QS-AFB-0010

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U-083. Evaluation of a Rapid, Fluorescent Stain for the Detection of Mycobacteria in Clinical Specimens

C. Hendry, K. Dionne, K. Carroll, N. Parrish;
Johns Hopkins Hosp., Owings Mills, MD.

Background: Due to the steady increase in Mycobacterial disease, rapid detection is essential for early diagnosis and treatment of infection. A common method used for screening clinical specimens suspected of containing mycobacteria is microscopic examination of stained smears for the presence of acid-fast bacilli (AFB). We compared 2 Auramine-O stains: the Remel TB Auramine-O stain (RAO) and the Rapid Modified Auramine-O stain from Scientific Device Laboratory (MAO).

Methods: The RAO procedure required 8 steps using 3 stains and ~22 minutes for completion. The MAO procedure required 6 steps using 2 stains and ~2 minutes for completion. Testing included pooled specimens from the following digested / decontaminated sources: tissue, sputum, bronchial lavage, peritoneal fluid, and (undigested) cerebrospinal fluid. Each source was divided into separate aliquots and inoculated with a dilution series of Mycobacterium gordonae to reflect the burden of organism typically seen in clinical samples. 100 duplicate slide sets were prepared according to manufacturer.s protocols and divided into sets .A. (RAO-stained) and .B. (MAO-stained). Slides were graded for quantity of organism, and brightness of both AFB and background debris.

Results: In comparing both methods, all slides were positive for AFB with no significant quantification difference in organism between stains. Approximately 40% of the MAO slides were brighter than their paired RAO counterpart. Overall, MAO-stained slides exhibited less background debris staining (4%) versus RAO stained slides (30%). MAO staining required significantly less time (~2 min) versus the RAO stain (~22 min).

Conclusion: Results of this study suggest that the MAO-stain has several favorable characteristics for use in a clinical laboratory setting: it is rapid, provides equivalent AFB quantitation as compared with the RAO stain, but with less non-specific background fluorescence. As such, the MAO stain has the potential to be more cost effective and efficient in presenting presumptive evidence of mycobacteria in clinical specimens.

Paper presented at the 108th meeting of ASM Boston MA, June 5, 2008

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