Gastrointestinal Infections VI Flashcards

Question 1

Q

Characteristic of vibrio parahaemolyticus?

Describe how it manifests as noninflammatory bacterial gastroenterisis.

Answer

A

Vibrio parahaemolyticuscurved gram (-) rod
- oxidase positive
- halophile – requires salt to grow
Manifestations
- 24 hr incubation
- explosive diarrhea to cholera-like illness
- headache
- abdominal cramps
- nausea
- vomiting
- low-grade fever

Question 2

Q

Common cause of Vibrio parahaemolyticus noninflammatory bacterial gastroenteritis?

Pathology?

Diagnosis?

Treatment?

Prevention?

Answer

A

Cause
- eating raw shellfish
Pathology
- thermostable Kanagawa hemolysin that induces chloride ion secretion
Diagnosis
- clinical presentation
- green colonies of TCBS agar
- beta hemolytic on human RBC agar plates; not on sheep RBC agar plates
Treatment
- oral replacement of fluids adn electrolytes
- antibiotics
prevention
- proper cooking of shellfish

Question 3

Q

Characteristic of vibrio cholerae?

Common causes and endemic areas?

Answer

A

Vibrio cholerae
- slightly curved gram-negative rod
- O1 and O139 serotypes (LPS) – severe disease
- non-O1/O139 types milder disease
Endemic in
- India, West Bengal, Bangladesh, South America, and Lousiana
- ingested in contaminated water and food (shellfish and crabs)

Question 4

Q

Symptoms of vibrio cholerae caused noninflammatory bacterial gsatroenteritis?

Pathology of disease?

Diagnosis?

Treatment?

Answer

A

symptoms
- abrupt onset of watery diarrhea
- no fever
- “rice water” stools
- vomiting may occur
Pathology
- large dose of cells needed
- attache to microvilli
- no invasion
- produce cholera toxin
- ADP robosylates GTP-binding protein
  - increase cAMP
    - inhibits NaCl absorption and stiumlates Cl^-secretion
Diagnosis
- clinical presentation
- plating stool on TCBS agar (yellow on TCBS)
  - thiosulfate-citrate-bile-salts-sucrose agar
- test for foxin in adrenal cell assay
Treatment
- replace fluids and electrolytes
- antibiotics reduce severity and length of disease

Question 5

Q

Question 6

Q

What are teh 3 major causes of parasitic gastroenteritis?

Answer

A

Giardiasis
Cyclosporiasis
Cryptosporidiosis
- chronic problem in immunocompromised

Question 7

Q

What is the usual cause of Giardiasis?

Symtoms?

Answer

A

Usually ingest water containing Giadia cysts
- become trophozoites in duodenum
Symptoms
- many asymptomatic
- watery diarrhea to malabsorption syndrome
- incubation period 1-4 weeks
- sudden onset of
  - foul-smelling watery diarrhea
  - cramps
  - flatulence
  - steatorrhea

Question 8

Q

Pathology of Giardiasis?

Diagnosis?

Treatment?

Prevention?

Answer

A

Pathology
- adhere to microvilli
- causes disaccharidase deficiency
- results in osmotic diarrhea
- bloating, flatulence, watery diarrhea
- if continue – malabsorption and fatty diarrhea can result
Diagnosis
- Hx of drinking contaminated water
- clinical symptoms
- confirmatory diagnosis – find organism in stool
Treatment
- see pharmacology notes
Prevention
- boil or filter all drinking water
- chlorination doesn’t kill the cysts

Question 9

Q

Etiological cause of cyclosporiasis?

Cause?

Pathology?

Answer

A

Etiology: Cyclospora cayetanesis
common water contaminant
- imported fresh fruits, vegetables & herbs
- sporulated oocysts are infectious form of the parasite
Pathology
- binds to epithelial cells in the small intestine
- causes secretory diarrhea
- mechanism unkown

Question 10

Q

Symptoms of Cyclosporiasis?

Diagnosis?

Treatment?

Prevention?

