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Basis of virulence in a Panton-Valentine leukocidin-negative community-associated methicillin-resistant

Yan Chen1, Anthony J Yeh2, Gordon Y C Cheung2

  • 1Pathogen Molecular Genetics Section, Laboratory of Human Bacterial Pathogenesis, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.

The Journal of Infectious Diseases
|August 21, 2014
PubMed

Insights

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are increasing globally. This study reveals alpha-toxin and Agr are key virulence factors in the PVL-negative ST72 CA-MRSA strain, differing from the US USA300 strain.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Genomics

Background:

  • Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are a growing global health concern.
  • Previous virulence analyses have primarily focused on the US endemic USA300 strain, leaving PVL-negative CA-MRSA strains understudied.
  • Understanding the molecular basis of virulence in diverse CA-MRSA strains is crucial for effective treatment and control.

Purpose of the Study:

  • To investigate the virulence determinants of a Panton-Valentine leukocidin (PVL)-negative CA-MRSA strain, ST72, from Korea.
  • To compare the virulence mechanisms of ST72 with the well-characterized USA300 strain.
  • To identify key factors contributing to the pathogenicity of PVL-negative CA-MRSA.

Main Methods:

  • Genome-wide analysis of the ST72 CA-MRSA strain to identify unique genetic loci.
  • Assessment of the impact of specific virulence factors, including phenol-soluble modulins (PSMs) and alpha-toxin, on bacterial lysis of neutrophils and erythrocytes.
  • In vivo experimental models to evaluate the role of Agr, PSMs, and alpha-toxin in skin infections.

Main Results:

  • Genome-wide analysis identified three strain-unique loci in ST72, none of which impacted virulence.
  • Phenol-soluble modulins (PSMs) and the Agr regulator significantly influenced neutrophil and erythrocyte lysis.
  • Alpha-toxin and Agr played major roles in in vivo virulence, with alpha-toxin being more critical than PSMs in experimental skin infections caused by ST72, unlike in USA300.

Conclusions:

  • The study confirms the significant roles of PSMs, alpha-toxin, and Agr in CA-MRSA virulence.
  • Distinct virulence factor importance was observed between the Korean ST72 and US USA300 CA-MRSA strains, highlighting alpha-toxin as a more critical factor in ST72 skin infections.
  • These findings underscore the need to consider strain-specific virulence mechanisms in combating CA-MRSA infections.
Keywords:
Panton-Valentine leukocidinalpha-toxincommunity-associated infectionmethicillin-resistant Staphylococcus aureusphenol-soluble modulins

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