microscopic observation drug susceptibility assay [MODS] for diagnosis of tuberculosis and detection of multi-drug resistance

ABSTRACT

Tuberculosis is a growing international health concern. It is the biggest killer among the infectious diseases in the world today. Early detection of drug resistance allows starting of an appropriate treatment. We evaluated the MODS assay for diagnosis of TB and detection of multidrug- resistance, 95 consecutive sputum samples collected from patients with suspected T8, were tested by smear, proportion method of susceptibility test using Lowenstein Jensen media and MODS. The results of MODS against proportion method of susceptibility test using Lowenstein Jensen media as the gold standard was evaluated. Out of 48 acid fast positive specimens, 14 [29.1%] isolates were resistant to one or the two of the tested anti-tuberculous drugs. Seven isolates [14.6%] had single drug resistance, including one isolate with rifampcin [RIF] monoresistance. Seven isolates [14.6%] were multidrug-resistant [resistant to both drugs]. 13 [27.1%] isolates were resistant to isoniazid [lNH], 8 [16.7%] isolates were resistant to RIF, thirty four test isolates [70.8%] and the control strain were susceptible. There was 97.9- 100% agreement between both reference method and MODS. The turnaround times from specimen processing to reporting of susceptibility results ranged between 6 and 11 [mean, 8 +/- 2.14] days by the MODS method, 41 and 63 [mean, 53.3 +/- 11.58] days by the reference proportion method. The detection rates were significantly faster for MODS than for proportion susceptibility test [P<0.001]. In conclusion, MODS appears to be a reliable, rapid, and convenient method for early diagnosis of tuberculosis [TB] and performing direct drug susceptibility tests in low-resource settings