Fish Microbiology and Quality Assurance

Unit 5 - Foodborne pathogens

5.6. Foodborne gastroenteritis caused by Vibrio cholerae
Characters

• Vibrio cholera is a causative organism of human cholera due to the consumption of contaminated food/water containing viable cells. V. cholera is a Gram negative, non spore forming, facultatively anaerobic, curved rods belonging to the family enterobacteriacea.
• The epidemic/pandemic cholera is caused by V. cholera serovar “O” Group 1 (O1) and consists of 2 biotypes Viz. classical and El-Tor based on biochemical tests. These have ability to agglutinate O1 antiserum. Strains that do not aglutinate in O1 antiserum are referred to as non O1 or non-agglutinating vibrios (NAGs). The non O1 strains are autochthonous to estuarine environment and are widely distributed. These are generally non-pathogenic but known to cause gastroenteritis, soft tissue infection and septicemia in humans.
• V. cholerae grow well at 37^oC, tolerant to alkali (pH up to 9.2), survive for long period in fresh and marine environment and enter in to VBNC phase during adverse conditions. Infections occur through oral route by contaminated food and water. Attach to intestinal mucosa and produce enterotoxin and cause loss of water and electrolytes due to the disruption in the cyclic AMP system.

Symptoms of illness
Symptoms vary from mild to severe diarrhea (rice water stool), abdominal cramps, nausea, vomiting, dehydration, shock and death in severe cases. Infection of non O1 serotype is associated with exposure to natural aquatic environments, consumption of seafood and exposure to polluted water. Non O1 V. cholerae show better survival and multiplication in a wide range of foods than O1 strains.

Conditions for outbreaks

• Consumption of live cells orally through food/water.
• Consumption of post process contaminated food.
• Consumption of food without heating before serving.
• Consumption of contaminated food/water.

Prevention of outbreaks

• Avoiding consumption of contaminated food and water.
• Preventing contamination by following sanitary measures.
• Keeping the surroundings of processing plant clean and disinfected.
• Adherence to good personal hygiene by food handlers.
• Use of potable water after chlorination.