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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

Internal Resources


Item Value
Available Stat? No
Performed by? Microbiology (AFB)
Sendout? no
In House Availability 7 days
Container type sterile, screw-capped container
Collection Instructions Because of the need for specimen concentration, whole specimens such as sputum, aspirates, urine, body fluids or tissue are preferred. Collect specimens in sterile screw-cap containers. If a specimen must be collected on a swab, moisten with sterile saline and place swab in a sterile screw-top tube with a few drops of saline or transport medium. Dry swabs are not acceptable. Negative results from swab specimens are not reliable. If exudates or fluids cannot be obtained, tissue biopsy is the most satisfactory material for culture. Do not put specimens for culture in formalin or any other histologic fixative. Label specimen with source and manner of collection.
Synonyms AFB, General Information;AFB Culture
Stability Deliver specimens immediately to Microbiology Laboratory (2M33) or hold at 4°C until delivery to avoid overgrowth of contaminating indigenous bacteria.
Additional information PROCESSING AND SMEAR: AFB specimen processing is performed once daily, beginning at 4:00 pm. Concentrated smears are stained with auramine-rhodamine fluorescent stain and routinely read the following morning. Smear results are available by 11:00 AM. Housestaff should mark the third (3rd) sputum sample as "sample #3." Smear results for samples labeled "#3" will be available by 11:00 PM on the day of receipt. The Infectious Diseases Fellow will be notified by telephone of all new patient positive smears.

CULTURE: Because of the slow growth rate of the pathogenic mycobacteria, specimens from sites that may be contaminated with indigenous flora must be decontaminated and concentrated in order to prevent overgrowth by other organisms, the most common cause of failure of cultures. Specimens from sites that are normally sterile are not decontaminated but concentrated by centrifugation when possible. The concentrated sediment is inoculated into AFB culture media and incubated for up to 8 weeks. Negative cultures are finalized after 8 weeks. Positive cultures are reported as soon as AFB are recovered. At SFGH, identification of Mycobacterium tuberculosis complex, Mycobacterium avium complex, and Mycobacterium gordonae are performed by nucleic acid probes. Other AFB are sent to SFDPH for complete species identification.

SUSCEPTIBILITY TESTING: See Mycobacteria, Susceptibility Testing
References 1. Isenberg, HD (ed), Clinical Microbiology Procedures Handbook, Vol. 1, ASM Press, Washington DC, 1992.

2. Kent, PT and GP Kubica. 1985. Public Health Mycobacteria: A Guide for the Level III Laboratory. U.S. Department of Health and Human Services. CDC. Atlanta GA.

3. Murray PR, et al. Manual of Clinical Microbiology, 8th ed. ASM Press, Washington, DC. 2003.
Last Updated 8/19/2009 1:31:21 PM
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