Definition and Use
- The mycobacterial blood culture is used for the detection of bloodstream infection due to Mycobacterium species. Mycobacteremia is most commonly seen in patients with AIDS, although it may occur in other congenital and acquired immunocompromising conditions, including patients taking chronic corticosteroid therapy, and malignancies. Growth of mycobacteria in culture requires the use of specialized, supplemented media with prolonged incubation time. Lysis of blood cells improves detection, by releasing phagocytized organisms, and is used in most methods (e.g., lysis " “centrifugation methods).
- Turnaround time: 4 " “8 weeks
Special Collection and Transport Instructions
- Collect 5 " “10 mL of blood in sodium polyanethol sulfonate (SPS) or heparin, or directly inoculate specific mycobacterial blood culture media. Inoculate the blood culture media or collection system according to the manufacturers instructions. Transport to the laboratory at room temperature.
Interpretation
- Expected results: No growth
- Positive results: Mycobacterium avium complex (MAC) is the most commonly isolated mycobacterial pathogen. M. tuberculosis may be isolated at the time of hematogenous spread associated with severe primary or reactivation disease. Rapidly growing mycobacteria, such as M. fortuitum, have been associated with chronic indwelling vascular catheters and other prosthetic material.
Limitations
- Some mycobacterial infections are rarely associated with mycobacteremia. EDTA or acid citrate dextrose (ACD)-anticoagulated blood should not be used for mycobacterial blood culture inoculum.
Suggested Reading
1CLSI. Principles and Procedures for Blood Cultures; Approved Guideline. CLSI document M47-A. Wayne, PA: Clinical and Laboratory Standards Institute; 2007.