Comparison of Legiolert and a Conventional Culture Method for Detection of Legionella pneumophila from Cooling Towers in Québec

2019 ◽  
Vol 102 (4) ◽  
pp. 1235-1240 ◽  
Author(s):  
Isabelle Barrette
Keyword(s):  
Legionella Pneumophila ◽  
Cooling Tower ◽  
Test Procedure ◽  
Agar Plate ◽  
Culture Method ◽  
Most Probable Number ◽  
Cooling Towers ◽  
Plate Method ◽  
Probable Number ◽  
Compliance Testing

Abstract Background: Legionnaires’ disease is a potentially lethal pneumonia contracted through inhalation of aerosolized water contaminated with Legionella bacteria. Detection and control of L. pneumophila, the primary species responsible for the disease, is critical to public health. In Québec, cooling towers and evaporative condensers are required to follow a maintenance and testing program to ensure L. pneumophila concentrations remain at acceptable levels. Objective: This study compared a new culture method based on the most probable number approach, Legiolert®, with the formal culture method used at EnvironeX for regulatory compliance testing to quantify L. pneumophila from cooling tower waters in Québec. Methods: A split-sample analysis was performed in which 401 samples from cooling towers in Québec were tested with both methods. Results: Results with 74 positive samples showed that Legiolert provided a significant increase in sensitivity for L. pneumophila compared with the agar plate method. Cooling tower samples often contain non-Legionella flora that necessitate multiple treatment and plating conditions to prevent interference with the test. Legiolert showed little to no impact from non-Legionella organisms in this study. Conclusions: Overall, Legiolert showed several advantages over the agar plate method, including increased sensitivity, reduced interference, a simplified test procedure, and an easy-to-read positive signal.

scholarly journals Confirming the Presence of Legionella pneumophila in Your Water System: A Review of Current Legionella Testing Methods

2021 ◽  
Author(s):  
James T Walker ◽  
Paul McDermott
Keyword(s):  
Legionella Pneumophila ◽  
Water System ◽  
Culture Method ◽  
Immunomagnetic Separation ◽  
Most Probable Number ◽  
Water Safety ◽  
Probable Number ◽  
Culture Independent ◽  
Multiple Species ◽  
Risk Managers

Abstract Legionnaires’ disease has been recognized since 1976 and Legionella pneumophila, still accounts for more than 95% of cases. Approaches in countries, including France, suggest that focusing risk reduction specifically on L. pneumophila is an effective strategy, as detecting L. pneumophila has advantages over targeting multiple species of Legionella. In terms of assays, the historically accepted plate culture method takes 10 days for confirmed Legionella spp. results, has variabilities which affect trending and comparisons, requires highly trained personnel to identify colonies on a plate in specialist laboratories and does not recover viable-but-non-culturable (VBNC) bacteria. Polymerase chain reaction is sensitive, specific and provides results in less than 24 h and determines the presence/absence of Legionella spp. and/or L. pneumophila DNA. Whilst specialist personnel and laboratories are generally required, there are now on-site PCR options but there is no agreement on comparing genomic units to colony forming units and action limits. Immunomagnetic separation assays are culture-independent, detect multiple Legionella species and results are available in 24 h, with automated processing options. Field-use lateral flow devices provide presence/absence determination of L. pneumophila serogroup 1 where sufficient cells are present, but testing potable waters is problematic. Liquid culture most probable number (MPN) assays provide confirmed L. pneumophila results in 7 days that are equivalent to or exceed plate culture, are robust and reproducible and can be performed in a variety of laboratory settings. MPN isolates can be obtained for epidemiological investigations. This accessible, non-technical review will be of particular interest to building owners, operators, risk managers and water safety groups to make informed decisions to reduce the risk of L. pneumophila.

RAPID EVALUATION OF VIABLE CELL COUNTS BY USING THE MICROTITER SYSTEM AND MPN TECHNIQUE

1969 ◽  
Vol 32 (10) ◽  
pp. 408-409 ◽  
Author(s):  
Daniel Y. C. Fung ◽  
Allen A. Kraft
Keyword(s):  
Cell Concentration ◽  
Agar Plate ◽  
Viable Cell ◽  
Most Probable Number ◽  
Plate Method ◽  
Probable Number ◽  
Bacterial Cultures ◽  
Cell Counts ◽  
Time Space ◽  
Wide Range

A rapid procedure was developed for estimating viable cell counts in bacterial cultures by combining the Microtiter system and Most Probable Number technique. The correlation coefficient of the data between this method and the agar plate method was statistically significant at the 1% level. The advantage of this Microtiter-MPN procedure are savings of time, space, and material. Since the method covers a wide range of dilutions, estimates of cell concentration for proper dilutions are not needed in advance of enumeration procedures. Data are obtainable as early as 6 hr after samples are placed in incubation.

