Colibacillosis

Escherichia coli is a part of the normal microflora of the human body, and also inhabits the intestinal tracts of other mammals. However, some E. coli pathotypes have acquired various putative virulence factors (VFs) from their environment.

Pathogenic E. coli strains are classified into six well-described categories (Kaper et al, 2004):

1. Enteropathogenic E. coli (EPEC)
2. Shiga toxin-producing E. coli (STEC)
3. Enterotoxigenic E. coli (ETEC)
4. Enteroinvasive E. coli (EIEC)
5. Enteroaggregative E. coli (EAEC)
6. Diffusely adherent E. coli (DAEC)

Enterotoxins produced by enterotoxigenic E. coli strains include heat-labile enterotoxin (LT), and /or heat-stable enterotoxins STa (STI) or STb (STII). These organisms also produce fimbrial adhesins that mediate the adherence of the bacterium to the mucosal surface. The fimbriae produced include K88, K99, 987P, F41 and F18. Some E. coli strains produce a Shiga toxin (Stx2e) and maybe cause edema disease in addition to post-weaning diarrhea.

Some E. coli strains produce no toxins, but efface the microvilli of the epithelial cells to which they attach (Taylor, 2013). Porcine attaching-effacing E. coli strains are known as enteropathogenic E. coli (EPEC). It is important to identify the virulence factors produced by ETEC or EPEC strains for many E. coli isolated from animals are nonpathogenic.nary tract infection now is thought of associated with E. coli colonization.

It has been suggested that the continuous use of antibiotics may contribute to a reservoir of drug-resistant bacteria which may be capable of transferring their resistance to pathogenic bacteria in both animals and humans (Han et al, 2007). As the incidence of carbapenem-resistant Enterobacteriaceae increased worldwide, polymyxins have been adopted as the last line of defense against Gram-negative bacterial infections (Liu et al, 2016). Resistance to polymyxins mainly depends on modification of lipopolysaccharide (LPS), which is often chromosomally mediated (Olaitan et al, 2014).

The principles of preventing an outbreak of colibacillosis revolve around hygiene and management factors aimed at reducing the buildup of pathogens and spread of infection , and establishing and maintaining piglet and sow immunity.

Piglets receive maternal antibodies specific to the E. coli in the immediate environment through colostrum, but only if the mother has been exposed to that environment. The degree of exposure to infection at birth and the immunity acquired through colostrum will determine whether clinical disease occurs (Taylor, 2013).

Antibiotics commonly used worldwide represent a relatively efficient way to eliminate infectious pathogens (Philips et al, 2004). Alternatives, such as organic acids or phytogenics, with antimicrobial effects have become increasingly important because of many countries banning the use of antibiotics to control bacterial infections in swine (Turner et al, 2001; Thacker, 2013).

Adapted from Taylor, 2013

• Animal keeper, stock person and veterinary hygiene
• Move and re-bed farrowing huts on clean ground after every litter
• Burn and remove old beds from paddocks
• Move farrowing site annually and keep stocking rate low
• Clean and disinfect equipment (especially important if pigs are housed), using appropriate detergents and disinfectants. Ensure that accommodation is dry before pigs are reintroduced

• Help sows to create and maintain a level, dry farrowing bed
• Add straw in small amounts frequently, in particular in wetter weather
• Avoid gaps around the base of the hut that cause drafts
• Carefully control sow feed levels, decreasing feed level by up to 0.5 – 1 kg per day four to five days pre-farrowing, to avoid udder edema
• Ensure that piglets are kept at the correct temperature, as chilling is a trigger for the disease 

• Expose in-pig gilts to farrowing beds and piglet feces
• Foster piglets only after that have taken colostrum
• Consider using E. coli vaccine for herds with persistent problems

• Low protein diets
• Organic acids or acidifiers
• Zine oxide
• Essential oils or phytogenic feed additives
• Eucalyptus oil-medium chain fatty acids

Organic acids are used to combat pathogenic bacteria in animals and in animal feed since decades. Using acid combinations instead of single acids may be more beneficial due to a broader spectrum of activity (Namkung et al., 2003).

Organic acids are well known to improve growth performance and modulate intestinal microbiota of pigs (Piva et al., 2002). Organic acids lower the pH in feed and the gastrointestinal tract, creating unfavorable conditions for potentially harmful bacteria (Freitag, 2007). In their undissociated form, they can penetrate the bacterial cell and stop the bacterial growth or may even kill the bacterial cell (Stonerock, 2007).

Organic acid-based feed additives, with or without the use of antimicrobial growth promoters (AGPs), can help alleviate the negative effects of E. coli infection in pigs. Optimizing the activity of organic acids with phytochemicals and permeabilizing substances is a possibility to strengthen the activity of organic acids against Gram-negative bacteria like E. coli and Salmonella.

Addition of phytochemical cynnamaldehyde (CA) inhibits the so called FtsZ protein and plays a major role in the cell division of potentially harmful bacteria (Domadia et al., 2007). Under normal circumstances, FtsZ polymerises into filaments, which assemble at the place within the cell, where the cell division takes place. There they form into a polymeric structure known as the ‚Z-ring‘on the inner membrane in the middle of the cell, which is responsible for the cell‘s division. CA inhibits not only the formation of FtsZ into filaments, but also inhibits essential processes involved in the Z-ring formation and its function and thus the cell division. This results in a reduction of the bacterial load, within the gastrointestinal tract.