Organism that causes emphysematous cholecystitis is:

Ref: Harrison's 18th editionExplanation:Emphysematous CholecystitisIt is thought to begin with acute cholecystitis (calculous or acalculous) followed by ischemia or gangrene of the gallbladder wall and infection by gas-producing organisms.Bacteria most frequently cultured in this setting includeAnaerobes, such as C. welchii or C. perfringensAerobes, such as E. coli.This condition occurs most frequently in elderly men and in patients with diabetes mellitus.The clinical manifestations are essentially indistinguishable from those of nongaseous cholecystitis.The diagnosis is usually made on plain abdominal film by finding gas within the gallbladder lumen, dissecting within the gallbladder w all to form a gaseous ring, or in the pericholecvstic tissues.The morbidity and mortality rates with emphysematous cholecystitis are considerable.Prompt surgical intervention coupled with appropriate antibiotics is mandatory.