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.