Escherichia coli has long been underestimated, traditionally considered as an environmental and opportunistic agent in immunocompromised animals, or as a complicating agent in viral infections in poultry.
However, for some years now, it has been considered a primary pathogen causing multi-million dollar losses worldwide, although it is difficult to estimate its real impact.
The economic impact has been related to a decrease in growth and seizures in the broiler processing plant, low production in laying hens, as well as an increase in mortality. Even when rearing conditions are inadequate, E. coli infections compromise bird welfare.
Escherichia coli was discovered in 1886 by Theodor Escherich, who found this microorganism in the feces of children. Since then, it has been considered a normal inhabitant of the intestinal biota of various animals and humans and plays a very important role in the digestion and regulation of the intestinal microbiota.
This bacterium belongs to the family Enterobacteriaceae, is gram negative, facultative anaerobic; it grows at temperatures between 15°C and 45°C, does not produce spores, can be motile or immotile and is normally a lactose fermenter, although there are strains that are not able to use this substrate.
This microorganism has been classified into three main groups:
Commensal strain.
Intestinal pathogenic strains (InPEC) or diarrheogenic strains.
Extraintestinal pathogenic strains (ExPEC), depending on their pathogenic potential.
The latter group includes uropathogenic strains (UPEC), those causing bacterial meningitis (BMEC) and those causing infections in birds known as avian pathogens (APEC).
BIOCHEMICAL IDENTIFICATION
Traditionally, its identification in the laboratory is based on its biochemical properties (Figure 1) since sophisticated equipment is not required, however, given the diversity of this bacterium it is not sufficient to know the virulence of the strain in question, nor is it possible to differentiate between pathotypes.
Therefore, other methods are required to elucidate whether a particular strain has the pathogenic capacity to cause an infectious problem in a flock.
Figure 1. Short biochemistry (from left to right) classic of an E. coli strain, TSI, citrate, LIA, urea and SIM
SEROTYPING
Serotyping has been used as a very useful tool for epidemiological purposes. In the case of this bacterium, the Kauffman-White scheme is used, similar to that of Salmonella, which is based on the identif...
