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Redwitz J, Streich P, Zamfir M, Walser-Reichenbach SM, Seidel M, Herr CEW, Heinze S, Quartucci C. Verification and application of qPCR and viability-qPCR for Legionella monitoring in evaporative cooling systems complementing the conventional culture method. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 953:176011. [PMID: 39236821 DOI: 10.1016/j.scitotenv.2024.176011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 08/09/2024] [Accepted: 09/01/2024] [Indexed: 09/07/2024]
Abstract
To date, in many countries the only legally valid method for evaporative cooling system (ECS) monitoring is the culture method. However, a duration of up to 14 days and a risk of underestimation of Legionella concentrations are seen as limitations of cultivation methods. Rapid cultivation-independent methods are an important step towards a more practicable monitoring of ECS to quickly control interventions if elevated concentrations of Legionella are found. Two commercial kits for quantitative polymerase chain reaction (qPCR) and viability-qPCR (v-qPCR) were studied, comprising sample filtration and DNA extraction. Cryopreserved Legionella pneumophila were established as calibration standard with intact (ILC) and total Legionella count (TLC) determined by flow cytometry before conducting spiking experiments in commercial mineral water and artificial process water. Final assessment was carried out using real ECS samples. Recovery and robustness ranged from 86 to 108 % for qPCR with a drop to 40-60 % for v-qPCR when compared to direct extraction, possibly attributable to cell damage during sample concentration. All methods including culture did perform well regarding linearity with R2 ≥ 0.95 for most trials. Detected concentrations in comparison to spiked Legionella counts differed with culture averaging 25 ± 7 % of spiked ILC and v-qPCR being closest to spiked concentrations with 65-144 %. In comparison, qPCR was several fold above spiked TLC concentrations. For real ECS samples Legionella spp. were detected in concentrations above 103 GU/100 mL by v-qPCR in 70-92 % of samples, depending on the kit used. Most of these samples were either culture-negative or not evaluable on agar plates. This study showed that a cryopreserved bacterial standard based examination is applicable and can be used for future v-qPCR verification. For assessment of differences in results between culture and v-qPCR/qPCR in ECS samples expert knowledge about the operating mode and used analytical methods is required. Guidelines addressing this issue could be a solution.
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Affiliation(s)
- J Redwitz
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany.
| | - P Streich
- Chair of Analytical Chemistry and Water Chemistry, TUM School of Natural Sciences, Technical University of Munich, Munich, Germany
| | - M Zamfir
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany
| | - S M Walser-Reichenbach
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany
| | - M Seidel
- Chair of Analytical Chemistry and Water Chemistry, TUM School of Natural Sciences, Technical University of Munich, Munich, Germany
| | - C E W Herr
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany; Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
| | - S Heinze
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany; Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
| | - C Quartucci
- Department of Occupational and Environmental Health, Epidemiology, Bavarian Health and Food Safety Authority, Munich, Germany; Institute and Clinic for Occupational, Social and Environmental Medicine, University Hospital, LMU Munich, Munich, Germany
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Corrigan A, Niemaseck B, Moore M, McIlwaine D, Duguay J. Performance evaluation of a low-throughput qPCR-based Legionella assay for utility as an onsite industrial water system monitoring method. J Ind Microbiol Biotechnol 2024; 51:kuae030. [PMID: 39165127 PMCID: PMC11388924 DOI: 10.1093/jimb/kuae030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2024] [Accepted: 08/19/2024] [Indexed: 08/22/2024]
Abstract
Legionella is a bacterial genus found in natural aquatic environments, as well as domestic and industrial water systems. Legionella presents potential human health risks when aerosolized and inhaled by at-risk individuals and is commonly monitored at locations with likelihood of proliferation and human exposure. Legionella monitoring is widely performed using culture-based testing, which faces limitations including turnaround time and interferences. Molecular biology methodologies, including quantitative polymerase chain reaction (qPCR), are being explored to supplement or replace culture-based testing because of faster turnaround and lower detection limits, allowing for more rapid water remediation measures. In this study, three methods were compared by testing industrial water samples: culture-based testing by a certified lab, high throughput qPCR testing (HT qPCR), and field deployable low throughput qPCR testing (LT qPCR). The qPCR test methods reported more positive results than culture testing, indicating improved sensitivity and specificity. The LT qPCR test is portable with quick turnaround times, and can be leveraged for environmental surveillance, process optimization, monitoring, and onsite case investigations. The LT qPCR test had high negative predictive value and would be a useful tool for negative screening of Legionella samples from high-risk environments and/or outbreak investigations to streamline samples for culture testing. ONE-SENTENCE SUMMARY This study compared three test methods for Legionella to evaluate performance of a low throughput quantitative polymerase chain reaction (LT qPCR) test for Legionella that can be used onsite; the study found that the high throughput (HT) and LT qPCR tests used in this study gave more positive results than culture testing, and the results indicated a similar negative predictive value for the HT and LT qPCR tests, supporting that the LT qPCR method could be useful for negative screening of Legionella samples in industrial water systems onsite.
