Validation of A Rapid Tuberculosis PCR Assay for Detection of MDR-TB patients In Sohag University Hospital

The aim of this work was to evaluate the value of polymerase chain reaction (PCR) in rapid detection of resistance to rifampin and isoniazid in TB patients. Sixty sputum specimens were collected from MDR-TB patients. In addition to 10 sputum samples from TB patients who were responders to treatment by first line anti-TB drugs. The isolates were identified, cultured and tested for detection of multidrug resistance mutations in ropB gene coding for RIF resistance and katG gene coding for INH resistance using PCR; and were compared to Lowenstein Jensen (LJ) culture drug susceptibility testing (DST) using the Proportion method as the ‘gold standard’. By using proportion method on LJ all 60 sputum samples of MDR patients were resistant to both INH and RIF. By PCR; rpoB gene coding for RIF resistance was detected in 59 clinical isolates. The sensitivity and specificity of mutation of rpoB gene for the 60 specimens were 98.3% and 100% respectively. katG gene coding for INH resistance was detected in 56 clinical isolates. The sensitivity and specificity of mutation of KatG gene for the 60 specimens were 93.3 % and 100 % respectively. The 10 sputum samples of TB patients who were responders to treatment were susceptible to first-line anti-TB drugs on LJ culture DST and no MDR genes were detected by PCR. Our study demonstrated that PCR analysis was rapid, sensitive and specific approach for detection of rpoB and katG genes within 48 hours, which is more rapid than drug susceptibility testing after the culture.