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56 Cards in this Set
- Front
- Back
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Def: Gastroenteritis
- most common cause? - symptoms? |
inflammation of the lining of the intestines caused by a virus, bacteria, or parasites
most common cause is Norovirus infection symptoms include: diarrhea, abdominal pain, vomiting, headache, fever, & chills |
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Def: Gastritis
Causes? |
inflammation, irritation, or erosion of the lining of the stomach
causes: excessive alcohol use, chronic vomiting, stress, certain medications, H. pylori, pernicious anemia, bile reflux, infection |
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Def: Enteritis
causes? |
inflammation of the small intestine
causes: usually bacteria or virus sometimes by autoimmune (i,e, Crohn's), certain drugs, radiation damage |
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Def: Colitis
Causes? |
inflammation of the large intestine
causes: infections, inflammatory disorders (colitis, Crohn's), ischemia, radiation |
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Def: Cholecystitis
Causes? |
inflammation of the gall bladder
causes: gallstones, infection, injury |
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Def: Dysentery
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diarrhea with pus and blood in the feces
causes: microbial deep invasion and/or cytotoxin destruction of colon |
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Def: Enteric fever
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a systemic infection starting in the GI tract
e.g. typhoid - an infection that causes diarrhea and rash - usually caused by Salmonella typhi |
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Def: tenesmus
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feeling of incomplete defecation
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Def: enterotoxin
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a harmful substance produced by certain bacteria that damages the GI tract causing cramps, N&V, diarrhea
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Def: cytotoxin
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a substance that is toxic to cells
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Def: exotoxin
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a toxin secreted by bacteria
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Def: Intoxication
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poisoning by a drug or toxic substance
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Def: Oral rehydration therapy
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the use of modest amounts of sugar and salt added to water to prevent or treat dehydration
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Def: Bile
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fluid made by the liver, stored in gall bladder that aids in digestion of lipids
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Following the GI tract from the mouth to the anus, what rough density of microbes
(sparse, heavy, etc.) do you find in each site? |
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What are the host defenses of the GI tract?
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1. Epithelium, mucus secretions
2. Peristalsis 3. Stomach acid 4. Bile 5. Secretory IgA, IgG 6. Phagocytes 7. GALT - gut associated lymphoid tissue 8. Normal flora |
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What are the four class examples of obligate human pathogens?
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1. Salmonella typhi
2. Shigella 3. Helicobacter pylori 4. Entamoea histolytica |
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What are the three zoonotic pathogens presented in class?
What is the unexpected source? |
1. E. coli
2. non-typhoid salmonella 3. Campylobacter Humans can be the source of infection, via fecal/oral transmission |
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What is the relationship between acid tolerance of a microbe and minimum inoculum required for infection?
What is the result of reduced gastric acidity? |
inversely proportional
high acid tolerance = low infectious inoculum (most inoculum make it through the stomach) low acid tolerance = high infectious inoculum (small % make it through the stomach) Reduced gastric acidity increases susceptibility to GI pathogens |
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What is the typical site, clinical features, and examples for infection via INTOXICATION mechanism?
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site: small intestine
cf: severe N&V and/or diarrhea ex: Staphylococcus aureus, Bacillus cereus |
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What is the typical site, clinical features, and examples for infection via SECRETORY TOXIN mechanism?
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site: small bowel
cf: profuse watery diarrhea, possibly pain &/or fever ex: ETEC, Vibrio cholerae, rotavirus |
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What is the typical site, clinical features, and examples for infection via CYTOTOXIN mechanism?
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site: large bowel
cf: bloody diarrhea, painful cramps, fever ex: EHEC, Shigella |
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What is the typical site, clinical features, and examples for infection via MUCOSAL COLONIZATION & DESTRUCTION mechanism?
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site: small bowel
cf: diarrhea, fever, N&V ex: EPEC, Salmonella, Campylobacter (early), rotavirus |
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What is the typical site, clinical features, and examples for infection via DEEP INVASION mechanism?
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site: large bowel
cf: purulent bloody dysentery, painful cramps, fever ex: EIEC, Shigella, Campylobacter (late), Entamoeba histolytica |
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What is the typical site, clinical features, and examples for infection via SYSTEMIC DISSEMINATION mechanism?
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site: GI to blood to liver to GI
cf: systemic signs and symptoms (enteric fever) ex: Salmonella typhi |
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How does Staphylococcus manifest as food poisoning?
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enterotoxins stimulate T lymphocytes in the gut
- a common skin microbiota, contamination is common in many foods, but not all strains are toxigenic |
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How does Bacillus cereus manifest as food poisoning?
