Bacterial Pathogens: Escherichia coli

Bacterial Pathogens: Escherichia coli

• Learning Outcomes:
  • Introduction to genera within Enterobacteriaceae
  • Different E. coli types causing various diseases
  • Enterotoxigenic E. coli (ETEC) causes gastrointestinal disease; producing heat-labile toxin (LT) and/or heat-stable toxin (ST)
  • E. coli (APEC) causing systemic disease in poultry
  • E. coli strains causing urinary tract infections (UTIs), especially in cats and dogs
  • Enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC) causing gastrointestinal infections, injecting proteins into host cells using a type 3 secretion system. EHEC pose a zoonotic threat from ruminants.

Enterobacteriaceae

• Majority of bacteria in the mammalian gastrointestinal tract are obligate anaerobes (e.g., Bacteroides, Fusobacterium)
• Enterobacteriaceae are a family of bacteria associated with the gastrointestinal tract. They are important pathogens (e.g., Shigella, Salmonella, Yersinia, Klebsiella, and Proteus).
• Many strains contain antibiotic resistance genes, which is a significant problem.
• Gram-negative, non-spore-forming rods, facultative anaerobes
• Motility often via peritrichous flagella.
• Simple nutrient media growth.
• Lack of cytochrome C (cytochrome oxidase).
• Classified based on lactose, glucose, motility, and urease production

E. coli Characteristics

• Colonizes most mammals shortly after birth, displacing other strains.
• Commensals, causing no disease or causing intestinal /extra-intestinal disease.
• Classified by somatic antigen O, capsule antigen K, and flagellar antigen H

E. coli Infections in Animals

• Colibacillary diarrhea: affects calves, lambs, and piglets; often involves ETEC binding to intestinal mucosa, producing LT and ST toxins.
• Systemic colibacillosis: affects multiple animals (calves, lambs, poultry) involving invasion from GI tract. More likely in colostrum-deprived animals
• Colibacillary toxaemia: seen in pigs; related to VTEC producing E. coli, specifically VT2e+. Also causes 'shock in weaner syndrome' and 'haemorrhagic colitis'.
• Urinary tract infections (UTIs): common in cats, dogs, and humans (UPEC strains).
• Environmental mastitis: common but usually mild

E. coli Virulence Factors and Types

• Different strains carry different virulence factors affecting disease types (e.g., toxins, adhesins)
• Enterotoxigenic E. coli (ETEC) cause diarrhea via toxins (LT & ST), impacting ion transport in the gut.
• Avian pathogenic E. coli (APEC) causes avian colibacillosis which leads to peritonitis, salpingitis, perihepatitis, pericarditis, and sepsis in poultry
• Uropathogenic E. coli (UPEC) involved in urinary tract infections, using fimbriae/ pili for adherence.
• Enteropathogenic E. coli (EPEC) leading to A/E lesions, secreting effector proteins altering cell signalling.
• Verotoxigenic/Shiga-toxin producing E. coli (VTEC/STEC) produce Shiga toxin (STx) that damages capillaries often leading to kidney and brain damage. VTEC often associated with contaminated meats/petting farms.

Summary of E. coli Enteric Infections

• Oral Infection (faecal-oral cycle): Colonization of intestinal mucosa requires adherence factors.
• Toxin Release: pathology related to toxin action, ETEC.
• Fluid Electrolyte Imbalance: (diarrhea; can be fatal) and brush border and mucosal damage from intimate bacterial association/T3S factors.
• Systemic Infection: Via 'permeable' mucosa, in very young animals (APEC). Leads to acute disease, fever, and endotoxic shock, or death.

Explore the fascinating world of Escherichia coli and its various pathogenic strains. This quiz dives into the role of E. coli in gastrointestinal diseases, urinary tract infections in animals, and the implications of different toxin types. Gain a comprehensive understanding of Enterobacteriaceae and the significance of these bacteria in both human and animal health.