Evaluation of the Colour Test for Detection of Multidrug - Resistant Mycobacterium Tuberculosis

Abstract

Background: The timely and cost-effective diagnosis of cases of tuberculosis is of utmost importance, particularly in developing countries where the disease poses a public health threat. The emergence of multi-drug resistant (MDR) Mycobacterium tuberculosis strains, further compounds the diagnosis and appropriate therapy. Rapid, resource-efficient and specific diagnosis of MDR M. tuberculosis is of utmost priority to control this global public health problem. Available diagnostic tests either provide accuracy at the expense of resources (the genotypic methods commonly used such as PCR), or compromise timeliness and specificity while providing a reasonable cost (phenotypic methods such as the proportional method). Objectives: The aim of this study was to evaluate the performance of the colour Test in detection of drug resistance among Mycobacterium tuberculosis isolates to Isoniazid (INH), Rifampicin (RMP) and Ciprofloxacin (CIP), with reference to the golden standard proportion method. Methodology: The colour Test combines the thin-layer agar technique with a simple colour-coded quadrant format, selective medium to reduce contamination and colorimetric indication of bacterial growth to simplify interpretation.This study was conducted on 50 M. tuberculosis strains of Egyptian cases diagnosed as pulmonary tuberculosis, in the National Central Laboratory, Ministry of Health, Egypt, during the period between October 2014 to June 2015. Results: This study shows that the sensitivity and specificity of the colour Test for RMP and INH were 100% and 90.3% respectively. The agreement of the colour Test with the PM was almost perfect agreement (87.6%). For CIP sensitivity and specificity were 96.7% and 90% respectively. Conclusion: The study demonstrates that the colour Test is reliable compared with the proportion method and offers an added advantage of a shorter turnaround time. It is additionally a simple, easy to interpret test. As such, the colour Test offers promise in the pursuit of simple, reliable, rapid and cost-effective techniques for the diagnosis of multi-drug resistant TB.