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Affiliation(s)
| | | | | | | | - Jeremy Duguay
- LuminUltra Technologies Ltd., 819 Royal Road, Building B, Fredericton, NB E3G 6M1, Canada
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3
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Grabowska-Grucza K, Kiersztyn B. Relationships between Legionella and Aeromonas spp. and associated lake bacterial communities across seasonal changes in an anthropogenic eutrophication gradient. Sci Rep 2023; 13:17076. [PMID: 37816753 PMCID: PMC10564844 DOI: 10.1038/s41598-023-43234-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 09/21/2023] [Indexed: 10/12/2023] Open
Abstract
Anthropogenic eutrophication of lakes threatens their homeostasis and carries an increased risk of development of potentially pathogenic microorganisms. In this paper we show how eutrophication affects seasonal changes in the taxonomic structure of bacterioplankton and whether these changes are associated with the relative abundance of pathogenic bacteria of the genera Legionella and Aeromonas. The subject of the study was a unique system of interconnected lakes in northern Poland (Great Masurian Lakes system), characterized by the presence of eutrophic gradient. We found that the taxonomic structure of the bacterial community in eutrophic lakes was significantly season dependent. No such significant seasonal changes were observed in meso-eutrophic lakes. We found that there is a specific taxonomic composition of bacteria associated with the occurrence of Legionella spp. The highest positive significant correlations were found for families Pirellulaceae, Mycobacteriaceae and Gemmataceae. The highest negative correlations were found for the families Sporichthyaceae, Flavobacteriaceae, the uncultured families of class Verrucomicrobia and Chitinophagaceae. We used also an Automatic Neural Network model to estimate the relative abundance of Legionella spp. based on the relative abundance of dominant bacterial families. In the case of Aeromonas spp. we did not find a clear relationship with bacterial communities inhabiting lakes of different trophic state. Our research has shown that anthropogenic eutrophication causes significant changes in the taxonomic composition of lake bacteria and contributes to an increase in the proportion of potentially pathogenic Legionella spp.
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Affiliation(s)
- Karolina Grabowska-Grucza
- Institute of Functional Biology and Ecology, Faculty of Biology, University of Warsaw, Żwirki i Wigury 101, 02-089, Warszawa, Poland.
| | - Bartosz Kiersztyn
- Institute of Functional Biology and Ecology, Faculty of Biology, University of Warsaw, Żwirki i Wigury 101, 02-089, Warszawa, Poland
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4
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Sauget M, Richard M, Chassagne S, Hocquet D, Bertrand X, Jeanvoine A. Validation of quantitative real-time PCR for detection of Legionella pneumophila in hospital water networks. J Hosp Infect 2023:S0195-6701(23)00195-0. [PMID: 37353007 DOI: 10.1016/j.jhin.2023.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 06/08/2023] [Accepted: 06/10/2023] [Indexed: 06/25/2023]
Abstract
BACKGROUND Rapid monitoring of Legionella pneumophila (Lp) is essential to reduce the risk of Legionnaires' disease in healthcare facilities. However, culture results take at least eight days, delaying the implementation of corrective measures. Here, we assessed the performance of a qPCR method and determined qPCR action thresholds for the detection of Lp in hospital hot water networks (HWNs). METHODS Hot water samples (n=459) were collected from a hospital HWNs. Lp were quantified using iQ-Check® Quanti real-time PCR Quantification kits (Bio-Rad) and the results were compared with those of culture. qPCR thresholds corresponding to the culture action thresholds of 10 and 1,000 CFU/L were determined on a training dataset and validated on an independent dataset. RESULTS Lp concentrations measured by culture and qPCR were correlated for both the training dataset (Spearman's correlation coefficient ρ = 0.687, p-value < 0.0001) and the validation dataset (ρ = 0.661, p-value < 0.0001). Lp qPCR positivity thresholds corresponding to culture action thresholds of 10 CFU/L was 91 genome units (GU) per liter (sensitivity, 86.4%; negative predictive value - NPV, 93.3%) and that corresponding to culture action thresholds of 1,000 CFU/L was 1,048 GU/L (sensitivity, 100%; NPV, 100%). CONCLUSION Detection of Lp by qPCR could be implemented with confidence in hospitals as a complement to culture in the monitoring strategy to speed up the implementation of corrective measures.
