Comparative Study of Growh of mycobacterium Tuberculosis on Modified Ogawa Media, Modified Lowenstein Jensen Media and 2% Buffered Lowenstein Jensen (BLJ) Media

Abstract

This prospective hospital based study was conducted from December 2005 to September 2006 atGerman-Nepal Tuberculosis Project- National Reference Laboratory (GENETUP-NRL),Kalimati, Kathmandu. In the present study, a total of 324 sputum samples from suspected TBpatients were collected. In all the samples 220 were smear positive and 104 were smear negativesamples as determined microscopically by standard fluorochrome method. In all the samples 177 were collected from patients suspected of pulmonary tuberculosis. All ofthe 324 sputum samples were divided into two equal halves and transferred in two calibratedcentrifuge tubes. All of the samples were decontaminated by 4% NaOH (Petroff’s method) andNekal-BX methods separately. Each decontaminated sample was cultured on three differentculture media; viz Modified Lowenstein-Jensen (MLJ), Modified Ogawa(MOG) and newlyproposed 2% Buffered Lowenstein-Jensen (BLJ) media. In all the smears positive samples 94.091% samples was culture positive in one or all culturemedia used. In all smear negative samples 9.62% samples were culture positive at least in oneculture media. Among smear positive samples decontaminated by 4% NaOH, 91.36%, 81.36%and 92.27% samples were culture positive on MOG, MLJ and BLJ medium, respectively.Similarly, in all smear positive samples decontaminated by Nekal, 92.72% were culturepositivein MOG, 87.73% in MLJ and 92.72% in BLJ. In all the smear negative samples decontaminated by 4% NaOH, 3.85%, 2.88% and 3.85%samples were culture positive on MOG, MLJ and BLJ medium. Similarly, among smear negativesamples decontaminated by Nekal, 4.81% were culture positive in MOG, 5.77% in MLJ and3.85% in BLJ. The MOG yielded more positive result (92.05%) followed by MLJ (84.32%) (P<0.01) and BLJ(92.50%). Among the decontamination techniques the Nekal method yielded better result(87.27%) than 4% NaOH (81.3%) for the recovery of bacteria on MLJ (P<0.05). No significantdifference obtained among samples decontaminated by 4% NaOH (91.36%) and Nekal (92.73%)with respect to recovery of bacteria on MOG (P>0.05). Similarly, no significant difference obtained among samples decontaminated by 4% NaOH(92.27%) and Nekal (92.73%) for the recovery of bacteria on BLJ (P>0.05). In all the smearnegative samples decontaminated by Nekal, highest culture positive result was observed on MLJ(5.77%) followed by BLJ (5.77%). While no significant difference was observed in the case of Nekal or 4% NaOH decontaminationmethod with respect to recovery of bacteria on MOG and BLJ. The result indicated that the BLJ medium is suitable for the recovery of bacteria followed byMOG and MLJ. However, the addition of 2% monopotassium phosphate buffer in MLJ yieldedsignificant increase in culture positive result. Similarly, the Nekal method was suitable decontamination method than 4% NaOH, for the better recovery of bacteria on MLJ.Bacteriological examination of sputum is essential for the diagnosis of pulmonary tuberculosis.The detection of acid-fast bacilli (AFB) in smears of sputum sample by Ziehl-Neelsen staining provides fastest evidence of the presence of Mycobacteria. However, the definitive diagnosis of Tuberculosis demands sputum positive culture for the M. tuberculosis which depends on the suitable decontamination method of the sputum sample and selection of suitable culture media. Key words:Mycobacterium tuberculosis, Decontamination and Homogenization, Petroff’s 4% NaOH method, Nekal-BX, Modified Lowenstein-Jensen media (MLJ), Modified Ogawa media(MOG), 2% Buffered Lowenstein-Jensen media (BLJ).