RESUMO
BACKGROUND: Only a few studies done earlier in India reveal the utility of real-time PCR in detecting drug resistance in cases of pulmonary tuberculosis. OBJECTIVES: The study was carried out to standardise real-time PCR (Quantitative real-time PCR, qPCR) targeting 16s RNA for the rapid detection of tuberculosis and its drug resistance from suspected TB patients. MATERIALS AND METHODS: Sputum samples from 100 clinically suspected tuberculosis patients, after processing were subjected to microscopy, MGIT culture and qPCR. qPCR targeted 16sRNA for detecting Mycobacterium tuberculosis complex, KatG and rpoB genes for detection of resistance to isoniazid and rifampicin respectively. 1% proportionate method and Line probe assay (Hain Lifesciences, Nehren, Germany) were used to confirm the MDR isolates. RESULTS: The study showed positivity of microscopy, culture and qPCR for M. tuberculosis as 37%, 44% and 46% respectively. Sensitivity of 100% and specificity of 96.5% in the detection of M. tuberculosis was observed for qPCR in comparison to culture. MDRTB was detected in 14 cases whereas monoresistance to rifampicin and isoniazid was detected in 1 and 3 samples respectively. CONCLUSION: Real-time PCR targeting 16sRNA, KatG and rpoB is a sensitive, specific, rapid and reliable technique to detect pulmonary tuberculosis and its MDR status directly from the sputum samples.
Assuntos
Resistência a Medicamentos/genética , Mycobacterium tuberculosis/isolamento & purificação , Reação em Cadeia da Polimerase em Tempo Real/métodos , Tuberculose Resistente a Múltiplos Medicamentos/diagnóstico , Antituberculosos/farmacologia , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Farmacorresistência Bacteriana Múltipla/genética , Humanos , Índia , Isoniazida , Testes de Sensibilidade Microbiana , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Rifampina , Sensibilidade e Especificidade , Escarro , Tuberculose Resistente a Múltiplos Medicamentos/tratamento farmacológico , Tuberculose Resistente a Múltiplos Medicamentos/microbiologiaRESUMO
The present cross-sectional study was conducted for the first time from the Udupi district of coastal Karnataka to know the prevalence of drug resistance and comparative analysis of MDR and non-MDR cases of pulmonary tuberculosis. Details of 862 smear positive cases of pulmonary tuberculosis with age ⩾15 years from 12 designated microscopy centres of the Udupi district were studied. Initially 2 sputum samples trailed by one follow-up sample were collected from each patient and processed for culture and drug sensitivity on the Lowenstein-Jensen medium. A total resistance of 33.4% was observed that includes the mono-resistance of 22.5%, multidrug resistance (MDR) of 6.3% and extensive drug resistance (XDR) of 0.3%. Significant odds ratio (OR) was observed in category 2 cases (OR 3.9) for the development of MDR tuberculosis. A significant statistical association was observed using Fisher's exact test while comparing mortality rate (19.3% vs. 1.8%), treatment failure (8.8% vs. 3.8%) and cure rate (68.4% vs. 85.4%) between MDR and non-MDR cases (p<0.001). Category 2 patients are important risk factors for the development of MDR in pulmonary tuberculosis. Due to high mortality and low cure rate in MDR cases it is imperative to know the drug sensitivity report before institution of anti-tubercular treatment.
