Some bacteriologic aspects of the epidemiology of pulmonary and extrapulmonary tuberculosis

A study was carried out to investigate the drug resistance patterns of the prevalent tubercle bacilli in pulmonary and extrapulmonary tuberculosis in and about the city of Lahore, Pakistan. This report includes 168 strains of Mycobacterium tuberculosis isolated from the same number of pulmonary tuberculosis cases (100 untreated cases, defined as patients either having no history of anti-tuberculous therapy or having had chemotherapy for not more than 10 days; 68 treated, defined as having had chemotherapy for more than 10 days), and 162 strains from the same number of extrapulmonary tuberculosis cases (77 untreated, 38 treated and 47 doubtful). The proportion method of drug susceptibility assay was employed. According to the procedures used in this study and with 1% as the critical proportion for resistance, bacterial resistance was found to be very prevalent in pulmonary tuberculosis. Even among those cases in which no history of previous treatment was elicited, 46% were found to be excreting populations of tubercle bacilli having some degree of resistance to one or more of the primary drugs--isoniazid, streptomycin and para-aminosalicylic acid. In treated cases, 86.8% were found to have some resistance to one or more drugs. Overall, resistance to streptomycin was found to be commonest. Drug resistance was observed to be somewhat less common in extrapulmonary than in pulmonary tuberculosis, with streptomycin resistance predominating. Although both catalase-positive and catalase-negative isoniazid-resistant strains of M. tuberculosis were isolated from patients with pulmonary disease, no catalase-negative strains were isolated from patients with extrapulmonary disease, suggesting limited pathogenic potentialities of catalase-negative strains for man. Epidemiologic aspects of these observations are discussed.