Diversity of antimicrobial resistance pheno- and genotypes of methicillin-resistant Staphylococcus aureus ST398 from diseased swine

J Antimicrob Chemother. 2009 Dec;64(6):1156-64. doi: 10.1093/jac/dkp350. Epub 2009 Sep 25.


Objectives: Fifty-four methicillin-resistant Staphylococcus aureus (MRSA) ST398 isolates from unrelated diseased swine collected all over Germany were comparatively investigated for their antimicrobial resistance and virulence properties, and for their genomic relatedness.

Methods: MICs of 30 antimicrobial agents were determined by broth microdilution. Resistance and virulence genes were detected via a diagnostic DNA microarray and specific PCRs. The genomic relationships were determined by ApaI-PFGE, spa typing and SCCmec typing.

Results: Twenty-two distinct resistance patterns were observed. All 54 isolates were tetracycline resistant, mediated by tet(M), tet(K) and/or tet(L), with 14 isolates being only resistant to beta-lactam antibiotics and tetracyclines. Trimethoprim resistance, seen in 28 isolates, was mostly due to the gene dfrK or dfrG. Among the 24 macrolide/lincosamide-resistant isolates, the genes erm(A), erm(B) and/or erm(C) were detected. The two chloramphenicol/florfenicol-resistant isolates harboured the gene fexA. The eight gentamicin-resistant isolates carried the gene aacA/aphD. Fifty-three isolates harboured SCCmec type V elements while the remaining one carried mecA and ugpQ, but no recombinase genes. All isolates were PVL negative, but one and three isolates, respectively, were positive for the enterotoxin B and enterotoxin K and Q genes. Eight different spa types were identified with t011 being the most predominant. Six ApaI-PFGE clusters with up to nine individual patterns were detected.

Conclusions: MRSA ST398 isolates varied slightly in their virulence properties and spa types but differed distinctly in their antimicrobial resistance pheno- and genotypes as well as their ApaI-PFGE patterns. These data underline the ability of ST398 to acquire genetic material that might increase antimicrobial resistance and virulence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / genetics
  • Bacterial Typing Techniques
  • Cluster Analysis
  • DNA Fingerprinting
  • Electrophoresis, Gel, Pulsed-Field
  • Genetic Variation*
  • Genotype
  • Germany
  • Methicillin-Resistant Staphylococcus aureus / classification*
  • Methicillin-Resistant Staphylococcus aureus / genetics
  • Methicillin-Resistant Staphylococcus aureus / isolation & purification
  • Methicillin-Resistant Staphylococcus aureus / physiology
  • Microarray Analysis / methods
  • Microbial Sensitivity Tests
  • Phenotype
  • Polymerase Chain Reaction / methods
  • Staphylococcal Infections / microbiology
  • Staphylococcal Infections / veterinary*
  • Swine / microbiology*
  • Swine Diseases / microbiology*
  • Virulence Factors / genetics*


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Virulence Factors