Abstract
Lactic acid bacteria can act as reservoirs of antibiotic resistance genes that can be ultimately transferred to pathogens. The present work reports on the minimum inhibitory concentration (MIC) of 16 antibiotics to 25 LAB isolates of five Lactobacillus and one Bifidobacterium species from the human vagina. Acquired resistances were detected to kanamycin, streptomycin, chloramphenicol, gentamicin, and ampicillin. A PCR analysis of lactobacilli failed to identify genetic determinants involved in any of these resistances. Surprisingly, a tet(W) gene was detected by PCR in two Bifidobacterium bifidum strains, although they proved to be tetracycline-susceptible. In agreement with the PCR results, no acquired genes were identified in the genome of any of the Lactobacillus spp. strains sequenced. A genome analysis of B. bifidum VA07-1AN showed an insertion of two guanines in the middle of tet(W) interrupting the open reading frame. By growing the strain in the presence of tetracycline, stable tetracycline-resistant variants were obtained. An amino acid substitution in the ribosomal protein S12 (K43R) was further identified as the most likely cause of VA07-1AN being streptomycin resistance. The results of this work expand our knowledge of the resistance profiles of vaginal LAB and provide evidence for the genetic basis of some acquired resistances.
Highlights
The extensive use of antibiotics has led to the emergence, evolution and spread of antibiotic resistance (AR) in pathogenic and non-pathogenic bacteria associated with humans, animals and the environment [1]
The antibiotics used to treat infections in humans are commonly the same as those used in veterinary medicine, which has resulted in the rapid dissemination of AR genes among bacteria associated with the food chain [4]
Lactic acid bacteria (LAB) are non-pathogenic, they can act as reservoirs of AR genes which might eventually be transferred via horizontal gene transfer (HGT) to pathogenic bacteria during food manufacture or after consumption [9]
Summary
The extensive use of antibiotics has led to the emergence, evolution and spread of antibiotic resistance (AR) in pathogenic and non-pathogenic bacteria associated with humans, animals and the environment [1]. The selective pressure imposed by the presence of antibiotics in the environment has driven the spread of AR by horizontal gene transfer (HGT) events [3]. The antibiotics used to treat infections in humans are commonly the same as those used in veterinary medicine, which has resulted in the rapid dissemination of AR genes among bacteria associated with the food chain [4]. LAB are non-pathogenic, they can act as reservoirs of AR genes which might eventually be transferred via HGT to pathogenic bacteria during food manufacture or after consumption [9]
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