CM- GI Tract Infections Flashcards
What is the route of infection for MOST GI pathogens?
What are the notable exceptions?
Majority of GI infections are fecal-oral transmission [person-to-person or animal-to-person] .
Penetration of Skin:
- strongyloides
- schistosoma
- Hookworm
Blood:
- Hep B
- Hep C
What are the four major defense mechanisms of the body against enteric pathogens?
- Stomach acid [hypochlorhydria or meds to reduce acid increase incidence of vibrio]
- Secretion of IgA
- Endogenous flora [prevent overgrowth of C. diff]
- Gut motility [prevent adherence to surface mucosa]
What are the 6 general syndromes of GI infection?
- Food poisoning
- Acute infectious diarrhea [secretory]
- Dystentery
- Hemorrhagic colitis
- Typhoid [enteric] fever
- Chronic [infectious] diarrhea in AIDs patients
What are the 4 non-inflammatory pathogens?
- ETEC/EPEC/EAEC
- viruses
- parasites [except amebiasis]
- V. cholera
What are the 7 inflammatory pathogens for the GI tract?
- EIEC
- EHEC
- shigella
- salmonella
- yersinia
- campylobacter
- E. histolytica
What part of the bowel is affected by food posioning?
What is the onset of illness?
What 4 pathogens can cause it?
Food poisoning affects the upper GI tract and has more vomiting than diarrhea.
It is rapid onset.
- S. aureus
- B. cereus
- C. perfringens
- C. botulinum [with peripheral nerve abnormality]
What part of the GI tract is affected by acute infectious diarrhea?
What are the 6 pathogens that can cause it?
It affects the small bowel. There is watery diarrhea and no leukocytes.
- ETEC/EPEC/EAEC
- Rotavirus
- Norovirus
- Giardia lamblia
- Cryptosporidium
- vibrio cholera
What part of the GI tract does dysentery affect?
What are the symptoms?
What are the 8 bugs that can cause it?
It affects the colon.
Fever, pain, bloody mucopurulent diarrhea [heavy fecal leukocytes]
- campylobacter
- shigella
- salmonella
- yersinia enterocolitica
- EIEC
- E. histolytica
- Strongyloides
- C. difficile
What part of the GI tract does hemolytic colitis affect?
What are the symptoms?
What bugs cause it?
It affects the colon.
Painful, bloody diarrhea, HUS, few or absent leukocytes
EHEC O157:H7
What part of the GI tract is affected by typhoid fever?
What are the symptoms?
What 3 bugs cause it?
It enters via the SB but then has systemic illness
(monocytic leukocytosis)
- S, typhi
- S. paratyphi
- Y. enterocolitica
What part of the GI tract is affected by chronic diarrhea in AIDS and immunocompromised patients?
What are the symptoms?
What 5 bugs cause it?
It affects the SB.
Watery diarrhea with no leukocytes
- cryptosporidium parvum
- microsporidia
- cyclospora cayetanensis
- CMV
- MAC
What are the 3 causes of GI infections that affect the small bowel?
- Acute infectious Diarrhea
- Chronic infectious diarrhea (HIV/immuno)
- Typhoid fever (enters SB then systemic)
Which 2 causes of GI infections affect the colon?
- Dysentery
2. hemolytic colitis
Which causes of GI infections cause watery diarrhea with few to no fecal leukocytes?
- Acute infectious diarrhea
- hemolytic colitis
- chronic infectious diarrhea
What causes pathogenesis in food poisoning? What is the notable exception?
What are symptoms? How long does it last?
The ingestion of preformed bacterial toxins in food (it is NOT the organism that causes it).
The exception is infant botulism where the spores of C. botulinum are ingested and transform into vegetative form.
The toxins cause nausea and vomiting that is rapid onset (1-3 hours) and is self-limiting (12-36 hrs)
What is the only food poisoning that can be life threatening without appropriate supportive care?
