FIELD EVALUATION OF THE DIRECT COLORIMETRIC NITRATE REDUCTASE ASSAY FOR THE SIMULTANEOUS DETECTION OF MDR- AND XDR-TB IN ARGENTINA

B IMPERIALE; MORCILLO N; JUAN CARLOS PALOMINO; ANANDI MARTIN

Florencia

Congreso; 34 Annual Congress of the European Socienty of Mycobacteriology; 2013

European Socienty of Mycobacteriology

FIELD EVALUATION OF THE DIRECT COLORIMETRIC NITRATE REDUCTASE ASSAY FOR THE SIMULTANEOUS DETECTION OF MDR AND XDR-TB IN ARGENTINA Objectives: The spread of MDR-TB and XDR-TB stresses the need for quick and affordable diagnostic tools, particularly for low- and middle-income countries, with a high prevalence of TB. The objective of this study was to evaluate the previously described Nitrate Reductase Assay for the simultaneous detection of MDR and XDR-TB patients directly on sputum samples (D-NRA). Methods: The performance of D-NRA was compared with the BACTEC MGIT960 assay under routine conditions. Sputum smear-positive samples were decontaminated with the NALC method and inoculated in Lowenstein-Jensen tubes containing drugs and 1 mg/ml of potassium nitrate. The following drugs were tested: rifampicin (RMP), isoniazid (INH), ofl oxacin (OFLO), kanamycin (KAN). Consecutive smearpositive samples (n= 92) were prospectively analysed with D-NRA and compared to BACTEC MGIT960 to detect resistance to INH, RMP, KAN and OFLO. PNB was included for the simultaneous identifi cation of Mycobacterium tuberculosis complex. Results: Out of 92 smear-positive samples, 6 failed to growth and 2 were identifi ed as non-tuberculosis mycobacteria. For the 84 samples that grew, the NRA sensitivity, specifi city, positive and negative predictive values for all drugs were 100%. The mean time to obtain results with the D-NRA was 13.9 days and the overall agreement between D-NRA and the BACTEC MGIT960 was 100% for all drugs. Conclusion: D-NRA offers timely drug resistance detection of M. tuberculosis resistance to fi rst- and second-line drugs. D-NRA was user-friendly, easy to implement in limited laboratory facilities and provide an easy interpretation of results by a simple visual change of color.