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Pharmacotherapy. 2007 Jan;27(1):3-10.

Antimicrobial susceptibility and staphylococcal chromosomal cassette mec type in community- and hospital-associated methicillin-resistant Staphylococcus aureus.

Author information

1
Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan 48201, USA.

Abstract

STUDY OBJECTIVE:

To differentiate the characteristics of community-associated methicillin-resistant Staphylococcus aureus (MRSA) and hospital-associated MRSA isolates on the basis of their susceptibility profiles, induction of clindamycin resistance, and staphylococcal chromosomal cassette (SCC) mec types.

DESIGN:

In vitro molecular and susceptibility study of isolates obtained from December 2004-January 2006 as part of a large, ongoing clinical study.

SETTING:

Level I trauma center in Detroit, Michigan. BACTERIAL STRAINS: Three hundred eight MRSA isolates randomly collected from patients; 130 were classified as community-associated, and 178 were classified hospital-associated by using definitions from the Centers for Disease Control and Prevention (CDC).

INTERVENTION:

Minimum inhibitory concentrations were tested on the basis of current guidelines from the Clinical and Laboratory Standards Institute.

MEASUREMENTS AND MAIN RESULTS:

All tested MRSA isolates were susceptible to daptomycin, linezolid, and vancomycin. In addition, community-associated MRSA isolates were significantly (all p < or = 0.05) more susceptible to trimethoprim-sulfamethoxazole (99%), clindamycin (96%), and a fluoroquinolone (76%) than hospital-associated MRSA isolates. Inducible resistance to clindamycin was demonstrated in 8.4% of community-associated MRSA isolates versus 50% of hospital-associated MRSA isolates (p < or = 0.001). Of interest, 35% of the MRSA isolates collected from hospitalized patients (> 48 hrs after admission and according to the CDC definition) possessed SCCmec type IV.

CONCLUSION:

Overall, inducible clindamycin resistance occurred at significantly higher rates in the hospital-associated MRSA isolates, susceptibility differed significantly between community- and hospital-associated MRSA, and most of the hospital isolates contained SCCmec type IV.

PMID:
17192156
DOI:
10.1592/phco.27.1.3
[Indexed for MEDLINE]

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