Abstract
Pretreatment, isoniazid-sensitive cultures ofM. tuberculosis were obtained from 36 patients at each of 9 centres (Britain, Teheran, Afghan-Pakistan border, East Africa, Madras, Rangoon, Djakarta, Hong Kong). In the guinea-pig, the virulence of the cultures was uniformly high. The mean virulence of cultures was lower in East Africa, lower still in Madras, but increased again in Rangoon and Bangkok, to reach a level only slightly lower than in British cultures at Singapore, Djakarta and Hong Kong. Thiacetazone resistance was rare in British cultures, very common in cultures from Madras, and fairly common in those from East Africa, Singapore, Djakarta and Hong Kong. These findings suggest the existence of 3 main types of bacilli, with independent evolution of factors affecting virulence and thiacetazone sensitivity.
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