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Affiliation(s)
- Marlène Sauget
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France; Centre de Ressources Biologiques, Centre Hospitalier Universitaire de Besançon, Besançon, France.
| | - Marion Richard
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France; Centre de Ressources Biologiques, Centre Hospitalier Universitaire de Besançon, Besançon, France
| | - Sophie Chassagne
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France
| | - Didier Hocquet
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France; Chrono-environnement, Université de Franche-Comté, CNRS, Besançon, France; Centre de Ressources Biologiques, Centre Hospitalier Universitaire de Besançon, Besançon, France
| | - Xavier Bertrand
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France; Chrono-environnement, Université de Franche-Comté, CNRS, Besançon, France
| | - Audrey Jeanvoine
- Hygiène Hospitalière, Centre Hospitalier Universitaire de Besançon, Besançon, France
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GVPC Medium Manufactured without Oxygen Improves the Growth of Legionella spp. and Exhibits Enhanced Selectivity Properties. Microbiol Spectr 2022; 10:e0240121. [PMID: 35315693 PMCID: PMC9045360 DOI: 10.1128/spectrum.02401-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycine-vancomycin-polymyxin-cycloheximide agar (GVPC) is a recommended medium for the detection of Legionella spp. in water samples. However, its quality could be improved in terms of recovery of Legionella spp. and selectivity properties. Modifications were introduced in GVPC manufacture: autoclaving conditions (115°C, 15 min) and atmosphere during component-stirring (removal of oxygen and N2 injection). The use of softer autoclaving conditions (115°C, 15 min) improved the growth of Legionella anisa by the spiral method and Legionella pneumophila after membrane filtration. The medium manufactured with O2 removal and autoclaving for 15 min at 115°C allowed a faster growth of L. pneumophila (colonies visible at day 2) and a notable increase of L. anisa growth (colonies appearing at day 3, and statistically significant numbers of CFU at day 5). After 3 to 5 days of incubation, the improved media showed higher selectivity properties, particularly for Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 9027. A further improvement was achieved by the addition of N2 during ingredient stirring, leading to a statistically significant faster growth of L. pneumophila at days 2 and 3 and L. anisa at day 3. Selectivity properties were also enhanced, resulting in the complete inhibition of both E. faecalis strains and Escherichia coli and complete-partial inhibition of P. aeruginosa. Oxygen removal during GVPC manufacture using a vacuum pump system promotes the growth of L. pneumophila and L. anisa, and markedly inhibits the growth of E. coli, P. aeruginosa, and E. faecalis. IMPORTANCE Currently, GVPC is a recommended medium for the detection of Legionella spp. in water samples. However, recovery of Legionella spp. and selectivity properties can be improved. GVPC medium manufactured without oxygen improved the growth of Legionella pneumophila and Legionella anisa. Oxygen removal during GVPC manufacture also improved selectivity properties. A further improvement was achieved by the addition of N2 during ingredient stirring, leading to a faster growth of L. pneumophila at days 2 and 3 and L. anisa at day 3 and enhancement of selectivity properties. The introduction of the modified GVPC medium in routine practice can allow a better detection of Legionella spp. in water samples.
