W L Chao1. 1. Department of Microbiology, Soochow University, Shih Lin, Taipei, Taiwan. wlchao@mail.scu.edu.tw
Abstract
AIMS: To evaluate the suitability of Colilert-18 in detecting Escherichia coli and total coliforms in tropical freshwater samples. METHODS AND RESULTS: 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. CONCLUSIONS: 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%. SIGNIFICANCE AND IMPACT OF THE STUDY: The high false-positive rate of Colilert-18, tempers its value for E. coli detection when used for tropical freshwater samples.
AIMS: To evaluate the suitability of Colilert-18 in detecting Escherichia coli and total coliforms in tropical freshwater samples. METHODS AND RESULTS: 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. CONCLUSIONS: 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%. SIGNIFICANCE AND IMPACT OF THE STUDY: 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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