Diversity of Mupirocin-Resistance Plasmids in Nosocomial Methicillin-Resistant Staphylococcus aureus Clones and Their Transfer Among Clinical Strains

Author(s): Marcia Giambiagi-deMarval, Ana Paula Couto Marques Cardozo, Viviane Coimbra-e-Souza, Katia Regina Netto dos Santos, Maria do Carmo de Freire Bastos, Ciro César Rossi

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent cause of difficult-to-treat infections in healthcare settings, with limited treatment options. Mupirocin, an antibiotic commonly used for nasal decolonization and MRSA transmission prevention, is increasingly ineffective due to global emergence of high-level mupirocin resistance, conferred by the mupA gene. This study examined the diversity and transmissibility of plasmids carrying mupA-mediated resistance from five MRSA strains obtained from nosocomial infections in Rio de Janeiro hospitals. Plasmid origin of mupA was confirmed through heat stress curing, plasmid extraction, and PCR. Resistance was associated with high-molecular-weight plasmids that could transfer to methicillin-sensitive S. aureus and subsequently to MRSA. Diversity of the plasmids was confirmed through analysis of insertion sequence IS257 presence, orientation, and distance from mupA, as well as restriction patterns. These findings highlight the need for careful monitoring of mupirocin use, given the decreasing treatment options for MRSA infections and the potential for easy transfer of mupirocin-resistant plasmids among Staphylococcus.