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Medical Microbiology > Lecture 4: Diseases Affecting the Digestive System; Learning Objectives > Flashcards

Lecture 4: Diseases Affecting the Digestive System; Learning Objectives Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Explain the digestive systems defense mechanism (3 types); its indigenous microbiota, and how the microbiota is shaped.

A

Defenses:

  1. oral cavity-mechanical forces, salivary flow, lysozyme, antibodies
  2. Stomach-low pH
  3. Intestines- mucous, antibodies, bile and enzymes

Indigenous Microbiota: varies depending on where in GI

Microbiota shaped by: Diet, medication, probiotics, prebiotics, fecal transplant

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2
Q

Defenses of oral cavity (4)`

A
  1. mechanical forces
  2. salivary flow
  3. lyzosyme
  4. antibodies
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3
Q

Defenses of stomach (1)

A
  1. low pH
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4
Q

Defense of intestines (4)

A
  1. mucous
  2. antibodies
  3. bile
  4. enzymes
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5
Q

Factors influencing GI microbiota (5) [adult]

A
  1. Diet
  2. Medication
  3. Probiotics
  4. Prebiotics
  5. Fecal Transplant
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6
Q

Factors shaping microbiota (3 stages)`

A
  1. Birth- Cesarian vs. vaginal
    - cesarian (streptococcus, corynebacterium, cutibacterium) *derived from skin
    - Vaginal (lactobacillius and Prevotella) * derrived from vagina
  2. Infancy
    - Breast Fed; oligosaccharides drive lactobacillus and bifidobacterium
    - Bottle fed: enteroccus, bacteriodes, clostridia, streptococcus
  3. Beyond: diet remains key, abx, lifestyle choices and genetics play a role
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7
Q

Dental Caries causes (3)`

A
  1. Tooth Decay
  2. Dietary carbohydrates
  3. Acidogenic bacteria
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8
Q

main acidogenic bacteria for dental caries

A
  1. streptococcus mutans
  2. streptococcus sobrinus

*ferment dietary carbohydrates into acids

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9
Q

Prevention for dental caries

A

fluoride

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10
Q

Periodontal disease (PD) stages and their causes (2)`

A
  1. Gingivitis: early stage, reversible*
    - biofilm forms on teeth
    - fusobacterium, prophyromonas, prevotella, and streptococcus injure periodontal tissue leading to gingivitis
  2. Periodontitis- seroius disease of soft tissue and teeth
    - P. gingivalis is key driver
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11
Q

PD clinical presentation

A
  1. ulcers and bleeding along ginigval margin
  2. degradation of periodontal ligaments and bone
  3. loosened or lost teeth
  4. Assoc. with CVD, Alzheimer’s, RA
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12
Q

Intoxicants vs. infection

-give examples of both

A

intoxicants: illnesses where bacterial toxins are ingested with food and water
infections: illnesses where live bacterial pathogens are ingested and grow in body

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13
Q

S. aureus vs. Clostridial* vs. B. cereus

A

SA: toxins in protein rich foods (meat and fish, dairy)

  • incubation: 1-6 hrs.
  • Gastroenteritis caused by enterotoxin
  • cramps. nausea, vomiting, weakness, diarrhea

Clost: contamininates meat, poultry, fish

  • resistant to heat, UV light, drying, disenfectants**
  • req. high infectious dose takes 8-24 hours to appear
  • abdominal pain, cramping, diarrhea
  • produces enterotoxin

B. Cereus:

  1. enterotoxin: meats, poultry, vegies
    - diarrhea
  2. Heat-stable toxin: rice
    - vomiting
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14
Q

Primary problem with cholera

A

extreme dehyrdration: up to 1 liter an hour

-fluid loss can thicken blood, leading to shock and coma

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15
Q

explain v. cholerae characteristics (7) and transmission mechanisms

A

Virbrio Cholerae

  • non-invasive (not bloody)
  • motile, aerobic, gram (-), curved rods
  • secrete cholera toxin: loss of fluids and electrolytes through diarrhea *extreme dehydration
  • cells susceptible to stomach acid
  • Spread through poor sanitation and water supplies contaminated by feces
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16
Q

Name 4 types of E. coli Diarrheas and their clinical manifestations

A
  1. Traveler’s Diarrhea: enterotoxic e. coli (ETEC)- 2 enterotoxins
  2. ETEP: enteropathogenic e coli- potentially fatal diarrhea in infants
  3. EIEC: Enteroinvasitve e. coli- bloody diarrhea like shigella
  4. EHEC: enterohemorrhagic e. coli
    - animal reservoir increasing chance of human contact
17
Q

