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J Antimicrob Chemother. 2015 Apr;70(4):1185-92. doi: 10.1093/jac/dku475. Epub 2014 Nov 27.

Community-associated MRSA strain ST72-SCCmecIV causing bloodstream infections: clinical outcomes and bacterial virulence factors.

Author information

1
Division of Infectious Diseases, Department of Internal Medicine, Kyung Hee University Hospital, Kyung Hee University School of Medicine, Seoul, Republic of Korea.
2
Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan, Seoul, Republic of Korea.
3
Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
4
Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan, Seoul, Republic of Korea Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
5
Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan, Seoul, Republic of Korea yskim@amc.seoul.kr.

Abstract

OBJECTIVES:

Community-associated MRSA (CA-MRSA) has emerged in the community and has recently been spreading in healthcare settings. The objectives of this study were to evaluate the clinical outcomes and bacterial virulence factors of the Korean CA-MRSA (ST72-SCCmecIV) strain, which causes bloodstream infections.

METHODS:

All adult patients with MRSA bacteraemia were prospectively enrolled. Clinical outcomes, microbiological characteristics and 40 bacterial virulence factors were evaluated.

RESULTS:

Of the 352 typed MRSA isolates, 342 isolates (97.2%) belonged to three Panton-Valentine leucocidin-negative strains: ST5-SCCmecII (70.2%), ST72-SCCmecIV (22.4%) and ST239-SCCmecIII (4.6%). The remaining 10 (2.8%) isolates from minor strains were excluded from the final analysis. After controlling for several confounding factors, ST72-SCCmecIV was associated with the lowest mortality (compared with ST5-SCCmecII, adjusted OR=0.26; 95% CI=0.13-0.54). However, MRSA isolates with vancomycin MICs of ≥ 1.5 mg/L were more common in ST72-SCCmecIV compared with ST5-SCCmecII (84.8% versus 66.7%; P=0.002). Reduced vancomycin susceptibility and vancomycin heteroresistance were not associated with mortality. Compared with ST5-SCCmecII isolates, ST72-SCCmecIV isolates were less likely to harbour multiple virulence genes. Of these genes, three staphylococcal superantigen genes were associated with mortality: sec (OR=2.31; P=0.002), sel (OR=2.55; P=0.003) and tst (OR=2.76; P<0.001).

CONCLUSIONS:

After controlling for confounding factors, ST72-SCCmecIV was independently associated with lower mortality compared with ST5-SCCmecII, suggesting this CA-MRSA strain to be of lower virulence. The lack of virulence genes, including staphylococcal superantigen genes, may play a role in the lower virulence of this strain.

KEYWORDS:

Staphylococcus aureus; bacteraemia; genotype; methicillin-resistant Staphylococcus aureus; outcome

PMID:
25433004
DOI:
10.1093/jac/dku475
[Indexed for MEDLINE]

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