Vibrio cholera bacteriology advanced.ppt

bacteriology

2. Q1.each of the following organisms is an important cause of
urinary tract infections EXCEPT:
(A) Escherichia tali
(B) Proteus mirabilis
(C) Klebsiella pneumoniae
(D) Bacteroides
Q2. Your patient is a 30-year-old woman with non-bloody
diarrhea for the past 14 hours. Which one of the following
organisms is LEAST likely to cause this illness?
(A) Clostridium difficile
(B) Streptococcus pyogenes
(C) Shigella dysenteriae
(D) Salmonella enteritidis

3. GenusVibrio
•General characteristics
Genus Vibrio contains 60 species
Members of this genus share many
characteristics with enteric bacteria such as
Escherichia and Salmonella
Primarily found in fresh water, shellfish and other
sea food and cause G/E.
Gram negative curved aerobic/facultative
anaerobes rods and motile (polar flagella),
 Oxidase positive
Readily killed by heat and drying; dies in polluted
water but may survive in clean stagnant water, esp.
if alkaline, or sea water for 1-2 weeks.

6. The growth of many Vibrio strains either requires
or is stimulated by NaCl (most are halophilic).
 Grow B/n 14-40
o
C and best at alkaline pH.
A large inoculum (10
8
) is required to cause
disease because the bacteria are susceptible to
the acidic stomach environment.
–Individuals with low HCl are susceptible.
 Both O and H antigens are present, but only O
antigens are useful in distinguishing strains of
vibrios that cause epidemics.
There are over 140 identified serogroups
based on O-antigen(O1-O139)

7. Only O1 and O139 are toxigenic (produce cholera
toxin) and cause epidemic cholera disease
Generally pathogenic vibrios include:
1) V. cholerae, serogroup O1 strains are associated
with epidemic cholera;
–O139 also can cause similar disease.
2) non-O1 V.cholerae and related strains cause
sporadic cases of cholera-like and other illnesses;
and
3) V. parahaemolyticus and other halophilic vibrios,
which cause gastroenteritis and extraintestinal
infections.

8. Epidemiology
V. cholerae is transmitted by contaminated water and food.
There are no known animal reservoirs, or animal or
arthropod vectors.
Among humans, long-term carriage is rare.
Vibrio O1 divided into 3 serotypes:-Inaba, Ogawa,
Hikojima
There are two biotypes (subdivisions) of the species, V.
cholerae:
• Classic and El Tor.
In contrast to the classic strain, the El Tor strain is
distinguished by the production of hemolysins, higher
carriage rates, and the ability to survive in water for
longer periods.

9. Outbreaks of both Classic and El Tor have been
associated with raw or undercooked seafood harvested
from contaminated waters.
Virulence factors ( O1, O139)
Cholera toxin(enterotoxin): also called Choleragen is
the most important virulence factor of V. cholerae.
Pili:- adherence to intestinal cells and binding site for
phages
Zonnula occludens toxin:- increase intestinal
permeability

10. Pathogenesis
Following ingestion, V. cholerae infects the small
intestine.
Adhesion factor(s) are important for colonization and
virulence.
Treatments that lessen gastric acidity, greatly reduce
the infectious dose.
The organism is noninvasive, and causes disease through
the action of an enterotoxin(Choleragen ) consists of an A
(active) subunit and a B (binding) subunit.
The B subunit (consisting of five identical monomers)
binds to the GM
1
ganglioside receptor of cells lining
the intestine.

11. The A subunit has two components:
A2, which facilitates penetration of the cell
membrane, and
 A1, which activates adenylate cyclase and
produces elevated levels of intracellular cAMP.
This, in turn, causes an out flowing of ions and
water to the lumen of the intestine.

12. G
M1

13. Pathogenesis: Mechanism of
Action: Overview

14. Some infections are asymptomatic or cause mild diarrhea
Incubation period id 1-4 days
Can cause severe disease resulting in abrupt watery diarrhea
and vomiting (20-30L/day)
“Rice-water stool” is characteristic
There are no RBC or WBC in the stool.
There is no abdominal pain
Results in severe fluid and electrolyte loss, dehydration,
shock, acidosis, anuria
Can progress to coma and death
Mortality rate in untreated cases is 60%
Patients with suspected cholera need to be treated prior to
laboratory confirmation, because death by dehydration can
occur within hours.
Clinical significance

15. Cholera Gravis
More severe symptoms
Rapid loss of body fluids
6 liters/hour,
10
7
vibrios/mL
Rapidly lose more than10% of
bodyweight
Dehydration and shock
Death within 12 hours or less

16. Consequences of Severe
Dehydration
Intravascular volume depletion
Severe metabolic acidosis
Hypokalemia
Cardiac and renal failure
Sunken eyes, decreased skin
turgor
Almost no urine production.

17. Diagnosis
No clinical manifestations help distinguish cholera
from other causes of severe diarrhea:
Enterotoxigenic E. coli
Viral gastroenteritis
Bacterial food poisoning
Gram Stain
Gram negative, curved rods of bacteria
Isolate V.cholerae from patient’s stool
Selective medium : TCBS (thiosulphate, citrate, bile
salt, sucrose agar) pH 8.5-9.5
–Vibrio cholerae is a sucrose fermenter
–Vibrio parahemolyticus is a non-sucrose fermenter
Diagnosis, Treatment, and Prevention

18. Yellow colonies from TCBS due to sucrose
fermentation
Alkaline peptone water, PH 8.6 is enrichment Alkaline peptone water, PH 8.6 is enrichment
media for V.cholerae-01media for V.cholerae-01
V cholerae will show colorless colonies on
MacConkey's agar because lactose is fermented
slowly
Oxidase positive
Serology
Using O1 or O139 polyvalent antisera
Agglutination with polyvalent antisera(O1)

21. Treatment
Fluid and electrolyte replacement
Antimicrobial drugs are not as important because they
are lost in the watery stool.
Antibiotics (doxycycline is the drug of choice) can
shorten the duration of diarrhea and excretion of the
organism.
Resistance via plasmids is developing
An attack is followed by immunity of unknown duration
•Prevention
Prevention relies primarily on public health measures that reduce
fecal contamination of water supplies and food.
Adequate cooking of foods can minimize transmission.

22. •These organisms are characterized by a requirement for
higher-than-usual concentrations of NaCl (ability to grow in
8%NaCl).
•They are common in coastal sea waters.
•Vibrio parahaemolyticus
–It is halophilic and does not ferment sucrose
–Results from ingestion of shellfish or raw fish
–Incubation period is 12-24 hours
–Causes cholera-like gastroenteritis with clinical picture varies from
mild to quite severe watery diarrhea, nausea, vomiting, abdominal
cramps, and fever.
–The disease is self-limiting, and antibiotics do not alter the course of
infection.
Vibrio parahaemolyticus and other halophilic,
noncholera vibrios.

23. –Produce Thermostable hemolysin/enterotoxin
•Vibrio vulnificus
–Causes septicemia following consumption of
contaminated shellfish
–Infections can result from washing wounds with
contaminated seawater (skin lesions)
–V. vulnificus and non-O1 produce capsule which helps to
cause disseminated infections
•For soft tissue infections, prompt administration of
antibiotics, such as tetracycline or cefotaxime, is
important