Evaluation of Colilert-18 for the detection of coliforms and Escherichia coli in tropical fresh water.

Department of Microbiology, Soochow University, Shih Lin, Taipei, Taiwan.
Letters in Applied Microbiology (Impact Factor: 1.75). 03/2006; 42(2):115-20. DOI: 10.1111/j.1472-765X.2005.01814.x
Source: PubMed

ABSTRACT To evaluate the suitability of Colilert-18 in detecting Escherichia coli and total coliforms in tropical freshwater samples.
Target organisms were isolated from yellow-fluorescent and yellow wells of Colilert-18/Quanti-Tray using m-TEC agar and m-ENDO LES agar respectively. All the selected isolates were first identified based on their fatty acid methyl ester profile. Isolates showing contradictory results to that of the Colilert-18 procedure were re-identified using API 20E strips. A total of 357 isolates, 177 from yellow-fluorescent wells and 180 from yellow wells, were identified.
The false-positive and -negative rates for E. coli detection using Colilert-18 were 36.4% and 11%, respectively, while for coliform detection the false-positive rate was 10.3%.
The high false-positive rate of Colilert-18, tempers its value for E. coli detection when used for tropical freshwater samples.

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