Abstract
This work characterizes a set of lactobacilli strains isolated from the stomach of healthy humans that might serve as probiotic cultures. Ten different strains were recognized by rep-PCR and PFGE fingerprinting among 19 isolates from gastric biopsies and stomach juice samples. These strains belonged to five species, Lactobacillus gasseri (3), Lactobacillus reuteri (2), Lactobacillus vaginalis (2), Lactobacillus fermentum (2) and Lactobacillus casei (1). All ten strains were subjected to a series of in vitro tests to assess their functional and technological properties, including acid resistance, bile tolerance, adhesion to epithelial gastric cells, production of antimicrobial compounds, inhibition of Helicobacter pylori, antioxidative activity, antibiotic resistance, carbohydrate fermentation, glycosidic activities, and ability to grow in milk. As expected, given their origin, all strains showed good resistance to low pH (3.0), with small reductions in counts after 90 min exposition to this pH. Species- and strain-specific differences were detected in terms of the production of antimicrobials, antagonistic effects toward H. pylori, antioxidative activity and adhesion to gastric epithelial cells. None of the strains showed atypical resistance to a series of 16 antibiotics of clinical and veterinary importance. Two L. reuteri strains were deemed as the most appropriate candidates to be used as potential probiotics against microbial gastric disorders; these showed good survival under gastrointestinal conditions reproduced in vitro, along with strong anti-Helicobacter and antioxidative activities. The two L. reuteri strains further displayed appropriated technological traits for their inclusion as adjunct functional cultures in fermented dairy products.
Highlights
Over recent decades, culture-independent techniques have revealed the stomach to be home to a well-adapted, nichespecific microbial community (Bik et al, 2006; Andersson et al, 2008; Delgado et al, 2013)
BACTERIAL ISOLATES AND GROWTH CONDITIONS Nineteen Lactobacillus isolates belonging to five different species were cultured from gastric biopsies and stomach juice samples provided by healthy subjects
TYPING OF LACTOBACILLI The isolates were genotyped by repetitive extragenic palindromic-PCR and by pulsed-field gel electrophoresis (PFGE) fingerprinting
Summary
Culture-independent techniques have revealed the stomach to be home to a well-adapted, nichespecific microbial community (Bik et al, 2006; Andersson et al, 2008; Delgado et al, 2013). Gastric microbial communities are of potential probiotic use in the treatment of several diseases, but only a few studies have attempted to cultivate their members (Adamson et al, 1999; Li et al, 2009; Delgado et al, 2013). The isolation and characterization of stomach originated strains could provide novel probiotic candidates with enhanced capacities to counteract gastric pathogens such as Helicobacter pylori (Cui et al, 2010). This Gram-negative, microaerophilic microorganism infects over 50% of the population worldwide (Bruce and Maaroos, 2008). Lactobacillus reuteri having anti H. pylori action is one promising approach (Francavilla et al, 2008)
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