DETECTION OF MYCOBACTERIUM TUBERCULOSIS IN CLINICAL SAMPLES BY SMEAR AND CULTURE

Abstract

Objective: A retrospective study was carried out in order to compare the smear stained by ZN and Lowenstein–Jensen (LJ) medium for the detection of Mycobacterium in clinical samples from different categories. Study Design: Laboratory based, Retrospective. Place and Duration: Sir Ganga Ram Hospital/ Fatima Jinnah Medical College, Lahore over a 5 year period between Jan 2001 and June 2006. Material and Methods: A total of 798 clinical samples were collected from patients of both sexes and all ages with a provisional diagnosis of tuberculosis. A Ziehl-Neelsen stain (ZN) and culture on LJ medium was performed for the detection of Mycobacterium. The specimen categories were sputum, pus, lymph node aspirate, urine and endometrial curetting. Results: Out of 5 types of 798 specimens received over a period of five years, only 46.3%) (n=369) were respiratory whereas the remaining 53.7% (n=429) were non respiratory tract category samples including sputum, pus, lymph node aspirate, urine and endometrial curetting. All were examined for the presence of acid-fast-bacilli (AFB) in ZN smear. Among these 3.578% gave a positive ZN stain while 11.65% were positive on culture. Out of a total of 369 respiratory tract category samples, 38 (10.3%) sputum samples were positive for AFB on both ZN and culture. Among the non respiratory tract category, 47 (28.2%) pus, 26 (31%) LN aspirate, 5 (15.6%) urine, 5 (3.42%) endometrial curetting were reported positive. Only 15.16% of clinical samples belonging to 5 different categories of specimens received from patients of both sexes with a provisional diagnosis of tuberculosis, tested positive for Mycobacterium by both ZN stain smear and culture on LJ medium. Among these, 3.57% were positive for AFB on ZN smear and 11.65% were positive on culture on LJ medium. Conclusion: These conventional techniques have proved to be reliable testing tools for detection of Mycobacterium tuberculosis in our settings but there is an urgent need to promote the use of Bactec and PCR for early detection and drug susceptibility keeping in view the rise in the number of multi-drug resistant cases of tuberculosis in the last few years.