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Microbiology > Bacterial Infections of the GI Tract 2 > Flashcards

Bacterial Infections of the GI Tract 2 Flashcards

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1
Q

MacConkey Agar:

Purpose of test

Positive Test

Negative Test

A
  1. Testing for lactose fermentation
  2. Agar/colonies turning RED indicates postive test
  3. Agar/colonies staying WHITE indicates negative test
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2
Q

Indole Test:

Purpose

Postive Test

Negative Test

A
  1. Test for indole production (from tryptophan)
  2. Positve test: RED color change
  3. Negative test: no color change
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3
Q

Hydrogen Sulfite Test:

Purpose

Postive Test

Negative Test

Salmonella reaction

Shigella Reaction

A
  1. Purpose of test is to see if organism can reduce sulfur compounds to sulfides
  2. BLACK PRECIPITATE indicates positive test. The organism produced FeS
  3. No black precipitate indicates a NEGATIVE test
  4. Salmonella is (+)
  5. Shigella is (-)
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4
Q

Enteropathic E. Coli (EPEC)

  1. Gram stain
  2. Aerobic abilities
  3. Invasiveness
A
  1. Gram stain negative
  2. Facultative anaerobe
  3. Moderately invasive
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5
Q

Enteropathic E. Coli (EPEC)

  1. Primary symptom
  2. What causes the symptoms
  3. Vulnerable populations
  4. Timing (8, 16, 16+)
  5. Inflammatory or non-inflammatory
A
  1. Primary symptom is watery diarrhea
  2. Cause of watery diarrhea is from microvilli destruction
  3. Infants and children are primary vulnerable popluation (P for pediatrics)
  4. Typically 16+ hours before onset of symptoms
  5. Non-inflammatory bacteria
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6
Q

Enteropathic E. Coli:

  1. Explain steps of pathogenesis

Keywords: Tir, Type III, Bfpa, F-actin

A
  1. EPEC injects Tir protein via Type III secretion and Bfpa
  2. Tir binds with Intimin
  3. F-actin polymerization occurs
  4. Rearranged actin causes microvilli destruction
  5. Without villi there is no fluid absorption…watery diarrhea
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7
Q

Enteropathic E. Coli:

Toxin Production?

Diagnosis: culture tests (2) and why they suck

Actual diagnosis method

Treatment

A
  1. No toxin production. Just watery diarrhea
  2. EPEC can ferment lactose (+ MacConkey) and produce Indol (+ Indol). Not great methods for diagnosis because most people have commensal, lactose fermenting, Indol producing bacteria.
  3. PCR is best method for diagnosis
  4. Supportive treatment and antibiotics if necessary (usually not)
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8
Q

Enterotoxigenic E. Coli

  1. Gram Stain
  2. Arerobic abilties
  3. Invasiveness
A
  1. Gram stain negative
  2. Facultative anaerobe
  3. Non- invasinve

1 and 2 are the same as EPEC

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9
Q

Enterotoxigenic E. Coli

  1. Disease nickname and why
  2. Primary symptom
  3. Leading _ _ cause of _ _in _ _world
A
  1. “Travelers Diarrhea” because associated with travel to developing countries and ingestion of contaminated water or ice
  2. Primary symptom is watery diarrhea
  3. Leading bacterical cause of diarrhea in developing world
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10
Q

Enterotoxigenic E. Coli

  1. How does it adhere to intestinal epithelium?
  2. Toxins produced (2) and how they work
  3. Inflammatory or Non-inflammatory?
  4. Timing
A
  1. Uses fimbriae to adhere to epithelial cells
  2. Toxins: LT and ST. LT is heat liable toxin while ST is heat stable toxin. Both cause increases in cAMP which causes efflux of Cl, K, Water, Na, and HCO3 which causes diarrhea
  3. Non-inflammatory
  4. 16+ hours after ingestion before onset of symptoms
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11
Q

