Effect of pH in the survival of Lactobacillus salivarius strain UCO_979C wild type and the pH acid acclimated variant

Background Bacterial acclimation involves cellular changes permitting the survival of a microorganism to prolonged acid pH exposure. The general aim of this work is to support this idea by determining the effect of pH in the survival of the human gastric derived probiotic strain Lactobacillus salivarius UCO_979C-1 (wild type) and L. salivarius UCO_979C-2 (acclimation to pH 2.6), which possesses anti-Helicobacter pylori properties. Results To assess this aim, the exopolysaccharide production through the phenol-sulfuric acid method was evaluated. Moreover, morphological and structural changes by transmission and scanning electron microscopy were observed. The bacterial survival was measured by viable count. The results showed that the acclimated variant strain synthesized higher levels of exopolysaccharide (690 ± 0.03 mg/L) more than the wild type (450 ± 0.12 mg/L). In addition, the acclimated variant preserved the viable count at pH 2.6 for 48 h, whereas the wild type strain decreases after 6 h and was non-viable at 24 h. Conclusion The results suggest that the acid stress acclimation of the strain L. salivarius UCO_979C-1 modified some cellular properties making this strain potentially useful as a gastric probiotic.

Low co-existence rates of Lactobacillus spp. and Helicobacter pylori detected in gastric biopsies from patients with gastrointestinal symptoms.

BACKGROUND: bacterial diversity of the stomach includes various species. Among them, Helicobacter pylori, a microorganism which has been associated to gastric diseases, is frequently isolated in this habitat. In addition, Lactobacillus spp., a genus including probiotic strains, has also been documented in this habitat. The co-existence of these two species in the stomach of symptomatic patient needs to be elucidated. AIMS: our goal was to establish if Lactobacillus spp. and H. pylori co-exist in the stomach mucosa of symptomatic patients. METHODS: gastric biopsies (antrum and/or the body) from 427 Chilean patients with gastrointestinal discomfort were analyzed. The H. pylori infection and/or Lactobacillus spp. colonization status was determined for each patient by standard culture techniques, and statistical correlations between the presence of those species and the age, gender, or the severity of the gastric disease were also established. RESULTS: only 6.1% of the samples presented co-existence of Lactobacillus spp. and H. pylori. This former species was isolated in 42.6% of the patients as unique species, while Lactobacillus spp. was isolated as single species in 19.4% of the individuals. Chronic non-atrophic gastritis was prevalent in Lactobacillus spp. non colonized individuals, while chronic non-atrophic and chronic atrophic gastritis diagnosis was similar in Lactobacillus spp. harbouring individuals (p < 0.001). The presence of Lactobacillus spp. Significantly increased with age (p = 0.005), independently of gender. CONCLUSION: the negative Pearson correlation between Lactobacillus spp. and H. pylori (r = -0.112, p = 0.020) indicates that the co-existence of both species is low in human gastric mucosa of symptomatic patients.

In vitro antagonism of rabeprazole and metronidazole upon clinical isolates of Helicobacter pylori.

BACKGROUND: Rabeprazole inhibits Helicobacter pylori in vitro. This property could influence the antibacterial activity of metronidazole or amoxicillin. Our goal was to evaluate in vitro the effect of rabeprazole upon the antibacterial activity of metronidazole and amoxicillin. METHODS: The minimal inhibitory concentration (MIC) was determined by agar dilution upon 30 clinical isolates, and the antibacterial effect of the combined drugs was estimated by calculating the fractional inhibitory concentration index (FICI). RESULTS: Nine strains (30%) were resistant to metronidazole (MIC 8-256 mg/l) while only 1 strain was resistant to amoxicillin (MIC 1.0 mg/l). Rabeprazole also inhibited H. pylori (MIC 0.125-1.0 mg/l). The association of metronidazole and rabeprazole showed synergism in 30% of the strains (FICI < or =0.25), but also antagonism in 23.3% of the clinical isolates (FICI > or =4.0). Mostly, amoxicillin-rabeprazole showed an effect of synergism (53.3%). CONCLUSION: The results presented suggest the need to keep in mind that failure in eradication therapies based on metronidazole and rabeprazole could be due to an antagonism of the drugs.