Forty-five lactic acid bacteria (LAB) were isolated from the vaginal specimens of healthy fertile women, and the identities of the bacteria were confirmed by sequencing of their 16S rDNA genes. Among these bacteria, only four isolates were able to resist and survive in low pH, bile salts and simulated in vitro digestion conditions. Lactococcus lactis 2HL, Enterococcus durans 6HL, Lactobacillus acidophilus 36YL and Lactobacillus plantarum 5BL showed the best resistance to these conditions. These strains were evaluated further to assess their ability to adhere to human intestinal Caco-2 cells. Lactococcus lactis 2HL and E. durans 6HL were the most adherent strains. In vitro tests under neutralized pH proved the antimicrobial activity of both strains. Results revealed that the growth of Escherichia coli O26, Staphylococcus aureus and Shigella flexneri was suppressed by both LAB strains. The antibiotic susceptibility tests showed that these strains were sensitive to all nine antibiotics: vancomycin, tetracycline, ampicillin, penicillin, gentamicin, erythromycin, clindamycin, sulfamethoxazole and chloramphenicol. These data suggest that E. durans 6HL and Lactococcus lactis 2HL could be examined further for their useful properties and could be developed as new probiotics.
INTRODUCTIONThe concept of eating or using live bacteria for health benefits goes back a hundred years (Metchnikoff, 1907). Lactic acid bacteria (LAB) are generally regarded as safe and constitute part of the probiotic concept, which has received significant attention over the past years (Metchnikoff, 1907;Salminen et al., 1998). Probiotics are live micro-organisms in the form of single or mixed cultures; when consumed at sufficient amounts, these probiotics provide beneficial health effects for hosts (Guarner et al., 2008;Lilly & Stillwell, 1965;Surawicz, 2003). Probiotics significantly affect the bioavailability of nutrients in the human body (Young & Huffman, 2003). These micro-organisms stimulate immune mechanisms and maintain normal human microbiota compositions; as a result, these micro-organisms reduce the risk of diarrhoea (Binns & Lee, 2010), antibiotic-related diarrhoea (Friedman, 2012), irritable bowel syndrome (Barouei et al., 2009;Parkes, 2010), inflammatory bowel disease (Geier et al., 2007;Gionchetti et al., 2002), vaginal infections (Reid & Bocking, 2003), atopic eczema (Bunselmeyer & Buddendick, 2010;Wickens et al., 2008), rheumatoid arthritis (Guarner et al., 2008) and cancers (Serban, 2014;Zhu et al., 2011). They are believed to be the dominant members of normal postpubertal and premenopausal vaginal microbiota (Nam et al., 2007). Clinical proof shows that the vaginal and urogenital floras play a dominant role in maintaining both protection from illnesses and the well-being of women (Burton et al., 2003 Liong, 2008).To obtain the ability to exert their probiotic effects, potential strains are expected to have desirable properties (Ouwehand et al., 1999; Zavisic et al., 2011). Probiotics have many selection criteria: human origin f...