Addition of catalase to Löwenstein-Jensen medium

Abstract

Middlebrook (1957) has recommended that catalase be added to egg media to promote the growth of isoniazid-resistant, catalase-negative tubercle bacilli. However, we have reported (Subbaiah and others, 1960) that the addition of catalase to Lowenstein-Jensen medium did not influence the number of positive cultures obtained, n01 the speed or the amount of their growth. Recently, Hawkins & Steenken (1961) have suggested that this finding might have been due to the inactivation of the catalase solutions during filtration through sintered glass. Prior to our investigation we found that a catalase solution sterilised by passage through a sintered glass filter in routine use was capable of catalysing the reduction of hydrogen peroxide in dilutions corresponding to those likely to be present on the surface of the egg medium. However, the activity of the solutions actually used in our study was not tested. Subsequent to publication we found that inactivation of the solutions occurred if the filters were inadequately cleaned, and that our usual method of cleaning with aqua regia was not always adequate. Since we were not certain that the catalase solutions used in our study had been active, and since we also wished to investigate the addition of higher concentrations of catalase to egg media, a second study, whose results are now available, was carried out in London.