Enterotoxigenic E. Coli

  1. Primary method of diagnosis
  2. Less common method of diagnosis given available resources
  3. Treatment
A
  1. Primary method is clinical history, especially with travel to endemic country
  2. DNA probes to detect LT and ST encoding genes in samples and cultures. Requires a research or reference lab
  3. Treatment is supportive and rehydration
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12
Q

Salmonella spp

  1. Number of serotypes of salmonella enterica serovar
  2. Which salmonella causes typhoid?
  3. Name 3 non-typhoidal salmonellas (etc…)
A
  1. Over 2500 serotypes
  2. Salmonella enterica serovar Typhi causes typhoid
  3. SES cholerasuis

SES Enteritidis

*SES Typhimurium* (strange name but non-typhoidal)

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13
Q

Salmonella Typi

  1. Gram stain
  2. Aerobic ability
  3. Shape and movement
  4. Acid tolerance
  5. Intracellular or extracellular
  6. Adapted to humans or not so much?
A
  1. Gram negative
  2. Facultative anaerobe
  3. Rods…motile flagella
  4. Acid tolerant
  5. Intracellular pathogen
  6. Highly adapted to humans
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14
Q

Salmonella Typhi

  1. Reservoirs
  2. Transmission route
  3. Infectious dose
  4. Who’s awesome?
A
  1. Humans are only known reservoir
  2. Fecal-oral transmission route
  3. Fair amount of infecting bacteria (10^5-10^6)
  4. You’re awesome
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15
Q

Salmonella Typi:

  1. Incubation time
  2. Put these symptoms in correct progression: typhoid fever, colonization of gallbladder, rising fever over 3 days, reinfection of intestines, andfever with headache
  3. Are shedders of S. Typhi symptomatic?
A
  1. Incubation time of S. Typhi is about 13 days
  • Fever with Headache
  • Rising fever over 3 days
  • Typhoid fever (like a 4 week fever)
  • GI symptoms: chronic colonization of gallbladder then reinfection of intestines
  1. Shedders are not symptomatic (Typhoid Mary)
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16
Q

Salmonella Typhy

  1. S. typhi adheres to which two types of cells?
  2. Uses what type of secretion system?
  3. Explain the pathogenesis using: T3SS, ssps, membrane ruffling, uptake, and escape
  4. Fever is caused by what toxin?
A
  1. S. Typhi adheres to M cells (immune cells) and enterocytes
  2. Type III secretion system
  • Type III secretion system injectes ssps (salmonella-secreted invasion proteins) into M cells.
  • Membrane ruffling causes uptake in to M cell vacuoles.
  • The SSPS escape the vacuole and are phagocytosed by macrophages
  • Macrophages go to lymph nodes
  • Salmonella escape macrophage into blood
  • Final result is bacteremia
  1. Fever is caused by LPS (endotoxin)
17
Q

Salmonella Typhi

  1. Diagnosis
  2. Which tests to use and results (3)
  3. Treatment (3 choices) and based on what
  4. Prevention (2)
A
  1. Diagnose via culture of stool and blood samples on selective media
  2. MacConkey/Lactose fermentation: negative, Indole: negative, Hydrogen Sulfite: positive
  3. Antibiotic therapy based on susceptibility profile. Can use Fluoroquinolone, trimethoprim-sulfamethoxazole, or broad spectrum cephlosporin
  4. Avoid sources of contamination (non-bottled water, ice, uncooked foods, and raw fruits and vegetables. Vaccine available but not very effective or useful
18
Q

One more time…name 3 kinds of non-typhoidal salmonella…go!

Disease of bloodstream, intestines, or both?

