The oral cavities of healthy infants harbor high proportions of Streptococcus salivarius strains with phenotypic and genotypic resistance to multiple classes of antibiotics.

In this study, we investigated the role of S. salivarius as a reservoir for antibiotic resistance genes (ARG) in the oral microbiota by analyzing 95 S. salivarius isolates from 22 healthy infants (2 to 16 months of age). Minimum inhibitory concentrations (MIC) of penicillin G, amoxicillin, erythromycin, tetracycline, doxycycline and streptomycin were determined. ARG profiles were assessed in a sub-set of 21 strains by next-generation sequencing of genomes (Illumina MiSeq), followed by searches of assembled reads against the Comprehensive Antibiotic Resistance Database (CARD). Strains resistant to erythromycin, penicillins and tetracyclines were isolated from 83.3, 33.3 and 16.6%, respectively, of infants aged 2-8 months with no prior antibiotic treatment. These percentages were, respectively, 100.0, 66.6 and 50.0% by 13 to 16 months of age. ARG or polymorphisms associated with antibiotic resistance were the most prevalent, and included macrolide efflux (mel, mefA/E, macB), ribosomal protection [erm(B), tet(M), tet(O)], and beta lactamase-like proteins. Phylogenetically related strains showing multidrug resistance phenotypes harbored multidrug efflux ARG. Polymorphic genes associated with antibiotic resistance to drugs affecting DNA replication, folate synthesis, RNA/protein synthesis, and regulators of antibiotic stress responses were detected. These data imply that S. salivarius strains established during maturation of the oral microbiota harbor a diverse array of functional...
Source: Journal of Medical Microbiology - Category: Microbiology Authors: Tags: J Med Microbiol Source Type: research