Answer

A

Symptom
- normal immune system
  - asymptomatic to prolonged diarrhea lasting a month or more
  - other symptoms include; fever, fatigue, flatulence, and belching
  - self-limiting, wax & wane, or result in prolonged diarrhea
  - fatigue and malaise may persist after diarrhea has resolved
Diagnosis
- look for variably staining acid-fast cysts in a stool smear
Treatment
- see pharmacology notes
Prevention
- in US avoid imported fresh fruits and vegetables

Question 11

Q

Common cause of Cryptosporidium?

Etiological cause?

Pathology?

Answer

A

Common water contaminant
- Lives in fish, mammals and reptiles
- small number of oocysts cause diarrhea
- immunocompromised more likely to have symptoms & develop chronic diarrhea
Pathology
- Afects ion transport
- Inflammatory damage of microvilli leading to malabsorption

Question 12

Q

Symptoms of Cryptosporidium?

Diagnosis?

Treatment?

Prevention?

Answer

A

Symptoms
- normal immune system
  - asymptomatic
  - self-limiting diarrhea (around 10 d duration)
- immunocompromised
  - diarrheal disease can be severe
  - 50 or more stools per day
  - last months to years
Diagnosis
- look for acid-fast cysts in stool smear
Treatment
- see pharmacology nots
- antidiarrheal drugs give temporary relief
Prevention
- avoid contaminated water sourcs

Question 13

Q

What is the etiological agent responsible for producing antibiotic-associated pseudomembranous colitis?

Virulence factors?

Symptoms?

Answer

A

Clostridiodes difficile - resistant to many antibiotics
- anaerobe
- produces A and B toxin
Symptoms
- asymptomatic to fulminatn colitis
  - depends on number of receptors for toxins on colon
- watery diarrhea
- crampy bilateral lower quadrant pain that decreases after bowel movement
- low-grade fever
- peripheral blood leukocytosis
5-10 days post antibiotic

Question 14

Q

Symptoms of a C. diff infection?

Answer

A

Symptoms
- pseudomembranous colitis – seen w/ colonoscopy
  - look for yellowish plaques
- fulminant colitis
  - diarrhea, but can be constipated
  - diffuse severe abdominal pain
  - hypoactive bowel sounds
  - abdominal distension & guarding
  - marked peripheral blood leukocytosis
  - complications
    - perforation
    - toxic megacolon

Question 15

Q

Diagnosis C. diff infection?

Treatment?

Prevention?

Answer

A

Diagnosis
- Hx antibiotic therapy
  - clindamycin & lincomycin
- ELISA for toxin A & B
- PCR for glutamate dehydrogenase screen of fecal sample
  - most sensitive
- 50% of time stool ahve fecal leukocytes and are heme positive
- endoscopy; yellow plaques
treatment
- withdraw antibiotic
- IV fluids/electryolyte
- NO ANTIMOTILITY DRUGS - increase canges toxic megacolon & full-blown colitis
- fecal transplantation
- megacolon: bowel resection & ileostomy
Prevention
- prevent spread to other patients and personnel
- avoid prolonged us of broad-spectrum antibiotics

Question 16

Q

Gereal symptoms invasive gastroenteritis?

Common etiological causes?

Answer

A

Symptoms
- fever
- abdominal pain
- pain while attampting to defecate (tenesmus)
Etiologies
- Campylobacter
- Shigella
- Salmonella
- EHEC
- EIEC
- Yersinia enterocolitica
- Entamoeba histolytica

Question 17

Q

Shape/characteristics fo Campyocater jejuni?

How is Campylobacteriosis often acquired?

Symptoms?

Answer

A

Characteristic
- S shaped (sagull)– hard to grow
Acquired
- non-chlorinated water
- undercooked or raw meat, unpasteurized milk, nonchlorinated H₂O
Symptoms
- most cases mild
- initial
  - periumbilical cramping
  - intense abdominal pain
  - malaise, myalgias, heaadache, vomiting
  - watery diarrhea most common
- inflammatory bowel disease
  - malaise, fever, abdominal cramps, tenesumu, blood stool, fecal leukocytes, indistinguishable from shigell salmonella, E. coli

Question 18

Q

Campylobacteriosis Pathogenesis?

