scholarly journals Marine Bacteria Cause False-Positive Results in the Colilert-18 Rapid Identification Test for Escherichia coli in Florida Waters

2002 ◽  
Vol 68 (2) ◽  
pp. 539-544 ◽  
Author(s):  
John M. Pisciotta ◽  
Damon F. Rath ◽  
Paul A. Stanek ◽  
D. Michael Flanery ◽  
Valerie J. Harwood
Keyword(s):  
Escherichia Coli ◽  
False Positive ◽  
Fecal Coliform ◽  
Membrane Filtration ◽  
False Positives ◽  
Fecal Coliforms ◽  
Marine Waters ◽  
E Coli ◽  
Marine Samples ◽  
Positive Results

ABSTRACT The Colilert-18 system for enumeration of total coliforms and Escherichia coli is approved by the U.S. Environmental Protection Agency for use in drinking water analysis and is also used by various agencies and research studies for enumeration of indicator organisms in fresh and saline waters. During monitoring of Pinellas County, Fla., marine waters, estimates of E. coli numbers (by Colilert-18) frequently exceeded fecal coliform counts (by membrane filtration) by 1 to 3 orders of magnitude. Samples from freshwater sites did not display similar discrepancies. Fecal coliforms, including E. coli, could be cultured from 100% of yellow fluorescent wells (denoting E. coli-positive results) inoculated with freshwater samples but could be cultured from only 17.1% of the “positive” wells inoculated with marine samples. Ortho-nitrophenyl-β-d-galactopyranoside (ONPG)-positive or 4-methylumbelliferyl-β-d-glucuronide (MUG)-positive noncoliform bacteria were readily cultured from Colilert-18 test wells inoculated with marine samples. Filtered cell-free seawater did not cause false positives. Coculture preparations of as few as 5 CFU of Vibrio cholerae (ONPG positive) and Providencia sp. (MUG positive) ml−1 inoculated into Colilert-18 caused false-positive E. coli results. Salinity conditions influenced coculture results, as the concentration of coculture inoculum required to cause false positives in most wells increased from about 5 CFU ml−1 in seawater diluted 1:10 with freshwater to ≈5,000 CFU ml−1 in seawater diluted 1:20 with freshwater. Estimated E. coli numbers in various marine water samples processed at the 1:10 dilution ranged from 10 to 7,270 CFU�100 ml−1, while E. coli numbers in the same samples processed at the 1:20 dilution did not exceed 40 CFU�100 ml−1. The lower estimates of E. coli numbers corresponded well with fecal coliform counts by membrane filtration. This study indicates that assessment of E. coli in subtropical marine waters by Colilert-18 is not accurate when the recommended 1:10 sample dilution is used. The results suggest that greater dilution may diminish the false-positive problem, but further study of this possibility is recommended.

scholarly journals Membrane filtration media for the enumeration of coliform organisms and Escherichia coli in water: comparison of Tergitol 7 and lauryl sulphate with Teepol 610

1980 ◽  
Vol 85 (2) ◽  
pp. 181-191 ◽  
Author(s):  
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
False Positive ◽  
Membrane Filtration ◽  
Sodium Lauryl Sulphate ◽  
Standard Medium ◽  
E Coli ◽  
Laboratory Trial ◽  
Positive Results ◽  
Filtration Technique

SUMMARYIn a multi-laboratory trial with the mombrane filtration technique, three surfactants – Teepol 610 (T610), Tergitol 7 (T7) and sodium lauryl sulphate (LS) – were compared in media for the enumeration of coliform organisms and Escherichia coli in water. A total of 170 samples of water (87 raw and 92 marginally chlorinated) were examined for colony counts of coliform organisms, and 185 water samples (94 raw and 91 marginally chlorinated) for E. coli. Slight differences in the confirmed colony counts between the three media were noted, but few of these were observed consistently in every laboratory. In most laboratories, T7 gave slightly higher counts of E. coli than LS with chlorinated waters; a higher incidence of false-positive results for E. coli at 44 °C was also noted with T7. As there were no outstanding differences in the trial, sodium lauryl sulphate, which is chemically defined, cheap and readily available, is therefore recommended for use at a concentration of 0·1% instead of Teepol 610 in the standard medium for the enumeration of coliform organisms and E. coli in water by the membrane filtration technique.

scholarly journals Comparison of Fecal Coliform Agar and Violet Red Bile Lactose Agar for Fecal Coliform Enumeration in Foods

