Isolation and antimicrobial resistance of Staphylococcus aureus on orthodontic pliers

Objectives: to quantify Staphylococcus aureus strains isolates on orthodontic pliers and to determine their susceptibility to some of the most common antimicrobial agents used in dentistry. Methods: the samples were collected in 300 orthodontic pliers during clinical activity of post-graduate orthodontics students. Sterile swabs with 0.1 mL 0.9% NaCl were rubbed against the pliers and the samples were distributed in Salt Manitol agar and aerobically incubated at 37ºC during 24 hours. The strains were isolated and the S. aureus were identified by biochemical tests. The antimicrobial resistance of the isolated microorganisms was evaluated by using commercial paper discs impregnated with the following antibiotics: ampicillin; amoxicillin; amoxicillin/clavulanic acid; azithromycin; cefadroxil; clarithromycin; clindamicin; erythromycin; penicillin G; methicillin, oxacillin and vancomycin. Results: S. aureus was found in 93 (31%) of the tested pliers. These isolated strains showed high resistance rates against beta-lactamic agents (95%). None of the strains were resistant to vancomycin and 5% of the strains were resistant to methicillin and oxacillin. Conclusion: The results suggested that the orthodontic pliers must be sterilized prior to the clinical use and the isolated S. aureus strains were resistant against some of the most used antimicrobial agents in dentistry.