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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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Inaccuracies of the ISO 11731 Method for Environmental Validation of Legionella in Building Water Systems: Opportunities to Improve Sensitivity and Detect Viable but Non-Culturable Legionella. Microorganisms 2022; 11:microorganisms11010094. [PMID: 36677386 PMCID: PMC9865130 DOI: 10.3390/microorganisms11010094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/24/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022] Open
Abstract
Current environmental diagnostics for the detection of Legionella fail to detect viable but non-culturable Legionella, have sensitivity limitations and are time-consuming (10-14 days to results). The objective of this study was to compare Legionella detection results between the standard ISO 11731 and an innovative Legionella detection method that utilizes a hybrid methodology of traditional microbiology and molecular detection. In this study, four hundred and seventy-six (476) potable building water samples were analyzed with ISO 11731 and the novel method in parallel. Of the 476 total samples that were tested, a discrepancy of 21% was observed when comparing the ISO 11731 method to the novel method. Separating the samples based on hazard control methods yielded a 15.4% discrepancy for chlorinated systems (n = 284) and a 29% discrepancy for monochloraminated systems (n = 192). The data presented here conclusively show inaccuracies in environmental validation for building water systems based on results returned by the standard ISO 11731 method. This is especially evident in systems primarily disinfected with monochloramines. Overall, these data highlight the need for new and innovative methods to overcome the inaccuracies of the traditional ISO 11731 spread plates to prevent disease and injury caused by Legionella.
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3
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Consonni M, Grassi A, Scuri S, Gori M, Tanzi E, Tesauro M. Assessing the viability of Legionella pneumophila in environmental samples: regarding the filter application of Ethidium Monoazide Bromide. ANN MICROBIOL 2021. [DOI: 10.1186/s13213-021-01653-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Purpose
Analyses of 34 water samples from 13 healthcare structures revealed how culture method and quantitative PCR (qPCR) often differ in the detection of Legionella pneumophila (Lp). With these considerations in hand, culture method, PCR and Ethidium Monoazide Bromide (EMA) qPCR have all been compared in order to detect Lp in water samples, identify a method able to speed up the procedures, detect the “viable but not cultivable” bacteria (VBNC) and exclude non-viable bacteria using a commercial kit for extraction and amplification as well as modification of the protocol.
Methods
Pure water samples artificially spiked with viable, non-viable and VBNC Lp ATCC 33152 were analyzed using a commercial kit for both qPCR and EMA-qPCR, while ISO 11731-2-2004 was used for culture method.
Results
Only 35% (12/34) of the environmental samples were positive in both culture and qPCR methods. With regard to EMA-qPCR, results showed the absence of dye toxicity on viable and VBNC strains and an incomplete effectiveness on the non-viable ones. In both viable and VBNC strains, a decrease of bacterial DNA amplification was recorded as a function of sample dilution but not of EMA concentration.
Conclusions
Discrepancies between culture method and EMA-qPCR were observed and may be due to different causes such as membrane-dye interactions, presence of interfering compounds and the sensitivity of the kit used.
Study significance and impact
In the presence of one or more suspected cases of nosocomial legionellosis, the application of a rapid molecular method able to identify only the viable and VBNC Lp would be useful in order to quickly identify the source of infection and to intervene with sanitation treatments. However, seeing that in our experience EMA pretreatment on the filter membrane did not come up with the expected results, it would be necessary to proceed with other experiments and/or different dyes.
