Podcast
Questions and Answers
In what unique ecological niche are Vibrio species, including V. cholerae, most commonly found?
In what unique ecological niche are Vibrio species, including V. cholerae, most commonly found?
- Marine and estuarine waters worldwide, thriving in saline environments with moderate temperatures. (correct)
- Deep-sea hydrothermal vent ecosystems characterized by extreme thermophilic conditions.
- Ubiquitous distribution in terrestrial desert environments, displaying exceptional desiccation tolerance.
- Endophytic associations within the root nodules of leguminous plants, contributing to nitrogen fixation.
What metabolic characteristic sharply differentiates Vibrio cholerae from strictly anaerobic bacteria?
What metabolic characteristic sharply differentiates Vibrio cholerae from strictly anaerobic bacteria?
- Facultative anaerobic nature, enabling both aerobic respiration and fermentative metabolism. (correct)
- Ability to utilize alternative electron donors, such as sulfur compounds, in the absence of oxygen.
- Strict requirement for anoxic conditions and the fermentation of complex polysaccharides.
- Obligate dependence on sulfate as the terminal electron acceptor during anaerobic respiration.
What enzymatic properties, crucial for diagnostic differentiation, are consistently displayed by Vibrio species?
What enzymatic properties, crucial for diagnostic differentiation, are consistently displayed by Vibrio species?
- Oxidase-negative and urease-positive, facilitating urea hydrolysis for nitrogen assimilation.
- DNase-positive and lipase-positive, indicative of extracellular degradation of nucleic acids and lipids.
- Catalase and oxidase positive, aiding in the detoxification of reactive oxygen species and electron transport. (correct)
- Coagulase-negative and catalase-negative, distinguishing them from pathogenic staphylococci.
What is the precise structural arrangement of flagella in most motile Vibrio species?
What is the precise structural arrangement of flagella in most motile Vibrio species?
What specific ionic compound is indispensable for the optimal in vitro propagation of all Vibrio species?
What specific ionic compound is indispensable for the optimal in vitro propagation of all Vibrio species?
Which specific serogroups of Vibrio cholerae are definitively linked to the etiological cause of cholera epidemics in humans?
Which specific serogroups of Vibrio cholerae are definitively linked to the etiological cause of cholera epidemics in humans?
Besides V. cholerae, which other Vibrio species are crucially recognized as significant human pathogens?
Besides V. cholerae, which other Vibrio species are crucially recognized as significant human pathogens?
What critical aspect of public infrastructure plays the most significant role in the epidemiology of cholera?
What critical aspect of public infrastructure plays the most significant role in the epidemiology of cholera?
What principle factor is most directly associated with the persistent endemicity of cholera in certain regions?
What principle factor is most directly associated with the persistent endemicity of cholera in certain regions?
What is the most typical morphological characteristic of Vibrio cholerae upon initial isolation from a patient sample?
What is the most typical morphological characteristic of Vibrio cholerae upon initial isolation from a patient sample?
During prolonged cultivation under non-selective conditions, what altered morphological form may Vibrio cholerae cells exhibit?
During prolonged cultivation under non-selective conditions, what altered morphological form may Vibrio cholerae cells exhibit?
Which colonial morphology is characteristically exhibited by Vibrio cholerae when cultured on nutrient agar under aerobic conditions?
Which colonial morphology is characteristically exhibited by Vibrio cholerae when cultured on nutrient agar under aerobic conditions?
What incubation temperature is optimally suited for the in vitro cultivation of Vibrio cholerae and most other Vibrio species?
What incubation temperature is optimally suited for the in vitro cultivation of Vibrio cholerae and most other Vibrio species?
What specific selective agar is frequently employed for the isolation and presumptive identification of Vibrio species from clinical specimens?
What specific selective agar is frequently employed for the isolation and presumptive identification of Vibrio species from clinical specimens?
In addition to selective agars, what other type of culture medium is advantageous for recovering Vibrio species, particularly from stool specimens?
In addition to selective agars, what other type of culture medium is advantageous for recovering Vibrio species, particularly from stool specimens?
What distinct colonial morphology is exhibited by Vibrio cholerae when grown on TCBS agar, providing a key diagnostic feature?
What distinct colonial morphology is exhibited by Vibrio cholerae when grown on TCBS agar, providing a key diagnostic feature?
What colonial characteristic distinguishes non-sucrose-fermenting Vibrio species, such as V. parahaemolyticus and V. vulnificus, when cultured on TCBS agar?
