scholarly journals Evaluation of a most probable number method for the enumeration of Legionella pneumophila from North American potable and nonpotable water samples

2017 ◽  
Vol 16 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Ray Petrisek ◽  
Jonathon Hall
Keyword(s):  
Legionella Pneumophila ◽  
Water Samples ◽  
Potable Water ◽  
High Specificity ◽  
Most Probable Number ◽  
Water Type ◽  
Probable Number ◽  
Standard Methods ◽  
Water And Wastewater ◽  
Higher Sensitivity

Abstract This study compares the performance of a novel most probable number (MPN) method (Legiolert™/Quanti-Tray®) with Standard Methods for the Examination of Water and Wastewater 9260 J for the enumeration of Legionella pneumophila from potable and nonpotable waters. Data from the study showed that Legiolert exhibited higher sensitivity for the detection of L. pneumophila for potable water and equivalent sensitivity for nonpotable water. The Legiolert medium had a high specificity with no false positive signals reported for either water type. The new method represents a significant improvement in usability and accuracy in the enumeration of L. pneumophila.

scholarly journals Comparison of two culture methods for the enumeration of Legionella pneumophila from potable water samples

2021 ◽  
Author(s):  
Laura A. Boczek ◽  
Min Tang ◽  
Casey Formal ◽  
Darren Lytle ◽  
Hodon Ryu
Keyword(s):  
Legionella Pneumophila ◽  
Water Samples ◽  
Potable Water ◽  
High Sensitivity ◽  
High Specificity ◽  
The United States ◽  
Contaminated Water ◽  
Plumbing System ◽  
Culture Methods ◽  
False Negatives

Abstract Legionella infections have steadily increased in the United States over the last 20 years, and most of these infections have been attributed to contaminated water. The gold standard for confirmation of Legionella presence in water is culturing with Buffered Charcoal Yeast Extract (BCYE) agar. Following many modifications, this method is still time-consuming, expensive, and can take longer than 10 days for full confirmation. The Legiolert is a newer and simpler culture product that is claimed to be able to quantify Legionella pneumophila in 7 days with high sensitivity and specificity and does not need further confirmation for the presence of L. pneumophila. This study compared the culturability of L. pneumophila occurring in a simulated home plumbing system using both Legiolert and BCYE agar methods. Out of 185 water samples, Legiolert and BCYE method detected L. pneumophila in 83 and 85% of the samples, respectively. The two methods were determined to be statistically equivalent for culturability of L. pneumophila, though the detected levels by Legiolert were slightly higher than the BCYE method. The molecular confirmation of positive (n = 254) and negative wells (n = 82) with Legiolert also showed a high specificity of 96.5% (i.e., 3.5% false positives (9/254) and 0% false negatives (0/82)).

Defined Substrate Technology Method for Rapid and Specific Simultaneous Enumerationof Total Coliforms and Escherichia coli from Water: Collaborative Study

1991 ◽  
Vol 74 (3) ◽  
pp. 526-529 ◽  
Author(s):  
Stephen C Edberg ◽  
Martin J Allen ◽  
Darrell B Smith
Keyword(s):  
Water Samples ◽  
Collaborative Study ◽  
Field Evaluation ◽  
Subsurface Water ◽  
Most Probable Number ◽  
Probable Number ◽  
Standard Methods ◽  
Total Coliforms ◽  
Wide Range ◽  
Repeatability And Reproducibility

Abstract The defined substrate technology (DST) method Is a reagent system designed to enumerate specific target microbes(s) from a mixture of bacteria. The system simultaneously enumerates total coliforms and Escherichia coll directly from a water sample. The reagent contains o-nitrophenyl-β-D-galactopyranoside (ONPG), which is hydrolyzed by total conforms to produce a yellow chromogen, and 4-methylumbelllferyl-β-D-glucuronide (MUG), which is hydrolyzed and fluoresces when E. coll organisms grow. Noncoliform bacteria are suppressed and cannot metabolize the indicator nutrients. Nine laboratories participated in a field evaluation of the method, which covered a wide range of surface and subsurface water sources and water-processing modalities, including the examination of natural samples. The DST system was compared to multiple-tube fermentation (MTF) (quantitative) and presence-absence (P-A) (qualitative) Standard Methods formats. Comparison of water samples from natural sources by using the most probable number (MPN) procedure showed that the DST test was equivalent to the currently used MTF test. Results from the DST and the qualitative P-A procedure showed that these tests agreed with each other in 94% of the water samples analyzed. Specificity of the DST method was established by subculturing a species consistent with a total conform or E. coll from each positive tube. Eight laboratories participated in a collaborative study of the method. Each laboratory received 3 concentrations of E. coll (organisms/100 mL): 10 (low); 60 (medium); and 120 (high). The DST test was inoculated from a split sample of each bacterial density In parallel with Standard Methods brilliant green lactose broth. Statistical analyses for repeatability and reproducibility showed the DST system to be equivalent to currently used standard methods. The DST method has been adopted official first action by AOAC for detection and enumeration of total coliforms and E. coll in water.

