A comparison of two specimen preparation methodologies and their effect on the outcome of standard diagnostic protocols used for mycobacteria detection

Abstract number: P2065

Objectives: Sputum and other respiratory specimens are the primary means to diagnose pulmonary tuberculosis and other mycobacteria infection. In order to be useful for diagnostic protocols, these specimens must be liquefied and decontaminated, but the failure to control pH inherent in conventional protocols for specimen preparation can significantly reduce the number of viable mycobacteria in the patient sample and negatively affect analytical protocols. In this study we attempted to examine the effect of two separate specimen preparation methods on the outcome of common diagnostic procedures for AFB infection.

Methods: Pulmonary samples submitted for diagnosis were split evenly and subjected to two separate specimen processing methodologies; the conventional methodology using NALC, 3% NaOH and M/15 Phosphate Buffer, and a new methodology offered by the NAC-PAC™ EA3 [Alpha Tec Systems Inc., Vancouver, WA]. Once prepared for diagnosis each sample was initially screened via Auramine O / Rhodamine B staining, and, if positive, organism concentration was graded based on the WHO/IUATLD evaluation scale. All samples were cultured using Lowenstein-Jensen medium at 36°Celsius for 8 weeks. Culture positive specimens were graded based upon the number of colony forming units present.

Results: Of the 113 samples submitted for diagnostics 22 were positive for AFB by either microscopy or culture. Of these positive samples all 22 were detected using the Alpha Tec methodology and 20 were detected using conventional specimen preparation methodology. The two samples undetected using conventional methodologies were smear negative but culture positive using the Alpha Tec methodology. One sample that was smear negative but culture positive using the conventional methodology was smear positive using the Alpha Tec methodology. Four smear negative culture positive samples showed non-correlating growth, three samples using the Alpha Tec methodology showed a greater number of AFB colonies, one sample using the conventional methodology showed a greater number of colonies.

Conclusion: The Alpha Tec NAC-PAC™ EA3 AFB Specimen Processing reagent system identified positive smears and cultures otherwise missed by the conventional NALC/NaOH/M/15 Buffer methodology.

Aggregated results

ATS91148 (3 with increased CFU, 2 undetected using NaOH/PBS)
NaOH/NALC93137 (1 with increased CFU)

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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