Slide culture of tubercle bacilli. IV. Further diagnostic trials.

Abstract

THE CONSTANTLY increasing number of publications concerning media and methods designed to provide more accurate, more rapid, and more reliable laboratory diagnosis of tuberculosis attests to the fact that at present no one method is entirely satisfactory. One of the problems has been to devise a procedure which would permit an earlier bacteriological diagnosis of the disease and which would be of greater assistance in clinical management during its course. It has been pointed out by Cummings' that the ideal culture medium should support rapid growth of small numbers of tubercle bacilli, should permit easy differentiation by colonial morphology between pathogenic and nonpathogenic acid-fast bacilli, should inhibit growth of contaminants, and should be simply and reproducibly prepared from readily available ingredients. Most of the media used in the diagnostic isolation of tubercle bacilli today do not satisfy all of these requirements. They contain complex organic materials such as animal sera, egg yolk, or potato extract, none of which can be reproducible from one batch to another. During the past ten years, however, a number of media which meet most or all of the requirements of the ideal culture medium have been devised. The development of these media and methods has been reviewed recently by Reed and Morgante.2 One of these is the slide microculture method originally described by Koch3 by which he was able to demonstrate growth of tubercle bacilli within a week. Adaptations of this method by Pryce4 and Rosenberg 5 for diagnostic use were very sensitive, but too cumbersome for routine use. A notable advance in technic was reported by Lowry and Berry 6 with the development of special culture tubes and decontamination tubes which permitted simple and safe handling of sputum smears dried on ordinary slides. Reed 7 in 1953 reported a modification of the slide culture method which yielded excellent results, and subsequently Simpson and Reed 8 carried out fairly extensive trials of the modified technic in a routine diagnostic laboratory. It was found that slide culture appeared to be superior to conventional methods particularly in terms of the number of positive cultures produced and in the time required for them to become positive. These diagnostic trials have been carried on for the past three years. It has always been accepted as precept that the use of a variety of media should produce an appreciable increase