Exam 5 (GI Tract Infections) Flashcards
Definitions of gastritis, gastroenteritis, diarrhea, dysentery, enteritis, enterocolitis, colitis
- Gastritis: inflammation of stomach - Gastroenteritis: inflammation of stomach and intestines - Diarrhea: frequent loose and fluid filled stools – usually from disease of small intestine - Dysentery: inflammatory disorder of GI associated with diarrhea that is blood and pus filled, with abdominal pain – usually from disease of large intestine - Enteritis: inflammation of intestines, esp small intestine - Enterocolitis: inflammation of mucosa of small and large intestine - Colitis: inflammation of large colon
Bacillus cereus. Characteristics of bacteria, disease/clinical presentation, pathogenesis, treatment, epidemiology
- Characteristics: G+ rod, spore forming - Disease: food poisoning a.) Emetic form: vomiting, nausea and abdominal cramps 1-8 hours after ingestion of contaminated food with preformed toxin b.) Diarrheal form: onset of diarrhea, nausea and abdominal cramps 8-16 hours after ingestion of contaminated food with organism - Pathogenesis: emetic form mediated by preformed heat-STABLE enterotoxin, MOA unknown. Diarrheal form requires bacterial multiplication and production of heat-LIABLE enterotoxin in intestine. - Tx: supportive - Epidemiology: emetic associated with improper cooked and stored rice. Diarrheal form associated with meat and vegetables.
Non-typhoidal Salmonella. Serovars, characteristics of bacteria, disease/clinical presentation, pathogenesis, diagnosis, treatment, epidemiology
- Serovars: Cholerasuis, enteritidis, typhmurium (not as human adapted) - Characteristics: G- rod, motile, flagellated (H antigen), facultative anaerobe, intracellular, acid tolerant - Disease: nausea, vomiting, abdominal cramps and water diarrhea. Persistent diarrhea for 3-4 days +/- blood with 50% of cases with fever (not prolonged), can be loose stool to severe dysentery-like diarrhea - Pathogenesis: a.) Adheres to M cells (Peyer’s) and enterocytes in SI b.) Phagocytosed into macrophage or type 3 secretion system allows for entry into cells and blood c.) After entry: 1.) rapid killing of macrophage via inflammatory response and/or 2.) carriage in macrophage of immunocompromised leading to systemic dissemination, bacteremia, arthritis, osteomyelitis, endocarditis - Diagnosis: detection of anti-Vi antigen abs, culture from blood and stool – non-lactose fermenting and produces H2S - Tx: for gastroenteritis tx supportively, but not with abx as it enhances carrier states. For systemic, tx with abx once resistance profile determined.
Strongyloides stercoralis. Disease caused/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Disease/clinical = strongylodiasis. Minimal symptoms with low worm burden including epigastric pain, tenderness, bloating, heart burn. Pulmonary involvement with inflammation. Eosinophilia seen. Hyperinfection = diarrhea that worsens, dissemination into lungs, CNS, peritoneum, liver and kidney – esp in immunosuppressed. - Lifecycle/patho: *can exist as free living nematode in soil, but can live in human host. Developmentally progresses to infectious larval form in external environment, penetrates skin or perianal or (intestines, once in) and travels into circulation into lungs and pharynx, swallowed into intestines where it matures into adult forms and sexually reproduces and lays eggs, which hatch and larva are excreted in stool. Hyperinfection d/t auto-infection. - Diagnosis: larvae in stool* not EGGS - Epidemiology: SE US and Appalachia
Distinguish between symptomatology between bacterial food poisoning or other generalized GI tract infections
- Symptoms for both include diarrhea, vomiting - Food poisoning is not typically associated with fever
Liver flukes. Name the genus/species, disease caused/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Liver flukes = fasciola hepatica (aka sheep liver fluke) and Clonorchis (opisthorcis) sinesis (aka Chinese liver fluke). - Clinical/disease: F.hepatica: liver tenderness, hepatomegaly, fever, eosinophilia, biliary obstruction can occur leading to jaundice. C. sinesis: asymptomatic with light infections. Heavy infection leads to biliary obstruction, jaundice, hepatitis, hepatomegaly, gallstones – also 10-15x more likely to develop bile duct CA. - Lifecycle/patho: a.) Fasciola hepatica: encysted material from freshwater consumed by human, excysts in duodenum, migrates to bile duct, penetrates intestinal wall, becomes adult in bile duct, releases unembryonated eggs in feces, penetrates snail, undergoes further development, released into freshwater, encysts onto water plants b.) Clonorchis sinesis: consumption of freshwater fish with encysted material, excysts in duodenum, migrates to bile duct, releases embryonated egg into feces, ingested by snail, release into water, penetrates scales of fish - Diagnosis: eggs in feces - Epidemiology: F. hepatica acquired through consumption of aquatic plants, worldwide including SE US. O. sinesis acquired through ingestion of undercooked freshwater fish
