Isolation of Staphylococcus aureus from environmental surfaces in an academic dental clinic.

BACKGROUND: Staphylococcus aureus is an important health care-associated pathogen that often is resistant to antibiotics. The authors conducted a pilot study to determine if abiotic surfaces in a dental clinic were contaminated frequently.

METHODS: The authors sampled surfaces with swabs that they then used to inoculate selective and differential media. CHRO-Magar Staph aureus (DRG International, Mountainside, N.J.) was the most effective. They used phenotypic and genotypic tests to identify presumptive S. aureus colonies. They determined the sensitivity of S. aureus isolates to five antibiotics, including oxacillin, according to the Kirby-Bauer method.

RESULTS: The authors recovered S. aureus from 20 of 429 surfaces (4.7 percent). Most isolates were resistant to penicillin but none were resistant to the other antibiotics. No isolate carried the mecA gene encoding resistance to methicillin. The authors considered one site to be highly contaminated (> 200 colony-forming units [CFUs]), but all other sites that tested positive yielded fewer than 5 CFUs.

CONCLUSIONS: Abiotic surfaces in the authors' dental clinic were not a reservoir for methicillin-resistant S. aureus. The authors identified and eliminated one nonclinical site of potential methicillin-sensitive S. aureus cross-contamination.

CLINICAL IMPLICATIONS: Periodic sampling of surfaces for S. aureus may be a useful adjunct to standard infection control practices in dental health care settings.