Antibiotic Resistance of Lactobacillus sp. Isolated from Commercial Probiotic Preparations

The aim of our study was to assess the antibiotic resistance among commercially available probiotic Lactobacilli. A total of 30 isolates were characterized after isolation from 19 commercial products, including Lactobacillus rhamnosus, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus reuteri, Lactobacillus plantarum and Lactobacillus fermentum. All the isolates were further subjected to antibiotic susceptibility test using disc diffusion method against a total of 45 antibiotics. Most of the isolates were found to exhibit multiple resistance against some of the most commonly used antibiotics. The isolates showed high level of resistance toward nalidixic acid, vancomycin, kanamycin, teicoplanin, co‐trimoxazole, amikacin, streptomycin, norfloxacin, cefepime and nitrofurantoin. Besides, isolates displayed a low level of resistance toward tobramycin, gentamicin, ampicillin, cefaclor, methicillin, penicillin, tetracycline, levofloxacin, azithromycin, chloramphenicol, amoxyclav, sulbactam, oxacillin, ofloxacin, ciprofloxacin, cloxacillin and novobiocin. All the isolates were found to be susceptible against cefatrixone, ceftazidime, cefadroxil, cefotaxime, cephalothin, cefoperazone and netillin, whereas none of the strains showed resistant to clindamycin, erythromycin, linezolid, quinupristin/dalfopristin and doxycycline. 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 as an important part of safety assessment for the evaluation of probiotics. PRACTICAL APPLICATIONS: Antibiotic resistance has become a major public health concern and is drawing the interest of health and research professionals all around the world. Commercial probiotics are generally considered as safe for humans but due to their very high consumption there is a need to put sufficient safeguards to protect the consumers from any adverse effects. The safety of these probiotic strains is becoming prerequisite with antibiotic resistance as an emerging issue and their potential to transfer antibiotic resistance genes to pathogenic/commensal bacteria cannot be neglected. The anticipated problem is that probiotic strains and starter cultures might contain naturally occurring antibiotic resistance genes which if present on mobile genetic elements can be transferred to commensal and pathogenic organisms in the gut. The European Food Safety Authority recommends that bacterial strains harboring transferable antibiotic resistance genes should not be used in animal feeds, fermented and probiotic foods for human use.