Correlation of Biofilm Formation and Caco-2 Cell Attachment Properties in Colonization Ability of Acid-Bile Resistant Fecal Lactobacillus plantarum Isolates

INTRODUCTION The microbiome of the human gastrointestinal tract is an entity affecting the functional features of our body including immunity and metabolism. This dynamic and complex microbial community is linked with our nutrition and physiology [1]. The gut microbiome comprises a vast diversity of microorganisms, and probiotics as members of the microbiome have received much attention from biomedicine specialist [2, 3]. The probiotic microorganisms are among the most exciting groups of the gut microbiome. They are beneficial microbes that confer health benefits upon the host when consumed appropriately [1]. In the last few years, various branches of health sciences have focused on identification of potential probiotics by screening for unique and main probiotic properties of the microorganism [4]. Lactobacillus, one of the two main probiotic genera, include over 200 species with hundreds of strains introduced as probiotics [5-7]. Due to the economic significance of these microbes, various biological features of them have been exhaustively studied [1]. Lactobacilli are actually among the most extensively studied probiotics due to: a) potential anti-inflammatory and anti-allergic effects, b) secretion of antimicrobial compounds, c) growing in aerobic and anaerobic conditions, and e) comprising many species identified as Generally Recognized As Safe (GRAS) by the Food and Drug Administration (FDA). Considering the niche-specific genome evolution of these lactic acid bacteria to specific environments like the gastrointestinal tract of various animals, the diverse array of the physiological traits, which are known as the probiotic properties, have become species and even strain specific [8]. The intestinal epithelium and the mucosa lining the GIT form a defensive physical barrier against potential exogenous invasions. Probiotics are expected to be able to survive transit through the harsh stomach environment and resist digestive bile salts [9, 10]. The microbes that resist the acid and bile salts must also possess a variety of characteristics which are critical for a potential probiotic strain to become stabilized in GIT. These features include adhesion to the intestinal epithelial cells, colonization in the intestinal tract, production of antimicrobial factors, and inhibition of enteropathogens [11-14]. The resident gut microbiome including members of the probiotic genera, mainly bifidobacteria and lactobacilli, are involved in improving the biological functions of their hosts by conferring them a health benefit. This phenomenon occurs via various ways including preserving the niche balance of the gut microbial community, preventing pathogens from colonization and reducing the probability of their invasive effects, promoting the mucosal and epithelial integrity and Introduction: The strain-specific capabilities of lactobacilli are critical for gut colonization. In this study, we evaluated various colonization determinants of 42 fecal Lactobacillus plantarum isolates from the healthy human fecal samples. Methods: We investigated the attachment to the Caco-2 cell line, biofilm formation ability and cell surface activity of the isolates. Such properties were comparatively studied, and the regression between these features was statistically analyzed. Results: Among our results 18 (42.9%) were non-adhesive, 11 (26.2%) moderate adhesive and 13 (31%) strongly adhesive. The results showed that some isolates were significantly capable of biofilm formation. The highest rate of auto-aggregation was recorded for L. plantarum isolate RPR 240 (58%). Conclusion: Our results revealed a high degree of variability among colonization characteristics of the L. plantarum isolates indicating strain-specificity. Also, the colonization properties of the potential probiotic isolates had no significant correlation with each other. Our results confirmed the necessity of further in vivo colonization assays for selection of probiotic candidates. J Med Microbiol Infec Dis, 2018, 6 (1): 13-19.