What colonial characteristic distinguishes non-sucrose-fermenting Vibrio species, such as V. parahaemolyticus and V. vulnificus, when cultured on TCBS agar?
What specific environmental pH range is optimally conducive to the proliferation of Vibrio species?
What specific environmental pH range is optimally conducive to the proliferation of Vibrio species?
What sensitivity trait is exhibited by Vibrio species upon exposure to acidic conditions?
What sensitivity trait is exhibited by Vibrio species upon exposure to acidic conditions?
What procedural recommendation should be meticulously followed when collecting stool specimens for Vibrio isolation to ensure optimal recovery of the bacteria?
What procedural recommendation should be meticulously followed when collecting stool specimens for Vibrio isolation to ensure optimal recovery of the bacteria?
For delayed processing of stool specimens suspected of containing Vibrio species, what transport medium is advised to preserve bacterial viability?
For delayed processing of stool specimens suspected of containing Vibrio species, what transport medium is advised to preserve bacterial viability?
In regions where cholera is endemic, what culture method is generally recommended for the immediate processing of stool samples to maximize Vibrio isolation?
In regions where cholera is endemic, what culture method is generally recommended for the immediate processing of stool samples to maximize Vibrio isolation?
What enrichment broth is most appropriate for recovering Vibrio species?
What enrichment broth is most appropriate for recovering Vibrio species?
Which biochemical characteristic serves as a crucial determinant in the presumptive identification of Vibrio cholerae and other Vibrio species?
Which biochemical characteristic serves as a crucial determinant in the presumptive identification of Vibrio cholerae and other Vibrio species?
What specific range of NaCl concentration is typically required for the growth of most Vibrio species, reflecting their halophilic nature?
What specific range of NaCl concentration is typically required for the growth of most Vibrio species, reflecting their halophilic nature?
What capacity distinguishes V. cholerae from most other Vibrio species in terms of their nutritional growth requirements?
What capacity distinguishes V. cholerae from most other Vibrio species in terms of their nutritional growth requirements?
What structural component primarily mediates the serologic specificity of Vibrio cholerae strains?
What structural component primarily mediates the serologic specificity of Vibrio cholerae strains?
Which specific serovars of Vibrio cholerae are definitively responsible for causing epidemic and pandemic cholera?
Which specific serovars of Vibrio cholerae are definitively responsible for causing epidemic and pandemic cholera?
Occasionally, what variant strains of Vibrio cholerae, are implicated as causative agents of cholera-like diarrheal disease?
Occasionally, what variant strains of Vibrio cholerae, are implicated as causative agents of cholera-like diarrheal disease?
What three serotypes determine the further subtyping of the V. cholerae serogroup Ol antigen?
What three serotypes determine the further subtyping of the V. cholerae serogroup Ol antigen?
What are the two principal biotypes of epidemic Vibrio cholerae that are definitively defined and characterized?
What are the two principal biotypes of epidemic Vibrio cholerae that are definitively defined and characterized?
What diagnostic property is exhibited by the El Tor biotype of Vibrio cholerae but not by the classic biotype?
What diagnostic property is exhibited by the El Tor biotype of Vibrio cholerae but not by the classic biotype?
Which methodologies can further subtype V. cholerae?
Which methodologies can further subtype V. cholerae?
What diagnostic utility does typing V. cholerae have?
What diagnostic utility does typing V. cholerae have?
What vital characteristic does V. cholerae O139 not possess?
What vital characteristic does V. cholerae O139 not possess?
What characteristic uniquely distinguishes clinical isolates of V. cholerae O1 from V. cholerae O139?
What characteristic uniquely distinguishes clinical isolates of V. cholerae O1 from V. cholerae O139?
What critical exotoxin, specifically elaborated by pathogenic strains of Vibrio cholerae, directly mediates the profound diarrheal symptoms associated with cholera?
What critical exotoxin, specifically elaborated by pathogenic strains of Vibrio cholerae, directly mediates the profound diarrheal symptoms associated with cholera?
What specific cellular receptor facilitates the entry of the A subunit of cholera toxin into intestinal epithelial cells, initiating the cascade of events leading to massive fluid secretion?
What specific cellular receptor facilitates the entry of the A subunit of cholera toxin into intestinal epithelial cells, initiating the cascade of events leading to massive fluid secretion?
