In vitro evalution of antibiotic resistance of Lactobacillus bulgaricus strains isolated from traditional dairy products

Abstract

The antimicrobial susceptibility of 20 Lb. bulgaricus isolates from traditional fermented milk-originated was assessed and then determined the ability to transfer antibiotic resistance genes to other bacteria. The minimum inhibitory concentration of each strain was determined using a standardized dilution method. All the tested strains were found to be susceptible to gentamicin, erythromycin, clindamycin, neomycin, tetracycline, linezolid, chloramphenicol, rifampicin, and quinupristin/dalfopristin, while their susceptibilities to kanamycin, ciprofloxacin, streptomycin, trimethoprim, ampicillin, and vancomycin varied. Polymerase chain reaction (PCR) was used to check whether specific antibiotic resistance genes were present in these Lb. bulgaricus. We detected the rpoB, erm(B), aadA, bla, cat and vanX. Finally, a filter mating assay was applied to investigate the transferability of these resistance markers; and we observe no antibiotic resistance transfer between bacteria. This work demonstrates a low risk of lateral transfer of the antibiotic resistance gene of Lb. bulgaricus.