Ans. is 'd' i.e., 4+ Bacteriological Index For Leprosy It is a rough index expressing probable number of acid fast bacilli for standardized microscopic field in skin smear. It is indicative of the load of bacteria at the site from which smear is taken. It does not differentiate between live and dead bacilli. It is not an indication of total bacillary load in the body. Ridleys scale is followed to calculate the bacterial index. = no bacilli in 100 fields 1+ = 1 - 10 bacilli in 100 fields 2+ = 1 - 10 bacilli in 10 fields 3+ = 1 - 10 bacilli in 1 fields 4+ = 10 - 100 bacilli in 1 field 5+ = 100 - 1000 bacilli in 1 field 6+ = >1000 bacilli in 1 field. Our patient has 10 - 100 bacilli in 1 field thus the bacteriological index is - 4+