Evaluation of a Rapid Assay for Detection of Rifampicin Resistance in Mycobacterium Tuberculosis: A Microbiological, Clinical and Epidemiological Study

Amer, Safaa A.; Amer, Amira F.; Tayel, Salwa EA.; Nour El-Din, Amina AM.; Mourad, Sahar M.

doi:10.21608/jhiph.2003.195831

Evaluation of a Rapid Assay for Detection of Rifampicin Resistance in Mycobacterium Tuberculosis: A Microbiological, Clinical and Epidemiological Study

Document Type : Original Article

Authors

¹ Microbiology and Immunology, Faculty of Medicine, Alexandria University, Egypt

² Community Medicine, Faculty of Medicine, Alexandria University, Egypt

³ Chest Diseases Department, Faculty of Medicine, Alexandria University, Egypt

10.21608/jhiph.2003.195831

Abstract

Background and Aim: Multidrug resistant Mycobacterium tuberculosis (MDR-TB) refers to drug resistance to at least two key anti tuberculous drug e.g. isoniazid and rifampicin. It is an increasing health risk and a threat to TB control programmes. Treatment of MDR-TB requires the use of less effective, more toxic and expensive drugs for longer periods Rifampicin resistance is a good predictor of MDR-TB. A rapid determination of rifampicin resistance is most useful from the clinical point of view since it will identify patients who will not respond to the WHO treatment regimens. This will allow alteration of treatment regimens in time to reduce spread of the disease i.e. it can have benefits for both the patient and the community.
The aim of the present study was to portray the clinical and epidemiological features of MDR-TB patient and to determine the ability of commercial kit [Fast Plaque TB-RifTM test] to correctly, within 48 hours, identify rifampicin susceptibility on strains of Mycobacterium tuberculosis cultured on solid media and compare it with a conventional method of susceptibility testing.
Methodology: Sputum specimens were collected from hospitalized patients with known or suspected pulmonary tuberculosis. These were examined microscopically after Ziehl-Neelsen staining. Specimens that were 1 + smear + ve were inoculated on L.J medium and incubated for 8 weeks. Forty five +ve cultures were tested for rifampicin susceptibility employing both the proportion and the Fast Plaque TB-RIFTM test.
Results: Fourteen strains [31.3%] were found to be rifampicin resistant and 31 strains [68.9%] were susceptible. Three out of the 14 resistant strains [21.4%] were isolated from newly diagnosed cases. The remaining 11 strains [78.6] were isolated from cases with history of previous treatment [relapses or treatment failure]. The sensitivity, specificity and overall accuracy of the gold standard conventional method.
Conclusion: Fast Plaque TB-RifTM test offers a performance comparable to the standard conventional method of rifampicin susceptibility testing. Furthermore, it has the advantage of quick results [within 48 hours] without the need for specialized equipment. This makes it a reliable rapid diagnostic tool in testing for rifampicin resistance and as an indicator of MDR in TB.

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