The Occurrence of Legionella Bacteria in Cooling Towers in South Africa

1991 ◽  
Vol 24 (2) ◽  
pp. 149-152 ◽  
Author(s):  
N. A. Grabow ◽  
E. J. Pienaar ◽  
R. Kfir
Keyword(s):  
South Africa ◽  
Most Probable Number ◽  
Cooling Towers ◽  
Probable Number ◽  
Service Water ◽  
Standard Plate ◽  
Viable Bacteria ◽  
Plate Counts ◽  
High Level ◽  
Biocide Treatment

A total of 510 service water samples from cooling towers throughout South Africa were analysed for the presence of Legionella bacteria. Legionella was detected using an immuno-labelling technique based on the most probable number principle. Only cultural (viable) bacteria were counted. Legionellae were found in most of the samples tested. However, in only 4% of the samples a high level of legionellae was recorded. No correlation was found between the numbers of legionellae and those of standard plate counts. Biocide treatment was shown to be effective in the removal of the bacteria from cooling towers after a 3-month treatment period.

Colony-Forming Unit Enumeration by a Plate-MPN Method

1983 ◽  
Vol 46 (10) ◽  
pp. 836-841 ◽  
Author(s):  
S-T. TAN ◽  
R. B. MAXCY ◽  
W. W. STROUP
Keyword(s):  
Standard Technique ◽  
Most Probable Number ◽  
Plate Method ◽  
Probable Number ◽  
Microbial Counts ◽  
Colony Forming Unit ◽  
Pure Cultures ◽  
Petri Plate ◽  
Mpn Test ◽  
Surface Plate

Concepts of the standard surface plate method and the most probable number method (MPN) were combined to provide a new enumeration technique (plate-MPN). Three discrete 0.01-ml samples of an appropriate decimal dilution were inoculated onto each quadrant of a pre-dried petri plate. The discrete spots from the inoculum were then observed for growth after incubation. Results were interpreted analogous to a 3-tube MPN test using presently available tables. Application of the test to pure cultures and mixed flora provided no evidence to indicate the plate-MPN technique to be any less accurate than the standard technique for microbial counts. The plate-MPN technique was less precise than the standard technique. However, the plate-MPN technique has many advantages over traditional methods.

scholarly journals Integrated Real-Time PCR for Detection and Monitoring of Legionella pneumophila in Water Systems

2006 ◽  
Vol 73 (5) ◽  
pp. 1452-1456 ◽  
Author(s):  
Diaraf Farba Yaradou ◽  
Sylvie Hallier-Soulier ◽  
Sophie Moreau ◽  
Florence Poty ◽  
Yves Hillion ◽  
...  
Keyword(s):  
Real Time ◽  
Legionella Pneumophila ◽  
Cooling Tower ◽  
Water System ◽  
Culture Method ◽  
Hot Water ◽  
Pcr Assay ◽  
Standard Culture ◽  
Serial Samples ◽  
Over Time

ABSTRACT We evaluated a ready-to-use real-time quantitative Legionella pneumophila PCR assay system by testing 136 hot-water-system samples collected from 55 sites as well as 49 cooling tower samples collected from 20 different sites, in parallel with the standard culture method. The PCR assay was reproducible and suitable for routine quantification of L. pneumophila. An acceptable correlation between PCR and culture results was obtained for sanitary hot-water samples but not for cooling tower samples. We also monitored the same L. pneumophila-contaminated cooling tower for 13 months by analyzing 104 serial samples. The culture and PCR results were extremely variable over time, but the curves were similar. The differences between the PCR and culture results did not change over time and were not affected by regular biocide treatment. This ready-to-use PCR assay for L. pneumophila quantification could permit more timely disinfection of cooling towers.

Effect of Trisodium Phosphate on Campylobacter Attached to Post-Chill Chicken Carcasses

1994 ◽  
Vol 57 (4) ◽  
pp. 324-326 ◽  
Author(s):  
MICHAEL F. SLAVIK ◽  
JEONG-WEON KIM ◽  
MICHAEL D. PHARR ◽  
DENNIS P. RABEN ◽  
SONIA TSAI ◽  
...  
Keyword(s):  
Culture Method ◽  
Trisodium Phosphate ◽  
Most Probable Number ◽  
Log P ◽  
Probable Number ◽  
Conventional Culture ◽  
And Control ◽  
Conventional Culture Method

