The endotoxin of the following gram negative bacteria does not play any pa in the pathogenesis of the natural disease –
Correct Answer: Vibrio cholerae
Description: Cholera Cholera, caused by Vibrio cholerae serotype O1, is the archetypal toxin-mediated bacterial cause of acute watery diarrhoea. The enterotoxin activates adenylate cyclase in the intestinal epithelium, inducing net secretion of chloride and water. V. cholerae O1 has two biotypes, classical and El Tor, and each of these has two distinct serotypes, Inaba and Ogawa. Following its origin in the Ganges valley, devastating epidemics have occurred, often in association with large religious festivals, and pandemics have spread worldwide. The seventh pandemic, due to the El Tor biotype, began in 1961 and spread the Middle East to become endemic in Africa, subsequently spreading throughout South and Central America. Numbers of cases of cholera have been increasing, with outbreaks in Ghana in 2014 and Tanzaniain 2015. El Tor is more resistant to commonly used antimicrobials than classical Vibrio, and causes prolonged carriage in 5% infections. An atypical serotype, O139, has been responsible for localised outbreaks in Bangladesh. Infection spreads the stools or vomit of symptomatic patients or of the much larger number of subclinical cases. Organisms survive for up to 2 weeks in fresh water and 8 weeks in salt water. Transmission is normally through infected drinking water, shellfish and food contaminated by flies, or on the hands of carriers. Clinical features Severe diarrhoea without pain or colic begins suddenly and is followed by vomiting. Following the evacuation of normal gut faecal contents, typical 'rice water' material is passed, consisting of clear fluid with flecks of mucus. Classical cholera produces enormous loss of fluid and electrolytes, leading to intense dehydration with muscular cramps. Shock and oliguria develop but mental clarity remains. Death from acute circulatory failure may occur rapidly unless fluid and electrolytes are replaced. Improvement is rapid with proper treatment. The majority of infections, however, cause mild illness with slight diarrhoea. Occasionally, a very intense illness, 'cholera sicca', occurs, with loss of fluid into dilated bowel, killing the patient before typical gastrointestinal symptoms appear. The disease is more dangerous in children. Ref Harrison20th edition pg 1132
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