Biotipos y susceptibilidad antimicrobiana de S. mutans en niños con y sin caries dental

Objectives: The main objective was to investigate the biotypes of S. mutans isolated from children with and without dental caries and determine its antimicrobial susceptibility. Methods: this descriptive observational study included 206 children aged 3 to 5 years of two preschool institutions in Bogota-Colombia. After isolation on agar Mitis Salivarius Bacitracin, S. mutans strains were identified by biochemical tests and biotyped by the api-ZYM system. The minimal inhibitory concentrations (MICs) of the S. mutans isolates were evaluated against penicillin, amoxicillin, cefazolin, erythromycin, clindamycin, imipenem, vancomycin and teicoplanin by an agar dilution method. Results: S. mutans was found in 30 of the 79 children without dental caries (38%) and in 56 of the 127 children with caries (44.1%). Children with cavities had a higher count of S. mutans compared to children without caries (p < 0.05). A total of 121 strains of S. mutans were identified in 86 children: 43 strains in 30 children with dental caries and 78 in the 56 children with dental caries. The 121 strains were grouped into 38 biotypes: 24 in the group caries and 14 in the group without caries. In the group caries the most common biotypes were the XV, XI, XII and XVII, respectively, with 26, 12, 11 and 4 strains and the group caries the most common biotypes were the XXVI, XX and XXXVI, respectively, with 14, 8 and 7 strains. All biotypes were highly sensitive to all antimicrobials tested; 50 and 90% of S. mutans strains were inhibited by using concentrations lower than 0.12 and 1 µg/ml, respectively, for all antibiotics studied. The lowest MICs average values were obtained for penicillin, erythromycin and imipenem. Conclusions: In the study population a wide variety of biotypes was found, isolates were highly sensitive to antimicrobials evaluated and in each clinical group were identified unique patters that could indicate a specific colonization.