Graphical Abstract
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Fisher KE, Wickenberg LP, Leonidas LF, Ranz AA, Habib MA, Buford RM, McCoy WF. Next Day Legionella PCR: a highly reliable negative screen for Legionella in the built environment. JOURNAL OF WATER AND HEALTH 2020; 18:345-357. [PMID: 32589620 DOI: 10.2166/wh.2020.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The opportunistic, waterborne pathogen Legionella caused 9,933 cases of Legionnaires' disease in 2018 in the United States (CDC.gov). The incidence of Legionnaires' disease can be reduced by maintaining clean building water systems through water management programs (WMPs). WMPs often include validation testing to confirm the control of bacteria, but the traditional culture method for enumerating Legionella requires 10-14 days to obtain results. A rapid DNA extraction developed by Phigenics and a real-time PCR negative screen for the genus Legionella provided results the day after sampling. This study evaluated the Next Day Legionella PCR (Phigenics, LLC) compared with the traditional culture method (ISO 11731) on 11,125 building water samples for approximately 1 year. Two DNA extraction methods (Methods 1 and 2) were compared. The negative predictive value (NPV) of the Next Day Legionella PCR in comparison to traditional culture for Method 1 was 99.95%, 99.92%, 99.85%, and 99.17% at >10, >2, >1, and >0.1 CFU/ml limits of detection, respectively. The improved DNA extraction (Method 2) increased the NPV to 100% and 99.88% at >1 and >0.1 CFU/ml, respectively. These results demonstrate the reliability of the genus-level Legionella PCR negative screen to predict culture-negative water samples.
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Affiliation(s)
- Katherine E Fisher
- Phigenics Research and Innovation Team, Nevada Center for Applied Research, Reno, NV, USA E-mail:
| | - Leah P Wickenberg
- Phigenics Research and Innovation Team, Nevada Center for Applied Research, Reno, NV, USA E-mail:
| | - Lesley F Leonidas
- Phigenics Analytical Services Laboratory (PASL), Warrenville, IL, USA
| | - Anna A Ranz
- Phigenics Analytical Services Laboratory (PASL), Fayetteville, AR, USA
| | - Michelle A Habib
- Phigenics Analytical Services Laboratory (PASL), Warrenville, IL, USA
| | - Rafael M Buford
- Phigenics Analytical Services Laboratory (PASL), Fayetteville, AR, USA
| | - William F McCoy
- Phigenics Research and Innovation Team, Nevada Center for Applied Research, Reno, NV, USA E-mail:
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5
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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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6
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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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7
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Ditommaso S, Giacomuzzi M, Memoli G, Cavallo R, Curtoni A, Avolio M, Silvestre C, Zotti CM. Reduction of turnaround time for non-tuberculous mycobacteria detection in heater-cooler units by propidium monoazide-real-time polymerase chain reaction. J Hosp Infect 2019; 104:365-373. [PMID: 31628958 DOI: 10.1016/j.jhin.2019.10.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 11/17/2022]
Abstract
BACKGROUND Invasive non-tuberculous mycobacteria (NTM) infections are emerging worldwide in patients undergoing open-chest cardiac bypass surgery exposed to contaminated heater-cooler units (HCUs). Although this outbreak has been investigated by culturing bacteria isolated from HCU aerosol and water samples, these conventional methods have low-analytic sensitivity, high rates of sample contamination, and long turnaround time. AIM To develop a simple and effective method to detect NTM in HCUs by real-time polymerase chain reaction (PCR), with a short laboratory turnaround time and reliable culture results. METHODS A total of 281 water samples collected from various HCUs at seven Italian hospitals were simultaneously screened for NTM by a propidium monoazide (PMA)-PCR assay and by conventional culture testing. The results were analysed with culture testing as the reference method. FINDINGS (i) The agreement between culture testing and PMA-PCR was 85.0% with a cycle threshold (CT) cut-off value of <38 vs 80.0% with a CT of <43, with a moderate Cohen's κ-coefficient; (ii) the CT cut-off value of <42 was deemed more suitable for predicting positive specimens; (iii) given the low concentration of target DNA in water samples, the minimum volume to be tested was 1 L. CONCLUSION The use of PMA-PCR for fast detection of NTM from environmental samples is highly recommended in order to ascertain whether HCUs may represent a potential source of human exposure to NTM. This reliable and simple method reduces laboratory turnaround time compared to conventional methods (one to two days vs eight weeks, respectively), thereby improving control strategies and effective management of HCUs.