A
  • Salmonella enterica serovar Cholerasuis
  • SES Enteritidis
  • SES Typhimurium

Enteric diseases so no bloodstream…most of the time

19
Q

Non-typhoidal Salmonella

  1. Gram stain
  2. Aerobic abilities
  3. Motility and shape
  4. Acid tolerance
  5. Intracellular or extracellular pathogen?
A
  1. Gram negative
  2. Facultative anaerobe
  3. Motile rods, flagellated
  4. Acid tolerant
  5. Intracellular pathogen
20
Q

Non-typhoidal Salmonella

  1. Prevalent in developed or developing countries?
  2. Vulnerable populations
  3. Animal reservoirs?
  4. Transmission route
A
  1. Developed countries
  2. Children and elderly
  3. Numerous animal reservoirs which makes it different than typhoidal salmonella
  4. Fecal oral route. Human-Human transmission is unlikely
21
Q

Non-typhoidal Salmonella

  1. Symptom onset
  2. Symptoms (4)
  3. Diarrhea attributes and duration
  4. Prevalence of fever
A
  1. Symptom onset is 6-48h post ingestion
  2. N/V/D and abd pain
  3. Persistent diarrhea for 3-4 days. Can be loose and watery to dysentery (bloody and purulent). Loose and watery is far more likely
  4. 50% of cases have fever
22
Q

Non-typhoidal Salmonella

  1. Pathogenesis
  2. What happens after entry into macrophages
A
  • Pathogenesis is very similar to salmonella typhi
    1. Rapid killing of macrophages. Causes inflammatory response which keeps disease confined to intestines. This leads to profuse, watery diarrhea
    2. Carriage in macrophage which only occurs in immunocompromised. Systemic dissemination occurs causing sepsis. Focal infections can cause osteomyelitis, endocarditis, and arthritis
23
Q

Non-Typhoidal Salmonella

  1. Diagnosis: two good ways
  2. Treatment
  3. Vaccine
A
  1. Diagnose via serology or culture (negative lactose, positive hydrogen sulfite)
  2. Treatment for salmonella gastroenteritis is supportive with electrolyte replacement. Antibiotics are NOT recommeded because it enhances carrier state. Only approved to prevent sepsis
  3. No vaccine available
24
Q

Campyloybacter jejuni

  1. Gram stain
  2. Shape
  3. Aerobic ability
  4. Animal reservoirs
  5. Invasiveness and location
A
  1. Gram negative
  2. Curved rod. “Seagull shaped”
  3. Microaerophilic
  4. Many animal reservoirs (turkeys and pets)
  5. Definitely invasive to jejunum, ilium, and colon
25
Q

Campyloybacter jejuni

Initial Symptoms (2)

Secondary symptoms

Incubation time

Associated syndrome

Campyloybacter jejuni is the most common cause of _ _ _ ?_

A

Initially causes ulceration and acute enteritis

These cause watery diarrhea and eventually sepsis

Incubation time is 2-11 days

Can cause Guillan-Barre syndrome

Campyloybacter jejuni is the most common cause of bacterial diarrhea

26
Q

Campyloybacter jejuni

Pathogenesis is similar to what other pathogen?

A

Campyloybacter jejuni pathogenesis is similar to Salmonella.

Not much is known about its mechanism though

27
Q

Campyloybacter jejuni

Diagnosis (1)

Treament for invasive and non-invasive forms

A

Diagnosis: Culture- selective media in a microaerophilic environment

Treatment for non-invasive form is supportive

Treatment for invasive form is based on susceptibility profile. Typically a macrolide such as erythromycin, azithromycin, quinolone, or biaxin.

Just know macrolide…I added that other stuff because funsies

28
Q

Guillain-Barre Syndrome:

Pathogenesis

Progression

Symptoms

What percentage of GBS is attributable to Campylobacter infections?

A
  1. Pathogenesis: acute, immune-mediated polyneuropathy

Progression: progressive, fairly symmetric muscle weakness with absent or depressed deep tendon reflexes

Symptoms vary but it is usually ascending

**30-40% **of GBS is attributable to Campyloybacter infections

29
Q

What pathogen should be seriously considered when a patient has diarrhea with neurological symptoms?

A

Campyloybacter jejuni

Microbiology (29 decks)

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