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GI Exam 3 > Micro > Flashcards

Micro Flashcards

1
Q

Large intestine normal flora

A

Anaerobes
Gram (-) rods
Entercoccus
Spirochetes

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2
Q

GI tract

A 
sterile at birth -> rapidly becomes colonized
flora varies between individuals
- benefits from flora:
- generate vitamins, help digestion
- stimulate development of immune system
- prevent establishment of infections
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3
Q

Food poisoning

A

true food poisoning occurs after consumption of food with pre-formed toxin already in it -> 30 min -6 hrs incubation period

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4
Q

Food-associated infections

A

Symptoms begin after longer incubation period and organisms produce the toxin in the GI tract or invade mucosal epithelium

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5
Q

2 organisms that can cause both food poisoning and food-associated infections?

A

Bacillus cereus, clostridium botulinum

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6
Q

Enterotoxin

A

bacterial exotoxin –> NOT AN ENDOTOXIN

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7
Q

Bacteria generating pre-formed toxins in food?

A
  1. Staph aureus
  2. Bacillus cereus
  3. Clostridium botulinum
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8
Q

Staph aureus

A

Gram (+) –> cocci –> catalase (+) –> coagulase (+)

  • N/V, stomach cramps, diarrhea for 1-3 days
  • 1-7 hr incubation period
  • once toxin gone –> illness gone
  • toxin can be ID in stool or vomit –> toxin causes illness not bacteria, the bacteria can’t survive the high temps or stomach acidity
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9
Q

Bacillus cereus

A

BOX-CAR SHAPED -> produces biofilms -> can produce chronic infection
Gram (+) -> large bacilli -> endospore forming -> facultative anaerobe -> mostly motile -> beta-hemolytic
- spores can survive rice cooking process

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10
Q

Bacillus cereus illness forms

A 
Emetic -> food poisoning (toxin pre-formed)
- 1-6 hr incubation
- N/V, resembles staph illness
Diarrheal -> food-borne illness (toxins formed in GI)
- 6-15 hrs incubation
- watery diarrhea and ab cramps
- similar to C. perfringens
BOTH LAST AROUND 24 HRs
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11
Q

Bacillus pre-formed toxin

A

Cereulide -> forms holes in cellular membrane

- VERY heat, and pH stable -> hard to kill

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12
Q

Bacillus toxin formed in GI tract

A

large molecular weight enterotoxin that causes intestinal fluid secretion
- for sicker populations, vancomycin can be used to treat

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13
Q

Diagnosis of bacillus

A

culture stool or vomit -> only during outbreaks

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14
Q

Clostridium botulinum

A

Gram (+) -> bacilli -> spore-forming -> obligate anaerobe -> motile
- can acquire through food, wound, or infants ingesting spores
Neurotoxin -> irreversibly blocks release of ACh from motoric end plate -> muscle weakness and paralysis
Diagnosis -> symptoms, history, physical exam -> botulism
- antitoxin if paralysis not yet complete

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15
Q

C. botulinum food associated illness

A

ingest toxin -> absorbed into blood stream
Symptoms:
double vision, blurred vision, slurred speech, dry mouth, weakness

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16
Q

Big 3 of bacterial sources of food-borne illness

A

Campylobacter jejuni -> invasion
Salmonella enterica -> invasion
Clostridium perfringens -> enterotoxin

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17
Q

Clostridium perfringens

A

Gram (+) -> bacilli -> spore-forming -> obligate anaerobe -> NON-MOTILE
- enterotoxin binds to receptors in endothelial junctions that generate pores
- diarrhea, ab cramps, 8-12 incubation, lasts less than 24 hrs
- NO FEVER OR VOMITING
- need a very large load, so not passed human-human
Diagnose by detecting toxin or bacteria in feces

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18
Q

Campylobacter jejuni

A

Gram (-) -> bacilli (spirilli) -> microaerophilic -> motile -> cold-sensitive (extremely hard to culture)
ZOONOSIS -> transmitted to humans from animals
- diarrhea, cramping, fever
- 2-5 days incubation, lasts a week
- symptoms a result from inflammatory response (host) and cell invasion
- Complication -> Guillain-Barre

