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95 Cards in this Set

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50% of travelers diarrhea is caused by _
MacConkey agar Inhibits
gram-positive growth

Further, there is a pink color change for lactose fermenters
Hektoen enteric ager is usually used to ID
Salmonella (black - H2S producer)

and Shigella (white)
Most bacteria that cause bloody stool are invasive. There is one exception however; what is the one bacteria that causes bloody diarrhea but is NOT invasive?
Enterohemorrhagic E Coli (0157:H7)
traveler's diarrhea is usually caused by
Enterotoxigenic E Coli (eTec)
A patient who has just returned home from guatemala presents with watery diarrhea. What is the most likely pathogen, and how long will this last?
this is the MC cause of traveler's diarrhea. But always remember there are others!

transient, only lasts 3-4 days

What age group is this UNLIKELY to be found in?
Between 5-15 yo.

ETEC are most common in those under 5 or older 15
E Colis that can cause watery diarrhea?
EPEC, ETEC, most Viral, (EAEC)
E Colis that can cause bloody diarrhea?
EHEC, Shigella spp./EIEC, (EAEC)
E Colis that can cause Watery + Mucus diarrhea?
EPEC, protozoans, some worms
Patient presents with bloody diarrhea. On hx you find out that last night she had steak for dinner last night. What is the most likely pathogen?
ETEC has what toxins?
AB toxin (LT)

and Small Peptide (ST).

What is the MOA
LT 1. Bind to membrane and targets ADP ribosylation of a G protein. The net effect is to increase the activity of AC, which increases cAMP and opens Cl- channel, letting it go out. Na+ follows to balance the charges, and water follows the Na+.

ST Targets Guanylate cyclase and has same effect: chloride channel opens, and water and ions are released.
EPEC is typically seen in what scenario?
Daycares, nurseries (dz of infants): watery diarrhea

What is the Patho?
It is an A/E (attachment and effacement pathogen),

ii. Takes type III secreteion system and injects proteins (Tir) into cytoplasmic membrane of host cell to act as tight junctions, other proteins rearrange cytoskeleton of host cell and strengthen the binding. IOW it Manipulates epithelium to create a “nest”
EHEC (0157:H7) is usually from what source

This is an AE
What is the common reservoir in EIEC?
What bacteria secretes the shiga toxin?
Shigella Dysenteriae type 1
What is the primary pathogenic toxin in EHEC (0157-H7)?
AB Toxin

what is it's patho?
targets the RIBOSOME (cleaves the adenine residue from 28S rRNA that leads to a shut out of host protein synthesis and eventually the death of the cell).
What is a severe complication that can arise from a patient infected with EHEC?

How do you treat them?
Filter blood and get rid of toxin

Antibiotics are typically not required
What is the classic finding in EAEC?
"Stacked brick" epithelium, grows in a very unique way

How do you treat?
Yersinia spp is very sensitive to _ levels.

This is mostly seen in what host?

Francisella tularensis is a gram (+/-) (rod/cocci).

How does it normally infect humans?
gram - rod

usually via insect bites. animals are reservoir
What is characteristic regarding Brucella infections?

How are these infections spread?
very slow growing, cultures take 8-10 days

Direct contact or ingestion of unpasteurized DAIRY products
Clostridium Difficile is a gram (+/-) (rod/cocci)
What are two complications that can occur with this infection?
gram + rod

May lead to psyedomembranous colitis (white patches) or complicated colitis (toxic megacolon)
Watery diarrhea is Usually due to _ or _
Vibrio Cholera and ETEC Enterotoxigenic escheria Coli
T. cruzi causes _and is transmitted by the bite of _
Chagas’ disease

the reduviid (kissing) bug.

