Detection of mycobacteria by radiometric and standard plate procedures.

A group of 89 smear-positive sputum specimens were evaluated by radiometric and standard plate procedures to determine the methodology which would provide the earliest detection of mycobacteria and maximum test sensitivity. Digested non-decontaminated specimens were concentrated and inoculated into modified selective BACTEC radiometric 7H12 broth and Mitchison selective 7H10 agar. Sodium hydroxide (1.5% final concentration) was then used to decontaminate these specimens. They were then concentrated and inoculated into both selective and nonselective 7H12 radiometric broths and into selective 7H10 and nonselective Middlebrook 7H11 agar media. The specimen processing and media combinations providing the earliest detection were non-decontaminated specimens with modified selective 7H12 BACTEC broth and decontaminated specimens with 7H12 BACTEC broths. Maximum sensitivity (percent positive) was obtained by using non-decontaminated specimens on Mitchison selective 7H10 Agar (98%) or decontaminated specimens in 7H12 BACTEC broth (95%). The decontamination process was found to reduce significantly the number of mycobacteria in clinical specimens, particularly the mycobacteria other than Mycobacterium tuberculosis. The specimen processing-media combinations providing the earliest detection and maximum recovery of mycobacteria (100%) were non-decontaminated specimens with modified selective 7H12 BACTEC broth or Mitchison selective agar and decontaminated specimens with 7H12 BACTEC broth or 7H11 agar.

Isolation of mycobacteria from undecontaminated specimens with selective 7H10 medium.

Media containing antimicrobial agents have been formulated for use as an adjunct to the standard media in an effort to reduce contamination and improve isolation of mycobacteria from clinical specimens. Selective 7H10 (S7H10) was developed for use in the isolation of mycobacteria from undecontaminated material. During a 33-month period, 10,782 clinical specimens were cultured in parallel on S7H10 without decontamination and on 7H11 after treatment with 2% sodium hydroxide-N-acetyl-L-cysteine. Results of this study show the overall contamination rate to be threefold lower on S7H10 than on 7H11 (304 versus 1,000). The number of specimens negative on NaOH-treated, 7H11-cultured specimens and contaminated on S7H10 was 282, whereas that negative on S7H10 but contaminated on NaOH-7H11 was 923. There were 6 positive cultures missed due to contamination on S7H10, compared with 61 on 7H11. Positive cultures on S7H10 outnumbered those on 7H11 by 106. This evaluation of S7H10 shows that it can be used with undecontaminated specimens in conjunction with standard methods and media for isolation of mycobacteria from clinical specimens.

Antibody formation in rabbits adapted and nonadapted to high altitude.

Antibody formation in high-altitude-acclimatized and nonacclimatized rabbits was investigated at altitudes of 14,100 (Pikes Peak, Colo.) and 5,330 (Denver, Colo.). Serum pools representing samplings of primary response were titered before and after treatment with 2-mercaptoethanol. Peak titers of 2-mercaptoethanolresistant and -sensitive humoral antibodies were higher in the animals adapted to an altitude of 14,100 ft and in nonadapted animals than in animals maintained at 5,330 ft.