Which of the following is true regarding anthrax -a) M' Fadyean reaction shows capsule b) Humans are usually resistant to infectionc) Less than 100 spores can cause pulmonary infectiond) Gram stain shows organism with bulging sporese) Sputum microscopy helps in diagnosis

Option b: Greenwood 16/e p226 says ‘Humans are relatively resistant to infection with B anthracis’ Option c: Harrison 17/e p1344 and 18/e p1769 says ‘While an LD50 of 10,000 spores is a generally accepted number for anthrax it has also been suggested that as few as one to three spores may be adequate to cause disease in some settings.’ Option d: Gram stain shows organism with non bulging spores. Bulging spores are seen for Clostridium Option e: Microscopy of the sample like lesion, blood, sputum reveals gram-positive bacilli in chain. Ref: Apurba Sastry’s Essentials of Medical Microbiology/ p250-53, Ananthanarayan 9/e p247-48, 8/e p243