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19
Q

Salmonella Enteritidis

A

Gram (-) -> bacilli -> non-spore forming -> H2S (+) and lactose (-) (special agar) -> motile, flagella

  • diarrhea, fever, cramps (cell invasion and host response)
  • 12 hr - 3 day incubation, lasts 7 days
  • spontaneous recovery, some may have reactive arthritis
  • diagnose with stool culture
  • treat with hydration
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20
Q

Vibrio

A

Gram (-) -> vibrio (curved rod) -> facultative anaerobe -> flagellated, motile -> oxidase (+) (special agar)
WATER LOVING
- mild, bloody diarrhea (not from invasion tho), cramps, fever, N/V
- lasts less than a week -> can spread in immunocompromised and cause death
- isolated from cultures of stool, wound, blood

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21
Q

Vibrio parahaemolyticus toxins

A

Enterotoxins -> cause cell lysis but do not invade
TDH or TRH
- if vibrio lacks these toxins it is not pathogenic
- shellfish/uncooked fish

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22
Q

Listeria monocytogenes

A
  • RARE but leading cause of food-borne illness death
    Gram (+) -> bacillus -> NON-FASTIDIOUS -> flagellated, motile -> non-spore forming -> oxidase (-)
    -vulnerable adults -> elders, pregnant, newborns –> opportunistic infection
  • fever, myalgia, stiff neck, meningitis, sepsis
  • positive ID from normally sterile site
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23
Q

Invasion of Listeria

A

immune cells spread listeria to other organs

  • trojan horse –> Actin-Actin polymerization
  • liver is major target
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24
Q

Shigella

A

Gram (-) -> bacillus -> facultative anaerobe -> non-spore forming -> non-motile (no flagella) -> mainly lactose negative and H2S negative
closely related to E. Coli -> invasive
Transmission –> mostly by passing stools and soiled fingers to someone elses mouth –> NASTY SHIT
- diarrhea (bloody), fever, cramps, 1-2 days following and lasts 7 days

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25
Q

Dysentery

A

frequent, small bowel movements with blood and mucus –> accompanied by bad rectal pain and spasm
- not a bad diarrhea -> something separate

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26
Q

Bacterial Dysentery

A 
Sudden onset
Fever
Chills
Pus in stool
Prostration
Acute
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27
Q

Shigella invasiveness

A
  • Shigella sonnei -> most common
  • Shigella flexnori -> dysentery
  • Shigella dysenteriae -> worst dysentery (invasive and toxin)
  • it’s invasive, if not treated it will cause systemic symptoms
  • Complication -> Hemolytic uremic sundrome
28
Q

Shiga toxin

A

phage-borne toxin –> verotoxin –> acts of vascular endothelial cells to stop transcription and cause cell death -> bloody diarrhea

29
Q

E. Coli

A

Gram (-) -> bacillus -> facultative anaerobe -> motile -> non-spore forming -> mainly lactose positive

  • most strains are non-pathogenic
  • the pathogenic strains have the toxin
  • profuse watery diarrhea and ab cramp
  • variable incubation period and lasts less than 10 days
30
Q

ETEC and EHEC

A

EHEC -> shiga toxin
- attaches to epithelium and releases toxin to stop transcription -> cell death -> blood diarrhea
ETEC -> enterotoxigenic E. Coli -> traveler’s diarrhea
- no attachment -> works like cholera (increase cAMP and watery diarrhea)

31
Q

Vibrio cholera

A

only serogroups O1 and O139 produce cholera toxin –> cause cholera
- actiavte adenylate cyclase -> increase cAMP -> decrease Na absorption -> increase Cl excretion -> watery diarrhea

32
Q

Cholera

A

ACUTE ILLNESS -> profuse watery diarrhea with “rice-water stools”
- vomiting, rapid HR, dehydration, dry mucous membranes, low BP, thirst, muscle cramps
Diagnosis only confirmed by isolation of organism from stools
- rehydration is most important

33
Q

S. typhi

A

untreated water is source -> causes Typhoid fever

  • only humans affected by serotype
  • life-threatening illness -> moves into bloodstream
  • HIGH FEVER, WEAKNESS, HEADACHE
  • flat, rose colored spots -> person can become a carrier
  • need Antibiotics
34
Q

Diarrheal pathogens and infectious dose?

