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MBio DOI:10.1128/mBio.00112-12

Comparative genomics of vancomycin-resistant Staphylococcus aureus strains and their positions within the clade most commonly associated with Methicillin-resistant S. aureus hospital-acquired infection in the United States.

Publication TypeJournal Article
Year of Publication2012
AuthorsKos, VN, Desjardins, CA, Griggs, A, Cerqueira, G, Van Tonder, A, Holden, MTG, Godfrey, P, Palmer, KL, Bodi, K, Mongodin, EF, Wortman, J, Feldgarden, M, Lawley, T, Gill, SR, Haas, BJ, Birren, B, Gilmore, MS
JournalMBio
Volume3
Issue3
Date Published2012
ISSN2150-7511
KeywordsAmino Acid Sequence, Bacterial Proteins, Cross Infection, Genomics, Humans, Methicillin Resistance, Methicillin-Resistant Staphylococcus aureus, Molecular Sequence Data, Phylogeny, Sequence Alignment, Staphylococcal Infections, Staphylococcus aureus, United States, Vancomycin Resistance
Abstract

UNLABELLED: Methicillin-resistant Staphylococcus aureus (MRSA) strains are leading causes of hospital-acquired infections in the United States, and clonal cluster 5 (CC5) is the predominant lineage responsible for these infections. Since 2002, there have been 12 cases of vancomycin-resistant S. aureus (VRSA) infection in the United States-all CC5 strains. To understand this genetic background and what distinguishes it from other lineages, we generated and analyzed high-quality draft genome sequences for all available VRSA strains. Sequence comparisons show unambiguously that each strain independently acquired Tn1546 and that all VRSA strains last shared a common ancestor over 50 years ago, well before the occurrence of vancomycin resistance in this species. In contrast to existing hypotheses on what predisposes this lineage to acquire Tn1546, the barrier posed by restriction systems appears to be intact in most VRSA strains. However, VRSA (and other CC5) strains were found to possess a constellation of traits that appears to be optimized for proliferation in precisely the types of polymicrobic infection where transfer could occur. They lack a bacteriocin operon that would be predicted to limit the occurrence of non-CC5 strains in mixed infection and harbor a cluster of unique superantigens and lipoproteins to confound host immunity. A frameshift in dprA, which in other microbes influences uptake of foreign DNA, may also make this lineage conducive to foreign DNA acquisition.

IMPORTANCE: Invasive methicillin-resistant Staphylococcus aureus (MRSA) infection now ranks among the leading causes of death in the United States. Vancomycin is a key last-line bactericidal drug for treating these infections. However, since 2002, vancomycin resistance has entered this species. Of the now 12 cases of vancomycin-resistant S. aureus (VRSA), each was believed to represent a new acquisition of the vancomycin-resistant transposon Tn1546 from enterococcal donors. All acquisitions of Tn1546 so far have occurred in MRSA strains of the clonal cluster 5 genetic background, the most common hospital lineage causing hospital-acquired MRSA infection. To understand the nature of these strains, we determined and examined the nucleotide sequences of the genomes of all available VRSA. Genome comparison identified candidate features that position strains of this lineage well for acquiring resistance to antibiotics in mixed infection.

URLhttp://dx.doi.org/10.1128/mBio.00112-12
DOI10.1128/mBio.00112-12
Pubmed

http://www.ncbi.nlm.nih.gov/pubmed/22617140?dopt=Abstract

Alternate JournalMBio
PubMed ID22617140
PubMed Central IDPMC3372964
Grant ListHHSN272200700055C / AI / NIAID NIH HHS / United States
AI083214 / AI / NIAID NIH HHS / United States
EY017381 / EY / NEI NIH HHS / United States
R01 AI072360 / AI / NIAID NIH HHS / United States
HHSN272200700055C / / PHS HHS / United States
P01 AI083214 / AI / NIAID NIH HHS / United States
HHSN27220090018C / / PHS HHS / United States
R01 EY017381 / EY / NEI NIH HHS / United States