title: Community- and health care-associated methicillin-resistant Staphylococcus aureus: a comparison of molecular epidemiology and antimicrobial activities of various agents.
abstract: 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.
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Wayne State University, MI 48201, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Tsuji
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rybak
authors.forename: Chrissy M
authors.initials: CM
authors.lastname: Cheung
authors.forename: Muhammad
authors.initials: M
authors.lastname: Amjad
authors.forename: Glenn W
authors.initials: GW
authors.lastname: Kaatz
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D005098:Exotoxins / Q000235:genetics; D006801:Humans; D007956:Leukocidins / Q000235:genetics; D016106:Methicillin Resistance / Q000235:genetics; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics
chemical_list: C095698:Agr protein, Staphylococcus aureus; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D015534:Trans-Activators