Abstract
Staphylococcus lugdunensis is a coagulase-negative staphylococcus known for its significant pathogenic potential, often causing severe infections such as endocarditis and bacteremia, with virulence comparable to S. aureus. Despite general susceptibility to most antibiotics, the emergence of oxacillin-resistant strains is increasingly concerning. This study conducted whole-genome sequencing on 20 S. lugdunensis isolates from Chang Gung Memorial Hospital to explore their genetic diversity, antimicrobial resistance mechanisms, and mobile genetic elements. The lugdunin biosynthetic operon, essential for antimicrobial peptide production, was present in multilocus sequence typing (MLST) types 1, 3, and 6 but absent in STs 4, 27, and 29. Additionally, IS256 insertion elements, ranging from 7 to 17 copies, were identified in four strains and linked to multidrug resistance. CRISPR-Cas systems varied across STs, with type III-A predominant in ST1 and ST6 and type IIC in ST4, ST27, and ST29; notably, ST3 lacked CRISPR systems, correlating with a higher diversity of SCCmec elements and an increased potential for horizontal gene transfer. Phage analysis revealed stable phage-host associations in ST1, ST6, and ST29, whereas ST4 displayed a varied prophage profile. Phenotypic resistance profiles generally aligned with genomic predictions, although discrepancies were observed for aminoglycosides and clindamycin. These findings highlight the complex genetic landscape and evolutionary dynamics of S. lugdunensis, emphasizing the need for genomic surveillance to inform clinical management and prevent the spread of resistant strains.