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36 Cards in this Set

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ETEC ***know***

FEATURE
Pathogenic
mechanism

Primary site



Mucosal
pathology

Epidemiology



Fever
Stools
Type

Blood
WBCs

transmission
enterotoxigenic i. coli

Enterotoxin
LT and/or ST
Small
intestine
Intact,
hyperemia

Traveler's
diarrhea,
Childhood
diarrhea
Absent

Copius,
watery
Absent
Absent

contaminated food and water
EIEC
Pathogenic
mechanism

Primary site



Mucosal
pathology

Epidemiology



Fever
Stools
Type

Blood
WBCs
-interoinvasive e. coli

Invades
enterocytes

Large
intestine
Necrosis,
ulceration
inflammation
Sporadic,
uncommon


Common

Scanty,
purulent
Common
Prominent
EHEC

Pathogenic
mechanism

Primary site



Mucosal
pathology

Epidemiology



Fever
Stools
Type

Blood
WBCs
etnterohemorrhagic

Shigalike
cytotoxin

Large
intestine
Effacement
of microvilli,
cell death
Hemorrhagic
colitis, HUS


Absent

Copius,
bloody
Prominent
Absent
EPEC
Pathogenic
mechanism

Primary site



Mucosal
pathology

Epidemiology



Fever
Stools
Type

Blood
WBCs
enteropathogenic e. coli

Adherence
to enterocytes

Small
Intestine
Effacement
Of
Rnicrovilli
Infantile,
Childhood
diarrhea

Common

Copius,
watery
Absent
Minimal
EAEC

Pathogenic
mechanism

Primary site



Mucosal
pathology

Epidemiology



Fever
Stools
Type

Blood
WBCs
enteroaggregative e. coli


?
?


?



Occasional

Watery

Absent
Absent
exotoxins vs. endotoxins and enterotoxins
exotoxins; released by all gram + except for listeria which produces endotoxins, and some -. exotoxin is released from cells
endotoxin is shed from cell membranes

-endotoxin is only released from gram - except for listeria, a gram +.
enterotoxins are exotoxins that act on GI
Shigella
-Bacteriology
-Closely related to
-Shigella are divided into four species (groups) based on
-4 groups
1. E. coli biochemically, antigenically
2. Non-motile
3. Do not ferment lactose
4. differences in Oantigens and some biochemical reactions

-a. Shigella dysenteriae (A) b . Shigellaflexneri (B) c. Shigella boydii (C) d . Shigella sonnei (
Epidemiology
-Shigellae are highly host adapted
-Important factors in transmission:

-effectivity rate
-Secondary attack rates
-Shigellosis in the U.S. affects what population
-where is it transmitted
-what type of shigella?
1. NEVER a commensal in the human intestinal tract
2. to humans
3. feces, fingers, food, and flies (four F's)
4. High infectivity rate: < 200 organisms cause infection
5. are high: 20-60%
6. pediatric disease affecting children less than 10 yrs. of age
a. Associated with daycare centers

b. Typically caused by S.sonnei (D)
Worldwide epidemics of what type of shigella are associated with high mortality
S.dysenteriae type 1 (Shiga bacillus) are associated with high mortality
Pathogenesis

-1 . Fundamental event in pathogenesis:
-Invasion is a 3-step process, explain.
-4 other actions to proliferate in cell
-invasion beyond what is unusual
-invasion of colonic mucosa

-a. Entry -- parasite directed endocytosis of M cells

1) genes (invasion plasmid antigens, Ipa) encoding for adherence and entry are found on a large 220-kb plasmid

2) shigellae adhere selectively to M cells; enter the basolateral aspect of colonic epithelial cells

3) shigellae cause death of macrophages by activating normal programmed cell death (apoptosis)

b. Escape from phagocytic vacuole
c. Actinpolymerization
d. Propulsion through cytoplasm by actin "tails"
c. Passage into adjacent cells through finger-like projections; invasion beyond lamina propria is unusual
(no further than mucosal layer)
Shiga toxin

-can cause
Not essential for invasion
b. Contributes to severity of disease
c. Can cause hemolytic-uremic syndrome
D. Clinical aspects
-Dysentery syndrome - classic

4 symptoms
a. Abdominal cramps

b. Tenesmus - painful straining to pass stools

c. Fever

d. Bloody, mucoid stools
clinical aspects
S.sonni diarrhea in the U.S.

