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Micro week 1 mini 2

Micro - GI (week 1)

What kind of motility is exhibited by H. pylori? Corkscrew motility.
What agar does H. pylori grow on ? (list non-selective and selective media) Non-selective: Chocolate agar, blood agar, brain-heart infusion. **Selective: Thayer-martin, Pylori, Dents**
What temp does H. pylori optimally grow at ? 42 degrees C. Microaerophillic (reduced O2)
What are the key identifying characteristics of H. pylori? Gram (-) Catalase (+). Oxidase (+), **UREASE (+)**. NON-HEMOLYTIC. Also: nalidixic acid resistant and nitrate reducing... thid differentiates it from other helicobacters
How is helicobacter differentiated from other species of helicobacter **It is nalidixic acid resistant and nitrate reducing**
What is the most common human infection H. pylori. Present in more than 1/3 of people. Often asymptomatic. Fecal oral route
What is the route of H. pylori transmission Fecal oral (rarely oral-oral)
What role to mucinase and phospholipase play in H. pylori? Helps with motility
What adhesins does H. pylori use? What does it bind? Uses *sialic acid and lewis X* to bind gastric epithelial surface
What kind of tranmission system is used by H. pylori ? type IV
How does H. pylori infection lead to increased acid production ? via platelet activating factor
What is the function of urease production by H. pylori To defend itself against gastric acid. H. pylori IS NOT an acidophile.
What is the function of arginase in H. pylori Protection against NO produced by the immune system
List the factors produced by H. pylori to protect it from immune response. SOD, Catalase, Arginase, O-antigen mimicry,acid inhibitory protein, urease, modiffied lipid A, flagellin structure also prevents inflammation
How is H. pylori dx'd Biopsy, brush, gastric juice, serology, stool, BREATH
How does the rapid urease test work? cells from biopsy are added to a small card containing urease and indicator. The pH change will result in a color change
What stains are used for H. pylori? Giemsa and Warthin-Starry Silver stain
Why serology not a good indicator of treatment progress with H. pylori? What is the best method? Because antibodies will remain long after the infection is cleared up, rseulting in a positiev result despite a cured infection. Measurement of antigens in stool is the best method.
Almost of duodenal ulcers are caused by H. pylori
What is the most common upper GI fungal pathogen? Candida albicans
What agar is candida commonly grown on Can grow on many types. Sabourauds and potato yeast agar are commonly used
How is candida identified? KOH preparation or PAS stain
List the normal flora of the GI tract 99.9% are anaerobes: Bacteroides, Clostridium, and Anaerobic cocci. 0.1% are anaerobes: E. coli, Klebsiella, Proteus, and enterococci
What is the normal fecal fluid excretion / day <150 mL/day
Most fluid absorption takes place in the: Small intestine (90% of fluid absorption). Net absorption is >8L/day
What is dysentary ? severe inflammatory diarrhea with mucus and blood in the feces (inflammation or cytotoxic destruction of colonic mucosa
Describe the 3 major mechansisms by which enteric infxon can occur: 1)shift in fluid balance (non-inflammatory diarrhea [watery]), 2)Inflammation/cytotoxic destruction of colonic mucosa (Dysentary), 3)penetration though intact mucosa of distal small intestine -->then it mutliplying in RES/lymphatic cells (enteric fever)
What are the common symptoms of gastroenteritis? Nausea, vomiting, diarrhea, and abdominal discomfort.
Diarrhea is due to a problem in what region of the GI tract? Dysentary? Enterocolitis? Diarrhea: Small intestine. Dysentary: colon, enterocolitis: SI AND COLON
Penetrating enteric infections are most commonly caused by what bacteria? Salmonella typhi
What is used for quantitative measurement of leukocytes present in stool ? Lactoferrin.
Increased fecal lactoferrin is seen in what type of enteric infections Inflammatory. May or may not be present in pentrating infections.
What is the most common bacterial agent involved in enteric infections in the US? Salmonella.
Pt presents with nausea, vomiting, abdominal cramps, and diarrhea *1-8 hours* following ingestion of meal. What is the likely mechanism of the symptoms? Pre-formed toxins. (1-8 = short incubation period = pre-formed toxin mediated symptoms) resolves w/i 12 hours
Pt presents with nausea, vomiting, abdominal cramps, and diarrhea *8-16 hours* following ingestion of meal. What is the likely mechanism of the symptoms? Toxins produced in body AFTER ingestion. Resolves in 24 hours
Pt presents with nausea, vomiting, abdominal cramps, and diarrhea 16-48 hours hours following ingestion of meal. What is the likely mechanism of the symptoms? infection by the organism.
S. aureus and B. cereus ingestion are likely to have what major presenting sx? vomitting 1-6 hours after a meal. (incubation period = 1-6 hours)
Pt with major presenting sx of vomiting 1-6 hours after a meal. What are the likely bacterial agents that can cause this? S. aureus and B. Cereus.
