Anti-Salmonella activity of lactobacilli from different habitats

Lactic acid bacteria (LAB) may contribute to the food safety. In the present study, the antagonistic activity of 45 Bulgarian Lactobacillus homo- and heterofermentative strains of human and dairy origin, and 4 multibacterial formulas against Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) was assessed. In vitro tests were performed in different model systems - milk, soymilk, De Man Rogose Sharp (MRS) medium, to simulate real conditions in the food chain. The highest antagonistic activity was observed with cell-free supernatants of exponential MRS broth cultures of the strains isolated from breast milk, followed by lactobacilli from white brined and green cheese. The detected antimicrobial activity against the pathogen was strain-specific and depended on the culture conditions. Lactobacillus (reclassified as Lactoplantibacillus) plantarum strains, cultivated in skimmed milk and whey protein medium, were able to inhibit S. Typhimurium growth, while a limited inhibitory activity was detected for fermented soymilks. A bacteriocinogenic Ligilactobacillus (the previous Lactobacillus) salivarius strain reduced the number of living pathogenic cells during co-cultivation in whole milk. The inhibition was significant only when L. salivarius was inoculated in predominance. In case of underrepresented LAB number, S. Typhimurium over-growth was observed. Eight lactobacilli in combination as a multibacterial co-culture expressed synergic antagonistic effect against Salmonella and were pre-selected as promising. Further characterisation of their active metabolites, however, is needed before their classification as bio-protective agents.

Antibiotic susceptibility of Lactobacillus plantarum strains, isolated from katak

Several Lactobacillus species are accepted as microorganisms with Qualified Presumption of Safety (QPS) in the EFSA’s list. One of them, Lactobacillus plantarum is a widely distributed species with a proven probiotic potential and technological relevance. In addition, every strain must complete several requirements, before implementation. Antibiotic susceptibility is one of EFSA’s important criteria regarding the safety of probiotics. The reason is to avoid any possibility of antibiotic resistance genes transfer to opportunistic pathogens in the gut. In the present study 14 Lactobacillus plantarum strains were assessed for susceptibility to 21 antibiotics from different groups. A high number of resistant strains was determined toward 12 antibiotics (penicillins – penicillin, piperacillin; IIIth generation cephalosporins – cefotaxime, ceftriaxone, ceftazidime; glycopeptides – vancomycin; tetracyclines – tetracycline; aminoglycosides – gentamicin; macrolides – clarithromycin; quinolones – nalidixic acid, ciprofloxacin, levofloxacin). Concerning the other tested antibiotics, strain-specific antibiotic-sensitivity patterns were observed. Antibiotic resistance was also discussed as an advantage in the selection of probiotic strains, however only when it is not transferable. Estimated susceptibility patterns of some of tested candidate probiotic strains are also important, considering the use of the latter as agents accompanying antibiotic therapy

Epigenetic alterations in patients with type 2 diabetes mellitus

Epigenetic changes, in particular DNA methylation processes, play a role in the pathogenesis and progression of type 2 diabetes mellitus (T2DM) linking genetic and environmental factors. To clarify this role, we have analyzed in patients with different duration of T2DM: (i) expression levels of methyl-CpG-binding domain protein 2 (MBD2) as marker of DNA methylation, and ii) methylation changes in 22 genes connected to cellular stress and toxicity. We have analyzed MBD2 mRNA expression levels in16 patients and 12 controls and the methylation status of stress and toxicity genes in four DNA pools: (i) controls; (ii) newly-diagnosed T2DM patients; (iii) patients with T2DM duration of <5 years and (iv) of >5 years. The MBD2 expression levels were 10.4-times increased on average in T2DM patients compared to controls. Consistent increase in DNA methylation fraction with the increase in T2DM duration was observed in Prdx2 and SCARA3 genes, connected to oxidative stress protection and in BRCA1 and Tp53 tumor-suppressor genes. In conclusion, increased MBD2 expression in patients indicated general dysregulation of DNA methylation in T2DM. The elevated methylation of Prdx2 and SCARA3 genes suggests disturbance in oxidative stress protection in T2DM. The increased methylation of BRCA1 and Tp53 genes unraveled an epigenetic cause for T2DM related increase in cancer risk.