Genomic portrait of community-associated methicillin-resistant Staphylococcus aureus ST772-SCCmec V lineage from India

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Gene Reports


Background: Significant changes in the epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) were recognised with the emergence of community-associated methicillin-resistant Staphylococcus aureus. However, studies on the molecular epidemiology and the genomic investigation of MRSA are limited in India.

Aim: The study was aims to understand the molecular epidemiology of MRSA causing bloodstream infection and also to investigate the origin and evolution of ST772 S. aureus isolated from India.

Methods: A total of 233 non-repetitive MRSA isolates were screened for the presence staphylococcal cassette chromosome (SCCmec) types, multi-locus sequence types (MLST) and staphylococcal protein A (spa) types. Whole genome sequence data of ST772-SCCmec V (n = 32) isolates were generated and comparative analysis was performed.

Results: MLST analysis revealed ten different clonal complexes and three singletons. ST772 (27%), ST22 (19%) and ST239 (16%) were the predominant MRSA genotypes in causing bloodstream infection. The spa types were highly diverse. Phylogenetic analysis revealed that nearly three-fourth of the Indian STT72-SCCmec V isolates belongs to dominant (ST772-A2) and emerging subgroups (ST772-A3). A pattern of increasing antimicrobial resistance was noticed in the dominant and emerging subgroups. An integrated resistance plasmid encoding resistance clusters for beta-lactam (blaZ), macrolides (mphC, msrA), and aminoglycoside resistance (aphA-III, sat-4, aadE) was identified in all isolates, except four basal strains. ST772-SCCmec V was emerged on the Indian subcontinent in 1964 and diverged into a dominant subgroup in 1991. Furthermore, the expansion is likely to be associated with the acqusition of mobile genetic elements such as integrated resistance plasmid and SCCmec V (5C2) as well as the fixation of double serine mutation (S84L, S80Y) in the quinolone resistance determining region.

Conclusions: ST772 S. aureus have consistent virulence and resistance determinants which may results in successful survival in both community and hospital settings.