Abstract
BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-associated infection, but there is growing awareness of the emergence of multidrug-resistant lineages in community settings around the world. One such lineage is ST772-MRSA-V, which has disseminated globally and is increasingly prevalent in India. Here, we present the complete genome sequence of DAR4145, a strain of the ST772-MRSA-V lineage from India, and investigate its genomic characteristics in regards to antibiotic resistance and virulence factors.ResultsSequencing using single-molecule real-time technology resulted in the assembly of a single continuous chromosomal sequence, which was error-corrected, annotated and compared to nine draft genome assemblies of ST772-MRSA-V from Australia, Malaysia and India. We discovered numerous and redundant resistance genes associated with mobile genetic elements (MGEs) and known core genome mutations that explain the highly antibiotic resistant phenotype of DAR4145. Staphylococcal toxins and superantigens, including the leukotoxin Panton-Valentinin Leukocidin, were predominantly associated with genomic islands and the phage φ-IND772PVL. Some of these mobile resistance and virulence factors were variably present in other strains of the ST772-MRSA-V lineage.ConclusionsThe genomic characteristics presented here emphasize the contribution of MGEs to the emergence of multidrug-resistant and highly virulent strains of community-associated MRSA. Antibiotic resistance was further augmented by chromosomal mutations and redundancy of resistance genes. The complete genome of DAR4145 provides a valuable resource for future investigations into the global dissemination and phylogeography of ST772-MRSA-V.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1599-9) contains supplementary material, which is available to authorized users.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-associated infection, but there is growing awareness of the emergence of multidrug-resistant lineages in community settings around the world
Gaps in the draft genome assemblies of other strains of ST772-MRSA-V (Figure 1) frequently occurred in the vicinity of transposases, suggesting that some of the short read assemblies were unable to bridge gaps associated with repetitive genomic elements
Its composition identified the element as transposon Tn4001 [33] [GenBank: AB682805.1] and it was present at the same location in all available genomes of ST772-MRSA-V, except strain 118 (Figure 1)
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospital-associated infection, but there is growing awareness of the emergence of multidrug-resistant lineages in community settings around the world. One such lineage is ST772-MRSA-V, which has disseminated globally and is increasingly prevalent in India. The draft genomes accommodate a novel prophage ΦIND772PVL, carrying the enterotoxin gene sea and an operon encoding Panton-Valentine Leukocidin (PVL), lukS/F-PV [21] This potent combination of toxins on the same prophage has so far not been reported in other strains of S. aureus [21]. Several genes encoding antibiotic resistance determinants (e.g., against beta-lactams, aminoglycosides, fluoroquinolones, tetracyclines) and non-synonymous mutations in resistance-associated genes have been discovered, which correspond to previously identified multidrug resistant phenotypes of ST772-MRSA-V [7,15,20,24]
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