[Acid-fast bacilli isolated from foot pads of nude mice infected with leprosy bacilli]

When leprosy bacilli grown in nude mouse foot pad were used for culture experiments, cultivable acid-fast bacillus was sometimes isolated as a contaminant. Whenever bacilli were inoculated to nude mice, the same leprosy bacilli were killed by autoclaving and were inoculated in to foot pads of 5 nude mice for examination of this cause of the contamination. Acid-fast bacillus was cultivated on 3% Ogawa egg medium at 33 degrees C from homogenates of foot pads of nude mice infected with M. leprae after one year and a while of infection. Foot pad of nude mouse injected with leprosy bacilli was cut off, ground in mortar and passed through sterile absorbent cotton and the filtrate was centrifuged at 10,000 rpm for 30 minutes. The sediment was inoculated on 3% Ogawa egg medium after treating with a small amount of sterile 1 N sodium hydroxide. Acid-fast bacilli were isolated from 3 out of 41 mice inoculoted with heat killed bacilli. The isolated acid-fast bacillus did not be observed in the same experimental group inocudated with live bacilli, positive cases were scattered in another groups. Four out of 16 tubes were positive for acid-fast bacilli in mice infected with Kurume-naha and 5 out of 7 tubes in the Amami-KM infected mouse group. The two negative tubes were discarded due to contamination. Kurume-Oki strain which has yellow colonial morphology was isolated from one out of 6 culture tubes. Strains Kurume-naha and Amami-KM have the same characteristics as follows: slow grower with pale yellow smooth colonial morphology, strongly positive for niacin production and ureas; positive for nicotinamidase, pyradinamidase and 68 degrees C catalase; no growth at 45 degrees C, negative for nitrate reduction, hydrolysis of Tween 80, diamine oxidase, heat stable acid-phosphatase and arylsulphatase; resistant to streptomycin, isoniazid, rifampicin and B 663. Two isolates were identified as Mycobacterium simiae from these characteristics. Characteristics of a Kurume-Oki isolate was as follows: slow grower with yellow smooth colonial morphology, positive for urease, 68 degrees C catalase, hydrolysis of Tween 80 and arylsulfatase; no growth at 45 degrees C, negative for niacin production, nicotinamidase, pyradinamidase, nitrate reduction, daimine oxidase and heat stable acid-phosphatase; resistant to streptomycin, isoniazid, rifampicin and B. 663. This bacillus was identified as Mycobacterium gordonae from these characteristics.(ABSTRACT TRUNCATED AT 400 WORDS)