Analysis of Antibiotic Susceptibility of Lactobacillus Strains Isolated from Adolescent Gut Microbiota.

The phenotypic antibiotic susceptibility was determined for 46 Lactobacillus strains isolated from the gut microbiota of healthy adolescents and considered as candidate probiotics. All tested strains were susceptible to amoxicillin. Most Lactobacillus strains demonstrated susceptibility (some of them only upon extended exposure) to tetracycline, clindamycin, erythromycin, chloramphenicol, and ampicillin. Resistance to penicillins is a characteristic feature of many Lactobacillus spp., but only 27 tested strains showed phenotypic resistance to oxacillin. Plasmid DNA was detected in eight of the 46 strains. None of the tested strains harbored the transmissible antibiotic resistance genes tetW, cat-TC, and ermC in either genomic or plasmid DNA. The results allowed identifying strains susceptible to the tested antibiotics, but further genetic analysis is required to confirm their safety profile.