A comparison of the sensitivity of Löwenstein-Jensen media prepared in different national bacteriological laboratories.

Data from certain WHO-assisted tuberculosis projects have shown that there is considerable variation in the proportion of positive cultures obtained with specimens either positive or negative on microscopy. Among the possible causes of this disparity, differences in the sensitivity of the culture media were considered to be of major importance. As the first step in an investigation of these differences, a series of comparative trials was carried out with Löwenstein-Jensen medium prepared under optimal conditions in seven European laboratories.It was shown that while there was no appreciable difference in sensitivity at different coagulation temperatures, there was wide variation between laboratories in the degree of colony growth according to the preparation of the medium and that the quality of the glass tubes used also affected the results. The increased growth when Petri dishes were used instead of glass tubes also indicates that other factors besides the nutrient value of the medium and the quality of the glassware may influence growth. It is concluded, therefore, that international comparison of culture results for mycobacteria is hardly possible, at present.