Acquisition of high-level mupirocin resistance in CoNS following nasal decolonization with mupirocin

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Mupirocin is used for Staphylococcus aureus decolonization.
• The development of mupirocin resistance, particularly high-level resistance mediated by the mupA gene in Coagulase-negative staphylococci (CoNS), is a growing concern.
• Quantifying this resistance acquisition is essential for understanding its clinical impact.

Purpose of the Study:

• To quantify the acquisition of mupirocin resistance in Staphylococcus aureus and CoNS among surgical patients undergoing peri-operative mupirocin treatment.
• To investigate the prevalence of the mupA gene in resistant CoNS isolates.

Main Methods:

• A prospective study involving 1578 surgical patients treated with nasal mupirocin and chlorhexidine soap.
• Nasal swabs were collected before treatment (T1) and post-surgery (T2).
• Staphylococci were cultured on selective media, identified by MALDI-TOF MS, and resistance confirmed by Etest, with mupA gene detection.

Main Results:

• Mupirocin resistance in CoNS increased significantly from 21% at T1 to 43% at T2 (P<0.001).
• Among patients not colonized initially, 37% acquired resistance, with a rate of 7.4/100 patient days.
• High-level mupirocin resistance (MIC >256 mg/L) was observed in 97% of resistant CoNS, with 99.5% harboring the mupA gene.
• No acquisition of mupirocin resistance was detected in Staphylococcus aureus.

Conclusions:

• Peri-operative mupirocin decolonization is associated with widespread acquisition of high-level mupirocin resistance in CoNS, primarily mediated by the mupA gene.
• Staphylococcus aureus did not acquire mupirocin resistance in this study.
• Monitoring mupirocin resistance development is recommended for CoNS when mupirocin-containing decolonization strategies are employed.