Pt presents with watery diarrhea 1-3 days after a meal. What bacterial agent? E. coli (ETEC) (C. perfringens has a shorter incubation period (8-16 hours) so it would have occured sooner.
Pt with water diarrhea 8-16 hours following a meal. Bacteria? C. perfringens
Pt with inflammatory diarrhea 2-48 hours after a meal. Bacteria? V. parahaemolyticus
List the common bacterial agents of inflammatory diarrhea: V. parahaemolyticus, L. monocytogenes, shigella, non-typhoidal salmonella, Campylobacter, E.coli (EHEC[aka STEC], SPEC, EIEC, EAEC)
What type of food intoxication (poisening due to the exotoxin of the bacteria) does not produce enterotoxin? C. botulinum (produces neurotoxin)
What is the mode of action by which Staphlococcal bacteria cause vomitting? Via binding of enterotoxins to neural receptors in upper GI that in turn, stimulate the vomitting center in the brain.
What is the most common staphylococal toxin? What is it produced? SE-A toxin (MC toxin). It is acquired from a bacteriophage
Sx of Staphylococcal food poisening ? vomiting +/- diarrhea (1 in 3) 1-6 hours after a meal.
Mayonaise is a common carrier of what bacteria ? S. aureus.
Staph toxin vs botulism toxin: which is heat stable / which is heat labile? toxins produced by staph (i.e. SE-A toxin) are heat stable, whereas botulism toxins are heat labile
What botulism toxins are asso with human disease? What is the mechanism? A, B, and E. Only one toxin is produced per isolate. It's mechanism of action is inhibition of Ach at the NM junction causing a decending flacid paralysis
Symptoms of botulism toxin poisening? decending paralysis starting at eye muscles. Begins with nausea, dry mouth +/- diarrhea. After 18-24 hours pt will be weak and dizzy with diplopia and dysphagia, dysarthria * constipation and abdominal pain. *no fever* death due to resp. paralysis
What is the most common form of botulism in the US? Infant botulism. Ingestion of spores found in environmental dust (can also come from honey, but this is a minor reservoir.This is NOT food-borne botulism as it is not the toxin that is ingested, but instead: the spores are ingested.
"floppy baby" indicates what kind of poisening ? infant botulism.
What tx is absolutely contraindicated in adult and infant botulism ANTIBIOTICS SHOULD NEVER BE USED
Would botulism is most commonly caused by source Injection of heroine / inhalation of cocaine.
What is the tx for wound botulism antitoxin antibiotics (penicillin G), surgical debridement, tetanus booster. (as opposed to adult and infantile infectious botulism where antibiotics are NEVER indicated)
How is botulism diagnosed? Based on clinical impression and history, with confirmation by cutlure or toxin activity in food, serum, or stool. TX INITIATED IMMEDIATELY ON SUSPICION (don't wait for labs!)
How is botulism treated? Trivalent antitoxin: human derived for babies, equine derived for >1 yo (only bind free toxin, arresting progression) along with Gastric lavage if food exposure was recent, ICU support with venitllation if needed.
What are the sx of C. perfringens food poisening ? Nausea, watery diarrhea and abdominal cramps ****NO VOMITING!****
What symptom is never present with C. perfringens? vomitting
Common sources of C. perfringens food poisening? Beef, chicken, gravy dishes prepared for banquets. Foods cookers earlier w/o adequate reheating
What is the mechanism of C. perfringens food poisening? (origin of toxin) *enterotoxin produced in the body after ingestion of vegetative cells in the food*.
What is the mechanism of TYPE A exotoxin of C. perfringens? A: damages brush borders in SI -> alters permeability in ilium ->loss of fluid / IC proteins.
How is Bacillus differentiated from clostridium in a lab? Bacillus = Catalase (+), clostridium = Catlase (-)
What are the two types of bacillus cereus food poisoning ? 1) short incubation (emetic) form: Nasusea, vomiting, ab cramps *NO DIARRHEA*. Resembles staph in sx and incubation period. (CASUSED BY ETE toxin aka CERULIDE 2) long incubation (Diarrheal form) Resembles C. perfringens.
Rice dishes held at room temperature are common sources of what type of food poisening ? Short incubation bacillus cereus food poisoning
What bacteria is associated with cereulide toxin? What is the MOA of this toxin? Cereulide (AKA ETE Toxin) is associated with bacillis cereus. It causes short incubation form of B. cereus poisening. It binds to 5-HT receptor of the vagus nerve and forms ion channels and holes in the cell membrane.
What is the MOA of the long incubation form of bacillus cereus food poisening ? heat labile enterotoxins produced in body AFTER INGESTION cause activation of intestinal adenylate cyclase -> increases fluid secretion into small intestine.
