The Vibrio genus contains motile, Gram-negative bacteria that are obligate aerobes. Vibrio rods have a recognizable curved shape and a single polar flagellum. Although Vibrio species are non-invasive pathogens, they cause some of the most serious cases of diarrhea and thousands of people die from infection annually. These waterborne organisms are transmitted to humans via infected water or through fecal transmission. Thus, in countries with poor sewage or water treatment cholera is sometimes seen in epidemic proportions.
Several species of Vibrio are known to be human pathogens, the most famous of which is V. cholerae (the causative agent of cholera). Cholera is characterized by severe diarrhea which has a rice-water color and consistancy. The diarrhea is so severe that about 60% percent of cholera deaths are due to dehydration. After cholera organisms are ingested, they descend to the intestinal tract where they bind to the epithelium and release their exotoxin, choleragen. This induces the epithelial cells to excrete salt. The cells then lose water which passively flows out of the cells. Fluid and electrolyte replacement is the key to treating cholera patients. Lab identification of V. cholerae is almost conclusive if the collected specimen is plated onto thiosulfate citrate bile sucrose (TCBS) agar. V. cholerae will form small yellow colonies on this medium. Simultaneous administration of doxycycline kills the organism.
Another species of Vibrio that causes diarrhea is V. parahaemolyticus. Raw seafood such as sushi and oysters is the source of human infection. Along with severe diarrhea, patients can also experience cramps, nausea, and fever. This disease is self-limiting and only lasts about three days. Therefore, no antiobiotic treatment is necessary in most cases.
V. vulnificus is also obtained from eating contaminated seafood. Unlike other Vibrio species,
this one is invasive and is able to enter the blood stream through the epithelium of the gut. Fever, vomiting,
and chills are the symptoms normaly associated with infection of this organism. Additionally, wound infection
may also occur from contaminated sea water. Cellulitis or ulcer formations may result. Treatment is usually
with tetracycline.