2002 ◽  
Vol 68 (4) ◽  
pp. 1631-1638 ◽  
Author(s):  
A. Leclercq ◽  
C. Wanegue ◽  
P. Baylac
Keyword(s):  
Escherichia Coli ◽  
Fecal Coliform ◽  
Food Samples ◽  
Fecal Coliforms ◽  
Predictive Values ◽  
Direct Plating ◽  
Hafnia Alvei ◽  
E Coli ◽  
Plating Method ◽  
Mashed Potatoes

ABSTRACT A 24-h direct plating method for fecal coliform enumeration with a resuscitation step (preincubation for 2 h at 37 ± 1°C and transfer to 44 ± 1°C for 22 h) using fecal coliform agar (FCA) was compared with the 24-h standardized violet red bile lactose agar (VRBL) method. FCA and VRBL have equivalent specificities and sensitivities, except for lactose-positive non-fecal coliforms such as Hafnia alvei, which could form typical colonies on FCA and VRBL. Recovery of cold-stressed Escherichia coli in mashed potatoes on FCA was about 1 log unit lower than that with VRBL. When the FCA method was compared with standard VRBL for enumeration of fecal coliforms, based on counting carried out on 170 different food samples, results were not significantly different (P > 0.05). Based on 203 typical identified colonies selected as found on VRBL and FCA, the latter medium appears to allow the enumeration of more true fecal coliforms and has higher performance in certain ways (specificity, sensitivity, and negative and positive predictive values) than VRBL. Most colonies clearly identified on both media were E. coli and H. alvei, a non-fecal coliform. Therefore, the replacement of fecal coliform enumeration by E. coli enumeration to estimate food sanitary quality should be recommended.

scholarly journals Detection of AmpC β-lactamases in Escherichia coli using different screening agars

2019 ◽  
Author(s):  
Evert den Drijver ◽  
Jaco J. Verweij ◽  
Carlo Verhulst ◽  
Joke Soer ◽  
Kees Veldman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Confidence Interval ◽  
Sensitivity And Specificity ◽  
False Positive ◽  
E Coli ◽  
Specificity And Sensitivity ◽  
Positive Results

AbstractThe aim of this study was to determine the performance of both cefotaxime and ceftazidime containing agars on the specificity and sensitivity for chromosomal AmpC-hyperproducing and plasmid AmpC harboring Escherichia coli compared to ESBL-producing E. coli and E. coli without ESBL, pAmpC or cAmpC hyperproduction. Second, we evaluated the influence of adding cefoxitin to these agars for detection of both chromosomal AmpC-hyperproducing and plasmid AmpC harboring E. coli.Four different homemade screening agars with cefotaxime (1mg/L), ceftazidime (1mg/L), cefotaxime (1mg/L) with cefoxitin (8mg/L), and ceftazidime (1mg/L) with cefoxitin (8mg/L) were compared to each other for the identification of AmpC producing E. coli. A total of 40 isolates with plasmid encoded AmpC β-lactamases, 40 isolates with alterations in the promoter/attenuator region of the AmpC gene leading to hyperproduction of the β-lactamase, 40 isolates with ESBL genes and 39 isolates lacking both a AmpC and ESBL genotype were used to test the four agars.The sensitivity and specificity were 100% (95% confidence interval (95% CI) 96.1% to 100%) and 48.1% (95% CI 38.6%-60.2%), respectively, for the cefotaxime agar; 100% (95% CI 96.1% to 100%) and 49.41% (95% CI 39.8%-61.4%), respectively, for the ceftazidime agar; 96.3% (95% CI 89.1% to 99.2%) and 77.2% (95% CI 66.7%-85.2%) respectively, for the cefotaxime with cefoxitin agar; 98.8% (95% CI) 92.6% to 99.6%) and 81.0% (95% CI 70.9%-88.3%) respectively, for the ceftazidime agar with cefoxitin. The main reason for false-positive results were ESBL-harboring strains that grew on various agars; therefore, the specificity of each agar reported here was influenced mainly by the proportion of ESBL isolates tested. In conclusion addition of cefoxitin to cefotaxime and ceftazidime containing agars had little influence on sensitivity, but increased specificity for the detection of AmpC in E. coli.