Trisodium phosphate (TSP) was evaluated as a means to reduce Campylobacter on chicken carcasses. Post-chill chicken carcasses were dipped into a 10% TSP solution at 50°C for 15 s. After storing the TSP-treated carcasses for 0, 1 or 6 days at 4°C, the carcasses were subjected to the recovery of Campylobacter. The incidence and reduction of Campylobacter attached to the carcasses were measured using a nitrocellulose (NC) membrane lift, conventional culture method, and a most probable number (MPN) technique. In trials 1 and 2, the incidence of Campylobacter was measured. For 1 day-stored groups, Campylobacter was present on 96 and 100% of control carcasses and present on 24 and 28% of TSP-treated carcasses as measured by NC membrane lift method. The reduction was less (4 to 36%) when measured by culture method. For carcasses immediately subjected for the recovery of cells after treatment, there was no difference between TSP-treated and control carcasses by either NC membrane or culture method. In trial 3, the reduction levels of Campylobacter were quantified by using a MPN method. The levels of Campylobacter on carcasses were decreased by 1.5 and 1.2 logs in 1- and 6-day stored, TSP-treated carcasses, respectively (p < 0.05). However, TSP treatment at 10°C reduced the level of Campylobacter only by 0.16 log (p > 0.10).

scholarly journals Bacteria and protozoa populations in groundwater in landfill area in São Carlos, SP

1999 ◽  
Vol 30 (3) ◽  
pp. 196-202 ◽  
Author(s):  
Roberta Fusconi ◽  
Mirna Januária Leal Godinho
Keyword(s):  
Heterotrophic Bacteria ◽  
Mean Value ◽  
Microbial Populations ◽  
Most Probable Number ◽  
Plate Method ◽  
Probable Number ◽  
Mean Values ◽  
The Mean ◽  
The Town ◽  
Microaerophilic Conditions

The microbial populations of groundwaters were analyzed in a region under the influence of a landfill (piezometer L12) in the town of São Carlos, São Paulo, Brazil, and in an area not influenced by the landfill (piezometer L5). Heterotrophic bacteria were counted by spread plate method and the number of protozoa was estimated by the most probable number method. There was a larger number of organisms in well L12, with a mean value of 15.76 x 104 CFU/ml for bacteria and 9.7 MPN/ml for protozoa, whereas the mean values for piezometer L5 were 2.88 x 104 CFU/ml for bacteria and 3.4 MPN/ml for protozoa. The greater abundance detected in piezometer L12 may be related to the influence of the leachate through the landfill on the microbial populations, also demonstrated by deoxygenation and by the high conductivity values (3530 µS/cm) compared to piezometer L5 (2.47 mg/L dissolved oxygen and 42 µS/cm conductivity). The most commonly detected protozoa were amoebae and flagellates. The density of flagellate protozoa determined under microaerophilic conditions was 10 times higher than that determined under aerobic conditions.

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.

Prevalence of Salmonella in Cashews, Hazelnuts, Macadamia Nuts, Pecans, Pine Nuts, and Walnuts in the United States

2017 ◽  
Vol 80 (3) ◽  
pp. 459-466 ◽  
Author(s):  
Guodong Zhang ◽  
Lijun Hu ◽  
David Melka ◽  
Hua Wang ◽  
Anna Laasri ◽  
...  
Keyword(s):  
United States ◽  
Culture Method ◽  
The United States ◽  
Most Probable Number ◽  
Contamination Level ◽  
Probable Number ◽  
Tree Nuts ◽  
Prevalence Estimates ◽  
Macadamia Nuts ◽  
Small Chain

ABSTRACT Nuts have been identified as a vector for salmonellosis. The objective of this project was to estimate the prevalence and contamination level of Salmonella in raw tree nuts (cashews, pecans, hazelnuts, macadamia nuts, pine nuts, and walnuts) at retail markets in the United States. A total of 3,656 samples of six types of tree nuts were collected from different types of retail stores and markets nationwide between October 2014 and October 2015. These samples were analyzed using a modified version of the Salmonella culture method from the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Of the 3,656 samples collected and tested, 32 were culturally confirmed as containing Salmonella. These isolates represented 25 serotypes. Salmonella was not detected in pecans and in-shell hazelnuts. Salmonella prevalence estimates (and 95% confidence intervals) in cashews, shelled hazelnuts, pine nuts, walnuts, and macadamia nuts were 0.55% [0.15, 1.40], 0.35% [0.04, 1.20], 0.48% [0.10, 1.40], 1.20% [0.53, 2.40], and 4.20% [2.40, 6.90], respectively. The rates of Salmonella isolation from major or big chain supermarkets, small chain supermarkets, discount, variety, or drug stores, and online were 0.64% [0.38, 1.00], 1.60% [0.80, 2.90], 0.00% [0.00, 2.40], and 13.64% [2.90, 35.00], respectively (Cochran-Mantel-Haenszel test: P = 0.02). The rates of Salmonella isolation for conventional and organic nuts were not significantly different. Of the samples containing Salmonella, 60.7% had levels less than 0.003 most probable number (MPN)/g. The highest contamination level observed was 0.092 MPN/g. The prevalence and levels of Salmonella in these tree nut samples were comparable to those previously reported for similar foods.

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