Bifidobacterium strains from resident infant human gastrointestinal microflora exert antimicrobial activity

Abstract

Background and aims-The gastrointestinal microflora exerts a barrier eVect against enteropathogens. The aim of this study was to examine if bifidobacteria, a major species of the human colonic microflora, participates in the barrier eVect by developing antimicrobial activity against enterovirulent bacteria. Methods-Antibacterial activity was examined in vitro against a wide range of Gram negative and Gram positive pathogens. Inhibition of Salmonella typhimurium SL1334 cell association and cell invasion was investigated in vitro using Caco-2 cells. Colonisation of the gastrointestinal tract in vivo by bifidobacteria was examined in axenic C3/He/Oujco mice. Antimicrobial activity was examined in vivo in axenic C3/He/Oujco mice infected by the lethal S typhimurium C5 strain. Results-Fourteen human bifidobacterium strains isolated from infant stools were examined for antimicrobial activity. Two strains (CA1 and F9) expressed antagonistic activity against pathogens in vitro, inhibited cell entry, and killed intracellular S typhimurium SL1344 in Caco-2 cells. An antibacterial component(s) produced by CA1 and F9 was found to be a lipophilic molecule(s) with a molecular weight of less than 3500. In the axenic C3/He/Oujco mice, CA1 and F9 strains colonised the intestinal tract and protected mice against S typhimurium C5 lethal infection. Conclusion-Several bifidobacterium strains from resident infant human gastrointestinal microflora exert antimicrobial activity, suggesting that they could participate in the "barrier eVect" produced by the indigenous microflora. (Gut 2000;47:646-652)

Premature or pathological aging: longevity

“…The gut microbiota is reported to contribute to human protein homeostasis, providing evidence that the intestinal microbiota is considered an important defence barrier. Probiotics can compete for some of the same attachment sites as pathogens use the same nutrients, and produce antimicrobial compounds that inhibit the growth of pathogen (LIÉVIN et al, 2000).…”

Identification and Characterization Indigenous of Lactobacillus spfrom Bovine Rumen Fluidof Slaughterhouse

“…Because the bacterial cell wall is comprised mainly of phospholipids, bile salt which is an emulsifier and solubilizes the lipid that can damage the bacterial cells [21]. [23,24]. Probiotic bacteria can lower the luminal pH through secretion of acetic and lactic acids, which inhibits the growth of some pathogens, including enterohemorrhagic E. coli (EHEC) [25].…”

Produção de bacteriocina por Bifidobacterium lactis a partir de soro de leite

“…Although some reports have suggested that the production of organic acids, via the heterofermentative pathways, is partially responsible for the inhibitory activity of bifidobacteria (Bruno and Shah, 2002;Ibrahim and Salameh, 2001), it is well accepted that at least some bifidobacteria also produce bacteriocins. In some cases, the antimicrobial activity was associated with the production of peptides, but the exact nature of the active substance was not determined (Anand et al, 1984(Anand et al, , 1985Bernet et al, 1993;Liévin et al, 2000;Meghrous et al, 1990); in other cases, the peptides involved were definitively identified. Table 1 contains a list of known Bifidobacterium-associated bacteriocins and putative bacteriocins as well as their main characteristics.…”

“…However, as the authors were specifically targeting antimicrobials able to inhibit Gram-negative bacteria, the active compounds were not isolated. Liévin et al (2000) were successful in demonstrating the antiSalmonella typhimurium activity of a highly lipophilic, low molecular weight (b3500 Da) compound produced by Bifidobacterium strains, which was precipitated with ammonium sulfate and partially purified by methanol-chloroform extraction and dialysis. However, once again, this compound was not further characterized.…”

“…Other alternatives include the use of acid or organic solvents as precipitating agents (Gibson and Wang, 1994a). Dialysis and ultrafiltration can also be used to further concentrate and purify bacteriocins, even though some Bifidobacterium-associated studies pointed out large product losses due to incomplete precipitation (Collado et al, 2005b;Liévin et al, 2000). The final purification step generally consists of reversed phase high-performance liquid chromatography (RP-HPLC) with acetonitrile gradient, which can be followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) or mass spectrometry for molecular size determination.…”