Both cause gastroenteritis but are distinct organisms.
Aspects for Study
Natural Life:
Exclusively infects humans, unlike Salmonella which infects animals and humans.
Human-specific, occasionally infects gorillas.
Shigella and E. Coli share high genetic similarity (over 97%).
Clinical Presentation:
Causes bacillary dysentery; differs from amoebic dysentery (hence the term is used to denote its bacterial nature).
Symptoms include:
Blood and mucus in stool.
Severe nausea, vomiting, headaches, and fever.
Contents can lead to dehydration due to lack of intake (not through diarrhea).
Dysenteryi species known for high mortality rates, especially in infants in developing countries (up to 50%).
Laboratory Identification:
Part of the Enterobacteriaceae family.
Non-lactose fermenter: MacConkey agar maintains the original color (no pink).
Confusion with E. Coli due to genetic similarity.
Use of biochemical tests (e.g., MIL tube for motility) and additional confirmatory tests (e.g., agglutination with antiserum).
Virulence Factors:
Very low infectious dose (1 to 10 cells can cause infection).
Type III secretion system:
Acts like a syringe to inject proteins into host cells (enterocytes), leading to cell death and rearrangement of cell architecture to aid bacterial movement.
Treatment:
Ciprofloxacin as a recommended treatment.
Rising concern over multi-drug resistance making treatment more difficult.
Key Points on Treatment and Public Health
Risk of multi-drug resistant strains spreading among populations, complicating treatment.
Importance of tracking outbreaks through laboratory confirmation as a notifiable disease.