scholarly journals Fermentation tube test statistics for direct water sampling and comments on the Thomas formula

2010 ◽  
Vol 8 (3) ◽  
pp. 431-437
Author(s):  
M. Nawalany ◽  
M. Loga
Keyword(s):  
Natural Waters ◽  
General Procedure ◽  
A Priori ◽  
Most Probable Number ◽  
Water Sampling ◽  
Probable Number ◽  
Standard Methods ◽  
Tube Test ◽  
Water And Wastewater ◽  
New Interpretation

This article describes a new interpretation of the Fermentation Tube Test (FTT) performed on water samples drawn from natural waters polluted by faecal bacteria. A novel general procedure to calculate the Most Probable Number of bacteria (MPN) in natural waters has been derived for the FTT for both direct and independent repetitive multiple water sampling. The generalization based on solving the newly proposed equation allows consideration of any a priori frequency distribution g(n) of bacterial concentration in analysed water as opposed to the unbounded uniform a priori distribution g(n) assumed in the standard procedures of the Standard Methods of Examining Water and Wastewater and ISO 8199:1988. Also a statistical analysis of the Thomas formula is presented. It is demonstrated that the Thomas formula is highly inaccurate. The authors propose, therefore, to remove the Thomas formula from the Standard Methods of Examining Water and Wastewater and ISO 8199:1988 altogether and replace it with a solution of the proposed generalized equation.

A Most Probable Number Method for the Enumeration of Legionella Bacteria in Water

1991 ◽  
Vol 24 (2) ◽  
pp. 143-147 ◽  
Author(s):  
N. A. Grabow ◽  
R. Kfir ◽  
W. O. K. Grabow
Keyword(s):  
Water Samples ◽  
Membrane Filtration ◽  
Quantitative Method ◽  
Fluorescent Antibody ◽  
Most Probable Number ◽  
Probable Number ◽  
Comparative Tests ◽  
Antibody Staining ◽  
Direct Fluorescent Antibody ◽  
Yeast Extract Agar

A new quantitative method for the enumeration of Legionella bacteria in water is described. Appropriate tenfold serial dilutions of water samples concentrated by membrane filtration are plated in triplicate on buffered charcoal yeast extract agar. After incubation for 3 days representative smears from individual plates are tested for the presence of Legionella by direct fluorescent antibody staining. The number of positive plates in each dilution is used to calculate the Legionella count by means of conventional most probable number statistics. In comparative tests on a variety of water samples this method yielded significantly higher counts than previously used procedures.

scholarly journals Quality of water sources in Southwestern Uganda using the compartment bag test (CBT): a cross-sectional descriptive study

2019 ◽  
Vol 9 (4) ◽  
pp. 683-693
Author(s):  
Richard Onyuthi Apecu ◽  
Lucas Ampaire ◽  
Edgar Mugema Mulogo ◽  
Fred Norman Bagenda ◽  
Afsatou Traore ◽  
...  
Keyword(s):  
Water Samples ◽  
Water Sources ◽  
World Health ◽  
Most Probable Number ◽  
Physical Parameters ◽  
Probable Number ◽  
Gravitational Flow ◽  
Quality Of Water ◽  
Compartment Bag Test

Abstract The aim of this study was to assess the bacteriological quality of water sources in the two rural areas of Uganda using the compartment bag test (CBT). In total, 200 water samples were collected from 69 different water sources and processed within 6 h of collection. Positive and negative controls were processed each day together with water samples. Physical parameters were measured in situ. Descriptive statistics were used to generate mean, minimum, maximum, standard deviations and percentages. The results indicated that 29% of the water sources met the National Standards and World Health Organization (WHO) Guidelines for drinking water. Sixty percent of the borehole, 44% of gravitational flow taps and 14% of roof rain water met the required standards. Of the open water sources, 75% of the rivers, 50% of open channels and 43% of unprotected dug wells plus 25% of protected springs and 9% of gravitational flow schemes had most probable number counts >100 Escherichia coli/100 mL of water. Most of the water sources in the study areas were not fit for human consumption without prior treatment. The CBT was found to be robust and easy to use in all field situations. The mean physical parameters of water sources were within the acceptable limits.

