Negatively stained leprosy bacteria. Mycobacterium leprae exhibit characteristic ropelike structures (mycolic acids) which are responsible for acid-fast reaction, the most distinctive property of the genus. .5% aqueous ammonium molybdate. leprosy, also known as Hansen's disease, is only contagious in its early phase when it is spread by nasal droplets. Rod-shaped gram-positive bacilli incubate in the host for 3-5 years, an deventually cause nerve damage to limbs and facial areas. Blindness, severe skin damage and disfigurement are common. Bacilli may be eradicated by drug therapy thorough surgery may also be required. TEm Magnifiacation -x21,000 at 70mm