A

the Dose matters!!!

  • low inoculum organisms -> tens to hundreds (common 2nd cases)
  • high inoculum organisms -> thousands (rare 2nd cases)
35
Q

Clostridium difficile

A

Gram (+) -> bacilli -> spore-forming -> obligate anaerobe -> motile
exotoxin causes cell death, shallow ulcers, and pseudomembranes
Diagnose -> stool smear, toxin detection, or scope

36
Q

Common features of parasite infections

A

long lasting or chronic -> often asymptomatic
Morbidity and mortality depend on
- parasite burden, species, preexisting immunity, patient comorbidities

37
Q

Prevention of infection is key

A

adequate disposal and treatment of waste
adequate treatment of drinking water
hand washing and food washing

38
Q

Protozoas

A

unicellular flagellated eukaryotes –> water-borne illness acquired by ingesting cysts or oocysts

  • Entamoeba
  • Giardia
  • Cryptosporidium
39
Q

Hemminths

A

multicellular eukaryote

  • Ascaris
  • Trichuris
  • Enterobius
  • Ancylostoma/Necator
  • Strongyloides
  • Diphyllobothrium
  • Echinococcus
  • Taenia
40
Q

Protozoan parasites

A
  • stomach/intestinal cramps, gas, nausea
  • fluid loss/diarrhea >1 week
  • gradual onset -> weeks
  • don’t treat with drugs –> hydration
  • acquire from contaminated water
41
Q

Giardia lamblia

A

“beaver fever”

  • symptoms for 1-2 weeks -> then come back again
  • parasite causes loss of epithelial absorptive surface area
  • ingest cysts -> trophozoites attach to mucosal lining –> cysts and trophozoites pooped out but only cysts found
  • FOUL-SMELLING DIARRHEA, fatty/greasy floating stools
  • filter/clean water
42
Q

Cryptosporidium parvum

A

cryptosporidiosis –> sanitation system failures (waterparks) OPPORTUNISTIC INFECTION

  • diarrhea for 1-2 weeks even up to month
  • absorption impaired and secretion enhanced by infected cells
  • watery, non-bloody stools -> disrupts epithelial microvilli
  • ingested oocysts –> sporozoites generate oocysts (SMALL)
43
Q

Entamoeba histolytica

A

Amebiasis –> tropical climates

  • amebic dysentery –> bloody, mucousy stool
  • can invade liver and form abscess
  • ID cysts in stool –> takes a specialist
  • can have mucosal invasion -> typical
  • blood vessel invasion -> travels to liver (abscess)
44
Q

Amebic Dysentery

A 
Gradual onset
No fever
No chills
No pus
Less prostration
Chronic
45
Q

Metronidazole, Tinidazole

A

Nitroimidazoles
- toxic metabolites generate free radicals -> induce DNA damage to parasite
- effective against Giardia, Amebic, but not cryptosporidium
- good bioavailability so will affect intestinal and systemic forms
S.E. = disulfiram rxn, nausea, diarrhea, metallic taste

46
Q

Nitazoxanide

A

unknown mechanism -> covers Giardia and cryptosporidosis

- rapidly metabolized to tizoxanide (primarily luminal)

47
Q

Iodoquinol

A

unknown mechaism
tox -> visual acuity (thyroid disease contraindicated)
luminal distribution
- covers amebic dysentery

48
Q

Paromomycin

A

Aminoglycoside, targets 30S subunit

  • targets intestinal protozoa (limited against cryptosporidium)
  • luminal distribution
  • diarrhea as a side effect
49
Q

TMP-SMX

A

broad spectrum antibiotics effective against apicomplexans

  • affects DHFR and is a PABA analog
  • selective against protozoa and bacteria DHFR
  • crosses BBB, well-tolerated
  • can interfere with intestinal flora
50
Q

