Abstract
In order to count Escherichia coli both sensitive and resistant to ampicillin in a paddy field community, the quantity of Colilert, the time for incubation, and concentration of ampicillin were studied. Colilert was dissolved with sterilized distilled water and dispensed into a 1.5ml centrifuging tube and the MPN method under 30- to 70-hours incubation was adopted for enumeration of E. coli. Commercial Colilert could be reused 20 times. Colilert containing 0.5mg/l of ampicillin was applicable for counting E. coli resistant to ampicillin.
