Microbial carcinogenesis: Lactic acid bacteria in gastric cancer.

While Helicobacter pylori is a fundamental risk factor, gastric cancer (GC) aetiology involves combined effects of microbial (both H. pylori and non-H. pylori), host and environmental factors. Significant differences exist between the gastric microbiome of those with gastritis, intestinal metaplasia and GC, suggesting that dysbiosis in the stomach is dynamic and correlates with progression to GC. Most notably, a consistent increase in abundance of lactic acid bacteria (LAB) has been observed in GC patients including Streptococcus, Lactobacillus, Bifidobacterium and Lactococcus. This review summarises how LAB can influence GC by a number of mechanisms that include supply of exogenous lactate -a fuel source for cancer cells that promotes inflammation, angiogenesis, metastasis, epithelial-mesenchymal transition and immune evasion-, production of reactive oxygen species and N-nitroso compounds, as well as anti-H. pylori properties that enable colonization by other non-H. pylori carcinogenic pathobionts.

Safety Evaluation and Colonisation Abilities of Four Lactic Acid Bacteria as Future Probiotics.

The study evaluated the safety and colonisation properties of four lactic acid bacteria (LAB), by determining their cell hydrophobicity and aggregation abilities. In addition, the presence of virulence and resistance genes was assayed in these probiotic candidates. Lactobacillus reuteri ZJ625, Lactobacillus reuteri VB4, Lactobacillus salivarius ZJ614 and Streptococcus salivarius NBRC13956 were tested for cell surface hydrophobicity abilities against xylene, chloroform and ethyl acetate. The isolates were also tested for auto-aggregation and co-aggregation abilities; the optical densities of cell growth were measured after 1, 2, 3 and 4 h of experimental set-up. DNA was extracted from all the four isolates and amplified using PCR with specific primers to detect virulence genes of adhesion collagen protein (ace) and aggregation substances (agg and asa); also, resistance genes of Vancomycin vanA, Vancomycin vanC1 and Vancomycin vanC2/3 were assayed in the four isolates. The isolates showed high hydrophobicity to all solvents: xylene (78-84%), chloroform (68-75%) and ethyl acetate (52-60%). High auto- and co-aggregations ranging from 60 to 70% and from 45 to 56% respectively were observed in the isolates after 4 h of incubation at 37 °C. Some of the tested isolates showed the presence of virulence and resistance genes; however, this does not indicate that these genes are unsafe because their transmission and expression abilities are unknown. Therefore, in this study, the isolates studied are considered safe for use as future probiotics, as revealed from results presented, which generally represents the scanned safety evaluations of the isolates as promising probiotics.

Antimicrobial activity, antibiotic susceptibility and virulence factors of Lactic Acid Bacteria of aquatic origin intended for use as probiotics in aquaculture.

BACKGROUND: The microorganisms intended for use as probiotics in aquaculture should exert antimicrobial activity and be regarded as safe not only for the aquatic hosts but also for their surrounding environments and humans. The objective of this work was to investigate the antimicrobial/bacteriocin activity against fish pathogens, the antibiotic susceptibility, and the prevalence of virulence factors and detrimental enzymatic activities in 99 Lactic Acid Bacteria (LAB) (59 enterococci and 40 non-enterococci) isolated from aquatic animals regarded as human food. RESULTS: These LAB displayed a broad antimicrobial/bacteriocin activity against the main Gram-positive and Gram-negative fish pathogens. However, particular safety concerns based on antibiotic resistance and virulence factors were identified in the genus Enterococcus (86%) (Enterococcus faecalis, 100%; E. faecium, 79%). Antibiotic resistance was also found in the genera Weissella (60%), Pediococcus (44%), Lactobacillus (33%), but not in leuconostocs and lactococci. Antibiotic resistance genes were found in 7.5% of the non-enterococci, including the genera Pediococcus (12.5%) and Weissella (6.7%). One strain of both Pediococcus pentosaceus and Weissella cibaria carried the erythromycin resistance gene mef(A/E), and another two P. pentosaceus strains harboured lnu(A) conferring resistance to lincosamides. Gelatinase activity was found in E. faecalis and E. faecium (71 and 11%, respectively), while a low number of E. faecalis (5%) and none E. faecium exerted hemolytic activity. None enterococci and non-enterococci showed bile deconjugation and mucin degradation abilities, or other detrimental enzymatic activities. CONCLUSIONS: To our knowledge, this is the first description of mef(A/E) in the genera Pediococcus and Weissella, and lnu(A) in the genus Pediococcus. The in vitro subtractive screening presented in this work constitutes a valuable strategy for the large-scale preliminary selection of putatively safe LAB intended for use as probiotics in aquaculture.