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.

Computer files and analyses of laboratory data from tuberculosis patients. II. Analyses of six years' data on sputum specimens.

Laboratory data on sputum specimens from patients with pulmonary mycobacterioses between 1968 and 1973 were analyzed. Specimens were cultured on Middlebrook 7H10 and/or 7H11 medium; blue light fluorescence microscopy was used to examine specimen smears. An admission series of 6 sputum specimens detected 94.7 per cent of all culture-positive patients. Only 62 per cent of patients who were culture positive in the admission series would have been detected by smear alone. Quantitative agreement of smear and culture results was seen only in the smear-numerous (more than 2 bacilli per high-power field), culture-numerous (more than 100 colonies per plate) category. Qualitative agreement of smear and culture was 71 per cent. A total of 123 smear-positive and culture-negative specimens, representing 9 per cent of the total number of positive smears, was found among 6,251 sputum specimens from 270 culture-positive ptients. At least one smear-positive and culture-negative specimen was obtained from 23 per cent of the patients evaluated. During this period, improved housekeeping measures and drying of culture plates reduced the culture contamination rate from 9.8 to less than 5 per cent.

Significant enhancement of T-strain mycoplasmal growth on supplemented Shepard's A6 differential agar.

Growth of T-strain mycoplasmas was significantly improved by supplementing Shepard's A6 medium with sodium thioglycolate, cysteine hydrochloride, mercaptoethanol, or dithiothreitol.

A method to render unstained mycobacterial smears safe for storage or shipment.

Sterilization and optimal staining of Mycobacterium tuberculosis in sputum smears was accomplished by heating at 65 C for 30 min followed by exposure for 10 min to 10% formaldehyde fumes.