Oral cavities of healthy infants harbour high proportions of Streptococcus salivarius strains with phenotypic and genotypic resistance to multiple classes of antibiotics

• Published in: Journal of medical microbiology Vol. 65; no. 12; pp. 1456 - 1464
• Main Authors: Palma, Thaís H, Harth-Chú, Erika N, Scott, Jodie, Stipp, Rafael N, Boisvert, Heike, Salomão, Mariana F, Theobaldo, Jéssica D, Possobon, Rosana F, Nascimento, Leandro C, McCafferty, Jonathan W, Faller, Lina, Duncan, Margaret J, Mattos-Graner, Renata O
• Format: Journal Article
• Language: English
• Published: England 01-12-2016
• Subjects: Anti-Bacterial Agents - classification; Anti-Bacterial Agents - pharmacology; Bacterial Proteins - genetics; Carrier Proteins - genetics; Drug Resistance, Multiple, Bacterial - genetics; Female; Genes, Bacterial; Genes, MDR; Genome, Bacterial; Genotype; Healthy Volunteers; Humans; Infant; Male; Membrane Proteins - genetics; Microbial Sensitivity Tests; Mouth - microbiology; Phenotype; Sequence Analysis, DNA; Streptococcus salivarius - classification; Streptococcus salivarius - drug effects; Streptococcus salivarius - genetics; Streptococcus salivarius - physiology
• ISSN: 0022-2615; 1473-5644
• DOI: 10.1099/jmm.0.000377

Emerging antibiotic resistance in the oropharyngeal microbiota, of which Streptococcus salivarius is a prominent species, represents a challenge for treating paediatric populations. In this study, we investigated the role of Streptococcussalivarius as a reservoir for antibiotic resistance genes (ARG) in the oral microbiota by analysing 95 Streptococcussalivarius isolates from 22 healthy infants (2-16 months of age). MICs of penicillin G, amoxicillin, erythromycin, tetracycline, doxycycline and streptomycin were determined. ARG profiles were assessed in a subset of 21 strains by next-generation sequencing of genomes, followed by searches of assembled reads against the Comprehensive Antibiotic Resistance Database. Strains resistant to erythromycin, penicillins and tetracyclines were isolated from 83.3, 33.3 and 16.6 %, respectively, of infants aged 2 to 8 months with no prior antibiotic treatment. These percentages were100.0, 66.6 and 50.0 %, by 13 to 16 months of age. ARG or polymorphisms associated with antibiotic resistance were the most prevalent and involved genes for macrolide efflux (mel, mefA/E and macB), ribosomal protection [erm(B), tet(M) and tet(O)] and β-lactamase-like proteins. Phylogenetically related strains showing multidrug-resistant phenotypes harboured 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 Streptococcussalivarius strains established during maturation of the oral microbiota harbour a diverse array of functional ARG, even in the absence of antibiotic selective pressures, highlighting a potential role for this species in shaping antibiotic susceptibility profiles of oropharyngeal communities.