Molecular characterization of commensal Escherichia coli adapted to different compartments of the porcine gastrointestinal tract

The role of Escherichia coli as a pathogen has been the focus of considerable study, while much less is known about it as a commensal and how it adapts to and colonizes different environmental niches within the mammalian gut. In this study, we characterize Escherichia coli organisms (n=146) isolated from different regions of the intestinal tracts of eight pigs (dueodenum, ileum, colon, and feces). The isolates were typed using the method of random amplified polymorphic DNA (RAPD) and screened for the presence of bacteriocin genes and plasmid replicon types. Molecular analysis of variance using the RAPD data showed that E. coli isolates are nonrandomly distributed among different gut regions, and that gut region accounted for 25% (

Novel Colicin F-Y of Yersinia frederiksenii Inhibits Pathogenic Yersinia Strains via YiuR-Mediated Reception, TonB Import, and Cell Membrane Pore Formation

A novel colicin type, designated colicin F-Y, was found to be encoded and produced by the strain Yersinia frederiksenii Y27601. Colicin F-Y was active against both pathogenic and nonpathogenic strains of the genus Yersinia. Plasmid YF27601 (5,574 bp) of Y. frederiksenii Y27601 was completely sequenced. The colicin F-Y activity gene (cfyA) and the colicin F-Y immunity gene (cfyI) were identified. The deduced amino acid sequence of colicin F-Y was very similar in its C-terminal pore-forming domain to colicin Ib (69% identity in the last 178 amino acid residues), indicating pore forming as its lethal mode of action. Transposon mutagenesis of the colicin F-Y-susceptible strain Yersinia kristensenii Y276 revealed the yiuR gene (ykris001_4440), which encodes the YiuR outer membrane protein with unknown function, as the colicin F-Y receptor molecule. Introduction of the yiuR gene into the colicin F-Y-resistant strain Y. kristensenii Y104 restored its susceptibility to colicin F-Y. In contrast, the colicin F-Y-resistant strain Escherichia coli TOP10F' acquired susceptibility to colicin F-Y only when both the yiuR and tonB genes from Y. kristensenii Y276 were introduced. Similarities between colicins F-Y and Ib, similarities between the Cir and YiuR receptors, and the detected partial cross-immunity of colicin F-Y and colicin Ib producers suggest a common evolutionary origin of the colicin F-Y-YiuR and colicin Ib-Cir systems

Escherichia coli Bacteriocins: Antimicrobial Efficacy and Prevalence among Isolates from Patients with Bacteraemia

Bacteriocins are antimicrobial peptides generally active against bacteria closely related to the producer. Escherichia coli produces two types of bacteriocins, colicins and microcins. The in vitro efficacy of isolated colicins E1, E6, E7, K and M, was assessed against Escherichia coli strains from patients with bacteraemia of urinary tract origin. Colicin E7 was most effective, as only 13% of the tested strains were resistant. On the other hand, 32%, 33%, 43% and 53% of the tested strains exhibited resistance to colicins E6, K, M and E1. Moreover, the inhibitory activity of individual colicins E1, E6, E7, K and M and combinations of colicins K, M, E7 and E1, E6, E7, K, M were followed in liquid broth for 24 hours. Resistance against individual colicins developed after 9 hours of treatment. On the contrary, resistance development against the combined action of 5 colicins was not observed. One hundred and five E. coli strains from patients with bacteraemia were screened by PCR for the presence of 5 colicins and 7 microcins. Sixty-six percent of the strains encoded at least one bacteriocin, 43% one or more colicins, and 54% one or more microcins. Microcins were found to co-occur with toxins, siderophores, adhesins and with the Toll/Interleukin-1 receptor domain-containing protein involved in suppression of innate immunity, and were significantly more prevalent among strains from non-immunocompromised patients. In addition, microcins were highly prevalent among non-multidrug-resistant strains compared to multidrug-resistant strains. Our results indicate that microcins contribute to virulence of E. coli instigating bacteraemia of urinary tract origin

