Antibiotic Susceptibility of Probiotic Bacteria

Abstract

Lactic acid bacteria (LAB) are a heterogeneous group of bacteria widely distributed in nature. These bacteria are found in gastrointestinal (GI) and urogenital tract of humans and animals; they are present on plant material, in milk and meat, and numerous fermented foods. Lactic acid bacteria have been associated with traditional dairy products, cereals, vegetable and meat fermented foods, due to their natural presence leading to spontaneous fermentation. They are also used as starter cultures in industrial food production, as well as in the production of probiotic products due to their potential health benefits to consumer. Milk and dairy products are the most examined food system for the delivery of probiotic bacteria to the human gut. The probiotic concept has progressed and is now in the focus of different research. Significant improvements have been made in selection and characterization of new cultures and their application in food production. The food products, which are produced by traditional methods, exhibit a rich biodiversity with the respect to bacterial contents. From these products, new probiotic strains with the potential functional properties can been isolated and selected. The selected strains have to be further characterized in order to be used in the food industry. Before the probiotics can benefit human health, they must fulfill several criteria including: a) scientifically validated health properties; b) good technological properties meaning that they can be manufactured and incorporated into food products without loosing viability, functionality and technological performance; c) high survival through the upper gastrointestinal tract and high viability at its site of action; d) antagonistic activity to pathogens; e) antibiotic susceptibility; and f) to be able to function in the gut environment. Bearing in mind importance of antibiotic resistance of LAB in food chain, antibiotic susceptibility of potential probiotic strains is a very important criteria for their selection. In the recent decade, releasing of antibiotics in biosphere seriously increased, leading to a strong selective pressure for the emergence and persistence of resistant LAB strains. Since LAB are naturally present in traditionally made fermented food and GI tract and are also added as starter culture or probiotic bacteria in industrial food production, concerns have been raised about the antibiotic resistance of these beneficial bacteria strains. Probiotic bacteria can help maintaining balance in gastrointestinal tract in cases of diarrhea caused by antibiotic treatment. However, there is high risk associated with the ability of these resistant strains to transmit the resistance gene to pathogenic bacteria in gut microbiota. This can complicate the treatment of a patient with an antibiotic resistant bacterial infection or disease. The circulation of genes coding for antibiotic resistance from beneficial LAB in the food chain via animals to humans is a complex problem. Therefore, there is a need to evaluate the safety of potential probitic strains regarding their ability to acquire and disseminate antibiotic resistance determinants in selection of LAB. In this study, importance of LAB in the food chain will be reviewed. Morphological and biochemical characteristics of lactobacilli, bifidobactera and enterococci, as well as criteria for probiotic selection and role of probiotics in health benefit will be discussed. Antibiotic susceptibility as criteria for potential probiotic bacteria selection and mechanisms of gene transfers will be considered.