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Nisar MA, Ross KE, Brown MH, Bentham R, Best G, Eyre NS, Leterme SC, Whiley H. Increased flushing frequency of a model plumbing system initially promoted the formation of viable but non culturable cells but ultimately reduced the concentration of culturable and total Legionella DNA. Heliyon 2024; 10:e32334. [PMID: 38933949 PMCID: PMC11200333 DOI: 10.1016/j.heliyon.2024.e32334] [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: 06/08/2023] [Revised: 05/30/2024] [Accepted: 06/02/2024] [Indexed: 06/28/2024] Open
Abstract
Legionella is the causative agent of Legionnaires' disease, and its prevalence in potable water is a significant public health issue. Water stagnation within buildings increases the risk of Legionella. However, there are limited studies investigating how stagnation arising through intermittent usage affects Legionella proliferation and the studies that are available do not consider viable but non culturable (VBNC) Legionella. This study used a model plumbing system to examine how intermittent water stagnation affects both VBNC and culturable Legionella. The model plumbing system contained a water tank supplying two biofilm reactors. The model was initially left stagnant for ≈5 months (147 days), after which one reactor was flushed daily, and the other weekly. Biofilm coupons, and water samples were collected for analysis at days 0, 14 and 28. These samples were analysed for culturable and VBNC Legionella, free-living amoebae, and heterotrophic bacteria. After 28 days, once-a-day flushing significantly (p < 0.001) reduced the amount of biofilm-associated culturable Legionella (1.5 log10 reduction) compared with weekly flushing. However, higher counts of biofilm-associated VBNC Legionella (1 log10 higher) were recovered from the reactor with once-a-day flushing compared with weekly flushing. Likewise, once-a-day flushing increased the population of biofilm-associated Vermamoeba vermiformis (approximately 3 log10 higher) compared with weekly flushing, which indicated a positive relationship between VBNC Legionella and V. vermiformis. This is the first study to investigate the influence of stagnation on VBNC Legionella under environmental conditions. Overall, this study showed that a reduction in water stagnation decreased culturable Legionella but not VBNC Legionella.
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Affiliation(s)
- Muhammad Atif Nisar
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
| | - Kirstin E. Ross
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
| | - Melissa H. Brown
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
- ARC Training Centre for Biofilm Research and Innovation, Flinders University, Bedford Park, SA, 5042, Australia
| | - Richard Bentham
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
| | - Giles Best
- College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
- Flow Cytometry Facility, Flinders University, Bedford Park, SA, 5042, Australia
| | - Nicholas S. Eyre
- College of Medicine and Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Sophie C. Leterme
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
- ARC Training Centre for Biofilm Research and Innovation, Flinders University, Bedford Park, SA, 5042, Australia
- Institute for Nanoscience and Technology, Flinders University, Bedford Park, SA, 5042, Australia
| | - Harriet Whiley
- College of Science and Engineering, Flinders University, Bedford Park, SA, 5042, Australia
- ARC Training Centre for Biofilm Research and Innovation, Flinders University, Bedford Park, SA, 5042, Australia
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Schwake DO, Sandrin T, Zhang L, Abbaszadegan M. Strain-Level Characterization of Legionella Environmental Isolates via MALDI-TOF-MS. Microorganisms 2022; 11:microorganisms11010008. [PMID: 36677300 PMCID: PMC9863361 DOI: 10.3390/microorganisms11010008] [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: 10/14/2022] [Revised: 12/04/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
As a waterborne pathogen of increasing concern, techniques for cost-effective and rapid characterization of Legionella are vital. This study examines the development of a Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF-MS) analysis methodology for this microbe. First, optimal sample preparation methods for the analysis of environmental Legionella isolates via MALDI-TOF-MS were determined. These methods were then implemented to perform strain-level characterization of environmental Legionella isolates from central Arizona. Results demonstrate that a MALDI-TOF-MS method involving BCYE agar-based culturing and protein extraction-based sample preparation yield high-quality mass spectra. Twenty-eight environmental Legionella isolates originating from two separate drinking water distribution systems were analyzed. Multiple species were detected, and strain-level characterization was achieved, with 12 unique strains distinguished. In addition, isolates of L. pneumophila, the most common species observed in the study, were correctly assigned to specific sampling sites. These results demonstrate the potential for this technique to be applied for sub-species characterization of Legionella with significant benefits over established methodologies.
