Lecture 16 and 17: GI Infections (!) Flashcards
Which family of gram (-) facultative, anaerobic, rod-shaped bacteria are commonly found in the GI?
Enterobacteria
Three ways the GI infections can be transmitted?
- Fecal oral
- Fomites
- Food and water borne
What’s the difference between Diarrhea and Dysentery–both of which are symptoms of GI infections?
True or False: C. perfringes, B. cereus, and S. aureus are associated with food BORNE DIARRHEAS
True
V. cholerae and ETEC cause infection by adherence to ___ and release of ___
A. enterocytes; toxoid
B. intestinal mucosa; toxoid
C. intestinal mucosa; toxin
C. intestinal mucosa; toxin
C. dif and EHEC cause infection by adherence to ___ and release of toxin resulting in destruction of ___ or ___
intestinal mucosa
brush border/mucosa
___ is the only pathogen to cause infection via mucosal invasion and proliferation within enterocytes
A. Salmonella
B. C. dif
C. EHEC
D. Campylobacter
E. Shigella
E. Shigella
Which three pathogens cause diarrheal disease via: mucosal translocation + proliferation within lamina propria and lymph nodes?
Salmonella
C. jejuni
Yersinia enterocolitica
Which two viruses can cause infection + destruction of enterocytes, resulting in osmotic diarrhea?
Rotavirus
Norwalk Virus
Which pathogen causes Gastritis?
H. pylori
H. pylori is…
- Gram (+) or (-)?
- Shape?
- Acid Intolerant/Tolerant?
- Gram (-)
- Curved Rod
- Motile
- Acid Tolerant
- Microaerophilic
- Non-invasive
Which enzyme does H. pylori have that permits it to be acid tolerant?
Urease
___: Most common virulence factor of H. pylori, which damages gastric epithelial cells by inducing vacuoles + is responsible for gastric ulcers (!!!)
A. Vacuolating Cytotoxin
(Vac A)
B. Cytotoxin Associated Gene A (CagA)
C. Urease
A. Vacuolating Cytotoxin
(Vac A)
___ is not found in all strains of H. pylori and increases virulence. Further, it induces inflammation + destruction of mucosa + is responsible for gastric cancer
A. Vacuolating Cytotoxin
(Vac A)
B. Cytotoxin Associated Gene A (CagA)
C. Urease
B. Cytotoxin Associated Gene A (CagA)
Clinical significance of Urease?
Degrades Urea to Ammonia and Bicarbonate
NH3 raises stomach acid, making it more basic, so that H. pylori can grow!
How do diagnose H. pylori?
Which two pathogens can cause watery diarrhea but no fever (afebrile)
A. ETEC
B. V. cholerae
C. E. coli
D. Cutibacterium acnes
A. ETEC (Enterotoxigenic E. coli)
B. V. cholerae
True or False: ETEC/E.coli are leading cause of Traveler’s Diarrhea
True
Features of E. Coli?
- Gram (+)/(-)
- Shape
- Aerobe? Anaerobe?
- Coliform?
E.coli
- Gram (-)
- Rod
- Facultative anaerobe
- Coliform: ferments lactose, produces gas + acid
ETEC (Enterotoxigenic E. coli) causes afebrile state + watery diarrhea by attaching to SMALL INTESTINES and secreting which two enterotoxins?
1) Heat Labile (LT): Antigenic, activates adenylyl cyclase and increases cAMP
2) Heat Stable (ST): Non-antigenic, activates guanylyl cyclase and increases cGMP
True or False: Both the toxins secreted by ETEC and the Cholera Toxin (similar to LT) cause mucosal cells to secrete fluid and electrolytes
True
True or False: E.coli is lactose positive (+)
True
___ is a high dose organism/pathogen that causes watery diarrhea without fever that uses saltwater or contaminated food (e.g shellfish) as a vehicle
A. E.coli
B. ETEC
C. V. cholerae
C. V. cholerae
True or False: V. cholerae are halophilic, non-invasive, gram negative curved rods
True
V. cholerae produces _____ toxin – which is similar to _____ of ETEC – and causes mucosal cells to secrete fluids + electrolytes. This secretion is responsible for disease manifestation
Cholera Toxin (CT);
Heat Labile (LT)
electrolytes and fluids
True or False: Heat Labile Toxin (LT) of ETEC is encoded on a bacteriophage
False - Cholera Toxin of V. cholerae is!
True or False: Cholera Toxin (CT) is an AB5 toxin that is heat-labile, just like Heat Labile Toxin (LT) of ___
ETEC
Which subunit of the cholera toxin binds to ganglioside (GM1) on the intestinal epithelial cells
A. Alpha
B. B subunit
C. A subunit
D. Beta subunit
B. B subunit
How do you diagnose V. cholera?
