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Escherichia Coli

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Escherichia coli (E. coli) 

Escherichia coli (E. coli) is a gram-negative, rod-shaped bacterium commonly found in the intestines of humans and animals. It was first identified by Theodor Escherich in 1885. While most strains are harmless or even beneficial, some can cause illness ranging from mild to severe. Young children, the elderly, and immunocompromised individuals, are at higher risk for severe E. coli infections 

Characteristics and Habitat 

E.coli are rod-shaped, gram-negative bacteria that can be found in:

  • Intestinal tracts of humans and animals 
  • Soil and water 
  • Food products 
  • Healthcare environments 

As facultative anaerobes, they can survive with or without oxygen. Many strains are motile, using flagella for movement. 

Role in Human Health 

In the gut microbiome, E. coli aids digestion, produces vitamins, and helps protect against harmful bacteria. It ferments undigested carbohydrates, producing beneficial short-chain fatty acids. 

Pathogenic Strains 

Several E. coli strains can cause illness: 

  • Enterotoxigenic (ETEC): Causes traveler’s diarrhea 
  • Enterohemorrhagic (EHEC)/Shiga toxin-producing (STEC): Can lead to severe complications like haemolytic uremic syndrome 
  • Enteroinvasive (EIEC): Causes dysentery-like symptoms 
  • Enteropathogenic E. coli (EPEC): Associated with diarrhea in infants. 

Transmission

E.coli spreads through:

  • Contaminated food (especially undercooked ground beef and raw produce) 
  • Contaminated water 
  • Person-to-person contact 
  • Animal contact 
  • Contaminated environments 

Illness Mechanisms:

E.coli can evade host defences and develop antibiotic resistance. It is the leading cause of uncomplicated UTIs and can result in severe conditions like haemolytic uremic syndrome (HUS) due to Shiga toxins, a potentially life-threatening condition affecting the kidneys.

Symptoms 

Intestinal illness:  

  • Diarrhea (watery or bloody), abdominal pain, fever, dehydration 

Extraintestinal infections: 

  • UTIs: Urinary frequency, pain, fever 
  • Pneumonia: Cough, fever, shortness of breath 
  • Meningitis (in newborns): Fever, irritability, rapid breathing 
  • Sepsis: Fever, chills, rapid heart rate, confusion 

Diagnosis  

Diagnosis involves assessing clinical symptoms and may include culturing blood, urine, or sputum.  

Treatment  

Treatment generally focuses on managing symptoms and preventing dehydration.  

Intestinal Illness: Managed with rehydration; antibiotics are typically avoided due to the risk of resistance. In severe cases, antibiotics may be considered, but not for suspected EHEC/STEC infections to prevent HUS. 

Extraintestinal Infections: Treatment depends on the site and severity of the infection, with antibiotics prescribed as necessary based on culture results. 

Antibiotic resistance, particularly with extended-spectrum beta-lactamase (ESBL) and carbapenemase-producing strains, complicates treatment. 

Prevention 

To reduce E. coli infection risk: 

  • Practice good hygiene, especially handwashing 
  • Cook meats thoroughly 
  • Avoid unpasteurized dairy and juices 
  • Wash produce before eating 
  • Drink treated or boiled water when traveling 
  • Clean/disinfect environments 

References