Panton-Valentine leukocidin-positive sequence type 88 methicillin-resistant Staphylococcus aureus emerging as nosocomial pathogen in Brazil.

OBJECTIVES: This study describes the genomic and phenotypic characteristics of a Panton-Valentine Leukocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (MRSA)-ST88, causing ventilator-associated pneumonia (VAP) in Brazil.

METHODS: The MRSA-ST88 isolate (SQ684) was recovered from a tracheal aspirate of a patient with VAP. Identification and antimicrobial susceptibility testing were performed using the BD Phoenix automated system, with vancomycin susceptibility and MICs for daptomycin and tigecycline confirmed by broth microdilution. Whole-genome sequencing (WGS) was conducted on the Illumina NextSeq 550 platform, followed by genomic analyses including MLST, SCCmec typing, resistome and virulome profiling, and core-genome SNP phylogeny incorporating international MRSA isolates.

RESULTS: WGS classified SQ684 as ST88 carrying SCCmec IVc (2B). Phenotypically, the isolate was resistant to oxacillin and azithromycin, and harboured multiple resistance genes, including mecA, blaZ, aminoglycoside and macrolide resistance determinants, as well as genes linked to efflux pumps, plasmid replication, and virulence factors such as PVL. Core-genome phylogeny revealed substantial divergence from 169 international MRSA-ST88 isolates (243-293 SNPs), consistent with long-term, geographically independent evolution within the ST88 lineage.

CONCLUSION: With only one previous clinical report of MRSA-ST88 in Brazil, the identification of an SCCmec IVc- and PVL-positive ST88 strain underscores the potential for CA-MRSA clones to infiltrate hospital settings. Continued genomic surveillance is critical to clarify its epidemiological dynamics and assess public health implications in Brazil.