Microbiology - chapter 9 - The enterics Flashcards
Two important biochemical properties that are used to classify enterics?
1 The ability to ferment lactose an convert it into gas and acid.
2 The production of H2S, ability to hydrolyze urea, liquefy gelatin and decarboxylate specific amino acids.
Four main groups of enterics?
1 Enterobacteriaceae
2 Vibrionaceae
3 Pseudomonadaceae
4 Bacteroidaceae
The 3 major surface antigens of the enterics?
1 O antigen - the most external LPS component of gram-negs.
2 K antigen - (K)capsule that covers the O antigen.
3 H antigen - subunit of bacterial flagella(only in motile bugs!)
The enterics can cause diarrhea. Describe 3 factors that alter the clinical manifestations of this “poopy” disease.
1 No cell invasion - diarrhea caused by eotoxins released in GI tract = watery diarrhea without systemic symptoms.
2 Invasion of intestinal epithelial cells - bacterial toxins destroy GI epithelium which result in systemic immune response = WBCs & RBCs in stool + fever.
3 Invasion of lymph nodes and blood stream - abdominal pain, WBCs and RBCs in stool. Systemic symptoms of fever, headache and elevated white count.
Normal nonpathogenic Escherichia coli + virulence factors =
= DISEASE. The normal GI flora can, due to exchange of DNA among the enterics, aquire virulence factors that makes them pathogenic.
Escherichia coli: four virulence factors?
1 Mucosal interaction - pili(adehesins), ability to invade tissue.
2 Exotoxin production - heat labile, heat stable & shigella like toxin.
3 Endotoxin - Lipid A portion of LPS
4 Iron-binding siderophore - obtains iron from human transferrin
Three groups of diarrhea producing Escherichia coli + some characteristics, plz?
1 EnteroToxigenic Escherichia coli (ETEC): Cause traveler’s diarrhea. These guys have pili(colonization factor). Heat stable + heat-labile toxins inhibit Na+ and Cl- resorption, as well as stimulating the secretion of Cl- and HCO3- into the intestinal lumen = watery diarrhea.
2 Enterohemorrhagic Escherichia coli (EHEC): have a shiga-like toxin that inhibit the 60s ribosome which results in intestinal epithelial cell death. The diarrhea is bloody and accompanied by severe abdominal cramps.
3 Enteroinvasive Escherichia coli (EIEC): These guys actually invade the epithelial cells, thereby producing a immune-mediated inflammatory reaction with fever.
Most common cause of gram-neg sepsis?
Escherichia coli
Name four species of shigella?
1 dysenteriae
2 flexneri
3 boydii
4 sonnei
Do shigella have flagella?
Shigella has no flagella. No flagella, its shigella. Shigella nie ma flagella.
What organism is the host for shigella?
Humans are the only host for shigella.
EHEC, EIEC and Shigella all have a toxin that works similarly. What is the toxin called and by what mechanism does it work?
Shiga toxin have an A subunit bound to 5 B subunits. The B subunits Bind to microvillous membrane in the colon, allowing for entry by the deadly A(Action) subunit. The A subunit inactivate 60s ribosome, inhibiting protein synthesis and killing the intestinal epithelial cell.
Bacteria that starts with S, is motile and never a part of normal intestinal flora?
Poem:
Salmonella have flagella.
They move around fast
and don’t belong in our ass.
What is the salmonella Vi antigen?
same as the K antigen, only named differently. Vi for Virulence. It is a polysaccharide that encapsulates the O antigen.
Salmonella causes four disease states in humans. Name them?
1 Typhoid fever
2 Gastroenteritis(diarrhea)
3 Sepsis
4 Carrier state
