National field evaluation of a defined substrate method for the simultaneous detection of total coliforms and Escherichia coli from drinking water: comparison with presence-absence techniques.

A defined substrate method was applied to drinking water to simultaneously enumerate total coliforms and total Escherichia coli directly from samples. After incubation at 35 degrees C for 24 h, the development of yellow in an initially colorless solution was specific for total coliforms; fluorescence at 366 nm in the same tube(s) or vessel demonstrated the presence of E. coli. No confirmatory or completed steps were necessary. Known as autoanalysis colilert (AC), this method was constituted as a presence-absence test and compared with the methods described in Standard Methods (SM) in the P-A format. Seven water utilities representing a wide geological and hydrological spectrum participated in the evaluation. A total of 702 split drinking water samples were analyzed. Of these, 358 were negative in both tests (SM- and AC-); 302 were positive (SM+ and AC+); and 42 were mixed (SM+ and AC-, 20; AC+ and SM-, 22). The overall agreement rate was 94%. Comparison of the SM and AC results by nonparametric statistics demonstrated no differences. Heterotrophic plate count bacteria exerted no discernible effect on the AC test. By subculture, each time the AC test was yellow, a total coliform was present; when the test was fluorescent, E. coli was isolated.     

National field evaluation of a defined substrate method for the simultaneous enumeration of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube fermentation method

A defined substrate method was developed to simultaneously enumerate total coliforms and Escherichia coli from drinking waters without the need for confirmatory or completed tests. It is a new method based on technology that uses a hydrolyzable substrate as a specific indicator-nutrient for the target microbes. No equipment other than a 35 degrees C incubator and long-wavelength (366-nm) light is necessary. To perform the test, one only has to add water to the powdered ingredients in a tube or flask. If total coliforms are present in the water sample, the solution will change from its normal colorless state (no target microbes present) to yellow. The specific presence of E. coli will cause the same tube to fluoresce under a longwave (366-nm) UV lamp. The test, called Autoanalysis Colilert (AC), was compared with Standard Methods for the Examination of Water and Wastewater 10-tube multiple tube fermentation (MTF) in a national evaluation. Five utilities, representing six U.S. Environmental Protection Agency regions, participated. All water samples came from distribution systems. Split samples from a wide variety of water sources were analyzed for the MPN-versus-MPN comparison. A total of 1,086 tubes were positive by MTF, and 1,279 were positive by AC. There was no statistical difference between MTF and AC. Species identifications from positive tubes confirmed the sensitivity of the AC. A national evaluation of the AC test showed that it: (i) was as sensitive as Standard Methods MTF, (ii) specifically enumerated 1 total coliform per 100 ml, in a maximum of 24 h, (iii) simultaneously enumerated 1 E. coli per 100 ml in the same analysis, (iv) was not subject to false-positive or false-negative results by heterotrophic bacteria, (v) did not require confirmatory tests, (vi) grew injured coliforms, (vii) was easy to inoculate, and (viii) was very easy to interpret.     

National field evaluation of a defined substrate method for the simultaneous enumeration of total coliforms and Escherichia coli from drinking water: comparison with the standard multiple tube fermentation method.

A defined substrate method was developed to simultaneously enumerate total coliforms and Escherichia coli from drinking waters without the need for confirmatory or completed tests. It is a new method based on technology that uses a hydrolyzable substrate as a specific indicator-nutrient for the target microbes. No equipment other than a 35 degrees C incubator and long-wavelength (366-nm) light is necessary. To perform the test, one only has to add water to the powdered ingredients in a tube or flask. If total coliforms are present in the water sample, the solution will change from its normal colorless state (no target microbes present) to yellow. The specific presence of E. coli will cause the same tube to fluoresce under a longwave (366-nm) UV lamp. The test, called Autoanalysis Colilert (AC), was compared with Standard Methods for the Examination of Water and Wastewater 10-tube multiple tube fermentation (MTF) in a national evaluation. Five utilities, representing six U.S. Environmental Protection Agency regions, participated. All water samples came from distribution systems. Split samples from a wide variety of water sources were analyzed for the MPN-versus-MPN comparison. A total of 1,086 tubes were positive by MTF, and 1,279 were positive by AC. There was no statistical difference between MTF and AC. Species identifications from positive tubes confirmed the sensitivity of the AC. A national evaluation of the AC test showed that it: (i) was as sensitive as Standard Methods MTF, (ii) specifically enumerated 1 total coliform per 100 ml, in a maximum of 24 h, (iii) simultaneously enumerated 1 E. coli per 100 ml in the same analysis, (iv) was not subject to false-positive or false-negative results by heterotrophic bacteria, (v) did not require confirmatory tests, (vi) grew injured coliforms, (vii) was easy to inoculate, and (viii) was very easy to interpret.     

