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micro q2 > Salmonella and Shigella > Flashcards

Salmonella and Shigella Flashcards

(74 cards)

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0
Q

how do strains evolve?

A
  • mutation

- acquiring additional genes by horizontal gene transfer

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1
Q

Strain

A

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

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2
Q

what varies within a strain?

A

surface components

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3
Q

serotype

A

stain that is differentiated by serological means

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4
Q

what does serotyping use?

A

specific antisera that contain antibodies to specific bacterial antigens

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5
Q

3 different types of surface elements

A

O antigens
H antigens
K antigens

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6
Q

O antigen

A

polysaccharide component of LPS

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7
Q

H antigen

A

flagellar antigen

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8
Q

K antigen

A

polysaccharide capsule component

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9
Q

O side chains

A

very easily recognizable by antibodies of the host and therefore they vary aid to help them get immunevasio

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10
Q

3 enterobacteria

A

Shigella
E.Coli
Salmonella

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11
Q

3 syndromes related to salmonella in man

A
  • -typhoid/enteric fever (S. typhi)
  • -septicemias (S. cholerasuis)
  • -acute gastroenteritis (S. enteriditis, S.typhimurium)
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12
Q

incubation period S.typhi

A

7-14 days, but may be subclinical with positive stoool culture

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13
Q

early GI phase of S. typhi

A

Episodic fever
bradycardia (slow heart rate) **
skin rash (Rose Spot)
leukopenia (low WBC count)

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14
Q

bacteremic phase s.typhi

A

enlarged liver and spleen

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15
Q

late GI phase s. typhi

A

intestinal hemorrgage or performation

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16
Q

how does S. typhi infect humans?

A

contaminated food or water

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17
Q

S. typhi and stomach acid

A

somewhat resistant

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18
Q

Steps to S. typhi pathogenesis

A

1- adhesions promote attachment to intestinal epithelium
2- induces bacterially-mediated endocytosis after adherence to the apical membrane of epithelial cells
3-ingestion by macrophages
4- survival inside phagocytotic vacuoles of macrophages (even frm acidic lysosomes)
5- kills macrophage and disseminate via thoracic duct to blood, liver, spleen, gall bladder
6- bacterial factors in blood stream cause fever and shock
7- reinvasion of the GI tract from gall bladder
8- GI bleed and sometimes diarrhea

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19
Q

how does s. typhi survive inside macrophage?

A

via Vi antigen (polysaccharide capsule)

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20
Q

pathogenicity islands

A

specialized genes for salmonella typhi virulence factors are encoded on these
–>aquired via horizontal gene tranfer

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21
Q

SPI-1

A

encode genes for invasion

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22
Q

SPI-2

A

encodes genes for intracellular survival

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23
Q

SPI-1 encodes a …

A

type III secretion system (T3SS)

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24
T3SS
specialized form of secretion wherein a protein moves across the bacterial cytoplasmic and outer membrane and across the host cell membrane through an injection needle
25
what is tranferred via T3SS?
effector proteins into host cell cytoplasm | in salmonella, specifically toxins that induce membrane ruffling by stimulating actin polymerization and endocytosis
26
lipid A component of LPS
endotoxin
27
endotoxin causes
fever and shcok
28
what does endotoxin do to immune system?
responds to low concentration to enable rapid pathogen clearance
29
Specifics of innate immune system responding to endotoxin
macrophages are activated by LPS-->secrete TNFa phagocytes and lymphocytes migrate into tissue increased platelet adhesion to blood vessel wall phagocytosis of bacteria local blood vessel occlusion plasma and cells drain to local lymph nodes remove of infection
30
endotoxic shock
``` can be lethal host response --fever --inflammation --hypotension --DIC and bleeding --organ failure due to lack of oxygen ```
31
what tends to cause localized inflammation due to LPS response
gram negative pathogens
32
weeks and salmonella
1st week: subclinical, positive stool culture 2nd - 3rd week: patients are asymptomatic after 3rd week: gall bladder is colonized during bacteremia
33
s.typhi treatment
fluoroquiolones (ciproflaxin) or third generation cephalosporon (ceftriaxone)
34
chronic carrier states of s..typhi
ampicillin or ciprofloxacin | cholecystectomy
35
prevention of typhoid fever
control of water supplies and sewage food safety pasteurization of milk and screening for carriers vaccines
36
two vaccines for typhoid
oral attenuated vaccine (ty21a) | Vi capsular polysaccharide vaccine-injection (ViCPS)
37
Cholerasuis source
swine
38
how do you get cholerasuis
oral ingestion of contaiminated foods
39
infectious dose of cholerasuis
1000 organisms
40
incubation period of cholerasuis
6-72 hours
41
symptoms of cholerasuis
high fever and bacteremia after onset of gastroenteritis
42
what develops in body tissues with cholerasuis
microabsesses
43
increased suceptibility cholerasuis
``` young age malaria immune dysfunction due to AIDS steroid use immune suppressive therapy sickle cell anemia ```
44
most common salmonella infections in US
CS enteriditis and S typhimurium
45
how many serotypes in enteriditis and typhimurium?
2,200
46
sources of enteriditis and typhimurium
poultry, pork, dog food, eggs (very common-inside & outside), pets, sandbox!
47
clinical syndrome enteriditis & typhimurium
symptoms 8-48 houts after ingestion | sudden onset headache, chills, abdominal pain, vomitting diarrhea w/ fever for 1-4 days
48
pathogenesis of salmonella (3)
LPS release T3SS toxins (pertussis-like) that promote inflammation and secretion
49
treatment of entero etc
fluid and electrolyte replacement | --antibiotics
50
Diagnosis of salmonella
-isolation in feces -fermented glucose, oxidase negative, reduce nitrate --does NOT ferment lactose --motile --produce H2S (black ppt) -urease negative indole negative
51
shigella
bloody diarrhea
52
shigella dysenteriae
most common species in developing world
53
shigella flexneri
common in developing countries (18% in us)
54
shigella sonnei
most common in US
55
shigella boydii
common in indian subcontinent
56
shigella is spread by
food, fingers, feces, flies
57
shigella+ animal reservoir
no
58
what does LPS do in shigella
fever
59
what does shiga toxin do
abdominal cramps
60
three clinical signs in shigella
fever diarrhea and bloody diarrhea with mucus abdominal cramps
61
bacteremia in shigella
rare
62
what syndrome can occur with shigella
hemolytic uremic syndrome
63
how long does shigella stay detectable in your feces
1-4 weeks after recoveryq
64
inoculum of shigella
100 bugs (and they have acid tolerance)
65
incubation period of shigella
1-4 days
66
where does shigella invaid
intestinal cells in the terminal ileum and colon-->uptake by macrophages into phagocytic vacuoles induced by T3SS shigella protein-->escape from phagocytic vacuole into cytoplasm and cell-to-cell spread (T3SS DEPENDENT)-->apoptosis of mphages
67
what is released in response to shigella
IL1 & TNF
68
intestinal ulcertaion can result frm
shiga toxin
69
shiga toxin
exotoxin with 2 subunits B- binds to receptor on intestinal cells A- interferes with function of 60s ribosomal rna, inhibiting protein synthesis
70
shigella is detected by
PMN in stool
71
important diagnostic traits of shigella
``` no gas with glucose fermentation lactose NONfermentors no H2S nonmotile O antigens, but not H indole and urease negative ```
72
treatment of Shigella
rehydration | sometimes antibiotics
73
preventionof shigella
improve sanitation no vaccine (live attenuated not effective) recombinant O antigen vaccine conjugated to inactivated Shiga toxin is a promisng vaccine not yet approved

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