Transmission and and clinical syndrome caused by C. diff and how spores contribute to hospital outbreaks

A

Gram +

watery diarrhea, fulminant colitis, rupture of intestine (megacolon)

abx eliminate normal flora and allow c. diff to grow uncrontrolably

spores: hard to clean
trans: spores

18
Q

Know the (2) types of Salmonella and differentiate based on clinical syndromes, transmission, and typical clinical course

A
  1. S. typhi
    - causes typhoid fever= blood infection
  2. Salmonella enterics serotype enteritidis
19
Q

Shigella Soneri

Know the agents, transmission, and clinical syndrome

A
  • gram (-) rod (closely related to e.coli)
  • causes S. dysenteriae: bloody diarrhea
  • transmission: contaminated eggs, shellfish, diary
20
Q

Hepatitis

transmission
vaccine?
clinical manifestations
prevention strategies

A

-transmitted Hep A) through food or water contaminated by feces of contaminated person OR raw shellfish
Hep B) through direct/indirect contac with body fluid like blood or semen (mother-child or sexually)
Hep C: blood transmission, innjection drug use, blood transfusions

  • 3 vaccines: HAVRIX and VAQTA -contain hep A only and TWINRIX contains hep B as well
    clin: anorexia, nausea, vomiting, fever, enlargement of liver, jaundice

Prev:

21
Q

Rotavirus

transmission
vaccine?
clinical manifestations
prevention strategies

A

*RNA virus

T: fecal-oral route

Vax: oral for infants

Clin: infects and damages and cells in small intestines, causes gastroenteritis and diarrhea

P: vaccine

22
Q

Noroviurs

transmission
vaccine?
clinical manifestations
prevention strategies

A

*RNA Virus

T: Fecally contaminated food or water, person-person, aerolization of vomited virus, contamination of surfaces

vax: none

Clin: most common cause of viral gastroenteritis in humans

P: hand washing and disenfectants

23
Q

Giardiasis

transmission
clinical manifestations
prevention strategies

A

Protozoan Parasite
Inflammatory

t: food or water contaminated with sewage containing dormant cysts also natural bodies of water

Clin: nausea, cramps, flatulence, diarrhea

*trophozoites emerge and attach to intestinal lining using a sucking disk

24
Q

Tape worm

transmission
life cycle
symptoms
infections

A

t: eggs enter human host through food- raw or undercooked especially
s: liver infection, abdominal pain, rupture of cysts can cause anaphylaxis

eggs hatch and parasite enters intestinal wall -> travel by blood to liver, lungs, and brain

25
Q

Roundworm

transmission
life cycle
symptoms
infections

A

eggs hatch and larvae penetrate skin -> larvae enter blood stream -> move through lungs and get swallowed -> adults enter intestins -> lay eggs -> eggs ingested -> back to lungs

26
Q

Hookworm

transmission
life cycle
symptoms
infections

A
  • Necator Americanus & Ancylostoma duodenale
    t: larvae in soil: penetrate skin of bare feet and enter blood stream
    s: cause itchy dermatitis

eggs hatch -> enter bloodstream through skin -> travel to lungs (causes mild pneumonia) -> swallow larvae

*suck blood from intestinal cappilaries- causes blood loss and anemia

27
Q

How is pinworm diagnosed

A

tape touched to anal region, tape placed on slide and examined under microscope for pinworm eggs

28
Q

Cryptosporidiosis

transmission
clinical manifestations
prevention strategies

A

Protozoan Parasite
Inflammatory

t: contaminated water, physical contact
clin: diarrhea lasting 1-2 weeks If immunocompromised cholera like dairrhea can occur

  • following ingestion oocysts dissolve and release sporozites that enter intestinal epithelial cells
  • asexual then sexual cycles produce infective oocytes
  • oocytes excreted in stool and contaminate water and food
29
Q

Cyclosporiasis

transmission
clinical manifestations
prevention strategies

A

Protozoan Parasite
Inflammatory

t: contaminated fresh produce and water
- make oocytes in intestine but aren’t infective (no fecal-oral transmission**)

clin: dairrhea, nausea, vomiting, bloating, cramping
- symptoms can last more than a month
* *Trimethoprim-sulfamethoxazole (TMP-SMX) treatment

30
Q

Amoebiasis

transmission
clinical manifestations
prevention strategies

A

Protozoan Parasite
Invasive

t: cysts enter body through food or water contaminated with feces
* caused by entamoeba hystolytica
- trophozoites emerge in the intestines

clin: trophozites cause loose stool, stomach cramping and pain
- lesions may form causing: pain, bloody stools, fever

Medical Microbiology (11 decks)

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