Previous epidemiological studies have demonstrated a potential link between the serotypes of Yersinia enterocolitica recovered from cattle, sheep and pigs and those isolated from human disease cases. ...Further studies utilizing amplified fragment length polymorphisms have shown a relationship at the genetic level between strains of biotypes 3 and 4 from humans and livestock, and also suggested that some biotype 1A isolates, classically defined as non-pathogenic, are closely related to biotype 3 and 4 isolates. This study sought to understand further the pathogenic potential of Y. enterocolitica isolates from livestock in Great Britain. A range of surrogate in vitro models, such as invasion of epithelial tissue cultures, survival in cultured macrophages and cytokine secretion response, was employed to assess the pathogenicity of 88 strains. The results suggested that all isolates examined were capable of adhering to and invading epithelial cells and of surviving within macrophages. However, the inflammatory response of the infected macrophages differed with the infecting Y. enterocolitica subtype, with the response to pathogenic biotype 3 and 4 isolates different to that observed with biotype 1A isolates, and with the biotype 3 O : 5,27 isolates recovered exclusively from animals. Infections of porcine tissue also suggested the possibility of host-tissue tropism within Y. enterocolitica subtypes.
Intestinal colonization by enteropathogenic and enterohemorrhagic Escherichia coli requires the locus of enterocyte effacement-encoded type III secretion system. We report that NleC and NleD are ...translocated into host cells via this system. Deletion mutants induced attaching and effacing lesions in vitro, while infection of calves or lambs showed that neither gene was required for colonization.
Three
Salmonella enterica serovar Orion var. 15+ isolates of distinct provenance were tested for survival in various stress assays. All were less able to survive desiccation than a virulent
S. ...Enteritidis strain, with levels of survival similar to a rpoS mutant of the
S. Enteritidis strain, whereas one isolate (F3720) was significantly more acid tolerant. The
S. Orion var. 15+ isolates were motile by flagellae and elaborated type-1 and curli-like fimbriae; surface organelles that are considered virulence determinants in Salmonella pathogenesis. Each adhered and invaded HEp-2 tissue culture cells with similar proficiency to the
S. Enteritidis control but were significantly less virulent than
S. Enteritidis in the one-day-old and seven-day-old chick model. Given an oral dose of 1 × 10
3 cfu to one-day-old chicken,
S. Orion var. 15+ isolates colonised 25% of liver and spleens examined at 24 h whereas
S. Enteritidis colonised 100% of organs by the same with the same dose. Given an oral dose of 1 × 10
7 cfu at seven-day old,
S. Orion var. 15+ failed to colonise livers and spleens in any bird examined at 24 h whereas
S. Enteritidis colonised 50% of organs by the same with the same dose. Based on the number of internal organs colonised, one of the three
S. Orion var. 15+ isolates tested (strain F3720) was significantly more invasive than the other two (B1 and B7). Also, strain F3720 was shed less than either B1 or B7 supporting the concept that there may be an inverse relationship between the ability to colonise deep tissues and to persist in the gut. These data are discussed in the light that
S. Orion var. 15+ is associated with sporadic outbreaks of human infection rather than epidemics.
Shiga toxin (Stx)-positive Escherichia coli O157:H7 readily colonize and persist in specific-pathogen-free (SPF) chicks, and we have shown that an Stx-negative E. coli O157:H7 isolate (NCTC12900) ...readily colonizes SPF chicks for up to 169 days after oral inoculation at 1 day of age. However, the role of intimin in the persistent colonization of poultry remains unclear. Thus, to investigate the role of intimin and flagella, which is a known factor in the persistence of non-O157 E. coli in poultry, isogenic single- and double-intimin and aflagellar mutants were constructed in E. coli O157:H7 isolate NCTC12900. These mutants were used to inoculate (10⁵ CFU) 1-day-old SPF chicks. In general, significant attenuation of the aflagellate and intimin-aflagellate mutants, but not the intimin mutant, was noted at similar time points between 22 and 92 days after inoculation. The intimin-deficient mutant was still being shed at the end of the experiment, which was 211 days after inoculation, 84 days more than the wild type. Shedding of the aflagellar and intimin-aflagellar mutants ceased 99 and 113 days after inoculation, respectively. Histological analysis of gastrointestinal tissues from inoculated birds gave no evidence for true microcolony formation by NCTC12900 or intimin and aflagellar mutants to epithelial cells. However, NCTC12900 mutant derivatives associated with the mucosa were observed as individual cells and/or as large aggregates. Association with luminal contents was also noted. These data suggest that O157 organisms do not require intimin for the persistent colonization of chickens, whereas flagella do play a role in this process.
Fish often fail to make detectable serum antibody after infection by virus. The object of this work was to develop an antibody forming cell assay to determine if such seronegative fish were making ...antibody. Inactivated Newcastle disease virus was used as the model antigen in 26 fish, 12 koi carp (Cyprinus carpioL.×Carassius carpioL.) and 14 common goldfish (Carassius auratusL.). Using the same immunoperoxidase detection systems for the assay of serum antibody and antibody forming cells in their mesonephros, four of the 26 fish produced serum antibody compared to 22 of the 26 fish producing antibody forming cells. Fish therefore make antibody more frequently than is determined by serology.
Intimin and EspA proteins are virulence factors expressed by attaching and effacing
Escherichia coli (AEEC) such as enteropathogenic and enterohaemorrhagic
E. coli. The EspA protein makes up a ...filament structure forming part of the type III secretion system (TTSS) that delivers effector proteins to the host epithelial cell. Bacterial surface displayed intimin interacts with translocated intimin receptor in the host cell membrane leading to intimate attachment of the bacterium and subsequent attaching and effacing lesions. Here, we have assessed the use of recombinant monoclonal antibodies against
E. coli O157:H7 EspA and intimin for the disruption of AEEC interaction with the host cell. Anti-γ intimin antibodies did not reduce either adhesion of
E. coli O157:H7 to host cell mono-layers or subsequent host cell actin rearrangement. Anti-EspA antibodies similarly had no effect on bacterial adhesion however they had a marked effect upon
E. coli O157:H7-induced host cell actin rearrangement, where both monoclonal and polyclonal antibodies completely blocked cytoskeletal changes within the host cell. Furthermore, these anti-EspA antibodies were shown to reduce actin rearrangement induced by some but not all other AEEC serotypes tested. Both polyclonal and monoclonal antibodies could be used to label
E. coli O157 EspA filaments and these immunoreagents did not inhibit the formation of such filaments. This is the first report of monoclonal antibodies to EspA capable of disrupting the TTSS function of
E. coli O157:H7.
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