Curved, Gram-Negative Bacilli Flashcards
General characteristics of Vibrio species
- Gram-negative curved or comma-shaped bacilli.
- Motile (polar, monotrichous flagellum), EXCEPT Vibrio metschnikovii; they exhibit “darting: or “shooting star” motility
- Non-spore-forming
- Facultative anaerobic
- Aquatic organisms that are found in fresh water, brackish or estuarine water, and marine or salt water
- Grow in alkaline media
- Most are halotolerant, some are halophilic
- Glucose fermentation
- Catalase(+), EXCEPT Vibrio metschnikovii
- Oxidase(+), EXCEPT Vibrio metschnikovii
What is the common name of V. cholerae ?
Komabacillus
Habitat of V. cholerae
Human colon
Can survive and grow in brackish water
What is the infectious dose of V. cholerae and why ?
They are sensitive to gastric acid hence high dose is required, 10^10 organisms per mL
Transmission of V. cholerae
Fecal-oral route, contaminated waters
Eating raw shellfish from contaminated waters
What are other names of cholera ?
Asiatic cholera or epidemic cholera
What is the incubation period of cholera ?
12 hours up to 3 days depending on the size of the inoculum ingested
Symptoms of cholera
sudden onset:
nausea
vomiting
abdominal cramps
profuse “rice water” diarrhea (stool resembles water in which the rice has been boiled) that may be as many as 10 to 30 per day
containing mucus, epithelial cells, and large numbers of vibrios
What can happen if cholera is left untreated ?
a rapid fluid and electrolyte loss that leads to: dehydration hypovolemic shock metabolic acidosis death in a matter of hours.
How does motility and mucinase assist V. cholerae in causing disease ?
aid in the penetration of the protective mucin layer that coats the surface of the gastroenteric mucosa
Characteristics of choleragen
cholera toxin is a heat-labile enterotoxin
the genes for which are encoded in a lysogenic phage consists of 2 subunits: A (active) subunits and binding (B) subunits
Differentiate the two peptides comprised of the A subunit of choleragens
A1 persists toxin activity, activates adenylate cyclase; hypersecretion of electrolytes (Na+, K+, HCO3−) and water out of the cell
A2, which facilitates penetration of the A1 subunit into the enterocyte
What is the structure of a choleragen ?
There are five B subunits per toxin molecule, arranged in a ring around a central core that contains the enzyme A1
What is the role of the B subunit of choleragens ?
B subunit binds the A2 subunit to the GM1 ganglioside receptor on the cell membrane of the enterocytes
Which antigenic structure forms the basis of a serotyping scheme that classifies the 139 strains of V. cholerae, designated from O1 to O139 ?
O antigen
What is the basis of the V. cholerae strains being designated into 3 major serogroups ?
agglutination with V. cholerae O1 polyvalent antiserum
Characteristics of serogroup V. cholerae O1
agglutinated by V. cholerae O1 antiserum
Includes virulent strains producing cholera toxin
Associated with epidemic cholera
Characteristics of serogroup V. cholerae non-O1
NOT agglutinated by V. cholerae O1 antiserum
Includes V. cholerae O2 up to V. cholerae O138
Does NOT produce cholera toxin; appear to produce a different enterotoxin
associated with isolated cases of diarrheal disease (NOT epidemic-associated)
Characteristics of serogroup V. cholerae O139
Not agglutinated by V. cholerae O1 antiserum
caused large epidemics of cholera in Bangladesh, India, and neighboring countries in 1992
Produces cholera toxin
Makes polysaccharide capsule like other non-O1 strains
What serogroup of V. cholerae is known as Bengal strain ?
V. cholerae O139
In the El tor strain of V. cholerae what has it shown in the Greig test ?
lysis of goat or sheep erythrocytes
What is the current predominant cholera pathogen ?
El Tor biotype of V. cholerae O1
What has been considered as the predominant epidemic strains of V. cholerae ?
Ogawa and Inaba strains
Differentiate the serotypes of V. cholerae O1
Ogawa has determinants A, and B (Ogawa)
Inaba has determinants A, and C (Inaba)
Hikojima produces all 3 antigens (A, B, C)
Prevention and control of V. cholerae
improvement of sanitation, particularly of food and water
Patients should be isolated
their excreta disinfected
Repeated injection of a vaccine containing either lipopolysaccharides extracted from vibrios or dense Vibrio suspensions can confer limited protection to heavily exposed persons