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Affiliation(s)
- S Ditommaso
- Department of Public Health and Pediatrics, University of Turin, Turin, Italy.
| | - M Giacomuzzi
- Department of Public Health and Pediatrics, University of Turin, Turin, Italy
| | - G Memoli
- Department of Public Health and Pediatrics, University of Turin, Turin, Italy
| | - R Cavallo
- Department of Public Health and Pediatrics, University of Turin, Turin, Italy; Microbiology and Virology Unit, University Hospital Città della Salute e della Scienza di Torino, Turin, Italy
| | - A Curtoni
- Microbiology and Virology Unit, University Hospital Città della Salute e della Scienza di Torino, Turin, Italy
| | - M Avolio
- Microbiology and Virology Unit, University Hospital Città della Salute e della Scienza di Torino, Turin, Italy
| | - C Silvestre
- AOU Città della salute e della Scienza, Turin, Italy
| | - C M Zotti
- Department of Public Health and Pediatrics, University of Turin, Turin, Italy
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8
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De Giglio O, Napoli C, Apollonio F, Brigida S, Marzella A, Diella G, Calia C, Scrascia M, Pacifico C, Pazzani C, Uricchio VF, Montagna MT. Occurrence of Legionella in groundwater used for sprinkler irrigation in Southern Italy. ENVIRONMENTAL RESEARCH 2019; 170:215-221. [PMID: 30594053 DOI: 10.1016/j.envres.2018.12.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 06/09/2023]
Abstract
Legionellae are opportunistic bacteria that cause various conditions after exposure to contaminated aerosols, ranging from a serious type of pneumonia to a mild case of an influenza-like illness. Despite the risks of exposure, little is known about the occurrence of Legionella in natural environments and, even though studies have shown that there is a potential risk of transmission via inhalation, it does not have to be detected in groundwater that is used for irrigation. The culture methods traditionally used to detect Legionella have several limits that can be partly solved by applying molecular techniques. Samples from 177 wells in Apulia, Southern Italy, were collected twice, in winter and in summer, and analyzed. When compared with the guidelines, 145 (81.9%) of the sampled wells were suitable for irrigation use. The culture-based method highlighted the presence of different species and serogroups of Legionella in 31 (21.2%) of the 145 wells that were shown to be suitable for irrigation use. A greater number of wells returned positive results for Legionella in summer than in winter (p = 0.023), and the median concentrations were mostly higher in summer (500 CFU/L) than in winter (300 CFU/L). The median temperature in the Legionella positive well waters was significantly higher than that in the negative ones, both in winter and in summer (p < 0.001). Using molecular techniques, Legionella non-pneumophila was found in 37 of the 114 wells earlier detected as suitable for irrigation use but negative for Legionella by the culture-based methods. The distribution of Legionella differ significantly in porous aquifers compared to the karst-fissured ones both with quantitative polymerase chain reaction (qPCR) (p = 0.0004) and viable cells by propidium monoazide (PMA-qPCR) (p = 0.0000). Legionella concentrations were weakly correlated with temperature of water both with qPCR (ρ = 0.47, p = 0.0033) and PMA-qPCR (ρ = 0.41, p = 0.0126). Our data suggest that water that aerosolizes when sprinkled on plants represents a potential source of Legionellosis, with a higher risk from exposure in summer. On a practical level, this finding is important for workers (farmers and gardeners) who are in contact with waters used for irrigation.
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Affiliation(s)
- Osvalda De Giglio
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
| | - Christian Napoli
- Department of Medical and Surgical sciences and translational Medicine, Sapienza University of Rome, Italy.
| | - Francesca Apollonio
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
| | - Silvia Brigida
- Water Research Institute, National Research Council, Bari, Italy.
| | - Angelo Marzella
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
| | - Giusy Diella
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
| | - Carla Calia
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
| | - Maria Scrascia
- Department of Biology, University of Bari "Aldo Moro", Bari, Italy.
| | - Claudia Pacifico
- Centre of Biostatistics for Clinical Epidemiology, School of Medicine and Surgery, University of Milano-Bicocca, Milano, Italy
| | - Carlo Pazzani
- Department of Biology, University of Bari "Aldo Moro", Bari, Italy.
| | | | - Maria Teresa Montagna
- Department of Biomedical Science and Human Oncology, University of Bari "Aldo Moro", Bari, Italy.