Two forms of B.cereus food poisening? emetic (preformed toxins) and diarrheal form (enterotoxins produced in the body following ingestion)
What are the two major types of virus that cause gastroenteritis? Rotavirus (Reoviridae) and Calciviruses (calciviridae)
Childhood diarrhea of viral origin is most commonly causes by what virus ? Rotavirus.
Diarrhea due to outbreak of a virus: What virus is most commonly involved? Calciviruses (noroviruses)
compare rotaviruses to calciviruses with regard to epidemiology and pt common affected Rotavirus is typically seen in childhood diarrhea (or eldery diarrhea) *immunity is usually developed by age 2, but old people gave week immune systems*...Calciviruses are typically seen in adults and outbreaks of diarrhea.
What are the key features of rotavirus? DSRNA, SEGMENTED (11 segments) NAKED.
Watery diarrhea of 5 days duration is most likely caused by what virus? rotavirus. Also presents with sudden onset of vomitting after 2 days.
What is the enterotoxin of rotavirus (NSP4)
What Immunoglobulis protects against second infection of rotavirus? IgA
What kind of vaccine is the rotavirus vaccine ? Live-attenuated vaccination
Describe the key features of norovirus: AKA Calcivirus. (+)ssRNA, Naked, icosahedral. Causative agent of viral gastroenteritis in adults and in outbreaks
Norovirus (aka calcivirus) vs rotavirus with regard to duration: ROtavirus is 5-7 days of diarrhea, usualy in young children and eldery patients. while norovirus is 2-3 days and doesn ot involve a fever, typically seen in adults and in outbreaks
What types of hepatitis are waterborne (enteric transmission) ? What types are parenterally xmitted A and E. Only cause AcutE disease... death is rare. Except for Hep E, which is often fatal in pregnant women. B, C, and D are parenterally xmitted.
What are the long term complications chronic hepatitis? Cirrhosis, decompesated liver dz, and Hepatocellular carcinoma
What hepatitis type when present with hep B, causes more severe hepatitis than chronic HBV alone? Hep B + Hep D together causes more severe hepatitis.
What virus(es) when present with Hep B, increase the risk of liver cirrhosis? Hep D as well as HIV both increase chances of liver cirrhosis when present with Hep B
HIV and ____ coinfection increase the risk of liver fibrosis Hep C
What is the only virus that requires coinfection with another type of virus? Hep D (think "D" for "Defective".) Hep D requires pre-infection with Hep B
What is the infection form of E. Histolytica? (cysts or trophozoites) cysts
Tear drop ulcers are symptomatic of what parasite? Entamoeba histolytica
Describe the cellular structure of entamoebas histolytica multinucleated cell (4 nuclei) with centrally located karysosome. Each nucleas has a cartwheel appearance.
What is a common source of giardia lamblia ? Commonly seen in people who have recently gone camping/hiking who drank from STREAM WATER. Causes fatty, foul-smelling, diarrhea of several days duration. No fever, blood, or pus.
Sx of Balantidiasis? Cause (parasite name) Caused by Balantidium coli. Diarrhea +/- mucus and blood, colitis, no extraintestinal spread
What is the main difference between intestinal sporozoa and other sporozoa? Intestinal sporozoa go through the sexual and asexual life cycles in the same host, while the others go through those cycles in seperate hosts.
What is the most important intestinal sporozoa ? Cryptosporidium parvum
Acid fast oocysts in the stool is diagnostic of: intestinal sporozoa. Most of cryptosporidium parva. (could also be isospora belli or cyclospora)
Pt with a hx of camping gets diarrhea after drinking stream water. NO FEVER, NO BLOOD IN STOOL Likely parasitic cause? Giardia lamblia (giardiasis).
Pt with a hx of swimming gets diarrhea. Likely parasitic dx? Cryptosporidium parvum. Dx'd via acid fast oocysts in the stool
Pt with FEVER, diarrhea, vomitting, and right sided pleuritic should pain and tear drop ulcers in intestines. Likely parasitic dx? Entamoeba histolytica (stage IV ((extraintestinal amoebiasis))
What is the confirmatory dx of Amoebiasis? specific IgM antibody, ELISA, PCR, etc
What is the most important interstinal ciliate? THere is only one intestinal ciliate. It is Balantidium coli (B.coli). Cause bilantidiasis.
What is the most important flagellate of the GI ? Giardia lamblia
Lactose intolerance is a feature of what parasitic GI infection? giardia lamblia (giardiasis)
Dx of giardia lamblia? fecal cysts or antibody detection
What is the clinical presentation of giardiasis? 4-6 loose, foul smelling, fatty BMs(steatorrhea)/day with weight loss, and *NO FEVER AND NO BLOOD IN STOOL* in a pt with a hx of hiking / drinking water from stream
Created by: Semester4



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