What GI condition can this bug cause?
Dental plaque is a biofilm formed by
Strep Viridans
Dental cavities are caused by
Strep Mutans
dietary sugar is acted on by bacteria and produces glucan and lactic acid, the acid melts the calcium enamel and causes tooth decay.
Trench Mouth (Acute necrotizing ulcerative gingivitis) is caused by _ and _
Treponema genus (spirochete) + anaerobic bacteria (fusobacterium)
Vibrio Cholera and ETEC Enterotoxigenic escheria Coli are the two most common pathogens that cause _
watery diarrhea
- fluid loss without cellular injury, infect the small intestine

Most pathogens that cause watery diarrhea run a brief self limiting course, except for _ which lasts for weeks
Giardia Lamblia

#1 water borne gi infection in the US
Shigella and enteroinvasive EC are the most common causes of _
dysentery diarrhea ("squirts")
infect the colon
-- blood and pus seen in stools, but doesn’t result in substantial fluid loss
A patient c/o diarrhea, abdominal pain, cramping, and pain on purging. What type of diarrhea is this?

Name some possible pathogens
enteroinvasive EC (clinically indifferentiable), or
Campylobacter jejuni (#1 bacterial cause of GI infection in US)
Pseudoappendicitis is caused by _
Yersinia enterocolitica

this condition is aka
Mesenteric Adenitis
Stool sample shows acid fast stained oocyst, what is the most likely pathogen?
#1 cause of infantile diarrhea in world (and US)

only ds RNA virus!
Two most common pathogens that cause traveler's diarrhea?
ETEC and Shigella
Hospitalized patient who is on prolonged antibiotics develops diarrhea, what is the likely pathogen?
Clostridium difficile
What type of virus is Hepatitis A?
Picornavirus - non enveloped ssRNA
What type of virus is Hepatitis B?
Incomplete dsDNA virus - member of Hepadnaviridae family,
An Incomplete dsDNA virus is nothing other than..
Hepatitis B

thus why it needs a reverse transcriptase
Hepatitis C is part of the _ family
Flaviviridae (+) ssRNA

How do you treat?
Interferon Alpha and ribavirin
The AB toxin of ETEC targets _
G proteins -- ADP ribosylation results in outflow of Cl into the gi lumen, ultimately causing watery diarrhea

And what about the AB toxin of EHEC?
This targets the 28 S ribosome, it causes cell death and is responsible for Hemolytic Uremic Syndrome which can be a complication of EHEC infection
HUC and TTP are associated with what GI infection?
EHEC infection - AB toxin

(Also can be Shigella dysenteriae which secretes the shiga toxin)

what is the primary source of this infection?
“Stacked brick” growth on top of epithelium:
Enteroaggregative (EAEC)
Rice water stool typically refers to which pathogen?
Vibrio Cholera
Gram negative bacillus, Very senisitive to Iron levels?
Yersinia spp

what is the primary reservoir?
Patient presents with high fever, headache, myalgias, and is extremely confused. PE shows an inflammed blister that is filled with pus and swollen lymph nodes. What do you suspect?
Franscella Tularensis

How do you confirm?
Serology (although it's negative in the first week)

NOT stool cultures
Older male presents with diarrhea, generalized arthralgia and back pain, sweats, fever (goes away at night), what do you suspect?

How do you confirm your dx?
Blood culture, VERY slow growing, takes 8-10 days
Characteristics of Clostridium difficile?
Gram + bacillis, spore former

Obligate anaerobe
*This typically hospital acquired but can be found in the community. Associated with antibiotic use!
What toxin is responsible Clostridium difficile diarrhea?
toxin A
Patient presents with a rash. Hx reveals that A few days earlier, they had brief diarrhea. What do you suspect?
Poliovirus ---
this is a very generalized question. but keep in mind that most picornaviruses present with very vague symptoms - tachycardia, photophobia, or rashes.
Also keep in mind, that blood and serum testing for picornavirus can be (+) up to months after GI symptoms have disappeared. SO just because Hartley says it's +, doesn't mean it actually is
Acute hepatitis in an acknowledged IV drug user would likely be caused by what hep virus?
Patient who was just on a Cruise ship presents with nausea, mild vomiting, and watery diarrhea. If you were to do a bx on her intestine, it would show blunted intestinal villi with crypt hyperplasia and an increase in PMNs and lymphocytes. Dx?
Norovirus - primary sx is nausea. This appears first

--> Gastric motor function appears to be delayed and may be the cause of the sx usually observed.
intense nocturnal perianal itching is a/w ....
Enterobius vermicularis (Pinworm)

How do you dx?
tape test
Lung symptoms and GI symptoms in the same patient should tip you off to what organism?
Ascaris Lumbricoides (Roundworm)

What phase of it's life cycle is found in the lungs?

