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Congo red medium to distinguish between invasive and non-invasive Escherichia coli pathogenic for poultry
Abstract:
In the course of our molecular studies of virulence factors associated with invasive avian Escherichia coli infections, it was first necessary to distinguish between common E. coli and those that cause septicemia in poultry. We found a direct correlation between the ability of clinical isolates of E. coli to bind Congo red dye (CR) and their ability to cause septicemic infection in chickens. This finding was supported by bacteriological studies of 30 broiler flocks (26 sick and 4 healthy) and by virulence studies in chickens and mice. All 144 isolates of E. coli from internal tissues of diseased birds were determined to be CR-positive (red colonies). Congo-red-positive E. coli colonies were isolated from air sacs, pericardium, liver, lung, joint fluid, and heart blood of chickens with lesions of colisepticemia. In contrast, of 170 E. coli isolates from the poultry house environment and from the trachea and cloaca of healthy birds, more than half were CR-negative (white colonies). No CR-negative (white) E. coli colonies were found in internal organs from birds with typical lesions of colisepticemia. We feel that these preliminary findings suggest that the CR dye binding could be used as a phenotypic marker to distinguish between invasive and noninvasive isolates.
Insights
Avian Escherichia coli (E. coli) invasive strains can be identified by their ability to bind Congo red dye (CR). CR-positive E. coli isolates from diseased chickens indicate septicemia, aiding in distinguishing invasive from noninvasive strains.
Area of Science:
- Veterinary Microbiology
- Bacteriology
- Poultry Pathology
Background:
- Avian infections caused by Escherichia coli (E. coli) pose a significant threat to poultry health.
- Distinguishing between common E. coli and virulent strains causing septicemia is crucial for effective disease management.
Purpose of the Study:
- To investigate the correlation between Congo red dye (CR) binding and the invasiveness of E. coli isolates from poultry.
- To identify a potential phenotypic marker for differentiating invasive E. coli strains in avian infections.
Main Methods:
- Bacteriological analysis of E. coli isolates from 30 broiler flocks (sick and healthy).
- Virulence studies using chickens and mice.
- Phenotypic characterization of E. coli isolates based on Congo red dye binding (CR-positive/red vs. CR-negative/white colonies).
Main Results:
- A direct correlation was observed between CR dye binding and the ability of E. coli to cause septicemic infection in chickens.
- All 144 E. coli isolates from internal tissues of diseased birds were CR-positive.
- CR-negative E. coli isolates were predominantly found in the environment and healthy birds, not in internal organs of septicemic birds.
Conclusions:
- Congo red dye binding serves as a reliable phenotypic marker for distinguishing invasive avian E. coli from noninvasive strains.
- CR-positive E. coli isolates are strongly associated with colisepticemia in poultry.
- This finding can aid in early identification and management of invasive E. coli infections in poultry flocks.
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