What is hepatitis and what are the 3 clinical presentations? Describe each presentation
- Inflammation of liver - Acute, chronic and fulminant hepatitis 1.) Acute: - Symptoms: prodrome (HA, arthralgia, myalgia, fatigue, nausea, vomiting, pharyngitis, mild fever 1-2 weeks) for 1-2 weeks prior to onset of jaundice, dark urine, acholic stool (light/clay-colored). - Labs: elevated bili, bili in urine, AST/ALT elevation as early as prodrome phase 2.) Chronic: hepatitis not resolved within 6 months – see symptoms and labs for acute 3.) Fulminant: rapid, severe onset of hepatitis including hepatic necrosis, encephalopathy, edema with complications that include: cerebral edema, brainstem compression, GI bleeding, sepsis, organ failure
Fecal sample is taken from patient and occult blood with fecal leukocytes are seen. Is this more likely an inflammatory or non-inflammatory bacterial infection?
- More likely inflammatory bacteria.
3 yo female to ED with malaise, abdominal cramps, bloody diarrhea. Parent concerned about her eating rare hamburgers that may be associated with recall. Rapid test of stool tests positive to EHEC O157:H7. Mechanism of action of toxin that could potentially cause fatal sequelae? 1.) Activation of adenylate cyclase leading to increased cAMP 2.) Activation of guanylate cyclase leading to increased cGMP 3.) Blocking translation by cleaving subunits of 60S ribosome 4.) Disruption of host cell cytoskeleton 5.) Block of ACh release at NMJ
- 3, sequelae = HUS
Trichuris trichuria. Disease caused/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Disease/clinical: most are asymptomatic. Symtomatic with high worm burder includes: bloody mucus diarrhea, frequent stools, rectal prolapse in children, can contribute to growth retardation and anemia in children d/t malabsorption and bleeding - Lifecycle/patho: Ingestion of embryonated egg, egg hatches in SI releasing larva, larva migrates to LI and matures into adults, adults have sex in lumen, female lays eggs. This is a geohelminth and eggs require period of time to develop in warm moist soil before becoming infectious again. - Diagnosis: identification of eggs (lemon-barrel shaped) in stool - Epidemiology: tropical, can be found in SE US, fecal-oral via contaminated soil
Isospora belli. Disease caused/clinical presentation, lifecycle/pathogenesis
- Disease/clinical = isosporiasis = fever, diarrhea and weight loss. Mostly affects immunocompromised = watery diarrhea, malabsorption, weight loss, electro imbalance, death - Lifecycle/patho: ingestion of mature oocyst (containing sporozoites), sporozoites excyst, divide and mature in intestinal mucosa, sexual form develops and produce fertilized cysts known as oocysts
Hepatitis B. Characteristics, disease caused, pathogenesis, vaccine, treatment, epidemiology
- Characteristics: Hepadnaviridae, partially dsDNA - Disease: acute and chronic hepatitis. Half of infected adults are asymptomatic. Risk of chronic infection correlated with age, younger = more chronic. - Pathogenesis: reverse transcription is part of life cycle. Exists as tubes/spheres, which are non-infectious particles and dane particles, which are complete infectious particles in tissues. HBs (surface) found on surface of particle, HBc (core) found underlying surface protein in core of particle, HBe is also found in core of particle. Destruction of hepatocytes mediated by CTLs - Vaccine: recombinant HBV vaccine 3 dose IM (recombinvax HB and Engerix B) - Tx: no treatment for acute hepatitis. Chronic infections can be treated with a.) lamivudine (RT inhibitor), b.) famciclovir/adefovir (nucleoside inhibitor) combined with IFN-alpha. Post-exposure Prophy: HBIG (hep B Ig) and vaccine can be used. - Epidemiology: body fluids (sexually, drug users, hospital workers)
Microsporidia. Disease caused/clinical presentation, lifecycle/pathogenesis
- Disease/clinical = microsporidiosis. Intestinal dz: Chronic debilitating diarrhea, anorexia, weight loss. Extraintestinal dz: keratoconjunctivitis (early sign of dissemination), symptoms dependent on organ system involvement. Mostly infects immunocompromised including AIDS pts. Clinical syndromes are species dependent. - Lifecycle/patho: obligate intracellular, ingestion of spores
What is floppy baby syndrome?