Evaluation of a rapid, defined substrate technology method for enumeration of total coliforms and Escherichia coli in chlorinated drinking water

A rapid, defined substrate technology method, commercially available as Colilert, simultaneously enumerates total coliforms and Escherichia coli in drinking water samples in 24 h without the need for confirmatory tests. The ability of this method to enumerate both total coliforms and E. coli in simulated chlorine-treated drinking water samples was compared with the standard UK method (minerals-modified glutamate most probable number) which requires up to 96 h to complete including confirmation. Statistical analysis by a nonparametric matched-pair test showed the Colilert method to be less efficient at detecting down to one E. coli in these samples compared to the standard UK method. No statistically significant difference between the two methods of enumeration for total coliforms was detected.     

Comparison of membrane filtration and Autoanalysis Colilert presence-absence techniques for analysis of total coliforms and Escherichia coli in drinking water samples

Over a 4-month period, 950 samples of treated drinking water were analyzed for total coliforms (TC) and Escherichia coli by both membrane filtration (MF) and Autoanalysis Colilert presence-absence (AC) techniques. The two tests agreed 97% of the time on the basis of presumptive TC results and 98.5% of the time on the basis of verified TC results. Samples which produced disagreement between the two tests were most often TC positive by MF and TC negative by AC. E. coli was recovered four times: twice by MF only, and twice by AC only but without the diagnostic fluorescence reaction. In two samples, E. coli could not be isolated from fluorescence-positive AC tests. On the basis of these results, the AC test was implemented as the routine analytical procedure for TC but not for E. coli.     

Enumeration of total coliforms and Escherichia coli from source water by the defined substrate technology

Many water utilities are required to monitor source water for the presence of total coliforms, fecal coliforms, or both. The Colilert system, an application of the defined substrate technology, simultaneously detects the presence of both total coliforms and Escherichia coli directly from a water sample. After incubation, the formula becomes yellow if total coliforms are present and fluorescent at 366 nm if E. coli is in the same sample. No confirmatory tests are required. The Colilert system was previously assessed with distribution water in a national evaluation in both most-probably-number and presence-absence formats and found to produce data equivalent to those obtained by using Standard Methods for the Examination of Water and Wastewater (Standard Methods). The Colilert system was now compared with Standard Methods multiple-tube fermentation (MTF) for the enumeration of total coliforms and E. coli from surface water. All MTF tubes were confirmed according to Standard Methods, and subcultures were made to identify isolates to the species level. The Colilert system was found equally sensitive to MTF testing by regression, t test, chi-square, and likelihood fraction analyses. Specificity of the Colilert system was shown by the isolation of a species of total coliform or E. coli after the appropriate color change. The Colilert test can be used for source water samples when enumeration is required, and the benefits previously described for distribution water testing--sensitivity, specificity, less labor, lower cost, faster results, no noncoliform heterotroph interference--are applicable to this type of water analysis.     

Comparison of membrane filtration and Autoanalysis Colilert presence-absence techniques for analysis of total coliforms and Escherichia coli in drinking water samples.

Over a 4-month period, 950 samples of treated drinking water were analyzed for total coliforms (TC) and Escherichia coli by both membrane filtration (MF) and Autoanalysis Colilert presence-absence (AC) techniques. The two tests agreed 97% of the time on the basis of presumptive TC results and 98.5% of the time on the basis of verified TC results. Samples which produced disagreement between the two tests were most often TC positive by MF and TC negative by AC. E. coli was recovered four times: twice by MF only, and twice by AC only but without the diagnostic fluorescence reaction. In two samples, E. coli could not be isolated from fluorescence-positive AC tests. On the basis of these results, the AC test was implemented as the routine analytical procedure for TC but not for E. coli.     

Enumeration of total coliforms and Escherichia coli from source water by the defined substrate technology.

Many water utilities are required to monitor source water for the presence of total coliforms, fecal coliforms, or both. The Colilert system, an application of the defined substrate technology, simultaneously detects the presence of both total coliforms and Escherichia coli directly from a water sample. After incubation, the formula becomes yellow if total coliforms are present and fluorescent at 366 nm if E. coli is in the same sample. No confirmatory tests are required. The Colilert system was previously assessed with distribution water in a national evaluation in both most-probably-number and presence-absence formats and found to produce data equivalent to those obtained by using Standard Methods for the Examination of Water and Wastewater (Standard Methods). The Colilert system was now compared with Standard Methods multiple-tube fermentation (MTF) for the enumeration of total coliforms and E. coli from surface water. All MTF tubes were confirmed according to Standard Methods, and subcultures were made to identify isolates to the species level. The Colilert system was found equally sensitive to MTF testing by regression, t test, chi-square, and likelihood fraction analyses. Specificity of the Colilert system was shown by the isolation of a species of total coliform or E. coli after the appropriate color change. The Colilert test can be used for source water samples when enumeration is required, and the benefits previously described for distribution water testing--sensitivity, specificity, less labor, lower cost, faster results, no noncoliform heterotroph interference--are applicable to this type of water analysis.     

