Invasive gram negative pathogens of GI tract Flashcards
what are the 3 mechanisms bacteria can use to cause infections
1 - invade the mucous membrane
2 - toxin producers
3 - hybrid of the two above
what are the 2 main gram (-) bacterial species that cause infections by invasion of the mucous membrane
salmonella and shigella
shigella species of gram negative pathogens has 4 subgroups distinguished by what antigen
O antigen (based on structure of LPS
what is RpoS ?
transcription factor that causes acid resistance in shigella allowing pathogen to pass through stomach
which gram negative bacteria has a small inoculum size ? large ?
shigella is small, salmonella is large
explain how shigella pathogens invade humans
1 - enter host M cells for transport to basal surface
2-released at lamina propria and ate by macrophages causing inflammatory response
3- pathogens not eaten ingested by epithelial cells and put in vesicle
4-shigella proteins lyse the vesicle
5- spread locally intracellulary via IcsA
which is resistant to pathogen infection in humans, the mucous surface or basal surface
basal surface
what do shigella pathogens produce to signal human M cells to pick them up for transport to basal surface
shigella pathogens have proteins called “invasion plasmid antigens”
what is IcsA
protein ATPase of shigella causing polymerization of actin which pushes shigella cells into adjacent epithelial cells w/o going into cytoplasm and getting destroyed by immune system
is shigella a localized infection or systemic ? why ?
localized because just stays in epithelial cells and away from blood stream
what develops when the invaded epithelial cells die off from shigella infection
ulcer
what specific subgroup of shigella induces a watery diarhea stool
shigella sonnei (most common)
what specific type of shigella produces the Shiga toxin and is the most severe of shigella diseases
Shigella dysenteria type 1
what does the Shiga toxin in shigela dysenteria cause
- kills intestinal epithelial and endothelial cells=more diarhea
- dirsupts Na absortion
Salmonella pathogen can cause what 2 diseases
1- Gastroenteritis
2-Typhoid fever