Community- and health care-associated methicillin-resistant Staphylococcus aureus: a comparison of molecular epidemiology and antimicrobial activities of various agents

Diagn Microbiol Infect Dis. 2007 May;58(1):41-7. doi: 10.1016/j.diagmicrobio.2006.10.021. Epub 2007 Feb 14.


The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is changing. We determined the inhibitory and bactericidal activity of select antimicrobial agents utilizing a well-characterized group of 200 staphylococcal cassette chromosome mec (SCCmec) type IV community-associated MRSA (CAMRSA) and 50 SCCmec type II health care-associated MRSA (HAMRSA). Differences in carriage of the Panton-Valentine leukocidin (PVL) genes, agr group, and agr function in CAMRSA and HAMRSA were also examined. Pulsed-field gel electrophoresis (PFGE) patterns were determined for a subset of study strains. CAMRSA typically belonged to the USA 300 PFGE profile, were associated with high rates of PVL carriage (78%), and primarily were agr group I. Susceptibility to daptomycin, linezolid, teicoplanin, and vancomycin was 100%. In contrast, HAMRSA isolates typically belonged to the USA 100 PFGE profile, were associated with low rates of PVL carriage (8%), and primarily were agr group II. Comparing susceptibilities between the 2 types of MRSA strains, there was a 2-fold increase in MIC for daptomycin, doxycycline, teicoplanin, trimethoprim-sulfamethoxazole (TMP/SMX), and vancomycin in HAMRSA versus CAMRSA. Levofloxacin and clindamycin susceptibly decreased dramatically by 66% and 54%, respectively, against HAMRSA versus CAMRSA. With respect to agr function, 3.5% of CAMRSA and 48% of HAMRSA displayed a down-regulated agr gene cluster. The comparative bactericidal activities of daptomycin were similar to those of vancomycin and clindamycin, but were significantly greater than those of linezolid, teicoplanin, and TMP/SMX against CAMRSA at 24-h terminal end points. Further studies are warranted against a larger number of molecularly defined, geographically diverse CAMRSA to confirm these findings.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / genetics
  • Bacterial Toxins / genetics
  • Chromosomes, Bacterial / genetics
  • Community-Acquired Infections / epidemiology*
  • Community-Acquired Infections / microbiology
  • Cross Infection / epidemiology*
  • Cross Infection / microbiology
  • Exotoxins / genetics
  • Humans
  • Leukocidins / genetics
  • Methicillin Resistance* / genetics
  • Microbial Sensitivity Tests
  • Molecular Epidemiology*
  • Staphylococcal Infections / epidemiology
  • Staphylococcal Infections / microbiology
  • Staphylococcus aureus / classification
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / genetics*
  • Trans-Activators / genetics


  • Agr protein, Staphylococcus aureus
  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Bacterial Toxins
  • Exotoxins
  • Leukocidins
  • Panton-Valentine leukocidin
  • Trans-Activators