New medium for the simultaneous detection of total coliforms and Escherichia coli in water.

A new membrane filter agar medium (MI agar) containing a chromogen, indoxyl-beta-D-glucuronide, and a fluorogen, 4-methylumbelliferyl-beta-D-galactopyranoside, was developed to simultaneously detect and enumerate Escherichia coli and total coliforms (TC) in water samples on the basis of their enzyme activities. TC produced beta-galactosidase, which cleaved 4-methylumbelliferyl-beta-D-galactopyranoside to form 4-methylumbelliferone, a compound that fluoresced under longwave UV light (366 nm), while E. coli produced beta-glucuronidase, which cleaved indoxyl-beta-D-glucuronide to form a blue color. The new medium TC and E. coli recoveries were compared with those of mEndo agar and two E. coli media, mTEC agar and nutrient agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide, using natural water samples and spiked drinking water samples. On average, the new medium recovered 1.8 times as many TC as mEndo agar, with greatly reduced background counts (< or = 7%). These differences were statistically significant (significance level, 0.05). Although the overall analysis revealed no statistically significant difference between the E. coli recoveries on MI agar and mTEC agar, the new medium recovered more E. coli in 16 of 23 samples (69.6%). Both MI agar and mTEC agar recovered significantly more E. coli than nutrient agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide. Specificities for E. coli, TC, and noncoliforms on MI agar were 95.7% (66 of 69 samples), 93.1% (161 of 173 samples), and 93.8% (61 of 65 samples), respectively. The E. coli false-positive and false-negative rates were both 4.3%. This selective and specific medium, which employs familiar membrane filter technology [corrected] to analyze several types of water samples, is less expensive than the liquid chromogen and fluorogen media and may be useful for compliance monitoring of drinking water.     

Evaluation of commercial presence-absence test kits for detection of total coliforms, Escherichia coli, and other indicator bacteria.

Evaluations of several commercial presence-absence (P-A) test kits were performed over a 6-month period in 1990 by using the Ontario Ministry of the Environment (MOE) P-A test for comparison. The general principles of the multiple-tube fermentation technique formed the basis for conducting the product evaluations. Each week, a surface water sample was diluted and inoculated into 25 99-ml dilution blanks for each of three dilutions. The inoculated dilution blanks from each dilution series were randomly sorted into sets of five. Three of these sets were inoculated into the P-A test kits or vice versa, as required. The other two sets were passed through membrane filters, and one set of five membrane filters was placed onto m-Endo agar LES to give replicate total coliform counts and the other set was placed onto m-TEC agar to give replicate fecal coliform results. A statistical analysis of the results was performed by a modified logistic transform method, which provided an improved way to compare binary data obtained from the different test kits. The comparative test results showed that three of the four commercial products tested gave very good levels of recovery and that the fourth commercial product gave only fair levels of recovery when the data were compared with the data from MOE P-A tests and membrane filter tests. P-A bottles showing positive results after 18 h of incubation that were subcultured immediately in ECMUG tubes frequently could be confirmed as containing total coliforms, fecal coliforms, or Escherichia coli after 6 h of incubation; thus, the total incubation time was only 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Limitations of highly sensitive enzymatic presence-absence tests for detection of waterborne coliforms and Escherichia coli.

This study presents evidence for the unfeasibility of enzymatic presence-absence tests to detect one total coliform or one Escherichia coli organism in 100 ml of drinking water within a working day. The results of field trials with prototype chemiluminometric procedures indicated that the sensitivity-boosting measures that are essential to achieve the required speed compromise the specificity of the tests.     

A new membrane filtration medium for simultaneous detection and enumeration of Escherichia coli and total coliforms.

Recovery of total coliforms and Escherichia coli on a new membrane filtration (MF) medium was evaluated with 25 water samples from seven states. Testing of the new medium, m-ColiBlue24 broth, was conducted according to a U.S. Environmental Protection Agency protocol. For comparison, this same protocol was used to measure recovery of total coliforms and E. coli with two standard MF media, m-Endo broth and mTEC broth. E. coli recovery on the new medium was also compared to recovery on nutrient agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide. Comparison of specificity, sensitivity, false positive error, undetected target error, and overall agreement indicated E. coli recovery on m-ColiBlue24 was superior to recovery on mTEC for all five parameters. Recovery of total coliforms on the new medium was comparable to recovery on m-Endo.     