- Aka Infant botulism. Occurs when infant ingests C. botulinum spores, often when fed honey. Don’t give infant honey until 1 year of age.
Listeria monocytogenes. Characteristics of bacteria, disease/clinical presentation, pathogenesis, diagnosis, treatment, epidemiology, complications
- Characteristics: G+ rod (sometimes in pairs) facultative anaerobe, intracellular survives in wide temp range, resistant to high salt concentrations and wide pH - Diseases: a.) Healthy individuals: typically asymptomatic, but may have fever, nausea and/or diarrhea b.) Bacteremia, meningitis and encephalitis in immunocompromised adults c.) Pregnant women present as other healthy individuals, but risk of transmission to neonate resulting in premie, abortion or still-birth d.) Neonates: granulomatosis infantiseptica (pyogenic granulomas over the entire body), meningitis, encephalitis. - Pathogenesis: internalin-A (intA) adheres to cells and taken up, internalized by endocytic vacuole, phagosome acidification activates listeriolysis O (LLO) that disrupts membrane and allows escape to cytosol. Replicates in host, ActA causes polymerization of actin and allows for spread to adjacent cells and blood stream. Infection disseminates to liver, spleen and CNS. - Diagnosis: culture of CSF and blood via cold enrichment selection, weakly beta-hemolytic, also motile - Tx: beta-lactam or trimethoprim-sulfamethoxazole - Epidemiology: associated with ready to eat meats, raw vegetables
Rotavirus. Characteristics, disease caused, pathogenesis, diagnosis, vaccine, treatment, epidemiology
- Characteristics: reovirus, segmented genome that remain in core during infection, non-enveloped - Disease: gastroenteritis (G1 most prevalent): vomiting, diarrhea, occasional cough and coryza (nasal mucosa inflammation), third have fever, can lead to malabsorption - Pathogenesis: low inoculum, infect cell at tip of villi in SI, damages infected cells (villi blunting) reducing absorptive capacity leading to fluid accumulation in lumen and diarrhea. Toxin (NSP$) causes Calcium and H2o release. - Diagnosis: ELISA from stool, also EM and RTPCR less commonly - Tx: oral rehydration for mild dehydration OR IV rehydration with severe dehydration. IgA in colostrum protective for neonates - Vaccines: oral live attenuated (Rotateq and Rotatrix) without risk of intussusception - Epidemiology: associated with disease in children mostly, including those that are immunocompromised, not opportunistic in HIV, seasonal variation, outbreaks in daycares
ETEC (enterotoxigenic E. coli). Characteristics of bacteria, disease/clinical presentation, pathogenesis, diagnosis, treatment
- Characteristics: G- rod, facultative anaerobe - Disease: T=Traveler’s (associated with travel to developing countries and consumption of water and ice) and infantile diarrhea, water diarrhea, no fever typically - Pathogenesis: a.) fimbriae (pili) adheres to epithelial cell, b.) toxins (plasmid encoded): LT (heat liable toxin) is an AB toxin that increases cAMP leads to ion and water efflux and ST (heat stable toxin) is a non-AB toxin that causes increase in cGMP (not via cell entry) and leads to same effect as LT - Diagnosis: clinical history, DNA probes to detect LT and ST genes - Tx: supportive
Nematodes (roundworms) that infect the GI tract
- Enterobius vermicularis (pinworm) - Trichuris trichuria (whipworm) - Ascaris lumbricoides - Necator americanus/ancylostoma duodenale (hookworm)
Helicobacter pylori. Characteristics of bacteria, diseases, pathogenesis, diagnosis, treatment
- Characteristics: G- curved rod, microaerophilic - Diseases: ulcers and chronic gastritis – stomach CAs in less than 1% of those infected - Pathogenesis: not well understood. Penetrate mucous layer of stomach’s epithelium attracted to hemin and urea. Cause inflammation. Releases urease that cleaves urea producing NH3 and CO2 neutralizing stomach acid in locality. H.pylori cytoxin (VacA) with NH3 destroy mucus-producing cells, exposing underlying CT. Has flagella and adhesins. - Diagnosis: urea breath test (radioactive), biopsy - Tx: abx and PPI
Bacteria associated with generalized GI tract infections and symptoms with onset 8-16 hours after ingestion. Why are symptoms later?
