Identification of contaminants during primary isolation of mycobacteria in the BACTEC system with the antimicrobial supplement PACT.

1500 sputum specimens and bronchial washings were cultured for mycobacteria. One half of the specimen was treated with N-acetyl-L-cysteine--sodium hydroxide (3%) (NALC) and the other with sodium dodecyl (lauryl) sulfate--sodium hydroxide (1%) (SDS). The different species of contaminants found with each pretreatment method with the BACTEC radiometric system were identified. Contamination occurred in 6% by using SDS and in 10% by using NALC. The SDS method was more effective against Bacillus ssp. and Streptomyces ssp., the major contaminants. However, the growth of Pseudomonas ssp. was a problem in both methods.