Which three pathogens are food borne diseases associated with Afebrile watery diarrhea (intoxication)?
- S. aureus
- Bacillus cereus
- Clostridium perfringens (Type A)
What are four features that are shared by: S. aureus, Bacillus cereus, and C. perfringens have in common (food borne pathogens - associated w/afebrile watery diarrhea)?
- Abx don’t help
- No RBC/WBC in stool
- Cause: inadequate cooking, holding temp
- Not transmissible
True or False: In the staphylococcal and emetic forms of Bacillus cereus, the food borne diseases are pre-formed in food
True
The diarrheal forms of ___ and ___ (type A) are associated with toxin released in gut from ingested bacteria – in food borne disease commonalities
C. perfringens (type A) and B.cereus
True or False: The emetic form of B. cereus is a toxin released in the gut from ingested bacteria while the diarrheal form is preformed in food
False
1) Emetic form of B. cereus = preformed in food
2) Diarrheal form of B. cereus = toxin release in gut from ingested bacteria
Features of S. aureus?
- Gram (+) or (-)
- Shape?
- Coagulase (+) or (-)
Gram (+)
Cocci
Coagulase (+)
What is the toxin produced by some S. aureus known as? Features?
SET (staph entertoxin)
- heat stable
- acute emetic and diarrheal disease when toxin consumed via foods
Which of the following pathogens may be found in processed meats, canned foots, potato salads, or boston cremes :c ????
A. S. aureus
B. Bacillus cereus
C. C. perfringens
A. S. aureus
True or False: When S. aureus produces its enterotoxin, it is ingested, absorbed in the gut, and acts on the vomiting center in the CNS
True
___ is a gram (+), aerobic, spore forming rod that can lead to food borne disease, particular if one eats potatoes, rice, or veggies
Bacillus cereus
Bacillus cereus produces two enterotoxins: a heat stable (emetic) form and a heat labile (diarrheal) form – which is preformed in food? which proliferates in small intestines?
Emetic form
- heat stable
- pre-formed in food
diarrheal form
- organism proliferates in small intestine => heat labile enterotoxin => s/s
Which form of entertoxin, produced by Bacillus cereus, functions by stimulating adenylate cyclase (much like ETEC and CT)?
A. Heat Stable (vomit)
B. Heat Labile (diarrheal)
B. Heat Labile (diarrheal)
Which of the following anaerobic, gram (+), spore forming rods may be found in meat, poultry????
A. S. aureus
B. Bacillus cereus
C. C. perfringens
C. C. perfringens
What are two features of the entertoxin of Clostridium perfringes?
A. Heat labile; acid labile
B. Heat stable; acid labile
C. Heat labile; base labile
A. Heat labile; acid labile
The enterotoxin made by C. perfringens (type A) functions by inhibiting ___ and ____ ion absorption
glucose; chloride
True or False: C. perfringens proliferates in the small intestines, which leads to entertoxin production, which produces s/s
True
How do you dx C. perfringens?
Detect spores in food or feces
What is an example of a Shiga-like/Verotoxin-toxin (STEC/VTEC) E.coli?
Enterohemorrhagic E.coli (EHEC, O157:H7)
Note: O157:H7 = sorbitol negative fermenter (therefore: white)
True or False: EHEC and STEC/VTEC are associated with diarrheas accompanied by a fever
False - w/ or w/o fever
Virulence factor used by Enterohemorrhagic E.coli?
A. Pili
B. Shiga-like toxin
C. Sorbital toxin
B. Shiga-like toxin (aka: verocytotoxin)
What are two effects of Shiga toxin?
1) GI Bleeds - hemorrhagic colitis
2) Hemolytic Uremic Syndromes - HUS
____: A triad that consists of hemolytic anemia + acute kidney failures + low platelet count
A. HUS
B. Hemorrhagic Colitis
A. Hemolytic Uremic Syndromes (HUS)
True or False: ETEC is a gram negative bacilli - most common serotype is O157:H7
False - EHEC
Why is STEC/EHEC able to be spread person to person?
A. Poor hygiene and low dose organism
B. Poor hygiene and high dose organism
A. Poor hygiene and low dose organism
True or False: Raw milk or apple juice could lead to STEC/EHEC
True
Two virulence factors used by STEC/EHEC?
- Pilli (adherence in small intestines)
- Stx (toxemia)
True or False: HUS is a bacteremia - not a toxemia
False - it is a TOXEMIA not a bacteriemia!
Are abx’s an effective tx for STEC/EHEC?
No! They can increase amount of toxin produced, leading to poor outcomes
Stx of the EHEC binds to the ___ receptors, which can be found in a renal and gut endothelial cells
A. Gb1
B. Gb2
C. Gb3
C. Gb3
Diagnosing STEC/EHEC?