- Bacillus cereus (diarrheal, emetic component is within 1-8 hour timeframe), Clostridium botulinum - These bacteria produce toxins after ingestion
Signs/symptoms of severe dehydration? What is the treatment?
- Rapid, weak pulse - Sunken eyes - Tears absent - Skin tenting - Lack or urination Treatment = IV rehydration
Taenia solium (pork tapeworm). Disease/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Disease/clinical: consumption of pork results in intestinal disease: generally asymptomatic, but abdominal pain, feeling of fullness in symptomatic patients. Ingestion of embryonated eggs results in extra-intestinal disease (cysticercosis) via human-human transmission d/t poor hygiene. Pathology dependent on location, most severe complication = neurocysticercosis = seizure and neuro deficits. - Lifecycle/patho: human consumption of pork containing cysticercus in the muscle, scolex attaches to intestine, gravid proglottids containing eggs released in feces and either: a.) consumed by swine or b.) via autoinfection or human-human transmission where eggs hatch in intestine and travel into circulation, cysticercus disseminate into lungs, brain or eyes creating space filling lesion - Diagnosis: proglottids or eggs in stool for intestinal infection, radiology and serology for extra-intestinal infection - Epidemiology: undercooked pork
Fasciolopsis buski. Disease caused/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Disease/clinical: single worm infection = focal inflammation, intermittent diarrhea. Multiple worms infection = continuous diarrhea, intestinal hemorrhage, ulceration, abscess formation - Lifecycle/patho: consumption of encysted material from freshwater source, excyst in duodenum, attaches to columnar epithelium of mucosa of SI, becomes adult, releases unembryonated egg in feces, penetrates snail, released in water from snail after development - Diagnosis: presence of eggs in stool - Epidemiology: fresh water fish / shellfish, vegetation/plants including water chestnuts. Found throughout China, SE Asia and India
22 college student with aversion to seafood participated in service trip to Haiti. Trip focused on providing care to people living in temporary camps after being displaced from home after recent earthquake. Several days after arriving and indulging in local cuisine provided by street vendors, student developed mild case of water diarrhea. Most likely cause of person’s diarrhea? A. Toxin production leading to efflux of electrolytes and water B. Decreased intestinal fluid absorption through loss of microvilli C. Descreased intestinal fluid absorption through coating of intestine in a pseudomembrane
- A
Vibrio species that cause gastroenteritis
- Vibrio cholerae - Vibrio parahaemolyticus
Normal microbiota in small intestine?
- Lactobacilli, streptococci, enterobacteria, bacterioides spp
What groups are susceptible to astrovirus?
- Infants, young children, elderly or healthy adults exposed to contaminated food and drink
Bacteria associated with watery (rarely bloody) diarrhea
- EPEC, ETEC, Clostridium perfringens, bacillus cereus, vibrio cholerae, Salmonella spp, Listeria monocytogenes
3 yo male to ED with diarrhea, fever, chills. Stool culture grew G- rods with white colonies on MacConkey agar and neg for H2s production. Which is most likely? A.) Campylobacter jejuni B.) Enterohemorrhagic E. coli C.) Salmonella typhimurium D.) Shigella sonneii E.) Vibrio cholerase
- D
Virotypes of E. coli, intestinal site of action and disease caused
1.) ETEC: enterotoxigenic (SI) – Traveler’s and infant diarrhea. Diarrhea is water. 2.) EPEC: enteropathogenic (SI) – Infant diarrhea. Diarrhea is non-bloody. 3.) EHEC: enterohemorrhagic (LI) – Hemorrhagic colitis and hemolytic uremic syndrome. 4.) EIEC: enteroinvasive (LI) – typical GI symptoms with watery diarrhea, followed by development of dysentery
Taenia saginata (beef tapeworm). Disease/clinical presentation, lifecycle/pathogenesis, diagnosis, epidemiology
- Disease/clinical: generally asymptomatic, but symptoms can include mild abdominal pain, feeling of fullness - Lifecycle/patho: infection generally with a single adult worm. Human consumes beef with cysticercus in muscle, scolex attaches to intestine, gravid proglottids in feces containing eggs, eggs ingested by cattle - Diagnosis: ID of proglottids/eggs in stool - Epidemiology: undercooked beef
Which hepatitis viruses lead to chronic hepatitis infections?
