Abstract

The present study is descriptive and analytical in nature, aimed to determine the correlation and compatibility rates of the detection methods of multiple tube fermentation (both traditional and direct techniques) using Escherichia coli (EC) Broth and plate count in special fecal Coli form culture media. The objective was to identify the one method among these which is economical, effective, rapid and easy to use under emergency conditions. Pour plate count using Eosin-methylene blue (EMB) was evaluated in comparison with the traditional, and direct multiple tube fermentation (MTF) as techniques used in enumerating thermo-tolerant bacteria and E. coli in water resources. Fourteen samples were required, based on a pilot study. However, 70 samples were analyzed to obtain a higher level of accuracy through three microbial laboratory methods, in evaluating raw water collected from wells, springs, and rivers as well as the effluent of wastewater treatment plants. A high Pearson correlation was found for enumerating thermo-tolerant bacteria. The results revealed that majority of the samples contained thermo-tolerant coli form. Based on the correlation coefficients, calculated among the three methods, economical considerations, test duration, and time to yield results, the plate count, the direct MTF, and the traditional MTF may be ranked in a descending priority order from the viewpoint of bacterial quality assessment of water resources for the emergency conditions and irrigation purposes. Conventional, direct MTF and plate count methods were powered in detection E. coli in rate of 95, 90 and 80% respectively.

Key words: Multiple tube fermentation, pour plate count, thermo-tolerant Coli form, agreement rate, water resources.