Bacteriological aspects of the second national survey of primary drug resistance in pulmonary tuberculosis, 1963

The bacteriological methods employed in the second national survey of the prevalence of primary drug resistance to streptomycin, PAS and isoniazid among adults with newly-diagnosed and previously untreated pulmonary tuberculosis have been described. Duplicate cultures were tested from a sample of patients. From the results, estimates were made of variation between duplicate cultures from the same patient, variation, between patients, and variation between the tests set up in different batches. For patients with sensitive strains there was significant variation between patients in the level of sensitivity to each of the 3 drugs. As a result of these statistical estimations, definitions of resistance based on a critical resistance ratio or minimal inhibitory concentration have been adopted; these are simpler to apply than those of the first survey (in 1955–56) and are more soundly based. Comparability between the 2 surveys was examined in tests on sensitive strains in each survey. The critical resistance ratios for streptomycin and PAS appeared equivalent, but the critical minimal inhibitory concentration for isoniazid was not quite equivalent in the 2 surveys, suggesting that the use of resistance ratios would have been advisable. Identification tests were undertaken on all strains. Of 911 patients with positive cultures, anonymous mycobacteria were isolated in 15 (1·6%). Ten of these were Myco. kansasii. Only 2 patients had strains of Myco. bovis. On décrit les méthodes bactériologiques employées lors de la 2 ème enquête nationale sur la fréquence de la résistance primaire vis à vis de la streptomycine, du PAS ou de l’isoni-azide chez des malades adultes nouvellement dépistés et non traités auparavant. Deux cultures furent testées pour un lot de malades. A partir des résultats obtenus on a pu estimer les variations entre 2 cultures d’un même malade, les variations entre malades, et les variations entre les tests pratiqués sur différents lots de milieux. Les malades possèdant des souches sensibles présentent des variations significatives entre eux dans le niveau de sensibilité à chacune des trois drogues. En conséquence de ces études statistiques, on a adopté des définitions de résistance basées sur une résistance-ratio critique ou une concentration minimale inhibitrice. Celles-ci sont plus simples à appliquer que celles employées lors de la Ière enquête (en 1955–56) et reposent sur des bases plus solides. La possibilité de comparer les deux enquêtes fut ap