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micro quiz 2 > MICR_040913 Salmonella_Shigella > Flashcards

MICR_040913 Salmonella_Shigella Flashcards

1
Q

What defines a bacterial strain?

A

population of organism within a species that descends from a single organism

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2
Q

What defines a bacterial serotype?

A

a strain that is differenitated by serological means (ie use of antisera to detect bacterial surface elements)

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3
Q

How do strains evolve/arise?

A

mutations, acquiring additional genes, rearragements - decreases detection or killing by host immune system

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4
Q

How does the body respond to LPS?

A

1) macrophages activated by LPS to secrete TNF in the tissue, 2) increased release of plasma proteins into tissue, 3) increased phagocyte and lymphocyte migration into tissue, 4) increased platelet adhesion to blood vessel wall, leading to local blood vessel occlusion. 5) Plasma and immune cells drain to local lymph node 6) removal of infection.

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5
Q

What is Lipid A?

A

endotoxin that contributes to gram (-) diseases

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6
Q

What causes endotoxic shock?

A

when there are sufficient quantities of endotoxin, such as lipid A, LPS

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7
Q

What is the O antigen? What is the functional signficance of it?

A

polysaccharide component of LPS (gram neg. only); different strains have different O-antigens, which helps with immune-evasion

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8
Q

What is the H antigen?

A

flagellar antigen

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9
Q

What is the K antigen?

A

polysaccharide capsule component

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10
Q

What are three members of the enterobacteriaciae (pathogens of the GI tract)

A

Salmonella, Shigela, Ecoli

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11
Q

What is the gram stain and shape of enteric pathogens?

A

gram (-), rods (Salmonella, Shigela, Ecoli)

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12
Q

What traits do enterobacteriaceae have in common?

A

1) facultative anaerobes 2) respire and ferment glucose 3) negative oxidase test for enterics, 4) E. coli can ferment lactose, Salmonella and Shigella cannot

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13
Q

What are the 4 strains of Salmonella and what clinical symptoms do they cause?

A

1) S. TYPHI - typhoid/enteric fever, 2) S. CHOLERASUIS - septicemia, 3) S. ENTERIDITIS or S. TYPHIMURIUM - acute gastroenteritis

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14
Q

What causes typhoid fever?

A

Salmonella typhi

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15
Q

What is the infectious dose of S. Typhi?

A

1000 to 10,000 cells

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16
Q

How is Salmonella typhi/typhoid fever spread?

A

poor hygiene conditions

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17
Q

What are the 3 phases of typhoid fever?

A

Early, Bacteremic, Late

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18
Q

What characterizes the EARLY phase of typhoid fever?

A

subclinical with (+) stool culture (first week)

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19
Q

What characterizes the BACTEREMIC phase of typhoid fever?

A

rose spots (skin rash), bradycardia, leukopenia (low WBC) (second-third week)

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20
Q

What characterizes the LATE phase of typhoid fever?

A

intestinal hemorhage and perforation

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21
Q

What is the pathogenesis of Salmonella typhi?

A

1) bypasses acidic conditions of stomach 2) enters intestines and attaches to intestinal epithelium via adhesins, 3) transferred to gut lymphoid tissue, where it is ingested by macrophages and replicates inside the phagosome, 4) causes macrophage lysis and 5) disseminates to blood, liver, gall bladder

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22
Q

What confers salmonella typhi virulence?

A

TWO PATHOGENICITY ISLANDS: SP1 - encodes T3SS genes for invasion. SP2 - encodes genes for intracellular survival. LPS - endotoxin that causes fever/shock

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23
Q

What is an example of SP1?

A

T3SS - Type III secretion system - a system by which S. typhi delivers toxins to macrophages to induce endocytosis

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24
Q

What is an example of SP2?

A

Vi antigen - enables survival of S. typhi within phagosome

25
Q

How does LPS contribute to S. typhi’s virulence?

A

its an ENDOTOXIN that causes fever (localized infection) and shock (sepsis/blood stream). Leads to fever, inflammation, hypotension, DIC, bleeding organ failure)

26
Q

How do you diagnosse S. typhi?

A

blood or stool culture

27
Q

How do you treat S. typhi?

A

Fluroquinolones (ciprofloxacin), Cephalosporin (ceftriaxone), Ampicillin, or Cholecystectomy

28
Q

Are there any vaccines for S. typhi?