Diagnosis?

Treatment?

Answer

A

Pathogenesis
- Shiga toxin
Diagnosis
- seagull shaped bacterial w/ darting motility in watery, bloody leukocyte-filled stool
- Campy-BAP or Skirrow media
treatment
- most self-lmiting
- oral rehydration; correct electrolyte imbalances
- Use antibiotic is patient has
  - fever
  - increasing bloody diarrhea
  - symptoms longer than a week

Question 19

Q

Characteristics of Shigella?

How is Shigellosis most often acquried?

Answer

A

Characeristics
- Group D- S. sonnei (most common in US)
- Group B- S. flexneri
- nonmotile, doe NOT ferment lactose, gram (-) rod
- resistant to stomach acid
Acquired
- fecal oral
- contaminated water sources
- daycare, nursing homes, prisions
  - food, fingers, feces, flies

Question 20

Q

Symptoms of Shigellosis?

Pathogenesis?

Diagnosis?

Treatment?

Answer

A

Symptoms
- incubation 36-72 hrs
- fever, abdominal cramping and pain
- watery diarrhea
- after 2 days diarrhea, then dysentery adn tenesmus
- may initiate septicemia by E. coli
- rarely gets into bloodstream
Pathogenesis
- Shiga toxin
Diagnosis
- clinical symptoms- presumptive diagnosis
- definitive Dx- isolate organism from stools
- grow on S-S agar
- fecal leukocytes will be present
Treatment
- usually self-limiting
- to shorten course adn limit person-to-person spread, treat with antibiotics
- dont give antidiarrheal compounds
- replace fluids & electrolytes
Prevention
- wash your hands

Question 21

Q

Characteristics of Salmonella?

How is Salmonellosis most often acquired?

What are the etiological agents responsible for enteric fever?

Answer

A

Charcteristics
- motile, nonlactose fermenting rods
Acquired
- from food, animals
- person-to-person from chronic carriers
Enteric fever
- S. Typhi
- S. Paratyphi A
- S. Schottmuelleri
- S. Hirschfeldii

Question 22

Q

Symptoms caused from Salmonella enteritis?

Symptoms caused from Salmonella septicemia?

Symptoms caused from Salmonella enteric fever

Answer

A

Enteritis
- ingest food
- 6-48 hr later: nausea, abdominal cramps, vomiting, nonbloody diarrhea (rarely causes bloody diarrhea). fever, headache myalgia
- lasts 2d-1 week
- usually self-limiting
Septicemia
- S. enterica most likely to cause
- high risk in pediatric, geriatric, and immunocompromised populations
- just like any other gram-negative sepsis
Enteric fever
- pass through lining of intestine
- engulfed by macrophages
- taken to liver, spleen, and bone marrow (replicate)
  - 10-14 days later gradually rising fever
  - lasts week of two
  - then diarrhea
  - can have skin lesions “rose spots”
  - colonization gallbladder = carrier state

Question 23

Q

Diagnosis Salmonellosis?

Treatment?

Prevention?

Answer

A

Diagnosis
- less inflammation compared to shigellosis
- fewere leukocytes in stool
- use S-S agar to isolate organisms
Treatment
- fluid replacement; NO antidiarrheals
- enteritis- self-limiting
- patients more likely to develop bacteremias shoudl be treated with antibiotics
- enteric fever- antibiotic therapy immediately
Prevention
- travelrs vaccination- for typhoid fever
  - oral live attenuated
  - Vi capsular polysaccharide vaccine- IM

Question 24

Q

Difference in the capabilities of EHEC and EIEC?

Answer

A

EHEC
- allow them to invated in cells & produce shiga toxin
  - causes HC and can damage kidneys –> HUS
  - most common cause of HC and HUS is E. coli O157:H7
    - O = LPS
    - H = flagella
EIEC
- can invade, but do NOT produce shigatoxin

Question 25

Q

Symptoms of EHEC?

Symptoms EIEC?

Diagnosis?