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9
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Optimization of viability qPCR for selective detection of membrane-intact Legionella pneumophila. J Microbiol Methods 2018; 156:68-76. [PMID: 30529241 DOI: 10.1016/j.mimet.2018.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 12/04/2018] [Accepted: 12/04/2018] [Indexed: 11/23/2022]
Abstract
Although a number of viability qPCR assays have been reported to selectively detect signals from membrane-intact Legionella pneumophila, the efficient suppression of amplification of DNA from dead membrane-compromised bacteria remains an ongoing challenge. This research aimed at establishing a new oligonucleotide combination that allows for a better exclusion of dead Legionella pneumophila on basis of the mip gene. Propidium monoazide (PMA) was chosen as viability dye. An oligonucleotide combination for the amplification of a 633 bp sequence was established with 100% specificity for different Legionella pneumophila strains compared with 17 other Legionella species tested. Apart from increasing amplicon length, the study aimed at optimizing dye incubation time and temperature. An incubation temperature of 45 °C for 10 min was found optimal. Dye treatment of heat-killed bacteria in the presence of EDTA improved signal suppression, whereas deoxycholate also affected signals from live intact bacteria. Suppression of signals from heat-treated bacteria was found to be approx. twice as efficient compared to a commercial kit, although the detection sensitivity is superior when targeting short amplicons. With a limit of detection of 10 genome copies per PCR well and a 6-log signal reduction of bacteria killed at 80 °C, the assay appears useful for applications where pathogen numbers are not limiting and where the priority is on the distinction between intact and damaged Legionella pneumophila for the evaluation of hygienic risk and of disinfection efficiency.
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10
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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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11
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Pacholewicz E, Buhler C, Wulsten IF, Kraushaar B, Luu HQ, Iwobi AN, Huber I, Stingl K. Internal sample process control improves cultivation-independent quantification of thermotolerant Campylobacter. Food Microbiol 2018; 78:53-61. [PMID: 30497608 DOI: 10.1016/j.fm.2018.09.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 08/30/2018] [Accepted: 09/26/2018] [Indexed: 11/26/2022]
Abstract
Quantification of Campylobacter is challenging and one major reason is the fact that bacteria lose cultivability due to cold or oxygen stress during storage at retail. Alternative live/dead discriminatory qPCR currently lacks standardization and might overestimate live cells in the presence of dead cells. In this study an internal sample process control (ISPC) was developed. The ISPC consists of a specified number of peroxide-killed C. sputorum cells to be added to each sample in order to monitor (i) the level of reduction of the signal from dead cells and (ii) DNA losses during sample processing. A species-specific fragment of the 16S rRNA gene of C. sputorum was selected as real-time PCR target, based on its similar size and gene copy number compared to the C. jejuni/coli/lari target and confirmed in an exclusivity study. Extension of the amplification oligonucleotides for the target of thermotolerant Campylobacter improved real-time PCR efficiency, rendering the method suitable for quantification according to international standards. Concordant PCR signal variation of both C. jejuni and C. sputorum targets in co-inoculated chicken rinses verified the suitability of the ISPC. This provides a crucial step towards implementation of cultivation-independent quantification for improved food safety of fastidious bacteria.
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Affiliation(s)
- Ewa Pacholewicz
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Christiane Buhler
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Imke F Wulsten
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Britta Kraushaar
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Huong Quynh Luu
- National Institute of Veterinary Research (NIVR), Hanoi, Viet Nam
| | - Azuka N Iwobi
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Ingrid Huber
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Kerstin Stingl
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany.