What symptoms does it present with?
C. botulinum - it causes descending paralysis and no risk for other infections
Diarrhea is the most common manifestation of GI infection. What are the 3 major types and how do they differ in presentation?
- Secretory - watery
- dysentery, diarrhea- fever and bloody diarrhea with mucus
- Hemorrhagic colitis- frank bloody diarrhea
What generally the cause of secretory diarrhea?
What 4 viruses cause it?
What 2 bacteria?
What 3 protozoan parasites?
Viruses are generally the cause and they are usually self-limited.
Viruses: rotavirus, norovirus, adenovirus, astrovirus
Bacteria: ETEC (traveler’s diarrhea), vibrio cholera
Protozoa parasite: Giardia, cryptosporidium, cyclospora
Pathologically, how do pathogens cause diarrhea?
They colonize the small bowel and stimulate fluid and electrolyte secretion by pharmacologic imbalance
What are typical routes of exposure of protozoa that cause secretory diarrhea (crypto, giardia, cyclospora) ?
Daycare centers
Food
Water
A man went to a camp in Texas and went recreationally swimming in a lake. What pathogen is he likely to get? What will it cause?
Giardia–> secretory diarrhea [acute infectious diarrhea]
A patient presents with fever, abdominal cramps, and bloody mucopurulent diarrhea. What part of the GI tract is most likely affected?
What are offending pathogens?
Colon- shigella, salmonella, campylobacter, yersinia and C. dificile
What is the pathogenesis of organisms that cause dysentery?
They colonize the colon and at first are confined to the epithelial layer.
As the disease progresses, more of the lamina propria is involved and crypt abscesses form.
What is the most frequent cause of acute infectious diarrhea in the US? What is the major vehicle to transmission in humans?
Campylobacter – transmitted by chicken
What pathogen, capable of dystentery, is ubiquitous to the environment and tends to colonize the GI tract of domestic animals?
Salmonella
What is the only natural reservoir of Shigella?
humans
A patient drank old milk and now presents with diarrhea and prominent RLQ pain. The stool has few if any leukocytes. What organism is it most likely?
What is the pathogenesis?
Yersinia enterocolitis - it penetrates the surface epithelium of the distal small intestine, makes its way deeper into tissue and gets to the lymph nodes.
It can cause mesenteric adenitis which mimicks acute appendicitis and bacteremia with hematogenous spread
What bug is frequently associated with prior antibiotic use and hospitalized patients?
C. difficile
How is C. difficile different from the other enteric bacterial pathogen?
How is the diagnosis made?
It is gram + and produces toxins
Diagnosis:
detecting toxins in feces
YOU CANNOT DO STOOL CULTURE
What drug is contraindicated in a patient with C. difficile infection?
Antidiarrheals because it will increase toxin contact with the colon possibly leading to translocation and sepsis
What are the 2 most serious consequences of EHEC O157:H7?
Who do these complications usually occur in?
HUS and TTP and these occur in the really young or really old
What kind of diarrhea does E. histolytica usually cause?
Are there leukocytes in the stool? Why or why not?
What are other complications of this parasite?
It causes dystentery (amebic colitis), however there are absent fecal leukocytes because ameba engulf RBCs and WBCs for food.
It can also have systemic effects and cause liver abscesses
It is often difficult to determine the etiology of a patient’s diarrheal syndrome on clinical grounds alone. What tests should you do to help differentiate organisms?
- Stool culture
- Examine stool for RBC and leukocytes [invasive bacteria vs. non-invasive viruses, parasites]
- Ova and Parasites [amebic, dysentery, giardia, helminth infections]
- Sigmoidoscopy/colonoscopy [if stool cultures and O&P are negative] to look for:
- toxin-negative C. diff
- Crohn, UC
What is typhoid fever?
How long does it typically last?
What are the symptoms?
It is a systemic febrile illness that last 3-5 wks.
