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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
Dysentery
frequent, small bowel movements with blood and mucus --> accompanied by bad rectal pain and spasm - not a bad diarrhea -> something separate
26
Bacterial Dysentery
``` Sudden onset Fever Chills Pus in stool Prostration Acute ```
27
Shigella invasiveness
- 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
Shiga toxin
phage-borne toxin --> verotoxin --> acts of vascular endothelial cells to stop transcription and cause cell death -> bloody diarrhea
29
E. Coli
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
ETEC and EHEC
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
Vibrio cholera
only serogroups O1 and O139 produce cholera toxin --> cause cholera - actiavte adenylate cyclase -> increase cAMP -> decrease Na absorption -> increase Cl excretion -> watery diarrhea
32
Cholera
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
S. typhi
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
Diarrheal pathogens and infectious dose?
the Dose matters!!! - low inoculum organisms -> tens to hundreds (common 2nd cases) - high inoculum organisms -> thousands (rare 2nd cases)
35
Clostridium difficile
Gram (+) -> bacilli -> spore-forming -> obligate anaerobe -> motile exotoxin causes cell death, shallow ulcers, and pseudomembranes Diagnose -> stool smear, toxin detection, or scope
36
Common features of parasite infections
long lasting or chronic -> often asymptomatic Morbidity and mortality depend on - parasite burden, species, preexisting immunity, patient comorbidities
37
Prevention of infection is key
adequate disposal and treatment of waste adequate treatment of drinking water hand washing and food washing
38
Protozoas
unicellular flagellated eukaryotes --> water-borne illness acquired by ingesting cysts or oocysts - Entamoeba - Giardia - Cryptosporidium
39
Hemminths
multicellular eukaryote - Ascaris - Trichuris - Enterobius - Ancylostoma/Necator - Strongyloides - Diphyllobothrium - Echinococcus - Taenia
40
Protozoan parasites
- stomach/intestinal cramps, gas, nausea - fluid loss/diarrhea >1 week - gradual onset -> weeks - don't treat with drugs --> hydration - acquire from contaminated water
41
Giardia lamblia
"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
Cryptosporidium parvum
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
Entamoeba histolytica
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
Amebic Dysentery
``` Gradual onset No fever No chills No pus Less prostration Chronic ```
45
Metronidazole, Tinidazole
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
Nitazoxanide
unknown mechanism -> covers Giardia and cryptosporidosis | - rapidly metabolized to tizoxanide (primarily luminal)
47
Iodoquinol
unknown mechaism tox -> visual acuity (thyroid disease contraindicated) luminal distribution - covers amebic dysentery
48
Paromomycin
Aminoglycoside, targets 30S subunit - targets intestinal protozoa (limited against cryptosporidium) - luminal distribution - diarrhea as a side effect
49
TMP-SMX
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
Enterobius vermicularis
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
Soil-transmitted Roundworms
Necator -> skin penetratioin Trichuris -> egg ingestion Ascaris --> egg ingestion Strongyloides --> skin penetration
52
Necator americanus
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
Strongoloides
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
Trichuris trichiura
egg ingestion -> dianose with eggs in feces (barrel-shaped) appearance - FINGER-CLUBBING - bloody diarrhea --> anemia
55
Ascaris lumbricoides
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
Treatment goal of helminths
remove adult worm - exploit biochemical differences between parasite and host - TARGET MOTOR ACTIVITY or reactions that generate metabolic energy
57
Albendazole, Mebendazole
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
Levamisole and pyrantel pamoate
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
Ivermectin
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
Tapeworms
``` segmented (proglottid) - taenia (beef or pork) - diphyllobothrium (fish) - echinococcus ZOONOTIC DISEASES ```
61
Diphyllobothrium
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
Taenia
beef or pork tapeworm - standard intestinal problems, stool contains eggs or proglottids - Cysticercosis --> migrate to muscle, brain, other tissue
63
Echinococcus
not really a GI illness --> oncosphere penetrates intestinal lining -> enters circulatory system -> cysts grow in organs - pain/discomfort in upper ab
64
Anti-tape worms
Albendazole and Mebendazole
65
Praziquantel
increased permeability of parasite to divalent cations --> contraction of musculature - well-tolerated, dizziness, nausea - used for tapeworms
66
Schistosoma
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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