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12
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Samhan FA, Stedtfeld TM, Waseem H, Williams MR, Stedtfeld RD, Hashsham SA. On-filter direct amplification of Legionella pneumophila for rapid assessment of its abundance and viability. WATER RESEARCH 2017; 121:162-170. [PMID: 28527390 PMCID: PMC5525548 DOI: 10.1016/j.watres.2017.05.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/08/2017] [Accepted: 05/12/2017] [Indexed: 05/14/2023]
Abstract
Guidelines and regulations to control Legionella pneumophila in cooling water systems of large buildings are evolving due to the increasing number of outbreaks. Rapid, on-site, simple, and sensitive quantification methods that are also able to assess viability may be extremely useful in monitoring and control. Culture-based methods for measuring L. pneumophila may take 4-10 days and qPCR-based methods are also slow, requiring at least a day from sample to result, albeit mainly due to the need for sample transport to a centralized laboratory. This study reports a rapid isothermal amplification method for L. pneumophila concentration and detection with live/dead differentiation under field conditions. Using an on-filter direct amplification (i.e., amplification of cells without DNA extraction and purification) approach with propidium monoazide (PMA), and a real time isothermal amplification platform (Gene-Z), L. pneumophila could be detected in 1-2 h at ∼1 cfu/100 ml of tap water. Signature sequences from 16S rRNA and cadA genes were used as genetic markers for L. pneumophila and loop-mediated isothermal amplification (LAMP) primers were designed using Primer Explorer V4. Result were also compared with direct amplification of cells spiked into distilled, tap, and cooling water samples as well as extracted DNA by qPCR. This method may be useful to managers of cooling water systems in large buildings for rapid detection of L. pneumophila. The overall approach of on-site sample concentration, on-filter amplification, and live/dead differentiation may be extended to other organisms where analytical sensitivity and speed are equally important.
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Affiliation(s)
- Farag A Samhan
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
| | - Tiffany M Stedtfeld
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
| | - Hassan Waseem
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
| | - Maggie R Williams
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
| | - Robert D Stedtfeld
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA
| | - Syed A Hashsham
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA; Center for Microbial Ecology, Michigan State University, East Lansing, MI, USA.
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13
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Bonetta S, Pignata C, Bonetta S, Meucci L, Giacosa D, Marino E, Gilli G, Carraro E. Viability of Legionella pneumophila in Water Samples: A Comparison of Propidium Monoazide (PMA) Treatment on Membrane Filters and in Liquid. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2017; 14:ijerph14050467. [PMID: 28448459 PMCID: PMC5451918 DOI: 10.3390/ijerph14050467] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/18/2017] [Accepted: 04/20/2017] [Indexed: 11/16/2022]
Abstract
Legionella pneumophila is a ubiquitous microorganism widely distributed in aquatic environments and can cause Legionellosis in humans. A promising approach to detect viable cells in water samples involves the use of quantitative polymerase chain reaction (qPCR) in combination with photoactivatable DNA intercalator propidium monoazide (PMA). However, the PMA efficiency could be different depending on the experimental conditions used. The aim of this study was to compare two PMA exposure protocols: (A) directly on the membrane filter or (B) in liquid after filter washing. The overall PMA-induced qPCR means reductions in heat-killed L. pneumophila cells were 2.42 and 1.91 log units for exposure protocols A and B, respectively. A comparison between the results obtained reveals that filter exposure allows a higher PMA-qPCR signal reduction to be reached, mainly at low concentrations (p < 0.05). This confirms the potential use of this method to quantify L. pneumophila in water with low contamination.
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Affiliation(s)
- Sara Bonetta
- Department of Public Health and Pediatrics, University of Torino, P.zza Polonia 94, 10126 Torino, Italy.
| | - Cristina Pignata
- Department of Public Health and Pediatrics, University of Torino, P.zza Polonia 94, 10126 Torino, Italy.
| | - Silvia Bonetta
- Department of Public Health and Pediatrics, University of Torino, P.zza 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.
| | - Giorgio Gilli
- Department of Public Health and Pediatrics, University of Torino, P.zza Polonia 94, 10126 Torino, Italy.
| | - Elisabetta Carraro
- Department of Public Health and Pediatrics, University of Torino, P.zza Polonia 94, 10126 Torino, Italy.
