The oral microbiota is characterized by high amount and diversity of microorganisms, some of them may be pathogenic under specific environmental conditions. Non-hemolytic streptococcal species are predominant in most ecological niches of the mouth in adults and children. Several species of this genera are pioneer microorganisms of the mouth of young children and influence in the development of oral microbiota through metabolic and genetic interactions with other microorganisms, and through interactions with host factors. The high microbial density of the oral ecological niches increases the genetic exchanges among organisms, promoting for example, the spread of genes involved in antibiotic resistance. In two projects supported by FAPESP (proc. 2010/06785-1; 2010/06786-8), we are characterizing the major taxonomic groups of oral streptococci, which are pioneer of the oral cavity of babies, including species of the groups Mitis, Sanguinis, and Salivarius. The aim of this project is to characterize the sensitivity to different antibiotics in pioneer streptococcal isolates of the oral cavity of babies, which were classified into the major taxonomic groups of non-hemolytic streptococci. To that purpose, the minimum inhibitory concentration (MIC) of amoxicillin, erythromycin, tetracycline, doxycycline, streptomycin and penicillin G will the determined in 279 strains, isolated from twenty four children with 2 to 16 months of age, using the micro-dilution method. Minimum bactericidal concentration (MBC) will be also determined in a subset of strains of each taxonomic group identified as antibiotic-resistant based in the MIC data. The clinical strains of each taxonomic group will be compared with the respective reference strains regarding the profiles of antibiotic sensitivity.
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