpine inhibition test showed that the minimal inhibitory concentration (MIC) decreased 2 to 32 times for MRSA to levofloxacin and rifampin.

MRSA have qacB, qacJ and smr active efflux systems, which play a very important role in multiple antibiotic resistance.