Assessment of phenotypic and genotypic antibiotic susceptibility of vaginal Lactobacillus sp

To assess antibiotic susceptibility of vaginal lactobacilli strains and provide the data required for assessing the potential of antibiotic resistance risk of new strains selected as probiotic.

Potential probiotic vaginal lactobacilli used in the study included 31 vaginal strains of Lactobacillus crispatus (n = 27), Lactobacillus gasseri (n = 3) and Lactobacillus jensenii (n = 1) obtained from the collection of Competence Centre on Health Technologies. Two commercial probiotic strains were used as controls (Lactobacillus rhamnosus GR-1 and Lactobacillus fermentum RC-14). The phenotypic and genotypic antibiotic resistances of the strains were determined by E-test and PCR methods. The location (chromosomal DNA or plasmid) of antibiotic resistance genes was also detected. All lactobacilli strains expressed high level of resistance to kanamycin, metronidazole, norfloxacin and trimethoprim/sulphamethoxazole. Some of the strains also expressed resistance to other antibiotics (chloramphenicol, vancomycin) indicating acquired resistance. I class integrons were found in 20% (6/31) of the strains. The RPP (ribosomal protection protein) gene was found to be positive in 30% (9/31) of the strains. Only one L. jensenii strain was determined with tet(M) gene. The tet(K) gene was positive in 26·7% (8/31) and erm(B) gene in 43·3% (13/31) of strains. Three RPP and both four tet(K) and erm(B) genes were located in plasmids.

High antibiotic resistance to clinically important antibiotics was demonstrated, including metronidazole, sulphonamides, aminoglycoside and quinolones. In addition, acquired tetracycline and erythromycin resistance genes were detected in either plasmid or chromosomal DNA of certain isolates, in some of the cases for the first time in the literature. It appears that antibiotic resistance genes erm(B) and tet(K) are widely spread in vaginal lactobacilli.

This study provides new data about antimicrobial resistance and genotypic diversity of vaginal Lactobacillus isolates. In addition, it provides data assessing the potential of antibiotic resistance risk of new strains selected as probiotic.