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14
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Leifels M, Hamza IA, Krieger M, Wilhelm M, Mackowiak M, Jurzik L. From Lab to Lake - Evaluation of Current Molecular Methods for the Detection of Infectious Enteric Viruses in Complex Water Matrices in an Urban Area. PLoS One 2016; 11:e0167105. [PMID: 27880820 PMCID: PMC5120873 DOI: 10.1371/journal.pone.0167105] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 11/07/2016] [Indexed: 11/22/2022] Open
Abstract
Quantitative PCR methods are commonly used to monitor enteric viruses in the aquatic environment because of their high sensitivity, short reaction times and relatively low operational cost. However, conclusions for public health drawn from results of such molecular techniques are limited due to their inability to determine viral infectivity. Ethidium monoazide (EMA) and propidium monoazide (PMA) are capable to penetrate the damaged or compromised capsid of the inactivated viruses and bind to the viral nucleic acids. We assessed whether dye treatment is a suitable approach to improve the ability of qPCR to distinguish between infectious and non-infectious human adenovirus, enterovirus and rotavirus A in surface water of an urban river and sewage before and after UV disinfection. Like the gold standard of cell culture assays, pretreatment EMA-/PMA-qPCR succeeded in removing false positive results which would lead to an overestimation of the viral load if only qPCR of the environmental samples was considered. A dye pretreatment could therefore provide a rapid and relatively inexpensive tool to improve the efficacy of molecular quantification methods in regards to viral infectivity.
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Affiliation(s)
- Mats Leifels
- Ruhr-University Bochum, Department of Hygiene, Social- and Environmental Medicine, Bochum, Germany
| | - Ibrahim Ahmed Hamza
- Environmental Virology Laboratory, Department of Water Pollution Research, National Research Centre, Cairo, Egypt
| | - Marion Krieger
- Ruhr-University Bochum, Department of Hygiene, Social- and Environmental Medicine, Bochum, Germany
| | - Michael Wilhelm
- Ruhr-University Bochum, Department of Hygiene, Social- and Environmental Medicine, Bochum, Germany
| | - Martin Mackowiak
- University of Duisburg-Essen, Faculty of Chemistry, Biofilm Centre – Aquatic Microbiology, Essen, Germany
| | - Lars Jurzik
- Ruhr-University Bochum, Department of Hygiene, Social- and Environmental Medicine, Bochum, Germany
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15
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Scaturro M, Fontana S, Dell’eva I, Helfer F, Marchio M, Stefanetti MV, Cavallaro M, Miglietta M, Montagna MT, De Giglio O, Cuna T, Chetti L, Sabattini MAB, Carlotti M, Viggiani M, Stenico A, Romanin E, Bonanni E, Ottaviano C, Franzin L, Avanzini C, Demarie V, Corbella M, Cambieri P, Marone P, Rota MC, Bella A, Ricci ML. A multicenter study of viable PCR using propidium monoazide to detect Legionella in water samples. Diagn Microbiol Infect Dis 2016; 85:283-288. [DOI: 10.1016/j.diagmicrobio.2016.04.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 03/21/2016] [Accepted: 04/11/2016] [Indexed: 11/26/2022]
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16
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Inkinen J, Jayaprakash B, Santo Domingo J, Keinänen-Toivola M, Ryu H, Pitkänen T. Diversity of ribosomal 16S DNA- and RNA-based bacterial community in an office building drinking water system. J Appl Microbiol 2016; 120:1723-38. [DOI: 10.1111/jam.13144] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 01/27/2016] [Accepted: 02/01/2016] [Indexed: 12/14/2022]
Affiliation(s)
- J. Inkinen
- Faculty of Technology; WANDER Nordic Water and Materials Institute; Satakunta University of Applied Sciences; Rauma Finland
| | - B. Jayaprakash
- Water and Health Unit; National Institute for Health and Welfare (THL); Kuopio Finland
| | - J.W. Santo Domingo
- U.S. Environmental Protection Agency, Office of Research and Development; Cincinnati OH USA
| | - M.M. Keinänen-Toivola
- Faculty of Technology; WANDER Nordic Water and Materials Institute; Satakunta University of Applied Sciences; Rauma Finland
| | - H. Ryu
- U.S. Environmental Protection Agency, Office of Research and Development; Cincinnati OH USA
| | - T. Pitkänen
- Water and Health Unit; National Institute for Health and Welfare (THL); Kuopio Finland
- U.S. Environmental Protection Agency, Office of Research and Development; Cincinnati OH USA
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17
