Abstract
Background: Streptococcus mutans, an organism colonizing the oral cavity, is considered to be the main cause of dental caries. In addition to dental caries and related pyogenic dental infections, S. mutans is also a very important endocarditis agent. The participation of this microorganism in both oral and non-oral diseases has prompted interest in the knowledge of this susceptibility to antimicrobial agents. The aim of this study was to determine the antimicrobial susceptibility of S. mutans biotypes isolated from children dental caries free. Methods: Unstimulated saliva samples were collected from 60 children, diluted and cultured onto mitis salivarius bacitracin (MSB) agar plates for the selective isolation and enumeration of S. mutans. The MSB agar plates were incubated anaerobically (H2:CO2: N2 10:10:80) for two days a 37 ◦C. The biotyping of S. mutans was realized using the api Zym system (bioMerieus; Marcy-lEtoile, France). The minimal inhibitory concentrations were evaluated against penicillin, amoxycillin, cefazolin, erythromycin, clindamycin, imipenem and vancomycin by using an agar dilution method with concentrations between 0.003 and 32 ug/ml. Results: Twenty biotypes were detected in the 74 strains of S. mutans isolated. The most frequent byotipes were the 2,3,10 and 13 (n = 6). Nineteen out of the 23 children in whom 2 strains of S. mutans were isolated, and 7 children in whom 3 strains of S. mutans were isolated presented different biotypes of S. mutans. All biotypes were highly sensitive to penicillin, amoxicillin, cefazolin, erythromycin, clindamycin, imipenem and vancomycin; 50 and 90% of S. mutans strains were inhibited by using concentrations of less than 0.12 and 0.5 ug/ml, respectively, for all antibiotics studied. Conclusion: S. mutans biotypes were highly sensitive to he antibiotics tested.
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