Developmental Morphology of Human and Avian Tubercle Bacilli on Bordet-Gengou Medium

Abstract

These observations on the developmental morphology of human and avian tubercle bacilli are in agreement with those made by Kahn 1 with H37 and a more recently isolated human strain, on Long's medium. Bordet-Gengou medium was chosen for this study, as it differs from Long's medium in not being synthetic, and is more highly enriched.

Smears were made at daily and weekly intervals from growth on Bordet-Gengou slants which were first tested for sterility by incubation at 37°C. for 24 hours. They were then seeded with a light inoculum. Prior to planting, smears were made of the inoculums. The slides were stained by a modified Ziehl-Neelsen method 2 which had been found excellent for demonstrating non-acid-fast forms of the tubercle bacillus. Each slide prior to staining was covered by a clean strip of filter paper to protect the smears as much as possible from particles of precipitated stain which might lead to inaccurate observations. The slides used were clean and free from grease. The strains employed were 2 recently isolated human strains H3 (Mishulow) and Arilotta (Alexander), and R and S strains of a dissociated avian strain obtained through Dr. Florence Sabin.

During the first week of incubation at 37°C. no growth was visible, but smears made during the first few days revealed segmenting acid-fast bacilli, acid-fast cocci and diplococci, and some non-acid-fast cocci and diplococci. Transitional diplococci were noted which appeared to consist of one acid-fast coccus and one smaller non-acid-fast coccus. After about 5 days only non-acid-fast cocci and diplococci appeared on the smears. No acid-fast bacilli were observed.