Comparison and Recovery of Escherichia coli and Thermotolerant Coliforms in Water with a Chromogenic Medium Incubated at 41 and 44.5°C

1999 ◽  
Vol 65 (8) ◽  
pp. 3746-3749 ◽  
Author(s):  
Jose L. Alonso ◽  
Adela Soriano ◽  
Oscar Carbajo ◽  
Inmaculada Amoros ◽  
Hemda Garelick
Keyword(s):  
Escherichia Coli ◽  
Membrane Filtration ◽  
Incubation Temperature ◽  
Lauryl Sulfate ◽  
Marine Waters ◽  
Sodium Pyruvate ◽  
Chromogenic Medium ◽  
E Coli ◽  
Thermotolerant Coliforms ◽  
Incubation Temperatures

ABSTRACT This study compared the performance of a commercial chromogenic medium, CHROMagarECC (CECC), and CECC supplemented with sodium pyruvate (CECCP) with the membrane filtration lauryl sulfate-based medium (mLSA) for enumeration of Escherichia coli and non-E. coli thermotolerant coliforms (KEC). To establish that we could recover the maximum KEC and E. coli population, we compared two incubation temperature regimens, 41 and 44.5°C. Statistical analysis by the Fisher test of data did not demonstrate any statistically significant differences (P = 0.05) in the enumeration of E. coli for the different media (CECC and CECCP) and incubation temperatures. Variance analysis of data performed on KEC counts showed significant differences (P = 0.01) between KEC counts at 41 and 44.5°C on both CECC and CECCP. Analysis of variance demonstrated statistically significant differences (P = 0.05) in the enumeration of total thermotolerant coliforms (TTCs) on CECC and CECCP compared with mLSA. Target colonies were confirmed to be E. coli at a rate of 91.5% and KEC of likely fecal origin at a rate of 77.4% when using CECCP incubated at 41°C. The results of this study showed that CECCP agar incubated at 41°C is efficient for the simultaneous enumeration of E. coli and KEC from river and marine waters.

Incidence of Fecal Coliforms and Serovars of Enteropathogenic Escherichia Coli in Naturally Contaminated Cheese

1988 ◽  
Vol 51 (5) ◽  
pp. 384-385 ◽  
Author(s):  
F. M. ABBAR
Keyword(s):  
Escherichia Coli ◽  
Fecal Coliform ◽  
Fecal Coliforms ◽  
Enteropathogenic Escherichia Coli ◽  
E Coli

A survey of 60 cheese samples from three different manufacturers and marketed in Mosul were analyzed during the summer of 1987 for fecal coliform counts and also for the presence of enteropathogenic Escherichia coli. Among these samples there was a wide variations in counts, which ranged from <10 to 26000/g while the average ranged from 500 to 14000/g. Only 43 E. coli isolates were recovered from the cheese. Four of them agglutinated with antisera used to screen for classical enteropathogenic sero types.

Characterization of O157:H7 and Other Escherichia coli Isolates Recovered from Cattle Hides, Feces, and Carcasses†

2004 ◽  
Vol 67 (5) ◽  
pp. 993-998 ◽  
Author(s):  
GENEVIEVE A. BARKOCY-GALLAGHER ◽  
TERRANCE M. ARTHUR ◽  
MILDRED RIVERA-BETANCOURT ◽  
XIANGWU NOU ◽  
STEVEN D. SHACKELFORD ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Seasonal Variations ◽  
False Positive ◽  
Significant Trend ◽  
Escherichia Coli O157 ◽  
Seasonal Prevalence ◽  
E Coli ◽  
Beef Processing ◽  
Positive Results