Answer

A

EHEC
- severe crampy abdominal pain, watery diarhea followed by bloody diarrhea
  - (hemorrhagic colitis; HC)
- Usually no fever
- HUS triad- acute renal failure, thrombocytopenia, microangiopathic hemolytic anemia (schistocyte)
- HC precedes HUS usually
EIEC
- watery diarrhea that can on occasion result in dysenteric stools
- not much if any fever
Diagnosis
- EHEC and EIEC
  - isolate and idnetify the organism
  - grow EHEC O157:H7 on sorbitol-MacCOnkey plates–can’t ferment sorbitol

Question 26

Q

Treatment EHEC and EIEC?

Prevention?

Answer

A

Treatment
- EHEC
  - avoid antimotility drugs adn antibiotics
    - antibiotics release more toxina nd increas change of HUS
- EIEC- normally self lmiting
  - avoid antimotility drugs
  - can use antibiotis in severe cases
Prevention
- EHEC
  - thoroughly cook hamburgers, drinkk pasteurized fruit juices
- EIEC
  - drink from safe water sources

Question 27

Q

Characteristics of Yersinia enterocolicica?

Answer

A

Characteristics
- gram (-) rod
- does not ferment lactose; urease positive
- motile at 25 but NOT at 37
- can grow at 4 degrees, but optimum is 25-28 degrees
- bull’s eye appearance on CIN agan

Question 28

Q

Manifestations of Yersinia enterocolitica?

Epidemiology?

Answer

A

Diarrhea
- subacute onset
- occasionally bloody stols; abodominal pain (right lower quadrant), fever, nausea, and comiting; pharyngitis
- longe duration 12-22 days
Septicemia
- can develop into septic shock
- infants, impaired immunity, iron-overload
Pseudoappendicitis
- colonies in ileum and appendix
- right lower abdominal pain, fever, vomiting, leukocytosis
- Post infectious sequaelae
  - erythema nodosum and reactive arthritis (northern european with HLA-B27)
Epidemiology
- humans and mmmals
- ingest- contaminated food/water
- contaminated blood transfusions

Question 29

Q

Diagnosis of Yersinia enterocolitica?

Treatment and prevention?

Answer

A

Diagnosis
- culture samples (stool, blood) on CIN medium incubate at room temperature for several days
- Bull’s eye appearance of colonies
- lactose negative; urease positive, motile at 25 but NOT at 37
Treatment
- supportive care and antibiotics
- avoid antimotility drugs
Prevention
- prevent contamination of food/wate by pets and otehr animals
- fully cook food and drink pasteurized milk and milk products

Question 30

Q

How is entamoeba histolytica often acquired?

How can you differentiate it from other amebiasis?

Answer

A

Acquired
- ingest cysts from contaminate dfood and water
Pathogenesis
- trophozoites live in proximal colon
- will ingest RBC (uniqe)
- can invate the liver, lungs, brain and bloodstream

Question 31

Q

Symptoms of Entamoeba histolytica infection?

Pathology?

Answer

A

symptoms
- incubation 1-5 days
- diarrhea, abdominl cramps, vomiting, tenesumu
- stools can be watry of dysenteric (watery wiht mucous adn blood)
- amebic abscess- abrupt onset of high fever, right upper quadrant pain, anorexia, nausea, vomiting
Pathology
- colonic ulcers, granulomas diffuse hepatitis, hepatic abscess, and rectal ulcerations
- in colon the trophozoites produce ulcers
- Flask-shaped ulcers
- In liver
  - necrosis of endothelium and penetrate periportal sinusoid to the loules
  - Aspirations- “Anchovy paste” appearance may form very large abscesses

Question 32

Q

Diagnosis, treatment and prevention of Entamoeba histolytica infection?

Answer

A

Diagnosis
- see parasite in feces
- leukocytosis in peripheral blood smea
- chest radiograph, CT or MRI for extra-intestinal infections
Treatment
- antiparasitic drugs
  - mild to moderate disease
  - drain liver abscess if larger than 12 cm
Prevention
- drink safe water