Identification and Characterization of Microcin S, a New Antibacterial Peptide Produced by Probiotic Escherichia coli G3/10

Escherichia coli G3/10 is a component of the probiotic drug Symbioflor 2. In an in vitro assay with human intestinal epithelial cells, E. coli G3/10 is capable of suppressing adherence of enteropathogenic E. coli E2348/69. In this study, we demonstrate that a completely novel class II microcin, produced by probiotic E. coli G3/10, is responsible for this behavior. We named this antibacterial peptide microcin S (MccS). Microcin S is coded on a 50.6 kb megaplasmid of E. coli G3/10, which we have completely sequenced and annotated. The microcin S operon is about 4.7 kb in size and is comprised of four genes. Subcloning of the genes and gene fragments followed by gene expression experiments enabled us to functionally characterize all members of this operon, and to clearly identify the nucleotide sequences encoding the microcin itself (mcsS), its transport apparatus and the gene mcsI conferring self immunity against microcin S. Overexpression of cloned mcsI antagonizes MccS activity, thus protecting indicator strain E. coli E2348/69 in the in vitro adherence assay. Moreover, growth of E. coli transformed with a plasmid containing mcsS under control of an araC PBAD activator-promoter is inhibited upon mcsS induction. Our data provide further mechanistic insight into the probiotic behavior of E. coli G3/10

Competitive interactions in Escherichia coli populations: the role of bacteriocins

Explaining the coexistence of competing species is a major challenge in community ecology. In bacterial systems, competition is often driven by the production of bacteriocins, which are narrow-spectrum proteinaceous toxins that serve to kill closely related species, providing the producer better access to limited resources. Bacteriocin producers have been shown to competitively exclude sensitive, nonproducing strains. However, the dynamics between bacteriocin producers, each lethal to its competitor, are largely unknown. In this study, we used in vitro, in vivo and in silico models to study competitive interactions between bacteriocin producers. Two Escherichia coli strains were generated, each carrying a DNA-degrading bacteriocin (colicins E2 and E7). Using reporter-gene assays, we showed that each DNase bacteriocin is not only lethal to its opponent but, at lower doses, can also induce the expression of its opponent's toxin. In a well-mixed habitat, the E2 producer outcompeted its adversary; however, in structured environments (on plates or in mice colons), the two producers coexisted in a spatially ‘frozen' pattern. Coexistence occurred when the producers were initiated with a clumped spatial distribution. This suggests that a ‘clump' of each producer can block invasion of the other producer. Agent-based simulation of bacteriocin-mediated competition further showed that mutual exclusion in a structured environment is a relatively robust result. These models imply that colicin-mediated colicin induction enables producers to successfully compete and defend their niche against invaders. This suggests that localized interactions between producers of DNA-degrading toxins can lead to stable coexistence of heterogeneously distributed strains within the bacterial community and to the maintenance of diversity

Liver involvement in HIV-infected patients diagnosed with syphilis

Liver involvement in syphilis has been studied in cohorts of human immunodeficiency virus (HIV)-negative individuals despite the scarcity of data on such HIV-infected patients. Th aim of this study was to assess hepatic involvement of HIV-infected patients diagnosed with syphilis. Patients with syphilis and liver involvement, including all stages of syphilis, were systematically identified in our HIV cohort between 2004 and 2008. Of the 1,599 HIV-infected patients identified during the study period, 100 were diagnosed with acute syphilis, all of whom were male. Of these 100 patients, 84 % were men who have sex with men. Laboratory parameters of liver involvement were present in 19 of the 100 HIV-infected patients with syphilis; these resolved after successful antibiotic treatment. Among these 19 patients, six were diagnosed to be in the latent stage, with elevated liver enzymes and parameters of inflammation representing the only distinctive feature. Based on our results, syphilis should be included in the differential diagnosis of increased liver enzymes in HIV-infected patients