In a previous study, the seasonal prevalence was reported for stx+ Escherichia coli O157:H7 in feces and on hides and carcasses of cattle at processing. Overall, 1,697 O157:H7 isolates have now been characterized for the incidence of (i) eaeO157, hlyA, stx1, and stx2 in the recovered isolates and (ii) presumptive rough and presumptive nonmotile isolates. Seven O157:H7 isolates (0.4%) lacked stx genes, although they carried eae and hlyA. All but one of the isolates carried both eae and hlyA. Approximately two-thirds of the isolates (64% when one isolate per sample was considered) carried both stx1 and stx2. E. coli O157:H7 cells that harbored both stx1 and stx2 were more often recovered from hides in the fall (79% of the fall hide isolates) and winter (84% of the winter hide isolates) than in the spring (53%) and summer (59%). Isolates recovered from preevisceration carcasses showed a similar but not statistically significant trend. Twenty-three of the 25 O157:H7 isolates carrying stx1 but not stx2 were recovered during summer. Fifteen presumptive rough and 117 presumptive nonmotile stx+ O157:H7 isolates were recovered. Ten (67%) of the presumptive rough isolates were recovered during summer. Ninety-five of the presumptive nonmotile isolates (81%) were recovered during fall. Forty-eight percent of the false-positive isolates (175 of 363) tentatively identified as O157:H7 were O157+ H7− and lacked eaeO157, hlyA, and stx. These data suggest that in beef processing samples (i) there are minor seasonal variations in the prevalence of stx genes among E. coli O157:H7 isolates, (ii) presumptive rough and presumptive nonmotile stx+ O157:H7 isolates are present, (iii) E. coli O157:H7 isolates lacking stx genes may be rare, and (iv) O157+ H7− isolates lacking stx genes can result in many false-positive results.

Seasonal Variation in the Fecal Coliform Population of Louisiana Oysters and its Relationship to Microbiological Quality

1987 ◽  
Vol 50 (7) ◽  
pp. 545-549 ◽  
Author(s):  
DIANE PAILLE ◽  
CAMERON HACKNEY ◽  
LAWERENCE REILY ◽  
MARY COLE ◽  
MARILYN KILGEN
Keyword(s):  
Escherichia Coli ◽  
Seasonal Variation ◽  
Antimicrobial Agent ◽  
Significant Relationship ◽  
Fecal Coliform ◽  
Microbiological Quality ◽  
Fecal Coliforms ◽  
Sewage Pollution ◽  
Klebsiella Species ◽  
E Coli

Seasonal variation was observed in the type of bacteria which comprised the fecal coliform population of oysters. Escherichia coli was the principal fecal coliform when water temperatures were below 22°C. Conversely, Klebsiella sp. predominated during the summer months. No significant relationship was observed between levels of E. coli and enterococci and non-E. coli fecal coliforms in oysters. Fecal coliform and E. coli levels were significantly (p >0.001) related in water. Klebsiella sp. isolated from oysters demonstrated considerably less multiple antimicrobial agent resistance than clinical isolates of K. pneumoniae. Fecal coliform-positive Klebsiella species had characteristics of environmental organisms. Results of this study suggest that high levels of non-E coli fecal coliforms in oysters harvested in the summer from beds meeting the fecal coliform water standard are not indicative of sewage pollution. Furthermore, it is suggested that the safety indicator in the guideline for oyster meats should be changed form fecal coliforms to E. coli.

Recovery of Fecal Coliforms and of Escherichia coli at 44.5, 45.0 and 45.5°C

1983 ◽  
Vol 46 (3) ◽  
pp. 172-177 ◽  
Author(s):  
K. F. WEISS ◽  
N. CHOPRA ◽  
P. STOTLAND ◽  
G. W. RIEDEL ◽  
S. MALCOLM
Keyword(s):  
Escherichia Coli ◽  
Incubation Time ◽  
Gas Production ◽  
False Positives ◽  
The Other ◽  
Fecal Coliforms ◽  
False Negatives ◽  
E Coli ◽  
Incubation Temperatures ◽  
Valid Criterion

Recovery rates of fecal coliforms and of Escherichia coli were determined at 44.5, 45.0 and 45.5°C in raw milk, ground meat and raw sewage. MPN values based on gas production (Standard MPNs) and on gas production and/or growth only (Total MPNs) were calculated for both fecal coliforms and for E. coli. The expected trend towards lower MPN values with increasing incubation temperature was more pronounced for the Standard MPNs than for the Total MPNs. The temperature effect was also strongly product - specific in that the Total and Standard MPNs for the fecal coliforms and the Standard MPNs for E. coli for sewage only differed significantly from one another within each determination at the three different incubation temperatures. The effect of length of incubation time on the ratios of E. coli to fecal coliforms was most pronounced at 45.5°C. Product specificity was again observed. The greatest increase in the recovery rate of aerogenic E. coli between 24 and 48 h of incubation time occurred in sewage (66%). For meat, the increase was 57% and for milk 46%. In terms of combined (aerogenic and anaerogenic) E. coli (expressed as Total MPNs), the increases were considerably less, but highest for the meat (33%), followed by sewage (29%) and by milk (21%). A breakdown of the E. coli isolates recovered from both gas-positive and gas-negative primary (fecal coliform) EC broth tubes showed that for the three products combined there were eight times as many false-positives at 44.5°C as at the other two incubation temperatures. In contrast, there were 12% false-negatives at 45.5°C compared to 3% at 45.0°C and 2% at 44.5°C. Since the high incidence of false-negatives (loss of E. coil) at 45.5°C is not counter-balanced by an enhanced specificity (fewer false-positives) over 45.0°C, the latter temperature is to be preferred. Meat yielded the lowest rate for false-positives at any of the three incubation temperatures. In contrast, at 45.5°C, it gave 21% false-negatives compared to only 9% for sewage and 10% for milk. On the other hand, milk contributed the most false-positives at 44.5°C (20%), compared to only 1% for meat and 3% for sewage. A potential loss of 21% of E. coli - containing EC broth tubes is hardly tolerable, reinforcing the contention that gas formation at evaluated temperatures is not a valid criterion of fecal origin.

