Clinical Features :
Causes enteric fever; Incubation period 7-14 days. Symptoms- headache, malaise, anorexia, coated tongue, abdominal discomfort. Step ladder pyrexia, relative bradycardia & toxemia. Rose spots, splenomegaly.
Complication : Intestinal perforation, hemmorhage
Additional points :
Infective dose : 200CFU to 10^6CFU
Vi, H, O antigens. Kauffman-White scheme for classification
Culture & Gram Reaction :
Specimen – Blood, urine, stool
Organism is aerobic & facultative anerobe
Large colonies, 2-3mm, circular, low convex, smooth
Pale colonies on MacConkey and DCA.
XLD agar – Pink with black centre
Wlison-Blair – large black colonies with metallic sheen
Selenite F & tetrathionate broth are enrichment media
Castaneda’s method of culture for repeated blood subcultures
Gram Negative bacilli, motile with peritrichate flagella
IMViC = – + – +
Urea not hydrolysed. Ferment sugar & form acid and gas.
Prevention and Treatment :
Bacilli killed at 55C in 1hr and at 60C in 15min. Boiling or chlorination destroy bacilli.
Ceftriaxone is DOC
Carrier treated with Ampicillin or Amoxicillin