Bacterial Gastroenteritis Flashcards
What are the oxygen requirements of the enterobacteriaceae?
Aerobic or facultative anaerobic
What is the structure of enterobacteriaceae? (4)
G- rods, 1-5 microm, inner and outer membrane, peptidoglycan
What are the virulence factors of enterobacteriaceae? (3)
Flagella (H antigen)
Capsule (K or Vi)
LPS (O antigen)
What are the 3 medically important enterobacteriaceae species?
Salmonella enterica
Shigella sonnei, flexneri
Escherichia coli
Are most enterobacteriaceae motile or non-motile?
Motile (generally have peritrichous flagella)
What enterobacteriaceae species are non-motile?
Yersinia, Klebsiella, Shigella (although most are motile)
What morphological characteristic of enterobacteriaceae aids in host cell attachment and horizontal gene transfer?
Fimbriae (pili)
What virulence factor of enterobacteriaceae is the lipid A component of LPS and can lead to septic shock in the blood stream?
Endotoxin
What virulence factor of enterobacteriaceae protects from phagocytosis and activation of host immune system (complement) (although not all enterobacteriaceae have it)?
Capsule
What virulence factor present in a lot of G- species helps move proteins across the membrane?
T3SS (type three secretion systems)
What are the oxygen requirements of salmonella species?
Facultative anaerobe
What are the 2 salmonella species?
Salmonella bongori and salmonella enterica
What are the primary methods of transmission/ sources for salmonella?
Ingestion of contaminated food or water (poultry, organic vegetables)
What are the secondary methods of transmission/ sources for salmonella?
Pet reptiles/ birds, backyard poultry flocks, direct person to person
How do you distinguish between different salmonella species?
Serotyping, based on flagellar (H) and LPS (O) antigens (they are unique)
What organism is often the cause of foodborne gastroenteritis and then subsequent bacteremia?
Non-typhoidal salmonella
What does it mean that S. Typhimurium is a generalist infection?
Infects a variety of hosts
cases self-limiting gastroenteritis in humans
What salmonella species is the most common clinical isolate but presents with an indistinguishable disease?
Salmonella enterica serovar Enteritidis
What feature of ALL Salmonella invades epithelial cells and acts as a virulence factor?
SPI1 (type three secretion system)
Once salmonella invades the epithelial cells, how is the host cell damaged?
Actin cytoskeletal changes and engulfment of bacterium
target actin and host cell signaling cascades
What it the final step of the salmonella life cycle?
Transit epithelial layer and gain access to systemic sites
What is the most important Escherichia species?
E. coli (should be included with Shigella)
Which E.coli strains are pathogenic and have acquired virulence traits?
ETEC (enterotoxigenic E.coli)
EHEC (enterohemorrhagic E.coli)
EIEC (enteroinvasive E.coli)
Shigella species
What organism is the common in young children or travelers and is acquired via contaminated food and water?
ETEC (enterotoxigenic E.coli)
Pt presents with watery diarrhea and intestinal cramps (3-5 days then clears). What are you concerned about?
ETEC (enterotoxigenic E.coli)
1-2 days post exposure
What are the 2 toxins of ETEC (enterotoxigenic E.coli)?
LT1 (heat liable toxin) and STb (heat stable toxin)
Which ETEC (enterotoxigenic E.coli) toxin binds to the same receptor as cholera toxin, activates host adenylate cyclase increasing cAMP levels and results in watery diarrhea from secretion of chloride ions from the cell and water flow into lumen of intestine?
LT1 (heat liable toxin)
Which ETEC (enterotoxigenic E.coli) toxin binds to the guanylate cyclase receptor on intestinal epithelial cells which leads to increased cGMP levels and secretion of fluids from cells?
STb (heat stable toxin)
What Escherichia species is a common cause of foodborne intestinal illness and aka STEC (Shiga toxin producing E. coli)?
EHEC (enterohemorrhagic E.coli)
For which Escherichia species are cattle an important reservoir?
EHEC (enterohemorrhagic E.coli)
What is the most common serotype of EHEC (enterohemorrhagic E.coli)?
O157:H7
Once salmonella invades the epithelial cells effectors lead to actin cytoskeletal changes which. This allows it to gain access to the systemic sites causing what?
SX of salmonella (gastroenteritis)
Is E. coli gram + or gram - ?
Gram-
ETEC is acquired via consumption of contaminated food and water? What is it aka?
Traveler’s diarrhea (watery diarrhea and cramps lasting 3-5 days)
What are the virulence factors of EHEC and Shigella? (3)
- STX (shiga like toxin) - (A-B toxin, binds only in human intestines, released after bacteriophage lyses in response to stresses on the bacterial cell)
- Intimin (adhesions, aid in bacteria binding to intestines)
- Tir (Acts as receptor for intimin w/in epithelial cells, will cause cell death)
What does the A-B toxin do?
B binds to receptor, A is internalized, stops protein synthesis –> cell death
What E. coli infection is very similar to shigella, processes no flagella or adherence factors, and causes profuse bloody diarrhea and dysentery?
EnteroInvasive E. coli (EIEC)
Is shigella gram + or gram- ?
Gram-
What differentiates shigella from other pathogenic E. coli?
Lac-
Shigella initially presents with watery diarrhea but can progress to what sx?
Severe diarrhea w/ blood and mucous (dysentery)
Where does shigella replicate?
Inside macrophages (then kills the cell to be released)
What happens once shigella is released from lysed macrophage?
invades basolateral membrane of epithelial cells which allows it to spread cell to cell and damage the mucosal layer or the GI tract
What Shigella organism is the only to produce shiga toxins?
S. dysenteriae (causes more severe disease)
What are the 2 shiga toxins release by S. dysenteriae?
Shiga toxin 1 (very potent, identical to shiga like toxin O157:H7)
Shiga toxin 2, same mechanism as 1 but different structure and immunogenicity
What toxins are produced by other shigella species (not S. dysenteriae)?
ShET1 and ShET2
- Less severe than shiga toxins
What is the virulence factors of Shigella?
Shigella toxins