Mupirocin and vancomycin susceptibility in MRSA colonising anterior nares of patients scheduled for cardiac surgery

Mupirocin has been recognised as the best and the most effective topical antimicrobial agent for decolonisation. With widespread use of mupirocin for decolonisation, increasing number of MRSA have developed resistance to mupirocin.

The society of thoracic surgeons recommends a glycopeptide (vancomycin) for cardiac surgical prophylaxis in patients known to be colonised with MRSA. Development of resistance to vancomycin among MRSA is a cause of concern.

Currently, there is very limited data regarding prevalence of mupirocin and vancomycin resistance in MRSA colonising the anterior nares of patients undergoing high risk surgeries.

To assess the prevalence of mupirocin and vancomycin resistance in MRSA colonising anterior nares of patients undergoing cardiac surgical procedures in our tertiary care hospital.

Screening for MRSA was done by disc diffusion method using Cefoxitin disc. Screening for MuL and MuH was done by disc diffusion method using mupirocin disc of strength 5 μg and 200 μg respectively. Screening for detection of reduced susceptibility to vancomycin was done by Agar Dilution method. The MIC of mupirocin and vancomycin determined by Agar dilution method.

Twenty two percent of MRSA isolates had MuL and eleven percent had MuH. One of the mupirocin sensitive MRSA, had a presumptively reduced susceptibility to vancomycin by BHI agar screen method.

Screening of patient populations for MRSA, MuH and VISA/VRSA colonisation, especially those undergoing high risk surgeries should be considered, to prevent self infection and nosocomial transmission of resistant strains.