Enterobius vermicularis

A

Pinworm -> DAYCARES

  • perianal pruritis, ab pain, anorexia, irritability
  • acquired by ingesting eggs (can remain viable for 2-3 weeks)
  • can have retroinfection with larvae crawling back in anus
51
Q

Soil-transmitted Roundworms

A

Necator -> skin penetratioin
Trichuris -> egg ingestion
Ascaris –> egg ingestion
Strongyloides –> skin penetration

52
Q

Necator americanus

A

skin penetration, but diagnosis made by detection of eggs in stool

  • after skin penetration -> circulatory system -> lungs -> cough -> swallow -> gut
  • pruritic papular erythematous rash
  • blood suckers -> anemia
53
Q

Strongoloides

A

skin penetration but diagnosis made by larvae in stool

  • skin penetration -> circulatory system -> lungs -> cough -> swallow -> gut
  • stomach and GI complaints
  • itchy red rash where worm entered skin (buttocks and thighs)
54
Q

Trichuris trichiura

A

egg ingestion -> dianose with eggs in feces (barrel-shaped) appearance

  • FINGER-CLUBBING
  • bloody diarrhea –> anemia
55
Q

Ascaris lumbricoides

A

egg ingestion
LOTS of people infected -> only a few symptomatic
- if symptomatic –> ab discomfort (severe -> obstruction)
- has lung stage that may cause cough -> charcot-Leiden crystals –> breakdown of eosinophils

56
Q

Treatment goal of helminths

A

remove adult worm

  • exploit biochemical differences between parasite and host
  • TARGET MOTOR ACTIVITY or reactions that generate metabolic energy
57
Q

Albendazole, Mebendazole

A

broad spectrum -> roundworms and tapeworms

  • bind to parasite beta-tubulin and inhibit microtubule formation -> may take days for death
  • albendazole better absorbed if targeting a tissue migrating larvae
  • S.E. = ab pain, nausea, dizziness, headache
58
Q

Levamisole and pyrantel pamoate

A

cholinergic antihelminths
- selectively opens AChR ion channels in nematode nerve and muscle –> increase Ca -> spastic muscle contraction -> unable to hold place -> swept away
S.E. = N/V, diarrhea
- poorly absorbed

59
Q

Ivermectin

A

binds to glutamate-gated chloride channels in invertebrate nerve and muscle cells -> deactivation of channel -> paralysis

  • well-tolerated, possible itching and dizziness, inflammation to death of worm
  • doesn’t cross BBB, targets parasites
60
Q

Tapeworms

A 
segmented (proglottid)
- taenia (beef or pork)
- diphyllobothrium (fish)
- echinococcus 
ZOONOTIC DISEASES
61
Q

Diphyllobothrium

A

acquired by eating muscle of fish where larvae are –> adheres to mucosa of intestine

  • diagnosed by standard intestinal problems, anemia with B12
  • stool contains eggs and/or proglottids
62
Q

Taenia

A

beef or pork tapeworm

  • standard intestinal problems, stool contains eggs or proglottids
  • Cysticercosis –> migrate to muscle, brain, other tissue
63
Q

Echinococcus

A

not really a GI illness –> oncosphere penetrates intestinal lining -> enters circulatory system -> cysts grow in organs
- pain/discomfort in upper ab

64
Q

Anti-tape worms

A

Albendazole and Mebendazole

65
Q

Praziquantel

A

increased permeability of parasite to divalent cations –> contraction of musculature

  • well-tolerated, dizziness, nausea
  • used for tapeworms
66
Q

Schistosoma

A

can cause intestinal (mansoni) or urogential (haematobium)
- infects snails –> humans are definitive host (sexual reproduction occurs)
- symptoms caused by immune system to egg stage
- eggs shed by worm become lodged in intestine –> inflammation
- can become a chronic illness with ab pain, enlarged liver, bloody stool or urine
- increased risk of bladder cancer
Diagnosis -> stool/urine samples
- treat with praziquantel and corticosteroids for inflammation

GI Exam 3 (10 decks)

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