Week 4: GI Tract Infections

This week in class we discussed gastrointestinal tract infections and pathogens.  Before identifying pathogens, it is important to know what is considered normal flora in the GI tract.  E. coli, Pseudomonas spp, most other nonfermnters, Enterococcus spp, coagulase negative Staphylococci, and most anaerobes considered to be normal flora in the lower intestinal tract.   Potential pathogens include Helicobactoer pylori, Salmonella, Shigella, Campylobacter spp, VIbrio cholera, Yersinia enterocolitica, enteropathogenic and enterotoxigenic E. coli, S. aureus, and Clostridium difficile.  These bacteria can cause diseases such as gastroenteritis, enteritis, infectious diarrhea, antibiotic associated diarrhea, pseudomembranous colitis, food poisoning, and dysentery. 

In order to cause disease, these bacteria can exhibit different mechanisms of pathogenicity.  Toxin production is one example.  Enterotoxins produced by enterotoxigenic E. coli, VIbrio spp, Clostridium perfringens, and Clostridium difficile cause cells to secrete ions into the lumen of the intestine. Fluids are then secreted in order to maintain osmotic stabilization which results in abdominal cramps.  Cytotoxins disrupt the structure o the individual intestinal epithelial cells causing inflammation and dysentery.  Enterohemorrhagic E. coli and Clostridium difficile secrete cytotoxins.  S. aureus, Bacillus cereus, and Clostridium botulinum secrete neurotoxins which can cause vomiting and flaccid paralysis.  Other mechanisms include invasion and attachment. 

I find it incredibly interesting how these tiny bacteria can secrete such harmful substances that can attack our bodies in such a specific way that can cause such terrible consequences. 

Here is the link to a quiz that you can take to test your knowledge of GI tract infections. 

GI tract Quiz