An abattoir worker presented with a malignant pustule on his hand that progressed to form an ulcer. Smear was taken from the ulcer and sent to laboratory for investigation. The diagnosis is:

Ans. a. Cutaneous anthrax (Ref: Harrison 19/e 261e-3, 18/e p1769-1771; Ananthnarayan 8/e p245)AnthraxAnthrax is a zoonoses, caused by Bacillus anthracisQ, that occurs primarily in herbivores Routes of Infection:Humans become infected when B. anthracis spores are introduced into the body by the following routes:Contact with infected animals or contaminated animal productsQInsect bitesQIngestionQInhalationQThree major clinical forms in Humans:CutaneousQ (MC)Gastrointestinal (rare)Inhalational or pulmonary (it causes hemorrhagic pneumonia)Woolsorters' disease* Occupational hazard for people who sorted woolQ* Most dangerous form of inhalational anthraxQHide porter's disease* Caused by contact with contaminated hair, wool, hides or products made from them (Hide-porter's disease)QMalignant pustule* Commonly seen in head and neckQ* Eschar stage that appears 2-6 days after the hemorrhagic vesicle dries to become a depressed black scabQ surrounded by redness and extensive edemaDiagnosis:Presumptive diagnosis of the anthrax is made by staining it with polychrome methylene blue stain, called as Mc-Fadyean's reaction.Mc-Fadyean's ReactionWhen blood films containing anthrax bacilli are stained with polychrome methylene blue stain for few seconds and examined under microscope, an amorphous purplish materialQ is noticed around bacilli.This represents the capsular material and is characteristic of anthrax bacilliQCulture Characteristics of Bacillus anthracisOn agar plate: Frosted glass appearanceQOn gelatin stab culture: Inverted fir tree appearanceQ