In its seventh report, published in 1960, the WHO Expert Committee on Tuberculosis "noted the need for international standards for the definition and determination of drug resistance which will permit comparisons to be made from one area to another, and recommended that the World Health Organization take appropriate steps to establish such standards".(10) Acting on this recommendation, WHO took the first step towards standardization by convening in Geneva, in December 1961, an informal international meeting of specialists in the bacteriology of tuberculosis. At this meeting an attempt was made to formulate prerequisites for reliable sensitivity tests and to specify the technical procedures for them.The first part of the present paper is a joint contribution by the participants in the meeting, summarizing the general conclusions reached and recommendations made with regard to tests of sensitivity to the three main antituberculosis drugs-isoniazid, streptomycin and p-aminosalicylic acid. The other three parts describe, in turn, three different tests for determining drug sensitivity-the absolute-concentration method, the resistance-ratio method and the proportion method-that are generally considered to give reasonably accurate results.

Aminosalicylic Acid↗

PubMed1963

DRUG SENSITIVITY-RESISTANCE DETERMINATION AND SIMPLE ENZYMATIC TESTS FOR THE DIFFERENTIATION OF MYCOBACTERIA.

Tests to determine mycobacterial sensitivity to antituberculosis drugs have become a routine procedure to enable clinicians to apply the most suitable treatment. However, while antimycobacterial drugs have been widely and successfully used in recent years, laboratory techniques for performing drug sensitivity tests have not yet been standardized and thus do not permit international comparison of results.Among the main hindrances to standardization are differences in the sensitivity of culture media, the capacity of some of the ingredients to adsorb certain drugs, the decomposition of some drugs when exposed to high temperatures during coagulation of solid media, and difficulties in the preparation of standard inocula.The techniques described in this paper have been used with success to determine the sensitivity to the three major antituberculosis drugs (isoniazid, streptomycin and p-aminosalicylic acid) of 600 strains of mycobacteria isolated from 200 newly diagnosed cases in a WHO-sponsored field trial. In all these patients, sputum conversion was achieved by treatment with a combination of the three drugs, without the emergence of resistant strains.The cytochemical tests recommended by the authors for routine use in the differentiation of mycobacteria are a combined test for catalase and peroxidase activity and either the niacin test or, preferably, the Virtanen-Griess nitrate test for differentiating Mycobacterium tuberculosis from Myco. bovis.

Aminosalicylic Acid↗

PubMed1963

WHO CO-OPERATIVE STUDIES ON A SIMPLE CULTURE TECHNIQUE FOR THE ISOLATION OF MYCOBACTERIA. 1. PREPARATION, LYOPHILIZATION AND RECONSTITUTION OF A SIMPLE SEMI-SYNTHETIC CONCENTRATED LIQUID MEDIUM; CULTURE TECHNIQUE; GROWTH PATTERN OF DIFFERENT MYCOBACTERIA.

Tuberculosis surveys are in progress in many countries that do not have adequate laboratory facilities for carrying out complicated bacteriological procedures. As part of a WHO co-operative research programme, studies have been undertaken with a view to developing a simple culture technique for the isolation of mycobacteria that does not require elaborate equipment. This paper is the first report on these co-operative studies.Storage and transport are known to affect adversely the viability of Mycobacterium tuberculosis in pathological specimens, thus giving rise to poor culture results and indicating the advisability of culturing such specimens on the spot. The preparation of the efficient and widely used Löwenstein-Jensen (L-J) culture medium, however, requires materials and facilities that are not easy available in developing countries. In an attempt to overcome this difficulty, the Tuberculosis Research Institute in Prague has developed a semi-synthetic liquid medium that can be prepared in bulk, concentrated and lyophilized, and sent even to distant laboratories.The present paper describes in detail the preparation of this lyophilized medium, which can be stored at room temperature for at least 6-12 months and is easy to reconstitute, and discusses the growth characteristics of mycobacteria multiplied in it.Experience in Czechoslovakia, where between 1953 and 1962 nearly 21 million cultures have been made with the medium, has shown that it is quite satisfactory and even slightly superior to L-J medium in certain respects.

Bacteriological Techniques↗

PubMed1963

WHO CO-OPERATIVE STUDIES ON A SIMPLE CULTURE TECHNIQUE FOR THE ISOLATION OF MYCOBACTERIA. 2. COMPARISON OF THE EFFICACY OF LYOPHILIZED LIQUID MEDIUM WITH THAT OF LOEWENSTEIN-JENSEN (L-J) MEDIUM.

This is the second report on a series of co-operative studies undertaken with the object of devising a simplified technique, suitable for use in developing countries, for the isolation of mycobacteria from pathological specimens.The first report described the preparation, reconstitution and properties of a simple lyophilized liquid culture medium. The present report describes three collaborative experiments in which the efficacy of this simple medium was compared with that of Löwenstein-Jensen (L-J) medium. Six national laboratories co-operated in two of the experiments, which were performed according to a special statistical design; and two central and six provincial laboratories took part in the third, which consisted in the routine culture in both media of a large number of specimens.In all but one laboratory, the liquid medium proved to be as good as, or better than, L-J medium, even under tropical conditions, while its contamination rate was in general no higher. There was a large measure of agreement between the results obtained with the two media, although a small proportion of cases could have escaped detection by either. Further, the lyophilized medium did not deteriorate on storage; this, together with its simplicity of preparation and reconstitution, would seem to recommend it for wider use.

Culture Media↗

PubMed1960