Quantitation of mycobacteria in blood specimens from patients with AIDS.

OBJECTIVE

To determine the effect of a delay in processing blood specimens, that may occur by mailing them to a specialized laboratory, on the quantitation of the number of mycobacteria.

DESIGN

Simulated blood specimens in sodium polyanetholium sulfonate (SPS)-containing vacutainers were spiked with Mycobacterium avium, and stored for 4 days after addition of clarithromycin or rifabutin, or remained drug-free. Daily samples were lysed with sodium desoxycholate, and inoculated onto 7H11 agar plates for the subsequent colony-forming units (CFU)/ml count. The isolation rates on two media, 7H11 agar and BACTEC 12B broth, were determined with 1212 specimens from AIDS patients.

RESULTS

The number of bacteria in blood specimens remained without substantial change during the period of storage, even in the presence of clarithromycin or rifabutin, especially after refrigeration for 2 or 24 h before storage. 7H11 agar and 12B broth were equally sensitive for isolation of M. avium.

CONCLUSIONS

A 4-day delay in processing blood specimens in SPS vacutainers does not affect the results of quantitation of the number of mycobacteria. Combined use of 12B broth and 7H11 agar increased the overall recovery along with an opportunity to quantitate the number of CFU/ml.