腸毒素大腸桿菌產生的毒素，包括熱不穩定性腸毒素（LT）及熱穩定性腸毒素（ST）。這些毒素可引起人畜下痢之疾病。於本研究，我們結合了對大腸桿菌LT I及ST II腸毒素基因具特異性之二組聚合　鏈反應（PCR）引子，組合為一多套式PCR套組，以同時檢測自來水及環境水中LT I及ST II型腸毒素大腸桿菌之存在。利用Chromocult coliform agar(CCA)，我們發現台中地區自來水及地下水，不含或僅含10 0 CFU/ml 之大腸桿菌及coliform菌；然四條近台中市之溪流皆含10 2～10 4 CFU/ml之高菌數大腸桿菌與coliform菌；且其中三條溪流水樣中含LT I及ST II型大腸桿菌或者只含ST II型之大腸桿菌。此結果顯示都市近郊之溪水以遭高量的微生物污染，應該儘速加以注意。

The enterotoxins produced by enterotoxigenic Escherichia coli (ETEC) cells include heat labile (LT) and heat stable toxins (ST). These toxins cause diarrheal in humans and domestic animals. In this study, we combined LT I and ST II gene specific PCR primers into a multiplex PCR systemand used this system for the simultaneous detection of LT I and ST II ETEC cells in tap water and environmental waters. Using Chromocult coliform agar (CCA), we found that tap water and underground water were contaminated with 0-10 0 CFU/ml of E. coli and coliform cells while the waters from four rivers near Taichung City were contaminated with 10 2 - 10 4 CFU/ml of E. coli and coliform cells. Furthermore, three of the four river waters were contaminated with LT I/ST II ETEC cells. The high levels of microfloral contamination in these river waters near an urban area should be attended to urgently.