LECTURE Flashcards
V. cholerae: common name
“Kommabacillus”
V. cholerae: habitat
human colon
Man is the only known reservoir of V. cholerae. Human carriage may persist after untreated infection for months after infection; however, permanent carrier state is rare. They can survive and grow in fresh and brackish water.
V. cholerae
V. cholerae: transmission
fecal-oral route.
The most common source of infection is contaminated water. Food, especially shellfish (contaminated from contaminated waters) eaten
raw, have also been a source of infection.
V. cholerae
Cholera, which is also known as
Asiatic cholera or epidemic cholera
The incubation period of Cholera is [?] depending on the size of the inoculum ingested.
12 hours up to 3 days
Symptoms include sudden onset of nausea, vomiting, abdominal cramps and 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 species
Cholera
In severe cholera, infected individual can lose several liters of fluid, as much as [?]. If left untreated, it can result in a rapid fluid and electrolyte loss that leads to dehydration, hypovolemic shock, metabolic acidosis, and death in a matter of hours.
20-30 liters per day
To cause disease, cells of V. cholerae must adhere to the gastric and intestinal mucosal epithelial cells of the host; two properties that aid in the penetration of the protective mucin layer that coats the surface of the gastroenteric mucosa.
Motility and mucinase
The cholera toxin is a heat-labile enterotoxin, the genes for which are encoded in a lysogenic phage.
Choleragen (cholera toxin)
Cholera is consists of 2 subunits:
A (active) subunits and binding (B) subunits
The A subunit is composed of two peptides:
A1 with toxin activity
A2
it activates adenylate cyclase, causing increased levels of cyclic adenosine monophosphate (cAMP) and hypersecretion of electrolytes (Na+, K+, HCO3−) and water out of the cell and into the lumen of the intestine. The net effect is that the gastrointestinal tract’s absorptive ability is overwhelmed, resulting in the massive outpouring of watery stools
A1 with toxin activity
facilitates penetration of the A1 subunit into the enterocyte
A2
[?] binds the A2 subunit to the GM1 ganglioside receptor on the cell membrane of the enterocytes. There are five B subunits per toxin molecule, arranged in a ring around a central core that contains the enzyme A1.
B subunit
Heat-labile substances that are found in all V. cholerae strains
H antigen
Cell wall lipopolysaccharides that confer serologic specificity to the bacterial cells
O antigen
V. cholerae strains are designated into 3 major serogroups based on agglutination with V. cholerae O1 polyvalent antiserum.
Serogroups of V. cholerae
- Is agglutinated by V. cholerae O1 antiserum
V. cholerae O1
- Is NOT agglutinated by V. cholerae O1 antiserum
V. cholerae non-O1
- Is NOT agglutinated by V. cholerae O1 antiserum
V. cholerae O139
There are two biotypes of V. cholerae serogroup O1 based on their differences in biochemical characteristics, which is associated with how they differ with respect to the severity of the disease they can cause.
Biotypes of V. cholerae O1
caused the epidemic cholera from early 1800s to early 1900 – during this time, there were 6 waves of cholera pandemic that spread across the world.
Classical strain of V. cholerae
was isolated in the early 1900s from Meccabound pilgrims at the El Tor Quarantine Station in Sinai Peninsula.
El Tor strain of V. cholerae
- Includes virulent strains producing cholera toxin
V. cholerae O1
- Associated with epidemic cholera
V. cholerae O1
- Includes V. cholerae O2 up to V. cholerae O138
V. cholerae non-O1
- Does NOT produce cholera toxin; but, they appear to produce an enterotoxin different from cholera toxin.
V. cholerae non-O1
- Has been associated with isolated cases of diarrheal disease (NOT epidemic-associated)
V. cholerae non-O1
- Represented a new serogroup, as it is a strain that could not be identified as any of the 138 known types of V. cholerae
V. cholerae O139
- Is also known as “Bengal strain” to indicate its first isolation from the coastal areas of the Bay of Bengal; it caused large epidemics of cholera in Bangladesh, India, and neighboring countries in 1992.
V. cholerae O139
- Produces cholera toxin in quantities similar to that produced by V. cholerae O1
V. cholerae O139
- Makes polysaccharide capsule like other non-O1 strains (V. cholerae O1 does not make a capsule.)
V. cholerae O139
- Has spread in epidemic proportions across the Indian subcontinent.
V. cholerae O139
These vibrios resembled classical V. cholerae in many way but caused lysis of goat or sheep erythrocytes in a test known as the Greig test.
El Tor strain of V. cholerae
has been found to be hardier and better capable of surviving in the environment
El Tor strain of V. cholerae
epidemic in the Phil in 1961 that has started the 7th pandemic. Currently, the El Tor biotype of V, cholerae O1 is the predominant ch
El Tor strain of V. cholerae
A number of tests differentiate them from classical V. cholerae
El Tor strain of V. cholerae
V. cholerae serogroup, in both the classical and the El Tor biotypes, are separated into 3 serotypes based on differences in antigen determinants on the O side chain of the lipopolysaccharide (LPS) antigen. These serotypes are important for epidemiological studies. These can be detected by agglutination with specific antiserum
Serotypes of V. cholerae O1
has determinants A, and B
Ogawa
has determinants A, and C
Inaba
produces all 3 antigens (A, B, C))
Hikojima
are considered the predominant epidemic strains.
Ogawa and Inaba
has been isolated in outbreaks , but its occurrence has been rare
Hikojima
Control rests on education and on improvement of sanitation, particularly of food and water.
PREVENTION AND CONTROL of Vibrio cholerae
Patients should be isolated, their excreta disinfected, and contacts followed up
PREVENTION AND CONTROL of Vibrio cholerae
Repeated injection of a vaccine containing either
lipopolysaccharides extracted from vibrios or [?] can confer limited protection to heavily exposed persons (eg, family contacts) but is not effective as an epidemic control measure.
dense Vibrio suspensions
inhabits seawaters
Vibrio parahaemolyticus