(they get coughed up and swallowed and then become adults)
What are two bugs that infect people through direct contact (ie via walking barefoot)?
Necator Americanus / Ancylostoma duodenale (hookworm)


Strongyloides stercoralis (threadworm):
iron deficiency anemia and "ground itch", and transient pneumonitis are a/w what bug?
Necator Americanus/ Ancylostoma duodenale (hookworm)
Note that ground itch can also be associated with Strongyloides stercoralis, but this isn't aw with iron def anemia (?) Dx this with larva (not eggs) in stool
calcified :puffed rice” lesions on plain x ray are a/w ....
taeniasis (tapeworms)

Source of infection?
eating undercooked meat, particularly in this case, ingestion of the eggs:
T. saginata (beef)
T solium (pork)
Biliary infections are usually transmitted via...
ingestion of poorly cooked, pickled or smoked fish
Patient presents with intense abdominal pain, bloody diarrhea, and vomiting. Shortly after admission she goes into shock and dies. Autopsy report determined cause of death is due to an intestinal perforation. Small intestine on examination shows severe necrosis. What is the likely bug that caused this?
Clostridium perfringens --- causing enteritis necroticans
35 people who all went to a company christmas party get diarrhea. Stool sample is obtained, and isolation of the organism shows double zone of hemolysis on blood agar. Dx?
clostridium perfringes

It has a max effect in the _ and min in the _
ileum, duodenum
Home canned vegetables are a source for what infection?
Clostridium botulinum
Patient presents with diarrhea, blurred vision, cranial nerve paralysis (EOM weakness), respiratory muscle weakness. What do you suspect?
Clostridium botulinum

How is this commonly transmitted?
Home canned vegetables
Acute GI and neurological symptoms should tip you off to what organism?
clostridium botulinum
Fried rice is associated with..
bacillus cereus...vomiting syndrome

what is the virulent factor?
heat stable toxin
Spaghetti sauces, dried potatoes, and dried milk are a/w what bug?
Bacillus Cereus - diarrhea syndrome

What is the pathogenesis?
heat labile enterotoxin stimulates adenylate cyclase in intestinal cells
- similar to E coli and Vibrio cholera toxins
"flask shaped ulcers" found in the small intestine is characteristic of
entamoeba histolytica

what is the characteristic microscopic feature?
4 nuclei in the cysts

(these are the protozoa that can cause hepatic abscesses, lung abscesses, or cutaneous abscess)
a 5 yr boy gets diarrhea which later becomes bloody and presents with lethargy and fatigue. Labs show elevated BUN and creatinine, and fragmented erythrocytes. Dx?
Hemolytic Uremic Syndrome
(seen in children under 10)

Caused by what bacteria, and what is the most likely source??

Undercooked beef
a 6 year old boy presents to ER with diarrhea, Mom tells you the dog had diarrhea about a week ago. What bug should you suspect?
Campylobacter....this can be transmitted from domestic animals to humans
Shiga toxin targets....
Source of vibrio parahemolyticus infections?
raw seafood (raw oysters)
(#1 bacterial cause of GI infection in US
Campylobacter jejuni
Patient presents with diarrhea, abdominal pain, and fever. He says prior to the diarrhea he was constipated. What should you consider?
Salmonella enterica, subtype Typhi

This is describing enteric fever, Note the Constipation at First
2 organisms that can cause HUC (renal failure in a younger patient) or TTP
EHEC or Shigella Dysenteri

Shigella typically doesn't occur in the US, so unless the patient specifically says they've been out of the country, think EHEC
Patient presents with abdominal cramping and diarrhea. They say that at first the diarrhea was watery and then it turned bloody. Hx reveals a recent hx of a chicken burrito. Dx?
Campylobacter Jejuni (#1 bacterial cause of GI infection in US)

How do you treat?
What condition is this patient at risk for?

