Vibrio and related organisms Flashcards
What are the general characteristics of Vibrionaceae?
Vibrionaceae are gram-negative bacilli, facultative anaerobes, and fermentative bacilli. They are primarily found in water sources and cause gastrointestinal diseases. They have polar flagella and are oxidase positive.
What are the most significant human Vibrios?
The most significant human Vibrios are V. cholerae (causes cholera), V. parahaemolyticus, and V. vulnificus.
What is the antigenic structure of V. cholerae?
V. cholerae has O lipopolysaccharide antigens that give serological specificity. It also has a single heat-labile flagellar H antigen, which is nonspecific.
What are the serotypes of the O1 serogroup of V. cholerae?
The O1 serogroup of V. cholerae is subdivided into three serotypes: Ogawa, Inaba, and Hikojima.
What is the role of the cholera toxin in the pathogenesis of cholera?
The cholera toxin is an exotoxin that induces a rise in cAMP inside intestinal epithelial cells, leading to hypersecretion of water and electrolytes (Na+, K+, Cl-, and HCO3-) into the intestinal lumen, causing massive watery diarrhea.
What are the symptoms of cholera?
Symptoms of cholera include profuse, watery diarrhea, vomiting, stomach cramps, leg cramps, mild fever, sunken eyes and cheeks, dry mucous membranes, and decreased urinary output.
What is the treatment for cholera?
The treatment for cholera includes fluid and electrolyte replacement, acid-base balance adjustment, and antibiotics such as tetracycline.
What is the selective medium for Vibrios, and how does V. cholerae appear on it?
The selective medium for Vibrios is Thiosulfate-citrate-bile salts-sucrose agar (TCBS). V. cholerae produces large (2–4 mm in diameter) yellow-colored colonies on TCBS due to sucrose fermentation.
What are the virulence factors of V. cholerae?
The virulence factors of V. cholerae include endotoxin (negligible significance), enterotoxin (cholera toxin), adherence factors, mucinase, and vascular permeability factor.
What are the differences between the Classic and El Tor biotypes of V. cholerae?
The El Tor biotype produces a hemolysin, is Voges-Proskauer test positive, and is resistant to polymyxin B, while the Classic biotype does not have these characteristics.
What is the role of the string test in identifying V. cholerae?
The string test is used to separate Vibrio species from other bacterial species, particularly Aeromonas. All V. cholerae strains are positive in the string test, while Aeromonas strains are negative.
What are the major diseases caused by Aeromonas?
The major diseases caused by Aeromonas are gastroenteritis and wound infections. It can also cause opportunistic systemic disease in immunocompromised individuals.
What are the biochemical characteristics of V. cholerae?
V. cholerae ferments glucose, maltose, mannitol, and sucrose but not lactose and arabinose. It reduces nitrate, is oxidase positive, indole positive, and halotolerant.
What is the role of mucinase in the pathogenesis of V. cholerae?
Mucinase causes extreme cellular desquamation, aiding in the colonization and spread of V. cholerae in the intestinal epithelium.
