Evaluation of Dot-Blot and Phage Replication Techniques for Detection of Drug Resistant Mycobacterium Tuberculosis

ABSTRACT

We have assessed the utility of two new methods; dot-blot and bacteriophage replication techniques; for use in a routine diagnosis laboratory in poor resource settings in the screening of drug resistant Mycobacteria tuberculosis by comparing with the conventional proportion method. A total of 145 M. tuberculosis clinical isolates were tested for resistance to rifampicin; isoniazid; streptomycin and ethambutol. The dot blot had sensitivities of 91.7; 100; 93.5and 85.7 and specificities of 99.2; 99.2; 99.1and 99.2 for rifampicin; streptomycin; isoniazid and ethambutol; respectively. The phage technique had sensitivities of 92and 84.6and specificities of 99.2and 99.2for rifampicin and streptomycin; respectively. Both techniques yielded results within 48 hours of receipt of the culture on solid media.The high sensitivity and specificity coupled with rapidity of results indicate that these methods are potentially useful tools for screening resistance to anti-tuberculosis drugs in our setting. However; the phage replication technique; which is simpler and technically less demanding; seems the most suitable for routine screening of drug resistant mycobacteria in resource deprived countries such as Tanzania. We are recommending further field evaluation of the phage replication method so that it can complement; and possibly replace; the conventional proportion method in drug susceptibility testing