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Septicaemic Escherichia coli and experimental infection of calves
Abstract:
Three strains of Escherichia coli with a common surface antigen, 31a, capable of adhering to calf enterocytes in vitro were compared to reference strains of septicaemic E. coli (RVC 330 and vir E. coli). The surface antigen 31a was present in the RVC 330 reference strain. E. coli vir had a surface antigen which was not present in E. coli 31a or E. coli RVC 330. The RVC 330 and vir reference strains also adhered to calf enterocytes in vitro. Oral infection of calves not receiving colostrum with E. coli 31a was generally followed by septicaemia and death in less than 48 h. Post-mortem examination revealed pneumonia and oedema of the kidneys and gall bladder. Oral infection of calves receiving colostrum had no effect, but intravenous inoculation produced arthritis within 15 days. The comparison of these results with those previously described by other workers did not lead to the identification of pathognomonic characteristics, which could be clearly correlated with properties specific to E. coli 31a. It is suggested that, like ColV and vir, antigen 31a may be a virulence marker for certain strains of bovine septicaemic E. coli. Furthermore, the 31a antigen appears to be carried on a plasmid.
Insights
Escherichia coli strain 31a, a bovine pathogen, causes septicaemia and death in calves lacking colostrum. This antigen may indicate virulence in bovine septicaemic E. coli, potentially plasmid-mediated.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Escherichia coli (E. coli) is a significant cause of bovine diseases.
- Certain E. coli strains possess surface antigens that contribute to virulence and disease manifestation.
- Understanding these virulence factors is crucial for developing effective control strategies in cattle.
Purpose of the Study:
- To investigate the pathogenic potential of a specific E. coli strain (31a) expressing a common surface antigen.
- To compare the adherence and virulence characteristics of E. coli 31a with reference septicaemic E. coli strains.
- To determine if the 31a antigen serves as a virulence marker in bovine septicaemic E. coli.
Main Methods:
- In vitro adherence assays of E. coli strains to calf enterocytes.
- Oral and intravenous inoculation of E. coli 31a into colostrum-deprived and colostrum-fed calves.
- Clinical and post-mortem examinations of infected calves.
- Comparison of findings with known virulence factors like ColV and vir.
Main Results:
- E. coli 31a adhered to calf enterocytes in vitro and caused septicaemia, pneumonia, and death in colostrum-deprived calves within 48 hours.
- Calves receiving colostrum were protected from oral E. coli 31a infection, but intravenous inoculation led to arthritis.
- The 31a surface antigen was also found in a reference septicaemic E. coli strain (RVC 330).
Conclusions:
- The 31a antigen is a potential virulence marker for bovine septicaemic E. coli, similar to ColV and vir.
- The 31a antigen is likely carried on a plasmid, suggesting a genetic basis for its role in virulence.
- Further research is needed to fully elucidate the role of antigen 31a in E. coli pathogenesis in cattle.