T2 - Micro - Lecture 7 - Secretory Diarrhea

Front 1

what categories of intestinal infections are there, what kind of diarrhea do they cause, and what general genuses make up each category?

Back 1

there are secretory, inflammatory, and invasive categories of intestinal infection.

secretory - typically e. coli or vibrio cholera. (entero invasive e. coli is invasive). get watery diarrhea (rice water) with no blood or pus. happens in PROXIMAL SMALL BOWEL.

inflammatory - typically caused by shigella. happens in COLON (think inflamed colon).
this is LOW VOLUME, but with some blood and mucus and fecal PMN's.

invasive - typically salmonella. distal small bowel. no blood or pus, high volume watery diarrhea. like secretory.

Front 2

how do you treat secretory diarrheal disease?

Back 2

oral rehydration therapy, no antibiotics.

Front 3

without details of how they work, what are major cholera virulence factors?

Back 3

motility, MUCINASE, binding receptors, and TOXIN PRODUCTION (cholera toxin).

Front 4

what's cholera toxin and how does it work?

Back 4

cholera toxin is an AB toxin that, like many others, is an ADP-ribosylation-driven process.


here, messing with G-proteins to keep them in the active state. Bind to and ribosylate Gs-alpha. So GTP's added, Gs-alpha travels over to adenylate cyclase and ups cAMP, so you get more Cl- efflux and less Na+ intake - so more water rushes out of the cell and doesn't get reabsorbed.

Can't hydrolyze GTP for GDP, so stay on permanently. ACTIVATES CFTR.

Front 5

what toxin works just like cholera toxin?

Back 5

the E. coli LT (heat liable toxin) works just like cholera toxin.

Front 6

if you've got a lab strain of e coli, what do you need to add to make it dangerous?

Back 6

both an adherence factor and a toxin of some kind.

note that because your gut is colonized by E. coli, and they're constantly fucking, all you need to get is a bad plasmid to turn your gut into a colony full of pathogenic E. coli

Front 7

What are the different E. coli's? he said we need to know them.

Back 7

ETEC - enterotoxigenic traveler's diarrhea. Has ST/LT toxins.

EIEC -enteroinvasive E. coli - watery at first, then kinda inflammatory-looking (scant + cells/blood).

EPEC - type III, pedistal, intimin, TIR, etc.

EHEC - shiga-like toxin. HUS

Enteroaggregative E. coli (EAggEC) - infants, aggregative adherence.

Front 8

which enteric pathogens can cause serious physical damage to tissue/invasion?

Back 8

Salmonella is our main invasive pathogen.

also listed are shigella
EIEC (just like shigella). note that shigella is considered an inflammatory diarrhea, so this is weird.

EHEC.

Front 9

what diseases can come from slamonella? how can you tell them apart from E. coli on plates?

Back 9

salmonella can cause THYPHOID FEVER or GASTROENTERITIS.

on MacConkey agar, everything should ferment lactose - if it doesn't, it's probably a pathogen, and salmonella's a common one.

Front 10

talk about the invasion and life span of both kinds of salmonella.

what virulence factors are on these?

Back 10

salmonella typhi (which carries the Vi-antigen, a coat protein) invades through M-cells on the gut surface (which normally sample around looking for baddies). They aren't killed in the cell - instead, they pass through the BL membrane (hence invasive) - here, they take up residence in macrophages.

Here, the two species deviate - if it's Tyhpi, it hops a ride in the macrophages into the liver and spleen, where it takes up residence and waits. Attacks as bacteremia, get typhoid fever. Eventually sits in galbladder kinda forever, where it can be passed from person to person in poop (typhoid mary had it in her galbladder).

typhomerium breaks out of the WBC's and attacks neighboring epithelial cells, causing all the shitty symptoms.

note that Typhimirium's virulence factors include LPS, adheions, etc.

Front 11

if you've got a lab strain of e coli, what do you need to add to make it dangerous?

Back 11

both an adherence factor and a toxin of some kind.

note that because your gut is colonized by E. coli, and they're constantly fucking, all you need to get is a bad plasmid to turn your gut into a colony full of pathogenic E. coli

Front 12

What are the different E. coli's? he said we need to know them.