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Vittal R, Raj JRM, Kumar BK, Karunasagar I. Advances in Environmental Detection and Clinical Diagnostic Tests for Legionella Species. JOURNAL OF HEALTH AND ALLIED SCIENCES NU 2021. [DOI: 10.1055/s-0041-1731863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Abstract
Legionella is a fastidious organism that is difficult to culture in the lab but is widely distributed in environmental, domestic, and hospital settings. The clinical manifestations due to Legionella infections range from mild fever to fatal pneumonia and multiorgan pathologies. Legionella outbreaks though prevalent globally are not reported in developing countries due to difficulties in isolating this organism and the lack of simple diagnostic protocols. Here, we review the literature from across countries to present various methods used to detect Legionella from environmental and clinical samples. We compare the sensitivity and the specificity of the conventional culture-based assays with the recent methods and discuss approaches to develop better detection and diagnostic tests. With better cost-effective detection techniques and regular monitoring of the susceptible sites, which may harbor Legionella colonies, most of the Legionella infections can be prevented. As a result, considerable burden, caused by Legionella infections, on the healthcare system, in especially economically weaker countries, can be mitigated.
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Affiliation(s)
- Rajeshwari Vittal
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Juliet Roshini Mohan Raj
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Ballamoole Krishna Kumar
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Indrani Karunasagar
- Nitte University Centre for Science Education and Research, Mangaluru, Karnataka, India
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7
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Hortelano I, Moreno MY, García-Hernández J, Ferrús MA. Optimization of pre- treatments with Propidium Monoazide and PEMAX™ before real-time quantitative PCR for detection and quantification of viable Helicobacter pylori cells. J Microbiol Methods 2021; 185:106223. [PMID: 33872638 DOI: 10.1016/j.mimet.2021.106223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 04/14/2021] [Accepted: 04/14/2021] [Indexed: 12/17/2022]
Abstract
Accurate detection of H. pylori in different environmental and clinical samples is essential for public health strtdudies. Now, a big effort is being made to design PCR methodologies that allow for the detection of viable and viable but non-culturable (VBNC) H. pylori cells, by achieving complete exclusion of dead cells amplification signals. The use of DNA intercalating dyes has been proposed. However, its efficacy is still not well determined. In this study, we aimed to test the suitability of PMA and PEMAX™ dyes used prior to qPCR for only detecting viable cells of H. pylori. Their efficiency was evaluated with cells submitted to different disinfection treatments and confirmed by the absence of growth on culture media and by LIVE/DEAD counts. Our results indicated that an incubation period of 5 min for both, PMA and PEMAX™, did not affect viable cells. Our study also demonstrated that results obtained by using intercalating dyes may vary depending on the cell stress conditions. In all dead cell's samples, both PMA and PEMAX™ pre-qPCR treatments decreased the amplification signal (>103 Genomic Units (GU)), although none of them allowed for its disappearance confirming that intercalating dyes, although useful for screening purposes, cannot be considered as universal viability markers. To investigate the applicability of the method specifically to detect H. pylori cells in environmental samples, PMA-qPCR was performed on samples containing the different morphological and viability states that H. pylori can acquire in environment. The optimized PMA-qPCR methodology showed to be useful to detect mostly (but not only) viable forms, regardless the morphological state of the cell.
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Affiliation(s)
- Irene Hortelano
- Research Institute of Water and Environmental Engineering (IIAMA), Universitat Politècnica de València, 46022, Valencia, Spain.
| | - María Yolanda Moreno
- Research Institute of Water and Environmental Engineering (IIAMA), Universitat Politècnica de València, 46022, Valencia, Spain
| | | | - María Antonia Ferrús
- Biotechnology Department, Universitat Politècnica de València, 46022, Valencia, Spain.
