Vibrio parahaemolyticus and Vibrio vulnificus.

Question 1

Vibrio parahaemolyticus: morphology and identification

Answer 1

Vibrio parahaemolyticus is a Gram-negative, curved, comma-shaped bacterium with a single polar flagellum. It is oxidase-positive and motile, similar to Vibrio cholerae. It grows on selective media like thiosulfate-citrate-bile salts-sucrose (TCBS) agar, where it produces green colonies due to non-fermentation of sucrose.

Question 2

Vibrio parahaemolyticus: virulence factors and pathogenesis

Answer 2

The primary virulence factors of V. parahaemolyticus include thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH), which damage host tissues by causing lysis of erythrocytes and other cells. V. parahaemolyticus is mainly associated with gastroenteritis, resulting from ingestion of contaminated seafood, particularly raw or undercooked shellfish.

Question 3

Vibrio parahaemolyticus: clinical findings

Answer 3

Vibrio parahaemolyticus infection typically causes gastroenteritis with symptoms like watery diarrhea, nausea, vomiting, abdominal cramps, and low-grade fever. In some cases, infection may lead to wound infections, especially after exposure to seawater. In severe cases, septicemia can occur, particularly in immunocompromised individuals.

Question 4

Vibrio parahaemolyticus: diagnostic laboratory tests

Answer 4

Diagnosis of V. parahaemolyticus involves stool culture on selective media like TCBS agar, where it produces green colonies. PCR testing can be used to detect virulence factors such as TDH and TRH. Further identification can be confirmed by biochemical tests and serotyping.

Question 5

Vibrio parahaemolyticus: treatment

Answer 5

Treatment for V. parahaemolyticus infection typically involves rehydration therapy to manage dehydration from diarrhea. Antibiotics are generally not required for mild cases but may be prescribed in severe cases or for immunocompromised patients. Common antibiotics include doxycycline and ceftriaxone.

Question 6

Vibrio parahaemolyticus: prevention and control

Answer 6

Preventive measures include proper cooking of seafood, especially shellfish, and avoiding raw or undercooked seafood. Good hygiene and sanitation practices in food handling and preparation are also essential to prevent infection.

Question 7

Vibrio vulnificus: morphology and identification

Answer 7

Vibrio vulnificus is a Gram-negative, curved, comma-shaped bacterium similar to other Vibrio species. It is oxidase-positive, motile, and grows on selective media like TCBS agar, where it produces green colonies due to non-fermentation of sucrose. It is more virulent than other Vibrio species and often causes serious infections.

Question 8

Vibrio vulnificus: virulence factors and pathogenesis

Answer 8

Vibrio vulnificus produces several virulence factors, including a capsule, which helps it evade host immune defenses, and proteases and cytotoxins that contribute to tissue destruction. It is primarily associated with wound infections and septicemia, particularly after exposure to seawater or consumption of contaminated seafood, especially oysters.

Question 9

Vibrio vulnificus: clinical findings

Answer 9

Infection with V. vulnificus can lead to severe wound infections, which may progress to necrotizing fasciitis. Septicemia can also occur, characterized by fever, chills, hypotension, and shock. In immunocompromised patients, particularly those with liver disease or iron overload, V. vulnificus infection can be fatal.

Question 10

Vibrio vulnificus: diagnostic laboratory tests

Answer 10

Diagnosis of V. vulnificus is made by culture from wound sites or blood on selective media like TCBS agar. PCR testing can confirm the presence of V. vulnificus, and serological tests may be used to detect specific antibodies. Blood cultures are particularly useful in cases of septicemia.

Question 11

Vibrio vulnificus: treatment

Answer 11

Treatment for V. vulnificus infection often requires aggressive therapy, including intravenous antibiotics (e.g., doxycycline, ceftazidime, or ceftriaxone) and surgical debridement in the case of wound infections. Early intervention is crucial to prevent mortality, especially in septicemic cases.

Question 12

Vibrio vulnificus: prevention and control

Answer 12

Preventive measures include avoiding exposure of open wounds to seawater, particularly in areas where V. vulnificus is endemic. Raw or undercooked shellfish, especially oysters, should be avoided by individuals with liver disease, immunocompromised states, or iron overload. Proper handling and cooking of seafood are essential to prevent infection.