A comparison of methods used to enumerate Escherichia coli in conventionally treated sewage sludge

• Published in: Journal of applied microbiology 2004-02, Vol.96 (2), p.375-383
• Main Authors: Eccles, J.P., Searle, R., Holt, D., Dennis, P.J.
• Format: Article
• Language: English
• Subjects: Bacteria (Enterobacteriaceae) (Escherichia); Bacteriological methods and techniques used in bacteriology; Bacteriological Techniques - methods; Bacteriology; Biological and medical sciences; biosolids; chromogenic; Colilert; Colony Count, Microbial - methods; Culture Media; E. coli; Escherichia coli - isolation & purification; False Negative Reactions; False Positive Reactions; Filtration; Fundamental and applied biological sciences. Psychology; Microbiology; MLGA; Reproducibility of Results; sewage; Sewage - microbiology; sludge
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1046/j.1365-2672.2004.02165.x

Aims:  This study examined the suitability of three analytical methods for isolating and enumerating Escherichia coli from conventionally treated sewage sludge. Methods and Results:  Crude sewage, mesophilic anaerobic digested (MAD) sludge, and final product sludge samples were taken from six sewage treatment works for analysis. Two of the three methods tested were membrane filtration techniques, utilizing chromogenic E. coli/coliform (CEC) media and membrane‐lactose glucuronide agar (MLGA); the third method was a most probable number (MPN) technique utilizing Colilert in Quantitray 2000 (Idexx). The methods were evaluated for variation, consistency, false‐positive and false‐negative results, as well as method correlation. The methods gave good and consistent recovery of E. coli for a range of conventionally treated sewage matrices. All of the methods had a false‐positive rate of