Abstract:

To assess the risk of antimicrobial resistant gene transfer from foodborne Lactobacillus strains to human
pathogens or opportunistic pathogens, we performed the detection of the resistant genes of erythromycin, vancomycin
and fluoroquinolones in resistant Lactobacillus strains. Erythromycin resistant gene msrC was shown in the plasmids
of Lactobacillus plantarum, Lactobacillus acidophilus and Lactobacillus delbrueckii, while negative results were
obtained for vancomycin and fluoroquinol ones. Filter mating was carried out at a donor/recipient ratio of 10:1 with
Staphylococcus aureus and E. faecalis as the recipients and L. delbrueckii the donors, respectively. In L. delbrueckii and
S. aureus mating pair, only one exconjugant was obtained, and the average gene transfer frequency of L. delbrueckii to
E. faecalis was 2.2 × 10-2, indicating that the mobile resistant gene from lactobacilli could disseminate to pathogens. The
growth rate of exconjugants was lower than the control, so exconjugants might be washed out more easily than their
susceptible counterpart when antimicrobial selective pressure was absent. The transfer of msrC from L. delbrueckii to
E. faecalis was not observed in gnotobiotic rats. Accordingly, lactobacilli widely used in foods now may not increase the
antimicrobial resistance in pathogens, thus threatening public health severely.

Key words: antimicrobial resistance, Lactobacillus, gene transfer, exconjugant, food safety