Back 12

ETEC - enterotoxigenic traveler's diarrhea. Has ST/LT toxins.

EIEC -enteroinvasive E. coli - watery at first, then kinda inflammatory-looking (scant + cells/blood).

EPEC - type III, pedistal, intimin, TIR, etc.

EHEC - shiga-like toxin. HUS

Enteroaggregative E. coli (EAggEC) - infants, aggregative adherence.

Front 13

which enteric pathogens can cause serious physical damage to tissue/invasion?

Back 13

Salmonella is our main invasive pathogen.

also listed are shigella
EIEC (just like shigella). note that shigella is considered an inflammatory diarrhea, so this is weird.

EHEC.

Front 14

what diseases can come from slamonella? how can you tell them apart from E. coli on plates?

Back 14

salmonella can cause THYPHOID FEVER or GASTROENTERITIS.

on MacConkey agar, everything should ferment lactose - if it doesn't, it's probably a pathogen, and salmonella's a common one.

Front 15

talk about the invasion and life span of both kinds of salmonella.

what virulence factors are on these?

Back 15

salmonella typhi (which carries the Vi-ANTIGEN, a coat protein) invades through M-cells on the gut surface (which normally sample around looking for baddies). They aren't killed in the cell - instead, they pass through the BL membrane (hence invasive) - here, they take up residence in macrophages.

Here, the two species deviate - if it's Tyhpi, it hops a ride in the macrophages into the liver and spleen, where it takes up residence and waits. Attacks as bacteremia, get typhoid fever. Eventually sits in galbladder kinda forever, where it can be passed from person to person in poop (typhoid mary had it in her galbladder).

typhomerium breaks out of the WBC's and attacks neighboring epithelial cells, causing all the shitty symptoms.

note that Typhimirium's virulence factors include LPS, adheions, etc.

Front 16

describe the time course for salmonella typhi.

what populations are at particular risk for salmonella poisoning?

Back 16

this can take 1-4 weeks to incubate, due to the weird progress to the spleen/liver, etc.

asplenic patients (and by default, those with sickle cell) are particularly at risk for salmonella infection due to the fact that capsuled bacteria are killed off by opsonisation, and without a spleen, there's not a good place for that to take place.

Front 17

what's different about the treatment of salmonella typhi vs. salmonella typhomerium?

Back 17

typhomerium, like most of the enterics, don't benefit much from antibiotic therapy.

tyhpi, on the other hand, depends on antibiotic treamtment for recovery.

Front 18

shigella - what are the two types? what's it related to?

Back 18

shigella is essentially EIEC.

two forms - shigella dystenteriae (common in third world, bad news) and shigella sonnei - more common in first world, not as bad.

Front 19

describe the relative infectivity of the different enterics -

Back 19

shigella is amazing because it can requires as few as 10 bacteria to cause infection. cholera and e. coli both require billions.

Front 20

describe the infectious life cycle of the shigella -

Back 20

they pass down through M cells, end up in macrophages, screw up the phagosomes, release IL-1 and kill the macs, then infect other enterocytes from the BL side. Lots of pus, PMN's called in, which pass up through the BL side into the epithelial layer, which allow shigella to pass up with them.

this is why the stools are full of PMN's and are mucoid.

Front 21

what does shiga toxin do? what can it cause?

Back 21

targets 60s ribosomes. Does this by pulling an adenine from a 28s ribosomal RNA. Stop protein synthesis.

Note that this causes ribosome to be unable to bind EF1 so you don't get protein elongation.

can cause HEMOLYTIC UREMIC SYNDROME (HUS). Note that EHEC produces essentially the same toxin.

Front 22

aside from our enterics just covered, what's the other big way you can get serious diarrhea and how can these bacteria cause it?

Back 22

you can ingest preformed toxins from other bacteria.

the big one we learned about is staph aureus - its toxin is a SUPERANTIGEN and causes T-cell activation.

note here that the onset of disease is faster and it resolves faster.

Bacillus Cereus can do this too (think serious diarrhea).

here, there shouldn't be fevers or mucous.