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8
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Baró A, Badosa E, Montesinos L, Feliu L, Planas M, Montesinos E, Bonaterra A. Screening and identification of BP100 peptide conjugates active against Xylella fastidiosa using a viability-qPCR method. BMC Microbiol 2020; 20:229. [PMID: 32727358 PMCID: PMC7392676 DOI: 10.1186/s12866-020-01915-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 07/20/2020] [Indexed: 12/16/2022] Open
Abstract
Background Xylella fastidiosa is one of the most harmful bacterial plant pathogens worldwide, causing a variety of diseases, with huge economic impact to agriculture and environment. Although it has been extensively studied, there are no therapeutic solutions to suppress disease development in infected plants. In this context, antimicrobial peptides represent promising alternatives to traditional compounds due to their activity against a wide range of plant pathogens, their low cytotoxicity, their mode of action that make resistance more difficult and their availability for being expressed in plants. Results Peptide conjugates derived from the lead peptide BP100 and fragments of cecropin, magainin or melittin were selected and tested against the plant pathogenic bacteria X. fastidiosa. In order to screen the activity of these antimicrobials, and due to the fastidious nature of the pathogen, a methodology consisting of a contact test coupled with the viability-quantitative PCR (v-qPCR) method was developed. The nucleic acid-binding dye PEMAX was used to selectively quantify viable cells by v-qPCR. In addition, the primer set XF16S-3 amplifying a 279 bp fragment was selected as the most suitable for v-qPCR. The performance of the method was assessed by comparing v-qPCR viable cells estimation with conventional qPCR and plate counting. When cells were treated with peptide conjugates derived from BP100, the observed differences between methods suggested that, in addition to cell death due to the lytic effect of the peptides, there was an induction of the viable but non-culturable state in cells. Notably, a contact test coupled to v-qPCR allowed fast and accurate screening of antimicrobial peptides, and led to the identification of new peptide conjugates active against X. fastidiosa. Conclusions Antimicrobial peptides active against X. fastidiosa have been identified using an optimized methodology that quantifies viable cells without a cultivation stage, avoiding underestimation or false negative detection of the pathogen due to the viable but non-culturable state, and overestimation of the viable population observed using qPCR. These findings provide new alternative compounds for being tested in planta for the control of X. fastidiosa, and a methodology that enables the fast screening of a large amount of antimicrobials against this plant pathogenic bacterium.
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Affiliation(s)
- Aina Baró
- Laboratory of Plant Pathology, Institute of Food and Agricultural Technology-CIDSAV-XaRTA, University of Girona, Girona, Spain
| | - Esther Badosa
- Laboratory of Plant Pathology, Institute of Food and Agricultural Technology-CIDSAV-XaRTA, University of Girona, Girona, Spain
| | - Laura Montesinos
- Laboratory of Plant Pathology, Institute of Food and Agricultural Technology-CIDSAV-XaRTA, University of Girona, Girona, Spain
| | - Lidia Feliu
- LIPPSO, Department of Chemistry, University of Girona, Girona, Spain
| | - Marta Planas
- LIPPSO, Department of Chemistry, University of Girona, Girona, Spain
| | - Emilio Montesinos
- Laboratory of Plant Pathology, Institute of Food and Agricultural Technology-CIDSAV-XaRTA, University of Girona, Girona, Spain
| | - Anna Bonaterra
- Laboratory of Plant Pathology, Institute of Food and Agricultural Technology-CIDSAV-XaRTA, University of Girona, Girona, Spain.
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Baymiev AK, Baymiev AK, Kuluev BR, Shvets KY, Yamidanov RS, Matniyazov RT, Chemeris DA, Zubov VV, Alekseev YI, Mavzyutov AR, Ivanenkov YA, Chemeris AV. Modern Approaches to Differentiation of Live and Dead Bacteria Using Selective Amplification of Nucleic Acids. Microbiology (Reading) 2020. [DOI: 10.1134/s0026261720010038] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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10
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Codony F, Dinh-Thanh M, Agustí G. Key Factors for Removing Bias in Viability PCR-Based Methods: A Review. Curr Microbiol 2019; 77:682-687. [DOI: 10.1007/s00284-019-01829-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 11/29/2019] [Indexed: 11/24/2022]
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Magin V, Garrec N, Andrés Y. Selection of Bacteriophages to Control In Vitro 24 h Old Biofilm of Pseudomonas Aeruginosa Isolated from Drinking and Thermal Water. Viruses 2019; 11:E749. [PMID: 31412645 PMCID: PMC6722843 DOI: 10.3390/v11080749] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/10/2019] [Accepted: 08/11/2019] [Indexed: 12/21/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that causes public healthcare issues. In moist environments, this Gram-negative bacterium persists through biofilm-associated contamination on surfaces. Bacteriophages are seen as a promising alternative strategy to chemical biocides. This study evaluates the potential of nine lytic bacteriophages as biocontrol treatments against nine environmental P. aerginosa isolates. The spot test method is preliminarily used to define the host range of each virus and to identify their minimum infectious titer, depending on the strain. Based on these results, newly isolated bacteriophages 14.1, LUZ7, and B1 are selected and assessed on a planktonic cell culture of the most susceptible isolates (strains MLM, D1, ST395E, and PAO1). All liquid infection assays are achieved in a mineral minimum medium that is much more representative of real moist environments than standard culture medium. Phages 14.1 and LUZ7 eliminate up to 90% of the PAO1 and D1 bacterial strains. Hence, their effectiveness is evaluated on the 24 h old biofilms of these strains, established on a stainless steel coupon that is characteristic of materials found in thermal and industrial environments. The results of quantitative PCR viability show a maximum reduction of 1.7 equivalent Log CFU/cm2 in the coupon between treated and untreated surfaces and shed light on the importance of considering the entire virus/host/environment system for optimizing the treatment.