Guillan Barre
Spaghetti sauces, dried potatoes, dried milk are common sources for what infection
Bacillus Cereus - Diarrhea syndrome
Custard infected with Staph Aureus will take how long to present symptoms in a patient who consumed it?
less than 6 hours - they have a preformed toxin
A patient who ate potato salal infected with Salmonella will start having diarrhea in what time frame after consumption?
Longer than 6 hours
double zone of hemolysis on blood agar and growth on egg yolk agar is characteristic of ...
clostridium perfringes
gram + spore former
Latex Agglutination test is dx for
c difficile (toxin present in stool but not bacteria)
Helicobacter pylori grows best in what kind of medium?
skirrow medium

what clinical test is used to diagnose an infection with h pylori
Urea breath test
_: curved gram negative rod found in salt water, they are often times linked end to tend, forming S shapes and spirals
Vibrio species

this causes what kind of gi sx?
watery diarrhea
Bile Salt Sucrose (TCBS) medium is selective and differential for...
Vibrio Species (curved gram - rod links together forming S)

How can you distinguish Vibrio cholerae from other vibrios?
grows under alkaline conditions,
What is the pathogenesis of a gram - curved rod that grows on TCBS medium and in alkaline conditions?
(vibrio cholera - rice water stool from shell fish)
CT toxin and AB toxin
B fragments bind to the GM1 ganglioside receptor and the active portion (A1) catalyzes the ADP-ribosylation of the Gs regulatory protein locking it into an active state.  Increase cAMP causes active secretion of Na Cl, K, and bicarbonate out of the cell into the intestinal lumen.
IOW: AB Toxin that increases secretion of water and electrolytes.
Watery diarrhea in a patient with a History of traveling on a cruise ship and consumption of shellfish should tip you off to what ?
Vibrio Parahaemolyticus

always think vibrio with shellfish
A chef at a seafood restaurant cuts herself which shucking oysters. She now presents with pus formation, swelling and redness in the surrounding tissue and diarrhea. What is the Dx and patho?
Vibrio vulnificus
- Produces powerful siderophores which scavenge iron from host transferrin and lactoferrin.
Shellfish - think vibrio

What if this scenario dealt with fresh water fish?
Mycobacterium mirium: Causes cellulitis and granulomatous lesions, associated with fresh water (tropical fish)
: Pathogenesis of V cholera is mediated by…
ADP ribosylation of Gs protein resulting in increased cAMP production
Skirrow agar is a good medium to grow what pathogens
h pylori or campylobacter jejuni
4/5 med students who ate at a local Mexican restaurant develop abdominal cramping and diarrhea mixed with blood. Stool exam revealed gram neg rod with polar flagella, which requires a special incubator for growth. The most likely source of infection is…

- describing campylobacter jejuni

how do you treat?
14 residents in a nursing home co fever, abdominal pain, and constipation for about 10 days. Blood culture confirms Salmonella enterica typhi as the causative agent. What is the primary source of infection?
Amebiasis, caused by _ , is known to cause what complications?
Entamoeba histolytica

Liver abscess (this is bc trophozoites invade intestinal mucosa and enter the blood stream, they can land anywhere in the body and cause abscess.)

What is the characteristic microscopic feature in these?
cysts with 4 nuclei
Guatamalan raspberry,
Cyclospora cayetanensis:
Patient presents with meningitis sx. Family says she had mild throat and gi symptoms last week. What do you suspect?
Poliovirus (Paralytic poliomelitits)
Trichuris trichiura (whipworm) route of entry?
fecal oral

how do you dx?
eggs in stool

presents with heavy infection, Epigastric pain, vomiting, distention, flatulence, anorexia and weight loss, eosinophilia
intense nocturnal perianal itching is a classic sign of what helminthic infection?
Enterobius vermicularis (Pinworm)
Ground itch with edema at the site of entry and petechial hemorrhages are suggestive of ...
Strongyloides stercoralis (threadworm): (D/D Necator Americanus and Ancylostoma duodenale (hookworm) also cause ground itch - these are a/w iron def anemia and transient pneumonitis)

How do you dx Strongyloids infection?
Larva in stool