Vibrio By Shadaab

CHOLERA Cholera is a gastro intestinal disease or infection. it is an acute infection by Vibrio cholera an enteric pthogen. Cholera, sometimes known as Asiatic or epidemic cholera, is an infectious gastroenteritis caused by enterotoxin-producing strains of the bacterium Vibrio cholera. Transmission to humans occurs through eating food or drinking water contaminated with cholera vibrios.

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Vibrio cholerae is a Gram-negative bacterium which is comma shaped. V. cholerae produces cholera toxin, an enterotoxin, whose action on the mucosal epithelium lining of the small intestine is responsible for the disease's infamous characteristic, exhaustive diarrhea. In its most severe forms, cholera is one of the most rapidly fatal illnesses known, and a healthy person's blood pressure may drop to hypotensive levels within an hour of the onset of symptoms. infected patients may die within three hours if medical treatment is not provided. In a common scenario, the disease progresses from the first liquid stool to shock in 4 to 12 hours, with death following in 18 hours to several days, unless oral rehydration therapy is provide. Rice grain like structures are seen in the stools of the patient which are the bacteria.

Symptoms: • • • •

Symptoms include profuse and painless watery diarrhea, effortless vomiting which causes loff of electrolytic equilibrium of the body. Loss of electrolytes causes death due to Hypovolomic shock. If the patient has a severe cholera it causes massive water loss from the body. In acute cholera there are a few complications like Muscle cramps, Renal failure, pulmonary edema due to heavy water loss.

Pathogenecity:

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The pathogen enters the body through the contaminated food and water. Vibrio are very sensitive pathogens so when they enter stomach the acidic juices of the stomach kill most of the vibrio. If a person drinks soda water and then eats or drinks the contaminated food or waterthe vibrio have better chances of survival because the acidic nature of the stomach is highly reduced due to the soda which is a base. The pathogen passes through the mucosa layer of the intestine and then enters the epithelium tissue. Heamagglutinin protease is the enzyme which helps the vibrio ti split th mucosa layer. Throughout the infection the pathogen is attached to the epithelial cells of intestine without causing any damage to the tissue. They multiply and produce various toxins like CHOLEROGEN and CHOLERA TOXIN.

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Cholera toxin is highly antigenic in nature. This toxin is a protein and it is a gene product but the gene which synthesizes this ptn is not possessed by vibrio. The gene is present in the bacteriophage of v. cholera where it acts as Vlasmid and can replicate. Choleratoxin has a molecular weight of 84000. It has 1A and 5B subunits. B sub-unit is attached to the G.M. A sub-unit is transported into the enterocyte(cells of enteron) where it breaks down into A1 and A2. The A2 fragment links the A1 fragment to the B sub-unit. The A1 fragment causes the activity of ADENYLATE CYCLASE which causes cyclic AMP. Over Production of cyclic AMP causes loss of fluids and electrolytes.

Susceptibility Recent epidemiologic research suggests that an individual's susceptibility to cholera (and other diarrheal infections) is affected by their blood type: Those with type O blood are the most susceptible,[18][19] while those with type AB are the most resistant. Between these two extremes are the A and B blood types, with type A being more resistant than type B.[citation needed] About one million V. cholerae bacteria must typically be ingested to cause cholera in normally healthy adults, although increased susceptibility may be observed in those with a weakened immune system, individuals with decreased gastric acidity (as from the use of antacids), or those who are malnourished. It has also been hypothesized that the cystic fibrosis genetic mutation has been maintained in humans due to a selective advantage: heterozygous carriers of the mutation (who are thus not affected by cystic fibrosis) are more resistant to V. cholerae infections.[20] In this model, the genetic deficiency in the cystic fibrosis transmembrane conductance regulator channel proteins interferes with bacteria binding to the gastrointestinal epithelium, thus reducing the effects of an infection. Epidemiology:

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Sporadic, endemic, epidemic and pandemic have all been caused due to Vibrio cholerae. In India its homeland is Ganga and Bhramaputra rivers. In early 18th centuary the disease was only confined to India. But during 1817-1923 cholera spread from Bengal. Bengal caused 6 pandemics. The variant which was spreading was the ELTOR strain. 1n 1991 the pandemic occurred in peru. Infection can occur to humans either from the patients or the carriers.

Lab Diagnosis:

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The stools are collected and examined before the administering of the antibiotics. Isolation of the bacteria is easy due to excess of cells.

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A lubricated Catheter is inserted into the rectum and the rectal swabs are collected. Transport media include VR medium or on Carry blair medium, alkaline peptone water is used in the media for optimum growth of the pathogen. Either MAC agar or TC(Theosulphate citric), BS(Bile salt) agar is used. The media should be fresh and not 3-4 days old. Incubation is at 37*c for 24 hours. Once the colonies are obtained after incubation the colonies are picked up with a straight wire. Agglutination with O antigen is done. Generally V. phage typing is done to identify the Bacterio phage.

Treatment: In all cases as soon as the symptoms are observed the first line treatment is to provide Oral rehydration therapy. This is effective to treat the infection. But in many rare cases antibiotics are also used but they are of secondary importance. Oral Tetra Cyclin is an effective drug against V.cholerae. Immunity:

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For any gastro intestinal infection the immunity is not available for lifelong period, it is only for a period of 6 months. Copro antibodies are formed which provide Local immunity they are mainly IgM, IgG, and IgA. When it comes to Vaccines the conc. Of Vibrio in Vaccine is usually 8000 mn/ml. For the first time live vibrios were used by Ferran. These live vibrios are killed by the body and thus immunity is obtained. Usually it is administered in Intramuscular region. This vaccine containes OGAVA and INABA serotypes. Oral vaccines have also been developed but they Failed.