- Fever
- bacteremia
- metastatic spread and multiple organ dysfunction
- NO DIARRHEA
How is S. typhi spread?
How can it cause a carrier state?
It is spread by ingesting material contaminated by infected feces of chronic carriers.
It causes a carrier state because it can cohabit humans in the gall bladder.
Most clinical labs routinely run culture of stools for what 4 organisms?
What happens if it is a different organism you are worried about?
Yersinia, Campylobacter, shigella, salmonella
Based on clinical history and stool leukocytes, if you are worried about a different organism, you need to make a specific request for the cultures
Who is typically affected by CMV infections?
What part of the GI tract is involved?
What are the clinical manifestations?
It affects AIDS patients with a low CD4.
CMV involves any region of the GI tract and causes chronic diarrhea.
CMV causes ischemic mucousal ulceration leading to:
diarrhea, ab pain, perforation, weight loss
When an AIDS patient’s CD4 is below 50, what pathogen are you concerned about for GI symptoms?
MAC
What is the typical workup for an AIDS patient with diarrhea?
What should always be done on stool samples from patients with AIDS?
What is the next step if the stool samples are not diagnostic and the diarrhea/weight loss persists?
First, start with H/P, CD4, routine labs
Next,
- bacterial cultures (campy, shigella, salmonella)
- O&P with acid fast stain [cyclospora, crypto]
- C. diff toxin screen [most aids patients are on antibiotics]
- biopsy of ulcerations for CMV and protozoa
If weight loss/diarrhea persist:
- upper endoscopy for aspirates and biopsies of the small bowel for : microsporidia, crypto, giardia that can be missed on stool
If endoscopy fails to yield the cause:
- EGD
What are the most common causes of GI illness in children infant–> preschool?
- Rota
- adeno
- bacteria
- giardia
What are the most common causes of GI illness in children 5-12?
- Noro
- giardia
- E. coli
- bacteria
What are the most common causes of GI illness in children >12?
- Noro
2. bacteria
What are risk factors for developing traveler’s diarrhea?
What is the median duration of travelers diarrhea?
Etiologically, what is the most common cause (50-75% of cases)?
Risks: destination, season, accomadations, food, age, origin of travel
MEdian duration: 3-5 days
Most common cause : bacteria (majority ETEC)
What are the 3 most common agents to lead to the overgrowth of C. diff?
- clindamycin
- amoxicillin-clavulanate
- cephalosporins
What are the 3 most serious side effects of C. difficile overgrowth?
- watery diarrhea
- pseudomembranous colitis
- toxic megacolon
How is diagnosis of C. diff made?
What is treatment?
Diagnosis:
- toxin in the stool [a endotoxin, b cytotoxin]
- finding pseudomembrane on endoscopy
Treatment:
- stop antibiotics
- treat with oral metronidazole or vancomycin
Usually diarrhea is self-limited and dont require workups. What 6 situations would warrant a workup?
- age
- risk of acquisition [day care, nursing home, water activity, pets]
- travel [ETEC, shigella, amebiasis, giardia]
- antibiotic use [C. diff]
- sexual practice [HIV risks]
- immune status
Examination of a patient with diarrhea should assess and screen for what 2 things?
What should the lab evaluation center around?
- assess volume depletion
- screen for inflammatory diarrhea [fever, blood and leukocytes in stool]
Lab eval should be:
1. electrolytes, renal function, leukocytosis
Specific diagnoses for pathogen associated GI issues is based on what 4 lab tests?
- Stool culture (routine) - campy. shig, salmo
- Stool culture (special)- EHEC, yersinia, vibrio
- Stool O/P - parasites
- Special tests - toxins for C. diff, Immunoassay for Rotavirus
What are the 5 steps of management for someone with severe or chronic diarrhea?
- Volume repletion
- antimotility agents [may be dangerous!]
- adbsorbent/anti-secretory agents [pepto]
- antimicrobials [many increase complications]
- prevention!!
