Antibiotic Resistance Profile and Safety Assessment of Lactobacillus acidophilus and Lactobacillus plantarum Isolated from Milk

In the era where developing antibiotic resistance is an emerging issue, probiotics are amongst the most promising therapeutic as well as prophylactic measures. One of the most commonly used probiotics in cheese, yoghurt, silage and preserved food such as pickles is lactobacilli. However, some studies have shown that some lactic acid bacteria (LAB) strains are resistant to antibiotics which pose a threat to human health. Hence, to evaluate the safety of L. acidophilus and L. plantarum, they were subjected to antibiotic susceptibility tests using the disc diffusion method against a total of 26 antibiotics. The isolates were found to exhibit multiple resistance against some of the most commonly used antibiotics. The isolates showed a high level of resistance toward ampicillin, amoxycillin, cefotaxime, nalidixic acid, streptomycin, kanamycin and nitrofurantoin. The isolates showed low levels of resistance toward cephalothin, amikacin, erythromycin and azithromycin. They were susceptible to ciprofloxacin, penicillin G, cloxacilln, ofloxacillin, norfloxacin, levofloxacin, moxifloxacin, sparfloxacin, enrofloxacin, gemifloxacin, chloramphenicol, gentamicin, co-trimoxazole and oxytetracycline. The present study showed that antibiotic resistance is prevalent in different species of probiotic strains, which may pose a food safety concern. Hence, antibiotic sensitivity should be considered an important part of safety assessment for the evaluation of probiotics. Therefore, the current study concluded that antibiotic resistance is prevalent among L. acidophilus and L. plantarum, which is major concern of food safety. Furthermore, studies to evaluate the presence of antibiotic resistance genes in commercially available probiotics should be conducted. Antimicrobial susceptibility tests should be considered as an essential measure for the assessment of the safety of probiotics.