- Hep B, C and D
Vibrio cholerae. Characteristics of bacteria, disease/clinical presentation, pathogenesis, diagnosis, treatment, epidemiology
- Characteristics: G- rod comma/curved shaped, facultative anaerobe, requires NaCl for growth - Disease: severe watery “rice water” stool with abrupt onset, requires 2-3 day incubation with 7 day duration, typically no fever - Pathogenesis: a.) TCP: toxin co-regulated pilus – adheres to SI epithelium b.) Cholera toxin: AB toxin – A activates adenylate cyclase increase cAMP production leading to massive ion and water efflux. Toxin encode on prophage, therefore transmissible - Diagnosis: culture - Tx: supportive (rehydration) therapy - Epidemiology: contaminated water, typing of bacteria based on O antigens, current pandemic with El Tor biotype is less severe disease, longer duration
Discuss diagnosis and serology between acute and chronic (replicative and non-replicative) HBV infections. What does serology look like for individual with vaccination to HBV and someone with past HBV infection? Window period serology?
- HBsAg = marker for active infection - Acutely infected: HBsAg +, anti-HBsAg -, HBeAg +, anti-HBe -, anti-HBc (IgM) + - Chronically infected: a.) Replicative (high infectivity): HBsAg +, anti-HBsAg -, HBeAg +, anti-HBe -, anti-HBc (IgG) + b.) Non-replicative (low infectivity): HBsAg +, anti-HBsAg -, HBeAg -, anti-HBe +, anti-HBc (IgG) + - Vaccinated: HBsAg -, anti-HBsAg +, anti-HBc (IgG) – (if never previously infected or + if previously infected) - Previous infection: HBsAg - , anti-HBsAg +, HBeAg-, anti-HBe +, anti-HBc (IgG) + - Window: anti-HBe and anti-HBc (IgM) positive, all other markers neg including anti-HBs
Normal microbiota in stomach?
- Lactobacilli
Poliovirus. Characteristics, diseases, diagnosis, vaccine, treatment, epidemiology
- Characteristics: Picornaviridae, stable at acidic pH, 3 genotypes-P1-3 - Diseases: 95% of infections are asymptomatic a.) Abortive poliomyelitis: sore throat, fever, vomiting, abdominal pain, constipation b.) Nonparalytic aseptic meningitis: non-specific prodrome, stiffness in back, neck or legs c.) Flaccid paralysis - Diagnosis: virus isolated from stool, sequenced - Vaccine: IM inactivated polio vaccine (inactivated through exposure to formaldehyde), previously live attenuated (1 in every 2 million doses caused VAPP = vaccine associated paralytic poliomyelitis), previously to this = inactivated Salk vaccine - Epidemiology: fecal-oral, last US case in 1979, 1994 = poliovirus free in Western Hemisphere, endemic in Afghanistan, Nigeria and Pakistan
4 classes of protozoa? Eukaryotes or prokaryotes? How do they replicate?
- Eukaryotes - 4 classes based on motility: ameba (pseudopodia), flagellates (flagella), sporozoans (gliding), ciliates (cilia) - Replicate: most via binary fission, some sporozoans can reproduce asexually or sexually
Identify the genus and species of the following nematode eggs
- from left to right: Enterobius vermicularis (pinworm), trichuris trichuria (whipworm), ascaris lumbricoides fertile egg, ascaris lumbricoides infertile egg, hookworm (necator americanus or ancylostoma duodenale)
