Microbiology
Summary
Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus are gram-negative, oxidase-positive, comma-shaped bacilli found in contaminated shellfish. Transmission is typically fecal-oral. V. cholerae's optimal growth occurs in alkaline, salty media. It attaches via toxin-coregulated pili and secretes cholera toxin. The toxin permanently activates stimulatory G protein, leading to increased cAMP, increased NaCl, H2O, and mucus in the gut lumen, causing rice-water diarrhea. Primary cholera treatment involves oral rehydration; antibiotics and IV fluids are reserved for severe cases.
Vibrio vulnificus and parahaemolyticus are both marine bacteria that can infect the gastrointestinal tract via ingestion of seafood or open wounds during beach activities. It's important to note that V. parahaemolyticus is the most common food-related Vibrio infection in the US, while V. vulnificus is the most deadly.
Lesson Outline
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FAQs
Vibrio bacteria are comma-shaped, gram-negative, and oxidase-positive bacilli belonging to the Vibrionaceae family. They are mostly found in aquatic environments, particularly in marine and estuarine habitats. The three major pathogenic Vibrio species affecting humans are Vibrio cholerae, Vibrio vulnificus, and Vibrio parahaemolyticus. Vibrio cholerae is responsible for cholera, whereas the latter two species are mainly associated with wound infections and gastroenteritis caused by consuming contaminated seafood.
Rice water diarrhea is a characteristic symptom of cholera, a severe diarrheal illness caused by Vibrio cholerae. The infection results in a rapid onset of watery diarrhea that appears pale and cloudy, resembling water in which rice has been rinsed. This is caused by a potent toxin called cholera toxin (CTX) produced by some strains of the bacteria. CTX triggers the production of excessive amounts of cAMP, which affects the ion exchange in intestinal cells, leading to a massive loss of water and electrolytes from the body, ultimately resulting in rice water diarrhea.
Cholera is diagnosed through the isolation of the Vibrio cholerae bacteria from a stool sample or rectal swab. As for treatment, the primary focus is on rapid rehydration using oral rehydration solution to replace fluid and electrolyte losses. Severe cases may require intravenous fluids and antibiotics, such as doxycycline or azithromycin. Preventive measures include practicing good hygiene, washing hands before handling food, and consuming safe water and food. Vaccination may be recommended for travelers or residents in regions where cholera is endemic or in outbreak situations.
Vibrio vulnificus and Vibrio parahaemolyticus infections primarily cause gastroenteritis, with symptoms including watery diarrhea, abdominal cramps, vomiting, nausea, and fever. In immunocompromised individuals or those with underlying health issues, these bacteria can also cause severe wound infections and bloodstream infections, which can be life-threatening. The transmission routes for both species involve the consumption of contaminated seafood, particularly raw or undercooked shellfish, or exposure to seawater or marine environments through open wounds.
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