ISOLATION OF TUBERCLE BACILLI FROM UNCENTRIFUGED SPUTUM ON PYRUVIC ACID MEDIUM

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Abstract
An acid-egg medium containing pyruvic acid in place of glycerol is described. More isolations of tubercle bacilli were made from uncentrifuged alkaline digests of sputum by culture on pyruvate acid-egg medium than on glycerol acid-egg medium. A cultural method in which uncentrifuged digested sputum was inoculated onto pyruvate and glycerol acid-egg media was compared with a technique in which the centrifuged deposit was cultivated on buffered pyruvic acid medium and Lowenstein-Jensen medium. The best results with microscopically negative sputum were given by culture of the centrifuged deposit, but for microscopically positive specimens, centrifugation gave no significant advantage over the method in which digested sputum was cultured directly on the 2 acid-egg media. Pyruvate media were superior to glycerol media for both centrifuged and uncentrifuged inocula. When egg media are used for the isolation of tubercel bacilli, at least 1 slope of medium containing pyruvate should be inoculated. Microscopically positive specimens of sputum need not be concentrated by centrifugation before culture; equally good results can be obtained by inoculation of pyruvate and glycerol acid-egg media with an alkaline digest of sputum.

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