Pathogenesis Of Colibacillosis Research Articles

Aerosol is the optimal route of respiratory tract infection to induce pathological lesions of colibacillosis by a lux-tagged avian pathogenic Escherichia coli in chickens

ABSTRACT Pathogenesis of colibacillosis caused by avian pathogenic Escherichia coli (APEC) in poultry is unclear and experimental studies reveal substantial inconsistency. In this study, the impact of three infection routes differing in the site of deposition of inoculum in the respiratory tract, were investigated. Two-weeks-old chickens were infected with a lux-tagged APEC strain via aerosol, intranasally or intratracheally, and sequentially sampled along with uninfected birds. At 1 and 3 days post infection (dpi), liver or spleen to body-weight ratios in all infected groups were significantly higher than in negative control, while at 7 dpi, such differences were significant in both organs in the aerosol-infected group. The infection-strain colonized tracheas and lungs in infected birds at 1 dpi and persisted until 7 dpi. Among infected groups, in lungs, bacterial load at 1 dpi was significantly lower in intranasally-inoculated birds. Histology revealed that, independent of infection route, lesions were mostly seen in the lower respiratory organs (lungs and air sacs) characterized by bronchitis/pneumonia and airsacculitis. Birds infected via aerosol showed the highest mean lesion score in lungs while intranasal application caused the mildest pathological changes, and difference between the two groups was significant at 1 dpi. In spleen, heterophilic infiltrations were prominent in affected birds. Interestingly, tracheas were pathologically unaffected. Altogether, the results demonstrated the importance of infection route, with aerosol being the most suitable to induce pathological lesions of colibacillosis without predisposing factors. Furthermore, the lux-tagged APEC strain was discriminated from native isolates enabling exact differentiation and enumeration. RESEARCH HIGHLIGHTS Lux-tagged APEC strain was used for infection to differentiate from native E. coli. Pathologically, lungs, air sacs and spleen but not trachea were affected. The route of infection strongly impacts the pathological outcome with APEC. The infection with APEC via aerosol caused the most severe lesions in chickens.

Co-infection of Chicken Layers With Histomonas meleagridis and Avian Pathogenic Escherichia coli Is Associated With Dysbiosis, Cecal Colonization and Translocation of the Bacteria From the Gut Lumen.

Histomonosis in chickens often appears together with colibacillosis in the field. Thus, we have experimentally investigated consequences of the co-infection of birds with Histomonas meleagridis and avian pathogenic Escherichia coli (APEC) on the pathology, host microbiota and bacterial translocation from the gut. Commercial chicken layers were infected via oral and cloacal routes with lux-tagged APEC with or without H. meleagridis whereas negative controls were left uninfected. Except one bird, which died due to colibacillosis, no clinical signs were recorded in birds infected with bioluminescence lux gene tagged E. coli. In co-infected birds, depression and ruffled feathers were observed in 4 birds and average body weight gain significantly decreased. Typhlitis caused by H. meleagridis was present only in co-infected birds, which also had pronounced microscopic lesions in systemic organs such as liver, heart and spleen. The 16S rRNA gene amplicon sequencing showed that in co-infected birds, corresponding to the severity of cecal lesions, microbial species richness and diversity in caeca greatly decreased and the abundance of the Escherichia group, Helicobacter and Bacteroides was relatively higher with a reduction of commensals. Most of the shared Amplicon Sequencing Variants between cecum and blood in co-infected birds belonged to Pseudomonas, Staphylococcus, and members of Enterobacteriaceae while those assigned as Lactobacillus and members of Ruminococcaceae and Lachnospiraceae were found mainly in negative controls. In infected birds, E. coli in the cecal lumen penetrated into deeper layers, a phenomenon noticed with higher incidence in the dead and co-infected birds. Furthermore, numbers of lux-tagged E. coli in caeca were significantly higher at every sampling date in co-infected birds. Altogether, infection of layers with H. meleagridis and E. coli resulted in more severe pathological changes, dramatic shift in the cecal mucosa-associated microbiota, higher tissue colonization of pathogenic bacteria such as avian pathogenic E. coli in the gut and increased penetration of E. coli from the cecal lumen toward peritoneum. This study provides novel insights into the parasite-bacteria interaction in vivo highlighting the role of H. meleagridis to support E. coli in the pathogenesis of colibacillosis in chickens.

