Isolation and antimicrobial resistance of Staphylococcus aureus isolates in a dental clinic environment.

OBJECTIVE: To determine the number of Staphylococcus aureus isolates collected in a dental clinical environment and to determine their susceptibility to antimicrobial agents commonly used in dentistry. SETTING: Undergraduate clinic of the Dental School of Piracicaba, University of Campinas, Brazil. METHODS: Sterile cotton swabs were used to collect the samples from dental-chair push buttons, light handles, 3-in-1 syringes, computer "Enter" keys, doorknobs, and X-ray tubes before, during, and after clinical procedures. These samples were spread on brain-heart infusion agar and were incubated at 37 degrees C for 24 hours. The resulting S. aureus isolates were counted and classified using Gram staining and biochemical tests. The counts among the 3 periods and the groups were analyzed by Kruskal-Wallis and Dunn tests (alpha =5%). Commercial paper disks containing widely prescribed antimicrobial agents (beta-lactams, macrolides, clindamycin, and vancomycin) were used to perform the antimicrobial susceptibility tests. RESULTS: An increase in the number of microorganisms was observed during clinical procedures (P<.05). The highest bacterial resistance rates were observed for the beta -lactam group. All isolated strains were sensitive to vancomycin, and 2% of them were resistant to methicillin. CONCLUSIONS: Clinical procedures increased the number and proportion of antimicrobial-resistant S. aureus isolates dispersed in a dental clinical environment. The present study highlights the need to establish strategies to prevent emergence of drug-resistant bacterial strains in dental settings.

Environmental contamination before, during, and after dental treatment.

PURPOSE: To verify environmental contamination by collecting microorganisms from dental equipment surfaces before, during and after clinical procedures. METHODS: Sterile swabs were used to collect the samples from dental-chair push buttons, 3-in-1 syringes, X-ray tubes, computer keys, doorknobs, and light handles before (P1), during (P2) and after (P3) clinical procedures, in the undergraduate clinic of the Dental School of Piracicaba, University of Campinas, Brazil. These samples were spread on BHI agar and incubated at 37 degrees C for 24 hours. Other dishes containing the same material were incubated at 37 degrees C in 10% CO2 for 48 hours. The resulting microorganisms were counted and classified using the Gram staining and biochemical tests. Microorganism counts among the periods and groups were analyzed by Kruskal-Wallis test (alpha=5%). RESULTS: The most prevalent microorganisms were Viridans group streptococci, Sthaphylococcus epidermidis and Baccillus subtilis. Push buttons were the most contaminated (P< 0.05). Microorganisms were most prevalent during clinical procedures (P< 0.05). Microorganism counts were higher in P2 than in P1 and P3 (P< 0.05). Clinical activity caused an increase in the number of environmental microorganisms, where Viridans group streptococci were the most prevalent contaminant found on equipment surfaces.