Enterobacteriaceae Family

  • Definition: Known as enterics, this family contains some of the most pathogenic organisms involved in intestinal infections.

  • Characteristics:

    • Gram-negative straight rods, non-spore forming.

    • Ubiquitous in soil, water, and food sources (fruits, vegetables).

    • All members of the family ferment glucose, are catalase positive but oxidase negative.

    • They are often motile with flagella and not nutritionally fastidious.

    • They reduce nitrate to nitrite.

Pathogenicity of Enterobacteriaceae

  • Pathogens categorized into two groups:

    • Frank Pathogens: Cause disease in healthy individuals. Major contributors to diarrhea and intestinal diseases globally.

    • Opportunistic Pathogens: Normally part of flora but can cause infections when the host is compromised.

  • Major Pathogenic Genera: Includes Salmonella, Shigella, Yersinia, and some Escherichia species.

Disease Mechanisms

  1. Diarrhea: Liquid or soft stool characterizing frequent excretion.

  2. Dysentery: Characterized by bloody, mucus-filled stools post frequent watery stools, often accompanied by abdominal pain and fever.

  3. Enteritis: Inflammation of the intestine, linked with gastrointestinal symptoms.

  4. Gastroenteritis: Involves both intestinal and stomach inflammation leading to symptoms like vomiting and diarrhea.

  5. Enteric Fever: Acute illness presenting with fever, headache, and abdominal pain, sometimes involving bacteremia.

Enteroinvasive E. coli (EIEC)

  • Causes dysentery-like symptoms without causing bloody diarrhea but may result in pus-filled stools.

  • Invasive, can penetrate intestinal cells leading to severe inflammation and discomfort.

Enteropathogenic E. coli (EPEC)

  • Commonly found in childhood diarrhea outbreaks, especially in day care settings. Adheres to intestinal cells and destroys microvilli without invading.

Enterotoxigenic E. coli (ETEC)

  • Known as traveler's diarrhea; caused by contaminated food or water, leading to severe, watery diarrhea without blood.

  • High infectious dose required for symptoms to manifest, lasting typically 1-5 days.

Enterohemorrhagic E. coli (EHEC)

  • An infectious strain defined by its strain type, notably E. coli O157:H7.

  • Associated with severe illness and can cause hemolytic uremic syndrome, potentially leading to kidney failure and death.

  • Transmission: Often linked to processed meats, unpasteurized dairy, or contaminated water sources.

General Notes on E. coli as Pathogen

  • Strains can be opportunistic or frank pathogens, depending on the context of infection and host condition.

  • Focus on safety measures in food preparation to prevent outbreaks of severe strains in casual dining settings.

Conclusion

  • Understanding the pathogenic characteristics of Enterobacteriaceae is key for diagnosis, treatment, and preventive measures in public health, especially concerning diarrheal diseases in children and individuals with compromised immune systems.