engleski

Prevalence of high-level mupirocin resistance among clinical staphylococcal isolates

Nasal carriers, especially those carrying methicilin-resistant Staphylococcus aureus (MRSA) are potent reservoirs of infection, presenting a risk factor for nosocomial infections outbreaks. Thereby, for the clearance of MRSA strains in patients, and health care personnel, a topical antibiotic mupirocin is commonly used. However, two different mechanisms of mupirocin resistance have been described: low-level and high-level resistance. High-level (HL) resistance has been often associated with decolonization failure and increasing recolonization rate. The aim of this study was to evaluate the prevalence of HL mupirocin resistance among staphylococcal isolates from Clinical Hospital Centre Rijeka, in period of three years (2012.-2014.). S. aureus, MRSA and methicilin sensitive (MSSA) strains, as well as coagulase negative staphylococci (CoNS) were tested to mupirocin, using a disc diffusion sensitivity test and 200µg mupirocin discs. From 690 isolates of S.aureus in 2012, 15.94% were MRSA strains, of which one third exhibited HL resistance to mupirocin. Among MSSA strains, only 93 (16%) were HL mupirocin resistant. In 2013, 11.11% MRSA strains were detected of total 747 S.aureus isolates. 35 (42%) of MRSA and 93 (14%) of MSSA isolates had HL mupirocin resistance. In 2014, 8.26% of total 626 S.aureus isolates were MRSA, among which 37% were HL resistant to mupirocin, while the same level of mupirocin resistance was detected in 14% of MSSA strains. In addition, the prevalence of HL resistance to mupirocin among total CoNS isolates was 41.8% in 2012, 43.3% in 2013, and 49.8% in 2014 respectively. Although percentage of MRSA strains among total S.aureus isolates is not high and continuously decreases in past three consecutive years in our Hospital, HL resistance to mupirocin was found in up to 42% of these strains. At the same time, 14-16% of MSSA strains were HL resistant to mupirocin. Further, HL mupirocin resistance was detected in almost half of CoNS isolates. Although this is probably not of clinical importance, it is not completely harmless while these strains may be marked as potential source of resistant genes.

staphylococci; mupirocin; resistance

Acknowledgement: “Molecular mechanisma of bacterial pathogenesis and response to stress” (M.A., grant No. 13.06.1.1.07. from the University of Rijeka, Croatia).