C. dif and Clostridioides difficile-associated disease (CDAD) are associated with diarrheas that present:
A. without a fever
B. without or with fever
C. with a fever
C. with a fever
___: Inflammation of large intestine
Colitis
___ is a gram (+), anaerobic rod, spore-form, that mostly has toxigenic strains
C. dif
C. dif can produce one or both of its toxins (Toxin _ or _)
How do these toxins function?
Toxin A/B
- Function as cytotoxins , disrupt protein synthesis within host cells
What are two pre-disposing factors to acquiring C. dif?
- Hospitalization
- Abx therapy
True or False: People on antacids or PPI have greater chance of developing C. Dif
True
True or False: C. Dif should be suspected in any patient with diarrhea who has received abx within the past two months/who have had diarrhea began 72 hrs or more after hospitalization
True
Febrile, Invasive Diarrheal Agents (Bacillary Dysentary) is associated with which pathogen?
Shigella
True or False: Shigella is a facultative, intracellular gram negative rod, non-motile. It is a lactose fermenter.
False - it is NOT a lactose fermenter (non coliform)
Bacillary dysentery (enterocolitis) –inflammation of small intestine and colon–is a clinical manifestation of ___
Shigella
How is Shigella transmitted?
1) Oral Fecal
2) Contaminated food
True or False: Shigella has very high infectious dose
False - very low infectious dose
How is Shigella classified?
By O antigen (serogroups)
S. dysenteriae, which is associated with HUS due to shiga toxin production, belongs to:
A. Group A
B. Group B
C. Group C
D. Group D
A. Group A
Taxonomy of Shigella?
True or False: Sheep and cows are the sole reservoir/host of Shigella
False - humans are sole reservoir/host
What is the most communicable bacterial diarrheal agent?
Shigella
What causes the inflammation, bleeding, abscess formation, and sloughing off of cells, as seen in Shigella?
Immune response
True or False: Shigella goes to the small intestines (diarrhea) then colon, where it escapes phagocytosed by macrophages
True
Shigella Virulence summary?
Which three pathogens are febrile, invasive diarrheal agents?
- C. jejuni
- Yersinia
- Salmonella
What three features do (C. jejuni, Yersinia, Salmonella – all of which are febrile, invasive diarrheal agents) have in common?
- Gram (-) and non-lactose fermenting
- Zoonosis
- Invasive (can cause bacteremia)
True or False: Of C. jejuni, Yersinia, Salmonella – only Yersinia and C. jejuni can survive in macrophages (facultative intracellular)
False - Yersinia and Salmonella can survive in macrophages but not C. jejuni
If a patient is infected with either: C. jejuni, Yersinia, or Salmonella and has a fever, what test should be done?
Blood culture to dx febrile, invasive diarrheal agents
___ is a gram (-) , oxidase (+) comma shaped motile rod that is NF in GIT of dogs, livestock
A. C. jejuni
B. Yersinia
C. Salmonella
A. C. jejuni
True or False: The virulence factor LT of C. jejuni is ~ to ETEC/CT
True
True or False: C. jejuni can be transmitted via raw milk, undercooked chicken and is a high dose organism.
Person to person spread is not usual.
False - it is low dose organism
True or False: C. jejuni is a intracellular pathogen that can cause inflammatory enteritis
False - extracellular pathogen that can cause inflammatory enteritis
How can you dx C. jejuni?
Look for WBC in stool
Which pathogen is an important cause of pseudoappendicitis?
Yersinia
- small motile rods
- safety pin
What are two ways to transmit Yersinia?
- blood transfusion
- food
- milk
- meat (canned)
Yersinia penetrates epithelial lining, specifically ___ and __.
Where does it live?
Ileum + Colon
Lives: lymphoid tissue
For yersinia, the ___ render killing by macrophage
OMP’s
True or False: Yersinia enterotoxin is similar to ST of ETEC
True
Dx yersinia?
Special media + cold enrichment
True or False: Salmonella is a non-lactose, fermenting, motile, gram (-) rod - non-coliform
True
True or False: S. typhi causes typhoid (enter) fever
True
True or False: Salmonella is a high dose organism that usually has animals as its reservoir – except in case of S. typhi (human host adapted)
True
Can salmonella survive in macrophages or disseminate via circulation?
Yes - can do both
Salmonella invades mucosa of which two organs?
Small Intestine and colon
How does Salmonella result in diarrhea? inflammation?
Diarrhea = stimulates fluid secretion
Inflammation = penetrates epithelial cells to lamina propria
True or False: Salmonella can cause toxemia
True
True or False: Shigella is lactose negative while E.coli is lactose positive
True
