Trends in the prevalence of primary drug resistance in pulmonary tuberculosis in france from 1962 to 1970: A national survey

Abstract

Between 1962 and 1970 70 hospital services distributed throughout France sent to the ‘Centre for the Study of Primary Resistance’ 11,643 strains of M. tuberculosis isolated from adult patients with pulmonary tuberculosis who had not previously been treated. Resistance tests were done by the method of proportions. The proportion of all strains resistant to 1 or more of the 3 main drugs (isoniazid, streptomycin and PAS) was 9·8 per cent. These were 7·6 per cent resistant to streptomycin, 4·3 per cent to isoniazid and 1·7 per cent to PAS. Resistance to only 1 drug was found in 6·8 per cent, to 2 in 2·2 per cent and to all 3 drugs in 0·8 per cent. The most frequent pattern of resistance was to streptomycin alone (4·7 per cent), then to isoniazid alone (1 ·7 per cent) and to both isoniazid and streptomycin (1 ·7 per cent). No consistent changes in the frequency of different types of resistance were observed during the 8 years of the investigation. The prevalence of primary resistance was higher in North African (13·0 per cent) and other foreign patients (12·9 per cent) than in French patients (9·2 per cent). The differences were greatest with isoniazid resistance (8·1 per cent in North Africans and 3·7 per cent in the French), as also were those with resistance to more than 1 drug (40 per cent of all resistant strains in North Africans and 29 per cent in the French). The prevalence was higher in those aged 15 to 20 years (12·3 per cent) than in patients more than 60 years old (7·6 per cent). Such differences existed for both resistance to isoniazid and resistance to more than 1 drug. Ethionamide resistance was systematically sought in 2,092 strains in 1964; thereafter tests were done only on strains found resistant to 1 of the 3 main drugs. Ethionamide resistance was found in 1·6 per cent of strains. It was most commonly found in association with isoniazid resistance (94 per cent of ethionamide-resistant strains). In two-thirds of such cases the isoniazid resistance was of a low level; resistance to ethionamide was rarely associated with resistance to thiacetazone. Primary resistance to the ‘minor’ drugs and those more recently introduced was studied from 1968 on all strains resistant to the main drugs. There were 3·7 per cent resistant to kanamycin, 1·5 per cent to cycloserine, 0·9 per cent to viomycin, 0·9 per cent to rifampicin and 0·6 per cent to ethambutol. When the analysis was restricted to those patients whose statement that they had not previously had antituberculosis drugs could, in the opinion of the physicians, be considered reliable, the prevalence of primary resistance in French patients remained almost unchanged (9·1 per cent). But it fell in North Africans from 13·0 per cent to 11·7 per cent and in other foreign patients from 12·9 per cent to 12·2 per cent. The epidemiological importance of primary resistance is discussed in relation to the prevalence reported in various countries, to the stability of the prevalence in France during the 8 years of the study and to the higher prevalence in the young and in foreign patients. Some interesting bacteriological aspects of a comparison between strains with acquired resistance and primary resistant strains are discussed.