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Affiliation(s)
- Vanessa Magin
- Centre Scientifique et Technique du Bâtiment, Plateforme AQUASIM, 44300 Nantes, France.
- Institut Mines Télécom Atlantique, Laboratoire de Génie des Procédés Environnement Agro-alimentaire (UMR CNRS 6144), 44300 Nantes, France.
| | - Nathalie Garrec
- Centre Scientifique et Technique du Bâtiment, Plateforme AQUASIM, 44300 Nantes, France
| | - Yves Andrés
- Institut Mines Télécom Atlantique, Laboratoire de Génie des Procédés Environnement Agro-alimentaire (UMR CNRS 6144), 44300 Nantes, France
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12
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Bonetta S, Pignata C, Bonetta S, Meucci L, Giacosa D, Marino E, Gorrasi I, Gilli G, Carraro E. Effectiveness of a neutral electrolysed oxidising water (NEOW) device in reducing Legionella pneumophila in a water distribution system: A comparison between culture, qPCR and PMA-qPCR detection methods. CHEMOSPHERE 2018; 210:550-556. [PMID: 30029147 DOI: 10.1016/j.chemosphere.2018.07.053] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 07/09/2018] [Accepted: 07/10/2018] [Indexed: 05/22/2023]
Abstract
Disinfection of hot water systems is critical for reducing Legionnaires' disease in high-risk buildings. The use of neutral electrolysed oxidising water (NEOW) is a promising method for the control of microorganisms in hot water systems. However, full-scale evaluations of the efficacy of NEOW devices to control Legionella pneumophila are currently lacking. The aim of this study was to assess the effectiveness of a NEOW device in reducing L. pneumophila in a hotel water network. Water samples (n = 67) were collected from different sites of a hotel distribution system before and after the installation of the NEOW device at the 1st, 4th, 8th and 12th week. Detection of L. pneumophila was performed comparing culture, qPCR and PMA-qPCR methods. Total bacterial counts (22 °C and 37 °C), Pseudomonas spp. and physico-chemical parameters were also monitored. The NEOW treatment resulted in a reduction of the amount of L. pneumophila positive samples (-32%) and of the number of heavily contaminated points (>104 CFU/L and >103 CFU/L) (-100% and -96%, respectively). Treatment maintained L. pneumophila at low levels (<102 CFU/L), which do not require specific intervention measures. The effectiveness of the disinfection system was also confirmed by PMA-qPCR (p < 0.001). The use of PMA resulted in a signal decrease in almost all samples upon the disinfection treatment. The NEOW disinfection device appears to be a promising approach to reduce the colonisation of hot water systems by L. pneumophila; however, further investigations are needed to ascertain its efficiency over longer time periods.
