Plasmid-Mediated Antibiotic-Resistant Pattern of Lactobacillus spp. Isolated From Dairy Products

Background: Microorganisms have potent activity for transferring antibiotic-resistant genes with eitherchromosomally- or plasmid-mediated characteristics. The purpose of this study was to isolate Lactobacillus fromdifferent commercial products and evaluate their potential in antibiotic-resistant development. Chromosomallyorplasmid-mediated resistant genes were investigated as well.Methods: In total, Lactobacillus strains were isolated from ۲۰ commercial dairy product samples such as cheeseand yoghurt. The isolates were phenotypic and molecularly identified and their antibiotic-resistant propertieswere assessed by the disk-diffusion method. Finally, the plasmid-mediated antibiotic resistant characters of theisolates were evaluated by plasmid curing via evaluated temperatures and acridine orange methods.Results: Five strains Lactobacillus paracasei, L. rhamnosus, L. casei, L. plantarum, and L. fermentum were isolateddifferent products. The results of the antibiotic susceptibility assay indicated that all strains were susceptible toamoxicillin and imipenem and resistant to ciprofloxacin and vancomycin. Furthermore, different responseswere observed among the isolates against streptomycin and gentamicin. The evaluation of plasmid-mediatedantibiotic resistance in the isolates revealed that streptomycin and gentamicin-resistant characters were ofplasmid-mediated type in L. rhamnosus and L. plantarum strains.Conclusions: In general, our finding demonstrated that some commercial Lactobacillus strains harbouredantibiotic-resistant genes. These genes can be located either in chromosome or plasmid group. Hence, thefrequency of antibiotic-resistant pathogenic bacteria might be increased after consuming some dairy productsbecause of the horizontal transfer of antibiotic-resistance genes among the bacteria.

Keywords:

Lactobacillus , Dairy products , Antibiotics , Plasmid-mediated gene