Novel-method for processing respiratory specimens for detection of mycobacteria by using C18-carbohxypropylbetaine: Blinded study

Charles G. Thornton, Kerry M. Maclellan, Thomas L. Brink, Denise E. Lockwood, Mark Romagnoli, June Turner, William G. Merz, Richard S. Schwalbe, Marcia Moody, Yvonne Lue, Selvin Passen

Research output: Contribution to journalArticlepeer-review

Abstract

A novel method for processing respiratory specimens to improve culture and acid-fast staining of mycobacteria is introduced. This new method utilized N,N-dimethyl-N-(n-octadecyl) N-(3-carboxypropyl)ammonium inner salt (Chemical Abstract Service no. 78195-27-4), also known as C13- carboxypropylbetaine (CB-18). In a blinded, five-center study, CB-18-based processing was compared to the standard method combining NALC and NaOH (NALC/NaOH). A total of 573 respiratory specimens were tested. Individual specimens were split approximately equally; the host institutions processed half of each specimen by the NALC/NaOH method, while the other half was processed with CB-18 at Quest Diagnostics - Baltimore. A total of 106 specimens were culture positive for acid-fast bacilli (AFB). Replacement of the primary decontamination agent with CB-18 caused changes in and diagnostic parameters. Aggregate culture sensitivity improved by approximately 43% (P < 0.01), and smear sensitivity improved by approximately 58% (P < 0.01). The sensitivity of smear relative to that of M. tuberculosis isolates exceeded 93% (P < 0.01) when specimens were processed with CB-18. The average times to a positive results were reduced by 7.3 days in liquid culture (P < 0.01) and 5.3 days on solid media (P < 0.05); however, the CB-18 method had a 20.8% contamination rate in liquid culture versus a rate of approximately 7.5% with NALG/NaOH processing. There were also unusual reductions in liquid culture sensitivity and smear specificity among CB-18-processed specimens. The characteristics of the latter parameters suggested that refinement of the CB- 18 processing method should allow further improvements in culture sensitivity. This study showed that the CB-18 method has the potential to improve both smear and culture detection for these important human pathogens.

Original languageEnglish (US)
Pages (from-to)1996-2003
Number of pages8
JournalJournal of clinical microbiology
Volume36
Issue number7
DOIs
StatePublished - Jul 1998

ASJC Scopus subject areas

  • Microbiology (medical)

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