For the first time, microcin-producing strains showing inhibitory activities against enteropathogen Salmonella enteritidis were isolated from poultry intestinal contents. Among the numerous strains isolated, two strains of Escherichia coli, named J02 and J03, showing the greatest activities against S. enteritidis, were studied. Biochemical tests and purification identified the main antagonist compound produced as microcin J25. In order to evaluate the protective potential of E. coli J02 and J03 against S. enteritidis infection, the ability of these strains to inhibit growth of S. enteritidis was investigated in mixed culture. A strong antagonist activity was obtained with a preculture phase of the active strain in minimal medium before incubation with S. enteritidis. In a bioreactor experiment simulating the chicken gastric and intestinal tract environment, a mixture of the two strains E. coli J02 and J03, provided an enhanced inhibitory effect. Microcinogenic strain activities were not affected by bile, pancreatic enzymes addition, or acidic conditions. These results suggest the relevant role of microcin-producing microorganisms in microbial intestinal ecology. To conclude, this study shows that microcin J25 strains could exert a beneficial protective effect against S. enteritidis growth in situ.

Seven strictly anaerobic strains showing anti‐Salmonella enteritidis activity were isolated from poultry caecal contents. Among them, the most inhibitory one, a strain of Fusobacterium mortiferum, called FM1025, was selected. Biochemical tests, showing the proteinaceous structure of the antagonist(s) produced, indicated that the strain Fus. mortiferum FM1025 synthesized (a) bacteriocin‐like compound(s) active against Salm. enteritidis. Among the other strains tested, both Gram‐negative and Gram‐positive bacteria were inhibited. These preliminary results suggested the important role of the Fusobacterium strains against pathogenic bacteria among the intestinal flora.

For the first time, microcin-producing strains showing inhibitory activities against enteropathogen Salmonella enteritidis were isolated from poultry intestinal contents. Among the numerous strains isolated, two strains of Escherichia coli, named J02 and J03, showing the greatest activities against S. enteritidis, were studied. Biochemical tests and purification identified the main antagonist compound produced as microcin J25. In order to evaluate the protective potential of E. coli J02 and J03 against S. enteritidis infection, the ability of these strains to inhibit growth of S. enteritidis was investigated in mixed culture. A strong antagonist activity was obtained with a preculture phase of the active strain in minimal medium before incubation with S. enteritidis. In a bioreactor experiment simulating the chicken gastric and intestinal tract environment, a mixture of the two strains E. coli J02 and J03, provided an enhanced inhibitory effect. Microcinogenic strain activities were not affected by bile, pancreatic enzymes addition, or acidic conditions. These results suggest the relevant role of microcin-producing microorganisms in microbial intestinal ecology. To conclude, this study shows that microcin J25 strains could exert a beneficial protective effect against S. enteritidis growth in situ.

No abstract

To screen, isolate, and characterize bacterial populations producing microcin J25, we report here two rapid, reliable, and sensitive methods, using polymerase chain reaction and colony blot hybridization with a digoxigenin-labelled probe. A sample of 26 Escherichia coli strains isolated from poultry intestinal contents was evaluated to detect the sequence of mcjA, the gene encoding the MccJ25 precursor. The two molecular techniques were compared with the commonly used cross-immunity tests. They generate accurate data with no obvious cross-reactions with other microcins. The results display that the producers of MccJ25 were widely distributed in the poultry intestinal habitat. The applications of these molecular methods will be useful in future studies of microcinogenic populations, and thus contribute to understand the relationships within the complex intestinal microbial ecosystem.