A comparative study on the pretreatment methods for the cultivation of Mycobacterium tuberculosis on LJ medium using pancreatin as digestant for sputa.

Pancreatin was used as mucolytic agent in combination with sodium hydroxide and oxalic acid. Assessment of the appropriate concentration of the two decontaminants and the optimum contact time was made. It was observed that 2.5% sodium hydroxide with a contact time of 20 min and 3.5% oxalic acid with a contact time of 30 min yielded better results as compared to other permutations tried. Sputum specimens from 368 cases admitted to Ojha Institute of Chest Diseases were cultured for Mycobacterium tuberculosis by the modified methods described here and compared with the standard method. Higher number of positive cultures from film positive, as well as film negative specimens and fewer negatives and contaminations were observed with pancreatin/3.5% oxalic acid method. Comparatively less positives and more negatives and contaminations were noted when pancreatin/2.5% sodium hydroxide combination was used. Standard method, as compared to the pancreatin/2.5% sodium hydroxide and pancreatin/3.5% oxalic acid methods, gave fewer positive cultures both from film positive specimens and film negative specimens and higher negatives and contaminations were observed. Merits and demerits of the three methods are discussed.