An Improved Membrane Filtration Method for Enumeration of Faecal Coliforms and E. Coli by a Fluorogenic β-Glucuronidase Assay

1993 ◽  
Vol 27 (3-4) ◽  
pp. 267-270 ◽  
Author(s):  
M. T. Augoustinos ◽  
N. A. Grabow ◽  
B. Genthe ◽  
R. Kfir
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
Membrane Filtration ◽  
Faecal Coliforms ◽  
Environmental Waters ◽  
Filtration Method ◽  
E Coli ◽  
Wide Range ◽  
Pure Cultures ◽  
Glucuronidase Assay

A fluorogenic β-glucuronidase assay comprising membrane filtration followed by selective enumeration on m-FC agar at 44.5°C and further confirmation using tlie 4-metliylumbelliferyl-β-D-glucuronide (MUG) containing medium was evaluated for the detection of Escherichia coli in water. A total of 200 typical blue and non-typical blue colonies were isolated from sea and fresh water samples using initial selective enumeration on m-FC agar. Pure cultures of the selected colonies were further tested using the MUG assay and identified using the API 20E method. Of the colonies tested which were shown to be positive using the MUG assay 99.4% were Escherichia coli. The results of this study indicate the combination of the m-FC method followed by the MUG assay to be highly efficient for the selection and confirmation of E. coli from a wide range of environmental waters.

Microbiological performance and salmonella dynamics in a wastewater depuration pond system of southeastern spain

1995 ◽  
Vol 31 (12) ◽  
pp. 239-248 ◽  
Author(s):  
Ana Emparanza-Knörr ◽  
Francisco Torrella
Keyword(s):  
Fecal Coliform ◽  
No Reduction ◽  
Agar Medium ◽  
Microbiological Quality ◽  
Total Coliform ◽  
Fecal Coliforms ◽  
Selective Media ◽  
E Coli ◽  
The Village ◽  
Final Effluent

The Salmonella presence and the microbiological quality indicators, total and fecal coliforms and coliphages of E. coli C, have been studied in a overloaded wastewater lagoon system treating urban wastewatrers of the village of Guardamar del Segura (Alicante, Spain). Classical microbiological technology to detect salmonellae was used, including pre-enrichment, enrichment, selective media plating and biochemical and serological confirmation. Water was physicochemically characterized according to COD, SS, temperature, pH and dissolved oxygen. The selective migration step through Rappaport-Vassiliadis semisolid agar medium was essential for the consistent detection of Salmonella in the different lagoon effluents. Total and fecal coliform levels of up to 105-106 MPN/100 ml were detected in the final effluent. High coliphage concentrations of 103-104 pfu/ml were also found in the effluent waters. Salmonella was always detected in 100 ml samples and eventually reached an order of value of 103 MPN/100 ml. Total coliform reduction was higher in the anaerobic ponds whereas fecal coliforms were more efficiently eliminated in the facultative (mostly “anoxic”) lagoons. Coliphage reduction was higher in the facultative lagoons when compared to the anaerobic ponds. On many occasions, no reduction or eventual increment of the concentration of salmonellae was detected in the effluents from the anaerobic ponds compared to concentrations of the patohogen in the influent raw wasterwaters. The possibility exists for a capacity of Salmonella to multiply in the anoxic phase of the wastewater treatment, but the presence of microorganisms in raw sewage waters which could maskSalmonella detection with the enrichment methodology employed cannot be ruled out.

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