False Positive Fecal Coliform in Biosolid Samples Assayed using A-1 Medium

Author: Baker Katherine H   Redmond Brady   Herson Diane S  

Publisher: Water Environment Federation

ISSN: 1061-4303

Source: Water Environment Research, Vol.77, Iss.4, 2005-07, pp. : 423-424

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Abstract

Two most probable number (MPN) methods—lauryl tryptose broth with Escherichia coli broth confirmation and direct A-1 broth incubation (A-1)—were compared for the enumeration of fecal coliform in lime-treated biosolid. Fecal coliform numbers were significantly higher using the A-1 method. Analysis of positive A-1 tubes, however, indicated that a high percentage of these were false positives. Therefore, the use of A-1 broth for 40 CFR Part 503 Pathogen Reduction (CFR, 1993) compliance testing is not recommended.