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Kirschner AK. Determination of viable legionellae in engineered water systems: Do we find what we are looking for? WATER RESEARCH 2016; 93:276-288. [PMID: 26928563 PMCID: PMC4913838 DOI: 10.1016/j.watres.2016.02.016] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 02/06/2016] [Accepted: 02/09/2016] [Indexed: 05/06/2023]
Abstract
In developed countries, legionellae are one of the most important water-based bacterial pathogens caused by management failure of engineered water systems. For routine surveillance of legionellae in engineered water systems and outbreak investigations, cultivation-based standard techniques are currently applied. However, in many cases culture-negative results are obtained despite the presence of viable legionellae, and clinical cases of legionellosis cannot be traced back to their respective contaminated water source. Among the various explanations for these discrepancies, the presence of viable but non-culturable (VBNC) Legionella cells has received increased attention in recent discussions and scientific literature. Alternative culture-independent methods to detect and quantify legionellae have been proposed in order to complement or even substitute the culture method in the future. Such methods should detect VBNC Legionella cells and provide a more comprehensive picture of the presence of legionellae in engineered water systems. However, it is still unclear whether and to what extent these VBNC legionellae are hazardous to human health. Current risk assessment models to predict the risk of legionellosis from Legionella concentrations in the investigated water systems contain many uncertainties and are mainly based on culture-based enumeration. If VBNC legionellae should be considered in future standard analysis, quantitative risk assessment models including VBNC legionellae must be proven to result in better estimates of human health risk than models based on cultivation alone. This review critically evaluates current methods to determine legionellae in the VBNC state, their potential to complement the standard culture-based method in the near future, and summarizes current knowledge on the threat that VBNC legionellae may pose to human health.
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Affiliation(s)
- Alexander K.T. Kirschner
- Medical University Vienna, Institute for Hygiene and Applied Immunology, Water Hygiene, Kinderspitalgasse 15, A-1090 Vienna, Austria
- Interuniversity Cooperation Centre for Water & Health, Austria
- Medical University Vienna, Institute for Hygiene and Applied Immunology, Water Hygiene Kinderspitalgasse 16, A-1090 Vienna, Austria . URL: http://www.waterandhealth.at
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18
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Cultural and Molecular Evidence of Legionella spp. Colonization in Dental Unit Waterlines: Which Is the Best Method for Risk Assessment? INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2016; 13:211. [PMID: 26861373 PMCID: PMC4772231 DOI: 10.3390/ijerph13020211] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 02/03/2016] [Indexed: 11/17/2022]
Abstract
Legionella spp. are ubiquitous in aquatic habitats and water distribution systems, including dental unit waterlines (DUWLs). The aim of the present study was to determine the prevalence of Legionella in DUWLs and tap water samples using PMA-qPCR and standard culture methods. The total viable counts (TVCs) of aerobic heterotrophic bacteria in the samples were also determined. Legionella spp. were detected and quantified using the modified ISO 11731 culture method. Extracted genomic DNA was analysed using the iQ-Check Quanti Legionella spp. kit, and the TVCs were determined according to the ISO protocol 6222. Legionella spp. were detected in 100% of the samples using the PMA-qPCR method, whereas these bacteria were detected in only 7% of the samples using the culture method. The number of colony forming units (CFUs) of the TVCs in the DUWL and tap water samples differed, with the bacterial load being significantly lower in the tap water samples (p-value = 0). The counts obtained were within the Italian standard range established for potable water in only 5% of the DUWL water samples and in 77% of the tap water samples. Our results show that the level of Legionella spp. contamination determined using the culture method does not reflect the true scale of the problem, and consequently we recommend testing for the presence of aerobic heterotrophic bacteria based on the assumption that Legionella spp. are components of biofilms.