Avian colibacillosis: still many black holes.

Avian pathogenic Escherichia coli (APEC) strains cause severe respiratory and systemic diseases, threatening food security and avian welfare worldwide. Intensification of poultry production and the quick expansion of free-range production systems will increase the incidence of colibacillosis through greater exposure of birds to pathogens and stress. Therapy is mainly based on antibiotherapy and current vaccines have poor efficacy. Serotyping remains the most frequently used diagnostic method, only allowing the identification of a limited number of APEC strains. Several studies have demonstrated that the most common virulence factors studied in APEC are all rarely present in the same isolate, showing that APEC strains constitute a heterogeneous group. Different isolates may harbor different associations of virulence factors, each one able to induce colibacillosis. Despite its economical relevance, pathogenesis of colibacillosis is poorly understood. Our knowledge on the host response to APEC is based on very descriptive studies, mostly restricted to bacteriological and histopathological analysis of infected organs such as lungs. Furthermore, only a small number of APEC isolates have been used in experimental studies. In the present review, we discuss current knowledge on APEC diversity and virulence, including host response to infection and the associated inflammatory response with a focus on pulmonary colibacillosis.

PapMutant of Avian Pathogenic Escherichia coli O1, an O1:K1:H7 Strain, Is AttenuatedIn Vivo

P or Pap fimbriae of avian pathogenic Escherichia coli (APEC) have previously been shown to be important in the pathogenesis of colibacillosis. However, no study has been done to ascertain the effects of deletion of the genes responsible for P fimbrial biogenesis on APEC's in vitro and/or in vivo characteristics. In the present study, all 11 genes of the pap gene cluster were deleted from APEC O1, the recently sequenced APEC strain, and the wild-type strain was compared to the mutant (ECPAP1) for changes in certain phenotypic characteristics and virulence for chickens. Both APEC O1 and ECPAP1 demonstrated mannose-sensitive agglutination of guinea pig and chicken erythrocytes, but only APEC O1 demonstrated mannose-resistant hemagglutination and P-receptor binding properties. The in vivo experiments revealed that ECPAP1 was markedly attenuated as compared to its wild-type strain APEC O1. These findings suggest that P fimbriae are involved in the virulence of APEC O1.

Avian pathogenic Escherichia coli bind fibronectin and laminin

Avian colisepticemia frequently occurs after respiratory tract damage, the primary site for infection allows bacteria to encounter an exposed basement membrane, where laminin and fibronectin are important components. We investigated the ability of an isolate of avian pathogenic Escherichia coli to bind fibronectin and laminin. Using Far-western dot blot analysis, we demonstrated the ability of this microorganism to bind basement membrane proteins fibronectin and laminin. Results from an ELISA-based approach indicate that the binding to these membrane proteins was bacterial-dose dependent. Furthermore, two specific E. coli polypeptides, of 32 kDa and 130 kDa, reacted with laminin and fibronectin, respectively. Further evaluation of these potential bacterial adhesins may provide insights into the pathogenesis of colibacillosis.

Rapid Detection of Virulence-Associated Genes in Avian Pathogenic Escherichia coli by Multiplex Polymerase Chain Reaction

