MICROM 442 Final: Shigella
Document Summary
Groups a, b, c cannot be distinguished biochemically. S. dysenteriae and s. flexineri cause more severe disease. S. sonnei disease is milder watery diarrhea instead of dysentery. Organism can be shed in stool for up to 6 weeks after infection. In us, person-to-person spread is most common mode of transmission. S sonnei and s, flexneri most common causes. Most cases occur in institutions or day care centers. In developing world, contaminated food sources commonly involved in transmission. S. dydenteriae is the most common cause of disease. Acid tolerant able to survive passage through the stomach. Invade cells of the large bowel leading to ulceration and abscesses. Virulence plasmid harbors invasion loci and type iii secretion apparatus. Strains that have lost virulence plasmids are avirulent. Disease progresses as bacteria spreads directly between cells. Also shields the bacteria from the immune system. Minor contributions to disease except for shiga toxin of s. dysenteriae.
