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.