Based on recently published prevalence data of virulence-associated factors in avian pathogenic Escherichia coli (APEC) and their roles in the pathogenesis of colibacillosis, we developed a multiplex polymerase chain reaction (PCR) as a molecular tool supplementing current diagnostic schemes that mainly rely on serological examination of strains isolated from diseased birds. Multiple isolates of E. coli from clinical cases of colibacillosis known to possess different combinations of eight genes were used as sources of template DNA to develop the multiplex PCR protocol, targeting genes for P-fimbriae (papC), aerobactin (iucD), iron-repressible protein (irp2), temperature-sensitive hemagglutinin (tsh), vacuolating autotransporter toxin (vat), enteroaggregative toxin (astA), increased serum survival protein (iss), and colicin V plasmid operon genes (cva/cvi). In order to verify the usefulness of this diagnostic tool, E. coli strains isolated from fecal samples of clinically healthy chickens were also included in this study, as were uropathogenic (UPEC), necrotoxigenic, and diarrhegenic E. coli strains. The application of the multiplex PCR protocol to 14 E. coli strains isolated from septicemic poultry showed that these strains harbored four to eight of the genes mentioned above. In contrast, those isolates that have been shown to be nonpathogenic for 5-wk-old chickens possessed either none or, at most, three of these genes. We found only one enterohemorrhagic (EHEC), one enteropathogenic (EPEC), and two enterotoxic (ETEC) E. coli strains positive for irp2, and another two ETEC strains positive for astA. As expected, UPEC isolates yielded different combinations of the genes iss, papC, iucD, irp2, and a sequence similar to vat. However, neither the colicin V operon genes cva/cvi nor tsh were amplified in UPEC isolates. The multiplex PCR results were compared with those obtained by DNA-DNA-hybridization analyses to validate the specificity of oligonucleotide primers, and the protocol was concluded to be a useful, sensitive, and rapid assay system to detect avian pathogenic E. coli and differentiate them from nonpathogenic strains and those belonging to other pathotypes.

Lesions and Bacteriological Findings in Colibacillosis of Calves

SUMMARY This paper records the gross lesions and the histological and bacteriological findings in a series of 25 calves, of which some died from colibacillosis and others were killed either in extremis or immediately after diarrhoea was first observed. The results of an experiment to determine the effects of post-mortem autolysis on the interpretation of the pathological findings are also recorded. The lesions included pulmonary oedema, oedema in the abomasum and enteritis which varied in its severity and distribution. The E. coli strains isolated from the majority of the calves were identified as serotypes 015 : K?, 026 : K60(B), 035 : K? and 078 : K80(B) but some calves yielded strains which failed to type. Nine of the calves were septicaemic and in six the E. coli were confined to the intestine. In the remainder, E. coli were isolated from the intestine and some other organs, principally the spleen. These findings are discussed in relation to the role of endotoxin in the pathogenesis of colibacillosis.

Dermal Reactions to Endotoxins in Calves: their Significance in the Pathogenesis of Colibacillosis

Summary Newly-horn colostrum-deprived calves and colostrum-fed calves of 3–7 and 7–14 days old were subjected to intradermal tests with endotoxin preparations from E. coli serotypes 078: K 80(B) and 0115:K?. (RVC58) which are common pathogens of calves, and from E. coli 0138: K81 (B) and S. gallinarum. Dermal reactivity to the endotoxins from the 2 E. coli serotypes commonly pathogenic for calves was in general more marked than that to the other 2 endotoxins. Also, a correlation was observed in colostrum-deprived calves between the dermal reactivity of the calves and their sensitivity to intravenous challenge with endotoxin. These findings are discussed in relation to the possible role of hypersensitivity and anaphylaxis in the pathogenesis of colibacillosis.

Anaphylactic Shock to Escherichia coli Endotoxin in Calves

Summary Calves were subjected to active, passive and reversed passive anaphylactic shock using E. coli endotoxin. Inactive and passive anaphylaxis, the severity of the shock that developed in response to a given dose of endotoxin was related to the degree of sensitisation. Castro-intestinal lesions were prominent in calves that showed the most protracted signs of shock and the significance of this finding is discussed in relation to the pathogenesis of colibacillosis.

The Effects of Escherichia coli Endotoxin in Calves

Summary Varied doses of E. coli endotoxin were administered to calves by intravenous, subcutaneous and oral routes. The dosage necessary to produce clinical signs and death differed considerably in individual calves. Susceptibility of calves to E. coli endotoxin did not correlate directly with the presence or absence of circulating antibodies. The gross lesions and histological fadings resembled those which occur in natural and experimental colibacillosis, and bore a close resemblance to those described in calves in association with anaphylactic shock. It is postulated that hypersensitivity and anaphylaxis may play a part in the pathogenesis of colibacillosis in calves.