Evaluation of PCR for direct detection of mycobacterium tuberculosis complex in sputum samples in Kampala, Uganda

Abstract

Objective: The aim of this study was to evaluate an in-house PCR for direct detection of Mycobacterium tuberculosis complex (MTC) in sputum samples.

Design: Across sectional study was conducted on samples isolates from suspected TB patients. Settings: Patients presenting to Mulago hospital Ward 5 TB Clinics for management and care from June 2014 to April 2015.

Subjects: Three sputum samples per patient were obtained from 30 patients with negative (N= 90) and 30 patients with positive (N= 90) ZN smear results for a total of 180 sputum samples was studied. The samples were processed using N-acetyl-L-cycteine and 4% NaOH. Genomic DNA was extracted from the sputum samples and used as template for IS6110-PCR. The prevalence of MTC bacilli in the sputum samples was determined.

Results: IS6l110-PCR detected MTC bacilli in 81% (73/90) sputum samples from patients with ZN-positive smears while it detected 51% (46/ 90) sputum samples from patients with ZN-negative. There were statistically significant associations between frequency in performing PCR on three sputum samples per patient and increased proportion of samples positive for MTC, p<0.05). All the 30 patients with ZN positive smears were positive on IS6110-PCR, while 80% (24/30) patients with ZN-negative smears were positive on IS6110-PCR. Chi square test revealed a statistically significant positive association between ZN positive and ZN-negative smears p<0.05.

Conclusion: In low income setting burden with high TB incidence and mortality, inhouse IS6110-PCR efficiently detects MTC bacilli in sputum samples and can be introduced for routine detection of these bacilli in isolates form pulmonary TB suspects.