Emergence of ileS2-Carrying, Multidrug-Resistant Plasmids in Staphylococcus lugdunensis

Area of Science:

• Medical microbiology
• Antimicrobial resistance research
• Molecular epidemiology

Background:

• Staphylococcus lugdunensis is an important human pathogen.
• Mupirocin is a key antibiotic for treating staphylococcal infections.
• Emergence of antibiotic resistance in S. lugdunensis poses a significant clinical challenge.

Purpose of the Study:

• To investigate the prevalence and genetic basis of mupirocin resistance in Staphylococcus lugdunensis isolates from Hong Kong.
• To characterize the resistance mechanisms and associated genetic elements.

Main Methods:

• Phenotypic detection of mupirocin resistance (high-level and low-level).
• Molecular analysis to identify resistance genes (ileS2) and mutations (V588F in ileS).
• Plasmid analysis and characterization of co-carried resistance determinants.
• Clonal analysis using prevalent typing methods.

Main Results:

• 10 (7.3%) and 3 (2.2%) of 137 S. lugdunensis isolates exhibited high-level and low-level mupirocin resistance, respectively.
• High-level resistance was mediated by the plasmid-borne ileS2 gene.
• Low-level resistance was associated with the V588F mutation in the chromosomal ileS gene.
• The majority of ileS2-positive isolates belonged to the predominant HKU1 clone.
• Plasmids carrying ileS2 were mosaic and harbored additional resistance genes.

Conclusions:

• Plasmid-mediated ileS2 is a significant mechanism for high-level mupirocin resistance in S. lugdunensis.
• Chromosomal mutations in ileS also contribute to lower-level resistance.
• The co-occurrence of multiple resistance determinants on plasmids highlights the potential for rapid dissemination of antibiotic resistance.