High prevalence of mupirocin resistance in methicillin resistant staphylococci and its clinical significance

Abstract

Background: With the increasing pressure to prevent MRSA infections, it is possible that there will be increased use of Mupirocin for nasal decolonization of MRSA. Mupirocin is bacteriostatic at low concentration near the MIC for staphylococcus aureus but it is bactericidal at concentrations achieved by topical administration (20,000ug/ml) with the 2% formulation. Earlier reported High level Mupirocin resistance strain is associated with decolonization failure. The present study was carried out to determine the rates of high level and low level Mupirocin resistance (MuH and MuL) in methicillin resistant Staphylococcus aureus and methicillin resistant coagulase negative staphylococci. Materials and methods: A prospective study was carried out on 104 non-duplicate Staphylococcal isolates from various clinical specimens were tested for Mupirocin resistance using 5µg and 200µg discs. Detection of Mupirocin resistance was done by the disk diffusion method using 5 μg and 200 μg Mupirocin disks to determine low- and high-level resistance, respectively. Results: Mupirocin resistance was 7.8%, and 4.6% in MRSA and 40% and 20% in MR-CONS for 5 µg and 200 µg disc respectively. Conclusion: Institutions that are considering the implementation of widespread Mupirocin use should consider these resistance issues and develop strategies to monitor the impact of Mupirocin use. Perioperative prophylaxis with nasal mupirocin therapy (PPNMT) can reduce the incidence of MRSA SSls after orthopaedic surgery, probably by reducing nasal MRSA carriage in the endemic setting, without selecting for mupirocin resistance.