ReviewAntibiotic resistance among commercially available probiotics

•Antibiotic resistance is a burning issue worldwide.•Probiotics can act as a mode of resistance transfer to pathogens.•Complete review of antibiotic resistance reported in commercial probiotics

Probiotics are known to have a long history of safe use and can be formulated into many different types of products, including foods, drugs, and dietary supplements. Several probiotic microorganisms like genus Lactococcus, Lactobacillus, Streptococcus, Enterococcus, Bifidobacterium, Pediococcus and Propionibacteria spp. are these days used in fermented dairy products and drug formulations. Due to their human consumption, safety of these organisms is of primary importance as their resistance towards antibiotics can be one of the possible threat. The gravity of this issue is further compounded by the possibility of bacteria to transfer resistance determinants horizontally to pathogens and commensal gut microbiota. Antibiotic resistance in these beneficial microbes, either intrinsic or due to any mutation does not manifest a safety concern in itself. Some probiotic strains with intrinsic antibiotic resistance per se could be useful for restoring the gut microbiota after antibiotic treatment. However, specific antibiotic resistance determinants carried on mobile genetic elements, such as tetracycline resistance genes, have often been detected in the typical probiotic genera, and hence constitute a reservoir of resistance for potential food or gut pathogens, thus representing a serious safety issue. Plasmid-associated antibiotic resistance, which occasionally occurs, is a matter of concern as it can be detrimental to use of probiotics owing the possibility of the resistance spreading to harmful microorganisms inhabiting the same niche. Further, the presence of transferable antibiotic resistance genes even to a less innocuous member of the gut microbial community poses a safety hazard and needs to be taken into account. Probiotic safety is beleaguered with the scarcity of well designed and targeted studies and needs to be dealt in right perspective. This review aims to deliberate on the presence of antibiotic resistance in commercially used probiotic organisms and their potential transfer to pathogens and other commensal microbiota present in the gut.