Activation of what specific intracellular signaling molecule results in prolonged hypersecretion of water and electrolytes?
Activation of what specific intracellular signaling molecule results in prolonged hypersecretion of water and electrolytes?
What is affected by the increased sodium chloride secretion, and absorption of sodium and chloride by the microvilli?
What is affected by the increased sodium chloride secretion, and absorption of sodium and chloride by the microvilli?
Flashcards
Vibrio Morphology
Vibrio Morphology
Comma-shaped, curved, or straight rods found worldwide in marine and estuarine waters.
Halophilic Nature
Halophilic Nature
Ability to grow in high salt concentrations.
Vibrio cholerae
Vibrio cholerae
A bacterium that causes cholera.
V. cholerae Morphology
V. cholerae Morphology
Signup and view all the flashcards
V. cholerae Colonies
V. cholerae Colonies
Signup and view all the flashcards
Selective Agar
Selective Agar
Signup and view all the flashcards
V. cholerae on TCBS
V. cholerae on TCBS
Signup and view all the flashcards
Vibrio Growth pH
Vibrio Growth pH
Signup and view all the flashcards
V. cholerae Diseases
V. cholerae Diseases
Signup and view all the flashcards
Oxidase Test Result
Oxidase Test Result
Signup and view all the flashcards
Capsule Production
Capsule Production
Signup and view all the flashcards
V cholerae Enterotoxin
V cholerae Enterotoxin
Signup and view all the flashcards
Enterotoxin Genes
Enterotoxin Genes
Signup and view all the flashcards
Direct Smears
Direct Smears
Signup and view all the flashcards
"Shooting star" motility
"Shooting star" motility
Signup and view all the flashcards
Rapid Growth
Rapid Growth
Signup and view all the flashcards
Study Notes
- Vibrios are bacteria commonly found worldwide in marine and estuarine waters
- They are comma-shaped, curved, or straight, and are facultatively anaerobic fermentative rods
- Vibrios are catalase and oxidase positive, and motile via monotrichous or multitrichous polar flagella
- They can grow in a range of 14–40°C and need sodium chloride (NaCl) to grow, making them halophilic
Vibrio cholerae Serotypes
- V. cholerae serogroups O1 and O139 cause cholera
- Other vibrios such as V. parahaemolyticus and V. vulnificus, are pathogens that cause skin and soft tissue infections, sepsis, or gastroenteritis
Vibrio Cholerae
- V. cholerae causes cholera
- Cholera epidemiology parallels the recognition and transmission of V. cholerae in water and the development of water systems
- Poor sanitation, direct contact, or consumption of contaminated water/food (e.g., used for drinking, cooking, bathing, or crop irrigation) are associated with cholera
Morphology and Identification
- Upon isolation, V. cholerae is a comma-shaped, curved rod of 2–4 µm long and is actively motile by a polar flagellum
- With prolonged cultivation, organisms can become straight rods that resemble Gram-negative enteric bacteria
Culture
- V. cholerae produces convex, smooth, round and opaque colonies that are granular in transmitted light
- V. cholerae and other vibrios grow well at 37°C on routine agar media to recover enteric bacteria
- Selective agars for Vibrio include thiosulfate-citrate-bile salts-sucrose (TCBS) agar and enrichment broth (e.g., alkaline peptone broth)
- All vibrios, including V. cholerae, grow well on TCBS agar
- V. cholerae produces yellow colonies (sucrose fermented) on TCBS agar which are visible against the dark-green background
- Non-sucrose-fermenting vibrios (e.g., most strains of V. parahaemolyticus and V. vulnificus) produce green colonies on TCBS agar
- Vibrios grow at high pH (8.5–9.5) and are killed by acid, stool specimens should be collected early and prompt inoculation onto appropriate agar media is necessary
- If specimen processing is delayed, mix the stool in a Cary-Blair transport medium and refrigerate
- In areas where cholera is endemic, direct stool cultures are taken on selective media (TCBS) and broth cultures (e.g., alkaline peptone water with 1% NaCl, pH 8.5)
- The use of TCBS agar for stool cultures in laboratories is unnecessary unless vibrios (e.g., V. parahaemolyticus) are frequent or seasonal (e.g., coastal U.S. regions with regular consumption of bivalve mollusks and crustaceans)
Growth Characteristics
- V. cholerae regularly ferments sucrose and mannose but not arabinose
- A positive oxidase test identifies V. cholerae
- Most Vibrio species are halophilic and require NaCl to grow, but V. cholerae can grow on most agar media without additional salt
