MICR_040913 Salmonella_Shigella Flashcards Preview

micro quiz 2 > MICR_040913 Salmonella_Shigella > Flashcards

Flashcards in MICR_040913 Salmonella_Shigella Deck (58)
Loading flashcards...
1

What defines a bacterial strain?

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

2

What defines a bacterial serotype?

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

3

How do strains evolve/arise?

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

4

How does the body respond to LPS?

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.

5

What is Lipid A?

endotoxin that contributes to gram (-) diseases

6

What causes endotoxic shock?

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

7

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

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

8

What is the H antigen?

flagellar antigen

9

What is the K antigen?

polysaccharide capsule component

10

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

Salmonella, Shigela, Ecoli

11

What is the gram stain and shape of enteric pathogens?

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

12

What traits do enterobacteriaceae have in common?

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

13

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

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

14

What causes typhoid fever?

Salmonella typhi

15

What is the infectious dose of S. Typhi?

1000 to 10,000 cells

16

How is Salmonella typhi/typhoid fever spread?

poor hygiene conditions

17

What are the 3 phases of typhoid fever?

Early, Bacteremic, Late

18

What characterizes the EARLY phase of typhoid fever?

subclinical with (+) stool culture (first week)

19

What characterizes the BACTEREMIC phase of typhoid fever?

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

20

What characterizes the LATE phase of typhoid fever?

intestinal hemorhage and perforation

21

What is the pathogenesis of Salmonella typhi?

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

22

What confers salmonella typhi virulence?

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

23

What is an example of SP1?

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

24

What is an example of SP2?

Vi antigen - enables survival of S. typhi within phagosome

25

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

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

26

How do you diagnosse S. typhi?

blood or stool culture

27

How do you treat S. typhi?

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

28

Are there any vaccines for S. typhi?

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

29

What causes septicemia?

Salmonella cholerasuis

30

How is Salmonella cholerasuis transmitted?

ingestion of contaminated foods