scholarly journals Is Drinking Water Sources Safe for Drink? A Multicenter Assessment of Fecal Contamination of Drinking Water Sources in Tigray Region, Ethiopia

2019 ◽  
Author(s):  
Goyitom Gebremedhn ◽  
Abera Aregawi Berhe ◽  
Abraham Aregay Desta ◽  
Lemlem Legesse
Keyword(s):  
Drinking Water ◽  
Water Samples ◽  
Fecal Coliform ◽  
Fecal Contamination ◽  
Water Sources ◽  
Capital City ◽  
Most Probable Number ◽  
Probable Number ◽  
Tigray Region ◽  
Drinking Water Sources

Abstract Background Fecal contamination of drinking water sources is the main cause of diarrhea with estimated incidence of 4.6 billion episodes and 2.2 million deaths every year. Methods A total of 145 water samples of different source type were collected from different areas in Tigray region from August 2018 to January 2019. The water samples from each site were selected purposively which involved sampling of water sources with the highest number of users and functionality status during the study period. Most Probable Number (MPN) protocol was used for the bacteriological analysis of the samples. Results A total of 145 water samples were collected from six zones in Tigray region, Ethiopia from August 2018 to January 2019. The study indicated that 63(43.5%) of the water samples were detected to have fecal coliform which is E.coli. In Mekelle city, which is the capital city of Tigray region, three in five 34(60.7%) of the collected samples were confirmed to have fecal coliform. Water samples from health facilities were 9.48 times [AOR=9.48, 95%CI: (1.59, 56.18)] more likely to have fecal coliform. Water samples from wells were 10.23 times [AOR=10.23, 95%CI: (2.74, 38.26)] more likely to have fecal coliform than water samples from Tap/Pipe. Similarly, water samples from hand pumps were 22.28 times [AOR=22.28, 95%CI: (1.26, 393.7)] more likely to have fecal coliform than water samples from Tap/Pipe. Water samples reported to be not chlorinated were 3.51 times [AOR=3.51, 95%CI: (1.35, 9.13)] more likely to have fecal coliform than water samples from chlorinated sources. Conclusion In this study all water source, including the chlorinated drinking water sources, were found highly contaminated with fecal origin bacteria. This may be mainly due to constructional defects, poor sanitation inspection, poor maintenance, intermittent water supply and irregular chlorination.

Detection of Coliform, faecal Coliform And Total Bacterial Count From Drinking Water Of Varanasi (U.P.) India

2021 ◽  
Vol 27 (2) ◽  
Author(s):  
Alok Kumar Singh ◽  
Anand Prakash Singh ◽  
Sanjay Srivastava
Keyword(s):  
Drinking Water ◽  
Water Samples ◽  
Tap Water ◽  
Bacterial Count ◽  
Most Probable Number ◽  
Total Bacterial Count ◽  
Indicator Organisms ◽  
Cross Sectional ◽  
Probable Number ◽  
Hand Pump

In India source of drinking water at Varanasi city for common people are tap water, well, hand pump, Ganga river and stored tank water collected from bore well. All water samples were studied to assess their bacteriological characteristics and suitability for potable purposes. A cross-sectional epidemiological method was adopted to investigate the drinking water of six different sites of Varanasi city. The bacteriological examination of water samples included the most probable number of presumptive coliforms, faecal coliforms, and total bacterial count. The results showed that the total coliform count was detected in all the site. In all the methods coliforms presence was indicated. Maximum number of coliform observed in all the seasons, were from river and well water followed by hand pump, tap water and stored tank. The most common group of indicator organisms used in water quality monitoring are coliforms. These organisms are representative of bacteria normally present in the intestinal tract of mammals including human. Contamination of water may occur through different way like sewage disposal in the river, seepage of bathing near sites, fecal excreta of human, bird and other animals. Improving and expanding the existing water treatment and sanitation systems are more likely to provide good, safe and sustainable sources of water in the long term.

scholarly journals Performance of Legiolert Test vs. ISO 11731 to Confirm Legionella pneumophila Contamination in Potable Water Samples

Pathogens ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 690 ◽  
Author(s):  
Maria Scaturro ◽  
Matteo Buffoni ◽  
Antonietta Girolamo ◽  
Sandra Cristino ◽  
Luna Girolamini ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Legionella Pneumophila ◽  
Water Samples ◽  
Gold Standard ◽  
Liquid Culture ◽  
Potable Water ◽  
Culture Method ◽  
Alternative Methods ◽  
Significant Difference