A medium detecting β-glucuronidase for the simultaneous membrane filtration enumeration of Escherichia coli and coliforms from drinking water

A medium for the single membrane enumeration of Escherichia coli and coliforms from potable water was developed by the modification of the standard UK membrane filtration medium. The medium, membrane-Lactose Glucuronide Agar (m-LGA), employs a chromogenic substrate for the detection of β-glucuronidase activity and sodium pyruvate to enhance recovery of chlorine-stressed coliforms. Escherichia coli identification was significantly improved on m-LGA with 98.6% of presumptive isolates confirming. Recovery of coliforms from drinking water samples was also significantly improved.     

Evaluation of colilert-marine water for detection of total coliforms and Escherichia coli in the marine environment.

A test that allows for early detection of fecally contaminated coastal water would enhance public health protection. Colilert-Marine Water (Colilert-MW; Environetics, Branford, Conn.) is a rapid 24-h test that has recently been developed to detect total coliforms and Escherichia coli in coastal water. We performed a premarketing evaluation of the Colilert-MW product, testing it in parallel with the multiple tube fermentation (MTF) method for 86 coastal water samples in southern California. Statistical analysis was performed by using paired t tests and linear regression. Bacterial isolates were evaluated by biochemical and genetic analysis. The results of this study showed a strong correlation between the traditional MTF and the Colilert-MW method for detection of total coliforms (r = 0.95) and E. coli (r = 0.89) in ocean water samples. Paired t-test results indicated that the Colilert-MW and MTF were equivalent in detecting E. coli and that the Colilert-MW may be more sensitive in the detection of total coliforms. We conclude that Colilert-MW would be a useful tool with which to monitor coastal beach water.     

A simple and cost-effective method for the quantification of total coliforms and Escherichia coli in potable water

In this study, a new simple and cost-effective method for the study of total coliforms and Escherichia coli in potable water, combining the use of lactose TTC agar and TBX agar, was developed and compared with methods using Chromocult agar and coli ID. The statistical analysis showed no significant difference and a good correlation (R(2)) between the three methods.     

Comparison of membrane filter, multiple-fermentation-tube, and presence-absence techniques for detecting total coliforms in small community water systems

Methods for detecting total coliform bacteria in drinking water were compared using 1,483 different drinking water samples from 15 small community water systems in Vermont and New Hampshire. The methods included the membrane filter (MF) technique, a 10-tube fermentation tube (FT) technique, and the presence-absence (P-A) test. Each technique was evaluated using a 100-ml drinking water sample. Of the 1,483 samples tested, 336 (23%) contained coliforms as indicated by either one, two, or all three techniques. The FT detected 82%, the P-A detected 88%, and the MF detected 64% of these positives. All techniques simultaneously detected 55% of the positives. Evaluation of the confirmation efficiency of the P-A technique showed 94% of the presumptive positives confirming as coliforms. Thirteen different species of coliforms were identified from the 37 tests in which the P-A was positive but the MF and FT were negative. The P-A test was simple to inoculate and interpret and was considerably more sensitive than the MF and slightly more sensitive than the FT in detecting coliforms in this type of drinking water supply.     

Comparison of membrane filter, multiple-fermentation-tube, and presence-absence techniques for detecting total coliforms in small community water systems.

Methods for detecting total coliform bacteria in drinking water were compared using 1,483 different drinking water samples from 15 small community water systems in Vermont and New Hampshire. The methods included the membrane filter (MF) technique, a 10-tube fermentation tube (FT) technique, and the presence-absence (P-A) test. Each technique was evaluated using a 100-ml drinking water sample. Of the 1,483 samples tested, 336 (23%) contained coliforms as indicated by either one, two, or all three techniques. The FT detected 82%, the P-A detected 88%, and the MF detected 64% of these positives. All techniques simultaneously detected 55% of the positives. Evaluation of the confirmation efficiency of the P-A technique showed 94% of the presumptive positives confirming as coliforms. Thirteen different species of coliforms were identified from the 37 tests in which the P-A was positive but the MF and FT were negative. The P-A test was simple to inoculate and interpret and was considerably more sensitive than the MF and slightly more sensitive than the FT in detecting coliforms in this type of drinking water supply.     

Comparison of Colilert with Dutch standard enumeration methods for Escherichia coli and total coliforms in water

The average recovery of Escherichia coli with Colilert was 26% (range 12–42%) and that for coliforms was 35% (range 4–140%, when compared with Dutch standard methods. In samples with low numbers of target organisms, Colilert gave false-negative results and was therefore regarded as an unsuitable alternative for Dutch standard methods.