Medically Important Vibrios
- V. cholerae serogroups O1 and O139 cause epidemic and pandemic cholera
- V. cholerae serogroups non-01/non-0139 are responsible for cholera-like diarrhea; mild diarrhea; and, rarely, extraintestinal infection
- V. parahaemolyticus causes gastroenteritis, wound infections, and septicemia
- V. vulnificus is responsible for gastroenteritis, wound infections, and septicemia Many vibrios share a heat-labile flagellar H antigen
- Antibodies to the H antigen are probably not involved in the protection of susceptible hosts
- V. cholerae has O lipopolysaccharides that confer serologic specificity
- Cholerae strains of serogroup O1 and O139 cause epidemic and pandemic cholera, with over 200 serogroups
- Non-O1/non-O139 V. cholerae strains cause cholera-like diarrheal disease
- Antibodies to the O antigens protect laboratory animals against infections with V. cholerae
- V. cholerae serogroup Ol antigen has determinants that allow further subtyping
- Serotypes are Ogawa, Inaba, and Hikojima
V. Cholerae Biotypes
- The biotypes of epidemic V. cholerae are classic strains and El Tor
- The El Tor biotype produces a hemolysin, tests positive on the Voges-Proskauer test, and is resistant to polymyxin B
- V. cholerae typing is used for epidemiologic studies, and tests generally are done only in reference laboratories
- V. cholerae 0139 is similar to the V. cholerae O1 El Tor biotype
- V. cholerae O139 does not produce the Ol lipopolysaccharide and does not have all the genes necessary to make this antigen
- V. cholerae O139 and other non-O1 V. cholerae strains, as well as V. vulnificus produce acidic polysaccharide capsules; however, V. cholerae Ol does not make a capsule
Vibrio Cholerae Enterotoxin
- V. cholerae produce a heat-labile enterotoxin with a molecular weight (MW) of about 84,000, consisting of subunits A (MW, 28,000) and B
- Ganglioside GM1 serves as the mucosal receptor for subunit B, promoting entry of subunit A into the cell
- Activation of subunit A 1 increases levels of intracellular cyclic adenosine monophosphate (cAMP) and results in prolonged hypersecretion of water and electrolytes
- There is an increase in sodium-dependent chloride secretion, and inhibited absorption of sodium and chloride by the microvilli takes place
- Electrolyte-rich diarrhea occurs with as much as 20–30 L/day resulting in dehydration, shock, acidosis, and death
- The genes for V. cholerae enterotoxin are located on the bacterial chromosome
- Cholera enterotoxin is antigenically related to LT of Escherichia coli and can stimulate the production of neutralizing antibodies
- The precise role of antitoxic and antibacterial antibodies in protection against cholera is not clear
Diagnostic Laboratory Tests
- Stool specimens should be collected early in the course of diarrheal illness and be inoculated within 2-4 hours of collection onto agar media, optimising vibrio recovery
- If processing of specimens is delayed, the stool specimen should be mixed in a Cary-Blair transport medium and refrigerated
Smears
- Direct detection of V. cholerae on smears made from stool samples is not distinctive of the organism, and therefore are not routinely recommended
- Dark-field or phase-contrast microscopy is used to detect V. cholerae Ol directly from stool samples or the enrichment broth
- Observation of “shooting star” motility suggests V. cholerae O1
- If the motility is extinguished after mixing the sample with a polyvalent Ol antiserum, the organism is confirmed as V. cholerae 01
- If there is no motility or the type of motility does not change after applying the antiserum, the organism is not V. cholerae 01
Culture
- Vibrios, including V. cholerae, grow well on most agar media (including MacConkey and blood agar) used in clinical laboratories
- Some strains of V. cholerae are inhibited on MacConkey agar
- Growth is rapid in alkaline peptone broth or water, containing 1% NaCl with a pH of 8.5, or on TCBS agar, typical colonies can be picked in 18 hours of growth
- For enrichment, a few drops of stool can be incubated for 6–8 hours in taurocholate peptone broth (pH, 8.0–9.0)
- Organisms from this culture can then be stained or subcultured onto other appropriate agar media
- Identification of vibrios, including V. cholerae, using commercial systems and kit assays is variable
- MALDI-TOF MS is a methodology for identification of vibrios, and studies have shown rapid and reproducible identification for V. parahaemolyticus
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