Detection and enumeration of Legionella in water samples is of great importance for risk assessment analysis. The plate culture method is the gold standard, but has received several well-known criticisms, which have induced researchers to develop alternative methods. The purpose of this study was to compare Legionella counts obtained by the analysis of potable water samples through the plate culture method and through the IDEXX liquid culture Legiolert method. Legionella plate culture, according to ISO 11731:1998, was performed using 1 L of water. Legiolert was performed using both the 10 mL and 100 mL Legiolert protocols. Overall, 123 potable water samples were analyzed. Thirty-seven (30%) of them, positive for L. pneumophila, serogroups 1 or 2–14 by plate culture, were used for comparison with the Legiolert results. The Legiolert 10 mL test detected 34 positive samples (27.6%) and the Legiolert 100 mL test detected 37 positive samples, 27.6% and 30% respectively, out of the total samples analyzed. No significant difference was found between either the Legiolert 10 mL and Legiolert 100 mL vs. the plate culture (p = 0.9 and p = 0.3, respectively) or between the Legiolert 10 mL and Legiolert 100 mL tests (p = 0.83). This study confirms the reliability of the IDEXX Legiolert test for Legionella pneumophila detection and enumeration, as already shown in similar studies. Like the plate culture method, the Legiolert assay is also suitable for obtaining isolates for typing purposes, relevant for epidemiological investigations.

scholarly journals Isolation and Enumeration of Escherichia coli from Soil and Water

2020 ◽  
Vol 36 (2) ◽  
pp. 75-77
Author(s):  
Anindita Bhowmik ◽  
Sunjukta Ahsan
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
Gas Production ◽  
Soil Samples ◽  
Most Probable Number ◽  
Biochemical Tests ◽  
Probable Number ◽  
E Coli ◽  
Dilution Series

Majority of the population of Bangladesh depend on tap or surface water as their source of water supply. This study was carried out to examine the microbial quality of both water and soil collected from different places using the multiple tube fermentation technique to determine coliform count by the most probable number (MPN) method in brilliant green lactose broth (BGLB) media.Inoculum from positive tubes of the presumptive test were further transferred on eosinemethylene blue (EMB) and MacConkey agar.The organisms isolated were further characterized using biochemical tests. Out of 93 water samples, 30 (32.26%) indicated the presence of lactose fermenter and gas producer in all 3 tubes of dilution series using inoculum quantities of 1.0, 0.1 and 0.01 ml, whereas out of 85 soil samples, 45 (52.94%) showed acid and gas production in all 3 tubes of dilution series.Among 85 soil samples, 40 samples that contained at least one positive in each dilution series and among 93 water samples, 31 samples that contained at least one positive in each dilution series were further re-identified with biochemical tests.This study showed 30.59% soil isolates and 26.88% water isolates were Escherichia coli which highlighted the fact that both water and soil act as a major reservoir of E.coli, which indicates possible fecal contamination as well as presence of potentially pathogenic E. coli. Bangladesh J Microbiol, Volume 36 Number 2 December 2019, pp 75-77

scholarly journals Investigating the presence of enteric bacteria and their antibiotic resistance in drinking water samples of slum households in Port City Chattogram, Bangladesh

2020 ◽  
Author(s):  
Sidratun Nur Chowdhury ◽  
Nazifa Rafa ◽  
Sayed Mohammad Nazim Uddin ◽  
A. K. M. Moniruzzaman Mollah
Keyword(s):  
Water Samples ◽  
Integrated Approach ◽  
Enteric Bacteria ◽  
Fecal Coliforms ◽  
Coliform Bacteria ◽  
Penicillin G ◽  
Most Probable Number ◽  
Port City ◽  
Probable Number ◽  
Unsafe Water

Abstract Globally, unsafe water supplies due to contamination with fecal coliforms are major issues in urban slums. To determine the presence of microbial risk, water samples were collected from three slums in the port city Chattogram and the most probable number (MPN) method was used to test for the presence of fecal coliform. All of the samples tested positive by the MPN test. The highest count was 1,100 MPN/100 mL and the lowest count was 7.2 MPN/100 mL. Water stored in containers was prone to being more contaminated than water collected directly from the source. To understand the antibiotic resistivity of the coliform bacteria isolated from the water samples, antibiotic susceptibility was evaluated using the Kirby-Bauer disc method for six antibiotics. All the bacteria were 100% resistant to penicillin-G and ampicillin, and 91.7% showed resistance to amoxicillin and mecillinam. An integrated approach to water, sanitation, and hygiene education must be undertaken when providing sustainable interventions in slums.

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