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19
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Ditommaso S, Giacomuzzi M, Ricciardi E, Zotti CM. Viability-qPCR for detecting Legionella: Comparison of two assays based on different amplicon lengths. Mol Cell Probes 2015; 29:237-43. [DOI: 10.1016/j.mcp.2015.05.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 05/20/2015] [Accepted: 05/22/2015] [Indexed: 11/24/2022]
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20
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Díaz-Flores Á, Montero JC, Castro FJ, Alejandres EM, Bayón C, Solís I, Fernández-Lafuente R, Rodríguez G. Comparing methods of determining Legionella spp. in complex water matrices. BMC Microbiol 2015; 15:91. [PMID: 25925400 PMCID: PMC4436101 DOI: 10.1186/s12866-015-0423-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 04/15/2015] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND Legionella testing conducted at environmental laboratories plays an essential role in assessing the risk of disease transmission associated with water systems. However, drawbacks of culture-based methodology used for Legionella enumeration can have great impact on the results and interpretation which together can lead to underestimation of the actual risk. Up to 20% of the samples analysed by these laboratories produced inconclusive results, making effective risk management impossible. Overgrowth of competing microbiota was reported as an important factor for culture failure. For quantitative polymerase chain reaction (qPCR), the interpretation of the results from the environmental samples still remains a challenge. Inhibitors may cause up to 10% of inconclusive results. This study compared a quantitative method based on immunomagnetic separation (IMS method) with culture and qPCR, as a new approach to routine monitoring of Legionella. RESULTS First, pilot studies evaluated the recovery and detectability of Legionella spp using an IMS method, in the presence of microbiota and biocides. The IMS method results were not affected by microbiota while culture counts were significantly reduced (1.4 log) or negative in the same samples. Damage by biocides of viable Legionella was detected by the IMS method. Secondly, a total of 65 water samples were assayed by all three techniques (culture, qPCR and the IMS method). Of these, 27 (41.5%) were recorded as positive by at least one test. Legionella spp was detected by culture in 7 (25.9%) of the 27 samples. Eighteen (66.7%) of the 27 samples were positive by the IMS method, thirteen of them reporting counts below 10(3) colony forming units per liter (CFU l(-1)), six presented interfering microbiota and three presented PCR inhibition. Of the 65 water samples, 24 presented interfering microbiota by culture and 8 presented partial or complete inhibition of the PCR reaction. So the rate of inconclusive results of culture and PCR was 36.9 and 12.3%, respectively, without any inconclusive results reported for the IMS method. CONCLUSION The IMS method generally improved the recovery and detectability of Legionella in environmental matrices, suggesting the possibility to use IMS method as valuable indicator of risk. Thus, this method may significantly improve our knowledge about the exposure risk to these bacteria, allowing us to implement evidence-based monitoring and disinfection strategies.
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Affiliation(s)
- Álvaro Díaz-Flores
- Departamento de Microbiología General III, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, Campus Moncloa, 28040, Madrid, Spain.
| | - Juan Carlos Montero
- Instituto de Ciencias de la Salud Ctra, de Extremadura Km. 114, 45600, Talavera de la Reina, Spain.
| | - Francisco Javier Castro
- Laboratorio Regional de Salud Pública Consejería de Sanidad y Consumo/Comunidad de Madrid, C/ Sierra del Alquife N 8, 2 Planta, 28053, Madrid, Spain.
| | - Eva María Alejandres
- Laboratorio Regional de Salud Pública Consejería de Sanidad y Consumo/Comunidad de Madrid, C/ Sierra del Alquife N 8, 2 Planta, 28053, Madrid, Spain.
| | - Carmen Bayón
- Laboratorio Regional de Salud Pública Consejería de Sanidad y Consumo/Comunidad de Madrid, C/ Sierra del Alquife N 8, 2 Planta, 28053, Madrid, Spain.
| | | | - Roberto Fernández-Lafuente
- Departamento de Biocatálisis, Instituto de Catálisis y Petroleoquímica, Consejo Superior de Investigaciones Científicas, Campus UAM-CSIC, 28049, Cantoblanco, Madrid, Spain.
| | - Guillermo Rodríguez
- Biótica, Bioquímica Analítica, S.L, Science and Technology Park of Jaume I University, Campus RiuSec - Espaitec 2, planta baja, E12071, Castellón de la Plana, Spain.
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