A

oral attenuated (Ty21a) an Vi antigen vaccine (ViCPS)

29
Q

What causes septicemia?

A

Salmonella cholerasuis

30
Q

How is Salmonella cholerasuis transmitted?

A

ingestion of contaminated foods

31
Q

How are the symptoms of s. cholerasuis?

A

Gastroenteritis, fever, bacteremia/septicemia, microabcesses in body tissues

32
Q

How would you confirm the presence of S. cholerasuis?

A

blood culture

33
Q

Who is most susceptible to s. cholerasuis?

A

young, immunocompromised patients (AIDs, drug users, immunosuppressive therapy), sickle cell anemia

34
Q

What causes acute gastroenteritis?

A

S. enteriditis and S. typhimurium

35
Q

How is S. enteriditis and S. typhimurium transmitted?

A

oral ingestion of contaminated foods (eggs, poultry, pork, fruits, veggies)

36
Q

What are some symptoms of an S. enteriditis and S. typhimurium infection?

A

headache, chills, abdominal pain, vomiting, diarrhea, fever

37
Q

Who is most susceptible to S. enteriditis and S. typhimurium?

A

immunocompromised patients (very old/young, AIDs, etc)

38
Q

What are 3 virulence factors of S. enteriditis and S. typhimurium?

A

1) LPS, 2) T3SS (invasion), 3) Toxins (inflammation/secretion)

39
Q

How would you confirm the presence of S. enteriditis?

A

stool culture

40
Q

How do you treat S. enteriditis and S. typhimurium?

A

Ampicillin/Trimethroprim, cephalosporin, fluroquinolone (FACT)

41
Q

What are the biochemical properties of salmonella infections?

A

(+) for glucose fermentation, nitrate reduction, H2S production; (-) for lactose fermentation, oxidase, urease, and indole activity

42
Q

How would you confirm the serotype of salmonella infections?

A

PCR for O and H antigens

43
Q

What does Shigella cause?

A

dysentery (bloody diarrhea)

44
Q

How is shigella spread?

A

4 F’s: food, fingers, feces, and flies

45
Q

What is the most common type of Shigella in the US? In developing countries?

A

US: S. sonnei. DEVELOPING COUNTRIES: S. dysenteriae and S. flexneri

46
Q

What are the symptoms of Shigella? What are they caused by?

A

1) Fever (LPS), 2) cramps and intestinal ulceration (Shiga toxin), 3) bloody diarrhea (malabsorption)

47
Q

What confers shigella virulence? (3)

A

1) acid tolerance, 2) T3SS system, 4) Shiga toxins (exotoxin A/B)

48
Q

What is the function of Shiga toxin A? B?

A

TOXIN A - interferes with protein synthesis. TOXIN B - binds to receptors on intestinal cells

49
Q

What is the pathogenesis of Shigella?

A

1) bypasses acidic conditions of stomach 2) enters intestines and attaches to ILEUM & COLON 3) transferred to gut lymphoid tissue, where it is taken up by macrophages and replicates inside the phagosome, 4) causes macrophage lysis and 5) release of new pathogens to infect new cells

50
Q

What is the Shiga toxin?

A

EXOtoxin produced by Shigella that 1) blocks protein synthesis, and 2) binds to intestinal cells (leads to fluid malabsorption, mucosal cell apoptosis, and ulceration)

51
Q

How would you diagnose Shigella?

A

stool culture

52
Q

What is the biochemical profile for Shigella?

A

(+) for glucose fermentation without gas, (-) for lactose fermentation, H2S production, urease, and indole activity

53
Q

How would you confirm the serotype of Shigella?

A

PCR for O antigens only - it doesn’t have H antigens

54
Q

How would you treat Shigella?

A

1) fluids/electrolytes, 2) antibiotics (Ciprofloxacin, Trimethroprim, Sulfa (if severe))

55
Q

What vaccine is available for Shigella?

A

recombinant O antigen conjugated to inactivated Shiga toxin

56
Q

How can Shigella be prevented?

A

better sanitation

57
Q

What is the Kigler Iron Agar test?

A

biochemical test that detects sugar (glucose, lactose) fermentation and gas (H2S) production

58
Q

How do you intepret a Kigler Iron Agar test?

A

Yellow Slant = fermented lactose. Yellow BUTT = fermented glucose. BLACK PPT = H2S production.

micro quiz 2 (8 decks)

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