Infection of Mice with Tubercle Bacilli Grown in Tween-Albumin Liquid Medium

Abstract

Tubercle bacilli, growing diffusely in liquid media containing a water dispersible ester of oleic acid (Tween 80), retain unaltered many of their morphological and biological properties. 1 , 2 The present paper describes the virulence of these cultures for mice of different genetic backgrounds inoculated under various experimental conditions. The cultures used in the infection tests to be reported were grown for 7-10 days in a medium containing 0.05% Tween 80 and 0.2% bovine albumin (serum Fraction V). 2 Macroscopically, these cultures appear homogeneous, but in reality consist of microscopical clumps. Their density corresponds to approximately 0.20 mg/cc in terms of dry weight of bacilli.

Mice, 3 to 6 weeks old, of the Rockefeller Institute strain inoculated intravenously with 0.01 cc of whole culture begin to lose weight during the second week after infection and die in 3 to 4 weeks with a disease primarily pulmonary. The pulmonary lesions consist of discrete and confluent nodules varying in size, pearly gray in color and firm in consistency. Stained microscopic sections show innumerable tubercle bacilli in these areas. Heart muscle is often infiltrated with very many small lesions. When the inoculum is reduced 10-fold to 0.001 cc, only an occasional animal dies after the 4th week of infection, although all animals sacrificed at this time show pulmonary lesions.

Much larger amounts of culture (0.5-1.0 cc) are required to produce death within 3 to 4 weeks when the infective dose is introduced by the intraperitoneal route. This minimal lethal dose can be reduced apprecia