A man, after skinning a dead animal, developed a pustule on his hand. A smear is prepared from the lesion showed the presence of Gram-positive bacilli in long chains which were positive for McFadyean&;s reaction. The most likely aetiological agent is

The person is likely to have anthrax caused by Bacillus anthracis. Anthrax is a zoonotic disease. Infected animals shed in discharges from mouth, nose and rectum, large numbers of bacilli that sporulate in the soil and remain as the source of infection. Bacillus anthracis is a gram-positive bacillus, found singly, in pairs or in sho chains, being surrounded by a capsule. M' Fadyean's reaction: When blood films containing anthrax bacilli are stained with polychrome methylene blue for a few seconds and examined under a Microscope, amorphous purplish material is noticed around the bacilli. This represents the capsular material and is characteristic of the anthrax bacilli. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 251