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Affiliation(s)
- Sara Bonetta
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy.
| | - Cristina Pignata
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy
| | - Silvia Bonetta
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy
| | - Lorenza Meucci
- Società Metropolitana Acque Torino S.P.A, C.so XI Febbraio 14, 10152, Torino, Italy
| | - Donatella Giacosa
- Società Metropolitana Acque Torino S.P.A, C.so XI Febbraio 14, 10152, Torino, Italy
| | - Elena Marino
- Società Metropolitana Acque Torino S.P.A, C.so XI Febbraio 14, 10152, Torino, Italy
| | - Ilaria Gorrasi
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy
| | - Giorgio Gilli
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy
| | - Elisabetta Carraro
- Department of Public Health and Pediatrics, University of Torino, Piazza Polonia 94, 10126, Torino, Italy
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Monitoring Viable Cells of the Biological Control Agent Lactobacillus plantarum PM411 in Aerial Plant Surfaces by Means of a Strain-Specific Viability Quantitative PCR Method. Appl Environ Microbiol 2018. [PMID: 29523544 PMCID: PMC5930365 DOI: 10.1128/aem.00107-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
A viability quantitative PCR (v-qPCR) assay was developed for the unambiguous detection and quantification of Lactobacillus plantarum PM411 viable cells in aerial plant surfaces. A 972-bp region of a PM411 predicted prophage with mosaic architecture enabled the identification of a PM411 strain-specific molecular marker. Three primer sets with different amplicon lengths (92, 188, and 317 bp) and one TaqMan probe were designed. All the qPCR assays showed good linearity over a 4-log range and good efficiencies but differed in sensitivity. The nucleic acid-binding dye PEMAX was used to selectively detect and enumerate viable bacteria by v-qPCR. The primer set amplifying a 188-bp DNA fragment was selected as the most suitable for v-qPCR. The performance of the method was assessed on apple blossoms, pear, strawberry, and kiwifruit leaves in potted plants under controlled environmental conditions, as well as pear and apple blossoms under field conditions, by comparing v-qPCR population estimations to those obtained by qPCR and specific plate counting on de Man-Rogosa-Sharpe (MRS)-rifampin. The population estimation did not differ significantly between methods when conditions were conducive to bacterial survival. However, under stressful conditions, differences between methods were observed due to cell death or viable-but-nonculturable state induction. While qPCR overestimated the population level, plate counting underestimated this value in comparison to v-qPCR. PM411 attained stable population levels of viable cells on the flower environment under high relative humidity. However, the unfavorable conditions on the leaf surface and the relatively dryness in the field caused an important decrease in the viable population. IMPORTANCE The v-qPCR method in combination with plate counting and qPCR is a powerful tool for studies of colonization and survival under field conditions, to improve formulations and delivery strategies of PM411, and to optimize the dose and timing of spray schedules. It is expected that PEMAX v-qPCR could also be developed for monitoring other strains on plant surfaces not only as biological control agents but also beneficial bacteria useful in the sustainable management of crop production.
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Dinh Thanh M, Agustí G, Mader A, Appel B, Codony F. Improved sample treatment protocol for accurate detection of live Salmonella spp. in food samples by viability PCR. PLoS One 2017; 12:e0189302. [PMID: 29232387 PMCID: PMC5726647 DOI: 10.1371/journal.pone.0189302] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 11/23/2017] [Indexed: 11/19/2022] Open
Abstract
Culture-based detection is still considered as the standard way for detection of Salmonella in foods, although molecular methods, such as viability PCR (vPCR), have been introduced to overcome some disadvantages of traditional culture methods. Despite the success of the vPCR methodology, the problem of false-positive results is a major drawback, especially when applied to environmental samples, hindering the interpretation of the results. To improve the efficiency of vPCR, many approaches have been introduced by several authors during the last years. In the present work, the combination of PEMAX dye, double tube change, and double photo-activation step was established as a strategy to improve vPCR protocol. By combining these approaches, we developed an improved sample treatment protocol able to neutralize DNA signals of up to 5.0×107 dead cells/sample from both pure culture and artificially contaminated food samples. Our results indicate that vPCR can work reliable and has a potential for high throughput detection of live Salmonella cells in food samples, minimizing false-positive signals.
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Affiliation(s)
- Mai Dinh Thanh
- Freie Universität Berlin, Department of Biology, Chemistry and Pharmacy, Berlin, Germany
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
| | | | - Anneluise Mader
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
| | - Bernd Appel
- German Federal Institute for Risk Assessment, Department Biological Safety, Berlin, Germany
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