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2 types of toxins:
Emetic toxin pre-formed in food causes vomiting 1-6 hr pc Diarrhetic toxin formed in intestinal lumen causes diarrhea 8-16 hr pc - a strain may produce one or both types, or neither |
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What are the four most common causes of bacterial enteric disease in the US?
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1. Campylobacter
2. Salmonella 3. Shigella 4. E. coli |
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Does Heliobacter cause enteritis?
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NO, it causes gastritis
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ETEC
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Enterotoxigenic E. coli
"traveler's diarrhea" secretory toxin |
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EPEC
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enteropathogenic E. coli
"infantile diarrhea" mucosal colonization and destruction similar to non-typhoid Salmonella |
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EIEC
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Enteroinvasive E. coli
bacillary dysentery - deep invasion similar to Shigella |
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EHEC
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enterohemorrhagic E. coli
hemorrhagic colitis, HUS cytotoxin - zoonosis from cow intestines or infected humans |
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HUS - Hemolytic uremia syndrome
cause? associated with what pathogens? clinical features Who at risk? |
caused by cytotoxin
associated with EHEC, some Shigella strains, other enteropathogens cf: thrombotic microangiopathy hemolytic anemia throbocytopenia w/ renal lesions renal failure Children & elderly are at increased risk of this rare disease |
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How does Salmonella manifest as Gastroenteritis?
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from mucosal colonization and destruction (EPEC)
- non-typhoid Salmonella - "rotton egg" odor of stool - relative resistance to bile salts |
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how does Salmonella manifest as Enteric Fever?
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from systemic dissemination
- mainly S. typhi - blood culture likely before stool - reservoir sites (gall bladder) lead to carrier state |
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What are the four causes of Enteric fever presented in class?
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1. Salmonella typhi
2. other Salmonella species 3. Yersinia enterocolitica 4. Campylobacter jejuni Note: colonization of gallbladder can lead to continuous fecal shedding by asymptomatic carrier |
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What is the timing of positive fecal, blood, and urine cultures for Typhoid?
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Shigella
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obligate human pathogen; fecal/oral
small inoculum required Can cause Bacillary dysentery via deep invasion Some strains make cytotoxin |
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Campylobacter
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most common bacterial enteric infection in US
fecal/oral, contaminated food & animals gastroenteritis from mucosal colonization and destruction rare enteric fever from systemic dissemination |
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Yersinia
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fecal/oral, animal transmission
gastroenteritis, diarrhea, occasional pseudoappendicitis |
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Y. pestis
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human-human transmission via fleas or respiratory droplets
plague: bubonic, pneumonic, septicemic |
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Vibrio cholerae
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fecal/oral
large inoculum required Cholera, voluminous watery diarrhea |
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Vibrio parahemolyticus
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salt water, shellfish, sushi
gastroenteritis, rare enteric fever |
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Vibrio vulnificus
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salt water, shellfish, skin abrasions
wound infection, septicemia NOT gastroenteritis - especially in immunocompromised & alcoholics |
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Listeria monocytogenes
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dairy & meat, direct animal contact, transplacental, perinatal
gram + rod; resistant to freezing, drying, heat gastroenterits |
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What are the symptoms of viral gastroenteritis?
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- watery diarrhea, N&V
- viral shedding for weeks after symptoms end - prolonged full recovery time |
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Rotavirus
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major viral agent in infants & young children
- vaccine since 2006 reducing prevelance gastroenteritis via secretory toxin, mucosal colonization & destruction diagnosed by stool ELISA |
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Norovirus
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very contagious; outbreaks
gastroenteritis |
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What condition do Adenovirus and astrovirus cause?
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gastroenteritis
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What are the three parasitic agents of enteric infection discussed in class?
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Entamoeba histolytica
Giardia lamblia Cryptosporidium parvum |
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What is the process of Entamoeba histolytica infection?
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Helicobacter pylori
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fecal/oral transmission
ulcers, gastitis, development of cancer - microbe avoids/survives acid environment |
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What medications can be used to treat enteric infections?
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1. maintain hydration and electrolytes
2. bismuth subsalicylate may have some antimicrobial activity 3. GI motility reducing agents (do NOT use if blood or pus in stool) 4. probiotic therapy - antibiotics often not indicated |
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Why are antibiotics generally not indicated for enteric infecions?
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1. infection is often self-limiting
2. duration of infection < time to achieve therapeutic antibiotic level 3. vomiting & diarrhea expel oral antibiotics 4. antibiotics may worsen situation by altering normal microbiota 5. no effective antibiotics for viral agents |
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What are the special cases when antibiotics might be used to treat enteric infections?
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1. at-risk patients
2. protracted and/or severe infections - often fluoroquinolones (ciprofloxacin) for bacteria; metronidazole for Entamoeba |
