RESUMO
The present study determined the effect of Clostridium perfringens isolates taken from necrotic enteritis (NE) outbreaks on organic farms in a NE virulence testing model. Thirteen strains were isolated in the course of the study. Six C. perfringens field isolates were taken from a naturally occurring NE outbreak on an organic farm. Polymerase chain reaction toxinotyping was used to establish C. perfringens strains, as well as to create a toxin profile. All field isolates were found to be type A and positive for alpha, beta-2 and netB toxin genes. During the NE virulence model, digesta samples were collected before oral inoculation to define the C. perfringens found as part of the natural flora. Three of the five natural flora isolates were found to be C. perfringens type E while the other two isolates were type A; only four of five isolates were positive for either netB or beta-2 toxin genes. Two isolates collected after inoculation were C. perfringens type A positive for cpb2 and netB. All isolates were tested positive for the quorum-sensing-related gene luxS, regardless of the strain source. The presence of luxS, alpha, netB and beta-2 toxin genes seems not to be a determinant of the disease as they were present in isolates from both outbreak birds as well as healthy and pre-inoculated birds. The C. perfringens field isolates induced mild NE lesions in one-half of the birds during the challenge study. Other mechanisms must play a role in the development of the disease beyond toxinotype, potentially including intestinal ecology and health, which would account for acute disease as seen in the field outbreak.
Assuntos
Toxinas Bacterianas/análise , Infecções por Clostridium/veterinária , Clostridium perfringens/isolamento & purificação , Clostridium perfringens/patogenicidade , Surtos de Doenças/veterinária , Enterite/veterinária , Doenças das Aves Domésticas/microbiologia , Sequência de Aminoácidos , Ração Animal , Animais , Toxinas Bacterianas/genética , Galinhas , Infecções por Clostridium/microbiologia , Infecções por Clostridium/patologia , Clostridium perfringens/classificação , Clostridium perfringens/genética , DNA Bacteriano/genética , Enterite/epidemiologia , Enterotoxinas/análise , Enterotoxinas/genética , Enterotoxinas/isolamento & purificação , Manitoba/epidemiologia , Necrose/epidemiologia , Necrose/veterinária , Agricultura Orgânica , Reação em Cadeia da Polimerase/métodos , Doenças das Aves Domésticas/patologia , RNA Ribossômico 16S/química , Alinhamento de Sequência , VirulênciaRESUMO
Bacteriophage-encoded genetic elements control bacterial biological functions. Enterohemorrhagic Escherichia coli (EHEC) strains harbor lambda-phages encoding the Shiga-toxin (Stx), which is expressed during the phage lytic cycle and associated with exacerbated disease. Phages also reside dormant within bacterial chromosomes through their lysogenic cycle, but how this impacts EHEC virulence remains unknown. We find that during lysogeny the phage transcription factor Cro activates the EHEC type III secretion system (T3SS). EHEC lambdoid phages are lysogenic under anaerobic conditions when Cro binds to and activates the promoters of T3SS genes. Interestingly, the Cro sequence varies among phages carried by different EHEC outbreak strains, and these changes affect Cro-dependent T3SS regulation. Additionally, infecting mice with the related pathogen C. rodentium harboring the bacteriophage cro from EHEC results in greater T3SS gene expression and enhanced virulence. Collectively, these findings reveal the role of phages in impacting EHEC virulence and their potential to affect outbreak strains.
Assuntos
Colífagos/metabolismo , Escherichia coli Êntero-Hemorrágica/efeitos dos fármacos , Escherichia coli Êntero-Hemorrágica/genética , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Proteínas Repressoras/farmacologia , Proteínas Virais Reguladoras e Acessórias/farmacologia , Fatores de Virulência/genética , Animais , Cromossomos Bacterianos/efeitos dos fármacos , Citrobacter rodentium/patogenicidade , Colífagos/genética , Modelos Animais de Doenças , Infecções por Enterobacteriaceae/metabolismo , Infecções por Enterobacteriaceae/patologia , Escherichia coli Êntero-Hemorrágica/patogenicidade , Escherichia coli Êntero-Hemorrágica/virologia , Escherichia coli/genética , Infecções por Escherichia coli/microbiologia , Proteínas de Escherichia coli/genética , Genes Bacterianos/efeitos dos fármacos , Células HeLa , Humanos , Lipídeos , Lisogenia , Camundongos , Camundongos Endogâmicos C3H , Proteínas Repressoras/genética , Toxina Shiga/genética , Fatores de Transcrição , Sistemas de Secreção Tipo III/efeitos dos fármacos , Sistemas de Secreção Tipo III/genética , Sistemas de Secreção Tipo III/metabolismo , Ensaio de Placa Viral , Proteínas Virais Reguladoras e Acessórias/genética , Virulência/efeitos dos fármacos , Virulência/genéticaRESUMO
Pathogenic gut bacteria, such as those comprising the Enterobacteriaceae family, have evolved sophisticated virulence mechanisms, including nutrient and chemical sensing, to escape host defense strategies and produce disease. In this review we describe the mechanisms utilized by the enteric pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 to achieve successful colonization of its mammalian host.