Specific properties of probiotic strains: relevance and benefits for the host.

Background: Probiotics have tremendous potential to develop healthy diets, treatment, and prevention. Investigation of in vitro cultural properties of health-promoting microorganisms like lactic acid bacteria (LAB) and bifidobacteria is crucial to select probiotic strains for treatments based on gut microbiota modulation to justify individualized and personalized approach for nutrition and prevention of variety of diseases. The was to study the biological properties of LAB and bifidobacteria probiotic strains, namely adhesive properties; resistance to antibiotics; and biological fluids (gastric juice, bile, pancreatic enzymes), and to overview the literature in the field.

Materials And Methods: We studied six LAB strains ( ІМV В-7279, ІМV В-7280, subsp. ІМV В-7281, LB-3 VK6, LE VK8, LM VK7), and two bifidobacteria strains ( VKL, VKB). We characterized tinctorial, culturally morphological, physiological, and biochemical properties of probiotic strains of LAB and bifidobacteria by commonly used research methods. Determination of the resistance to antibiotics was carried out using disc-diffusion method. The effects of gastric juice, bile, and pancreatin on the viability of LAB and bifidobacteria were evaluated. Adhesive properties of LAB and bifidobacteria to epithelial cells were assessed calculating three indicators: average adhesion rate (AAR), participation rate of epithelial cells (PRE), and adhesiveness index of microorganisms (AIM). Electron microscopy of LAB and bifidobacteria cells was conducted.

Results: The studied strains of LAB and bifidobacteria did not form spores, were positively stained by Gram, grow on medium in a wide range of pH (1.0-9.0, optimum pH 5.5-6.5), were sensitive to a wide range of antibiotics; and showed different resistance to gastric juice, bile, and pancreatic enzymes. The most resistant to antibiotics were LB-3 VK6 and LE VK8 strains. The most susceptible to gastric juice was LM VK7, which stopped its growth at 8% of gastric juice; IMV B-7279, VKL, and VKB strains were resistant even in the 100% concentration. Strains IMV В-7279, IMV В-7280, VKL, VKB, LB-3 VK6, LE VK8, and subsp. IMV В-7281 were resistant to pancreatic enzymes. Adhesive properties of the strains according to AIM index were high in IMV В-7280, VKL, and VKB; were moderate in subsp. IMV В-7281; and were low in IMV В-7279, LB-3 VK6, LE VK8, and LM VK7.

Conclusion: We recognized strain-dependent properties of studied LAB and bifidobacteria probiotic strains (adhesive ability, resistance to antibiotics, and gut biological fluids) and discussed potential for most effective individualized treatment for gut and distant sites microbiome modulation.