Comparative evaluation of modified m-FC and m-TEC media for membrane filter enumeration of Escherichia coli in water

Abstract

Two media used to detect fecal coliforms in water by membrane filtration, m-FC and m-TEC, were modified and supplemented with the chromogenic substrate 5-bromo-6-chloro-3-indoyl-beta-D-glucuronide (BCIG) and were compared for quantitative recovery of Escherichia coli. Student's t test of data from 181 water samples of sewage, rivers, lakes, and wells did not demonstrate any statistically significant differences (P = 0.05) in the enumeration of E. coli with these media. Target colonies were confirmed to be E. coli at rates of 98.6 and 97.3% by using FC-BCIG and TEC-BCIG media, respectively. Glucuronidase-negative isolates of E. coli were encountered at the same frequency (6.0%) on both media. This collaborative study demonstrated that either modified basal medium could be used successfully for detection of E. coli in various nontreated waters within 24 h.