Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Causing Healthcare-Associated Bloodstream...

The molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) impact transmission, clinical presentation, and treatment. Contemporary data on the molecular epidemiology of MRSA causing healthcare-associated (HA) infections in Latin America are scarce. In this study, we aimed to assess the molecular epidemiology, virulence genes, and antimicrobial susceptibility of MRSA bloodstream infections (BSI) isolates from Brazil.

A multicenter, prospective study in 14 Brazilian hospitals was conducted from August/2022 to August/2023. MRSA isolates recovered from HA-BSIs were sent to a central laboratory for whole-genome sequencing (WGS) and antimicrobial susceptibility testing.

Of 255 S. aureus, 66 (25.9%) were MRSA, and 47 were submitted to WGS. The most frequent clonal complex (CC) was CC5 (n = 34, 72.3%), mostly of sequence types (ST) 105 (19/34; 55.9%) and ST5 (6/34; 17.6%). ST105(CC5)-SCCmecII-t002 was the commonest strain (10/47, 56.2%), detected in three of four studied regions, followed by the ST8(CC8)-SCCmecIV strains with distinct spa types (9/47; 19.2%). Three new MLST alleles were discovered, resulting in new ST designations 10,174, 10,175, and 10,176. Furthermore, the resulting phylogeny revealed three well-defined clades. Twenty-eight virulence genes were detected. All isolates were susceptible to vancomycin, linezolid, and ceftaroline, while susceptibility to daptomycin and delafloxacin was 88.9% and 51.2%, respectively.

The recently reported ST105(CC5)-SCCmecII-t002 clone has disseminated in hospitals from different Brazilian regions, together with other lineages that have been previously associated with community-associated infections, composed a new molecular landscape of MRSA causing HA BSIs in Brazil.