Stool microscopy reveals
a. Fever

b. Systemic symptoms

c. Watery diarrhea

3. -large numbers of fecal leukocytes
tx
1. Disease is usually self-limiting
prevention
1. Sewage disposal
2. Water chloh nation
3. Insect control - flies are important vectors
4. Good individual sanitary practices - hand-washing
5. Proper food preparation
6. Vaccines are under investigation
Salmonella

Bacteriology
-ferments lactose
-produces what
-used to isolate from stool
-used to confirm tests
-talk about variance
Non-lactose fermenters
2. Produce hydrogen sulfides from sulfur-containing amino acids
3. Selective media is used to isolate salmonellae from stools
4. Panels of biochemical tests are used to confirm infection
5. 1500 distinct variants exist based on antigenic analysis of O/K/H antigens
Disease Syndromes



-pathogens found in

infection related to
-Gastroenteritis

humans, livestock,

mammals, reptiles, birds and insects

-Infection related to improper food handling
most common vehicles of infection
Poultry products including eggs, 75% comes from veggies
Peak incidence
- summer/fall
2 major types of disease
S. typhimurium, S. enterifzdis
Highest attack rates: Outbreaks occur in
____have been associated with infections
7) children <5, adults >70

8) nursing homes, hospitals, mental institutions

a) Exotic pet turtles, reptiles
Pathogenesis

-Major pathogenic mechanism
invasion
Sequence of events
a) Adherence to the brush border of intestinal cells causes membrane "ruffles"

b) Bateria are internalized by pinocytosis

c) Bacteria enter lamina propia - endure host inflammatory response
Clinical Manifestations
Symptoms begin
-symptoms
-diarrhea process
-fever
-infecting dose
-24 to 48 hours following ingestion of contaminated food or water

2) Nausea, vomiting, cramping, diarrhea - "food poisoning"
3) Diarrhea persists 3 to 4 days, resolves spontaneously

4) Fever is present in 50% of patients

5) infecting dose >10 5 bacilli
Treatment
Fluids and electrolyte replacement
2) Antibiotics not typically used in healthy adults
3) Antibiotics are recommended for groups of patients at risk for bacterernia
a) Newborn infants
b) Patients X50 yrs of age
c) Patients with lymphoproliferative disorders
d) Patients with anatomic cardiovascular disease
e) Patients with bone or joint disease
f) Patients with transplants
g) Patients with AIDS
Typhoid Fever (enteric fever)

-Epidemiology
1) Worldwide cause of morbidity and mortality
Pathogenesis
1) S. typhi enter and kill M cells

2) Organisms invade macrophages, multiply
3) Organisms spread to the reticuloendothelial system and reach the blood stream
. Clinical Manifestations
-Enteric fever is a
-Incubation period Characterized by what symptoms
-GI, fever/heart, liver
multiorgan-system. infection
2) - 14 days
3) fever, relative bradycardia, headache

a) Faint rash occurs with early fever (rose spots)

b) Fever persists for weeks

4) Constipation is more common than diarrhea
5) Bacteremia may lead to infection at other sites
6) Intestinal perforation may occur
7) Infection in biliary tree leads to chronic cami er state
Diagnosis
Early - positive blood cultures

2) Later - positive stool, urine cultures
Bacteremia common in who and by what.
-infection of what might occur?
. Bacteremia during gastroenteritis is common in the very young, very old and immunocompromised

b. Invasion of the blood stream may occur in the setting of either gastroentenitis or as a part of the entenic fever syndrome

c. Infection of a pre-existing structural abnormality (such as skeletal lesions, cardiovascular lesions) may occur
Asymptornatic Carrier State
Defined as persistence of salmonellae in the stool or urine for periods of a year or longer

b. Biliary tree, abnormal urinary tract may be Iocations where organisms are harbored

c. Food handlers who are caniers are reservoirs for epidemics

d. Antibiotic treatment variably successful in eradication
Yersinia
Bacteriology
Coccobacilli which demonstrate bipolar staining
2. Some strains grow better at temperatures below 37*C
3.
-Species of major clinical significance
a. Y. pestis -plague (will be discussed in Zoonoses lecture)

b. Y. enterocolitica

c. Y. pseudotuberculosis
Pathogenesis
1. Enteropathogenie Yersinia invade M cells of Peyer's patches

2. Sequence of events: ingestion --- > invasion of M cells of Peyer's patches --- > proliferation in lymph nodes --- > small intestinal inflammation and ulceration
Clinical manifestations of Yersinia infections
Y enterocolitica
a. Enterocolitis

1) Fever

2) Diarrhea

3) Abdominal pain

b. Acute mesenteric lymphadenitis
c. Terminal ileitis
d. Septicemia
Yersiniapseudotuberculosis
Acute mesenteric lymphadenitis

1) Fever
2) Pain
3) Nfimics acute appendicitis
4) Diagnosis is made by isolation of organisms from lymph nodes, less commonly from blood