Efficacy of a Biphasic Culture Medium for recovery of mycobacteria in smear negative sputum samples

Abstract

Introduction: Tuberculosis (TB) remains a major global health problem worldwide and rank as the second leading cause of death from an infectious disease, after the HIV.

The aim of the study: To evaluate the efficiency of a Biphasic culture media for the isolation of Mycobacterium tuberculosis (MTB) in smear negative sputum samples in clinically suspected cases of pulmonary tuberculosis.

Material and methods: A total hundred (n=100) LED smear negative sputum samples were collected. Samples were subjected to concentration and decontamination by two methods (N-Acetyl-L-Cysteine (NALC) oxalic acid and Cetyl Pyridium Chloride (CPC) and sodium chloride) and then inoculated on LJ and biphasic media for isolation of MTB.

Results: Among hundred LED smear negative sputum samples, 15% (n=15) mycobacterial isolates were obtained on culture.  Of these 15 cases, 66.66% (n=10) were positive on LJ media, whereas 93.33% (n=14) were positive for MTB on Biphasic Media. Growth on Biphasic media was exhibited within 2 weeks as compared to LJ media (4 weeks). The rate of Contamination was 5% and 7% on LJ and biphasic media respectively.

Conclusion: Biphasic medium was superior to the conventional LJ medium in being rapid, easy to use and interpret, and significantly low time-to-growth detection, but was expensive with higher contamination rate.