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Affiliation(s)
- David Otto Schwake
- Department of Natural Sciences, Middle Georgia State University, 100 University Pkwy, Macon, GA 31206, USA
| | - Todd Sandrin
- School of Mathematical and Natural Sciences, New College of Interdisciplinary Arts & Sciences, Arizona State University at the West Campus, 4701 W. Thunderbird Road, Glendale, AZ 85306, USA
| | - Lin Zhang
- China Innovation Center, Shimadzu (China) Co., Beijing Branch, Beijing 100020, China
| | - Morteza Abbaszadegan
- School of Sustainable Engineering and the Built Environment, Arizona State University at the Tempe Campus, 1151 S. Forest Ave, Tempe, AZ 85281, USA
- Correspondence:
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Zhang XH, Ahmad W, Zhu XY, Chen J, Austin B. Viable but nonculturable bacteria and their resuscitation: implications for cultivating uncultured marine microorganisms. MARINE LIFE SCIENCE & TECHNOLOGY 2021; 3:189-203. [PMID: 37073345 PMCID: PMC10077291 DOI: 10.1007/s42995-020-00041-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 03/25/2020] [Indexed: 05/03/2023]
Abstract
Culturing has been the cornerstone of microbiology since Robert Koch first successfully cultured bacteria in the late nineteenth century. However, even today, the majority of microorganisms in the marine environment remain uncultivated. There are various explanations for the inability to culture bacteria in the laboratory, including lack of essential nutrients, osmotic support or incubation conditions, low growth rate, development of micro-colonies, and the presence of senescent or viable but nonculturable (VBNC) cells. In the marine environment, many bacteria have been associated with dormancy, as typified by the VBNC state. VBNC refers to a state where bacteria are metabolically active, but are no longer culturable on routine growth media. It is apparently a unique survival strategy that has been adopted by many microorganisms in response to harsh environmental conditions and the bacterial cells in the VBNC state may regain culturability under favorable conditions. The resuscitation of VBNC cells may well be an important way to cultivate the otherwise uncultured microorganisms in marine environments. Many resuscitation stimuli that promote the restoration of culturability have so far been identified; these include sodium pyruvate, quorum sensing autoinducers, resuscitation-promoting factors Rpfs and YeaZ, and catalase. In this review, we focus on the issues associated with bacterial culturability, the diversity of bacteria entering the VBNC state, mechanisms of induction into the VBNC state, resuscitation factors of VBNC cells and implications of VBNC resuscitation stimuli for cultivating these otherwise uncultured microorganisms. Bringing important microorganisms into culture is still important in the era of high-throughput sequencing as their ecological functions in the marine environment can often only be known through isolation and cultivation.
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Affiliation(s)
- Xiao-Hua Zhang
- College of Marine Life Sciences and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071 China
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, 266100 China
| | - Waqar Ahmad
- College of Marine Life Sciences and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Xiao-Yu Zhu
- College of Marine Life Sciences and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
| | - Jixiang Chen
- School of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou, 730050 China
| | - Brian Austin
- Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA Scotland, UK
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4
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van der Loo C, Bartie C, Barnard TG, Potgieter N. Detection of Free-Living Amoebae and Their Intracellular Bacteria in Borehole Water before and after a Ceramic Pot Filter Point-of-Use Intervention in Rural Communities in South Africa. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:3912. [PMID: 33917870 PMCID: PMC8068299 DOI: 10.3390/ijerph18083912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 03/26/2021] [Accepted: 04/02/2021] [Indexed: 11/21/2022]
Abstract
Free-living amoebae (FLA) are ubiquitous in nature, whereas amoeba-resistant bacteria (ARB) have evolved virulent mechanisms that allow them to resist FLA digestion mechanisms and survive inside the amoeba during hostile environmental conditions. This study assessed the prevalence of FLA and ARB species in borehole water before and after a ceramic point-of-use intervention in rural households. A total of 529 water samples were collected over a five-month period from 82 households. All water samples were subjected to amoebal enrichment, bacterial isolation on selective media, and molecular identification using 16S PCR/sequencing to determine ARB species and 18S rRNA PCR/sequencing to determine FLA species present in the water samples before and after the ceramic pot intervention. Several FLA species including Acanthamoeba spp. and Mycobacterium spp. were isolated. The ceramic pot filter removed many of these microorganisms from the borehole water. However, design flaws could have been responsible for some FLA and ARB detected in the filtered water. FLA and their associated ARB are ubiquitous in borehole water, and some of these species might be potentially harmful and a health risk to vulnerable individuals. There is a need to do more investigations into the health risk of these organisms after point-of-use treatment.
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Affiliation(s)
- Clarissa van der Loo
- Water and Health Research Centre, Faculty of Health Sciences, University of Johannesburg, Johannesburg 2094, South Africa; (C.v.d.L.); (T.G.B.)
| | | | - Tobias George Barnard
- Water and Health Research Centre, Faculty of Health Sciences, University of Johannesburg, Johannesburg 2094, South Africa; (C.v.d.L.); (T.G.B.)
| | - Natasha Potgieter
- Environmental Health, Domestic Hygiene and Microbial Pathogens Research Group, Department of Microbiology, University of Venda, Thohoyandou 1950, South Africa
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5
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Nisar MA, Ross KE, Brown MH, Bentham R, Whiley H. Legionella pneumophila and Protozoan Hosts: Implications for the Control of Hospital and Potable Water Systems. Pathogens 2020; 9:pathogens9040286. [PMID: 32326561 PMCID: PMC7238060 DOI: 10.3390/pathogens9040286] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 04/10/2020] [Accepted: 04/14/2020] [Indexed: 12/12/2022] Open
Abstract
Legionella pneumophila is an opportunistic waterborne pathogen of public health concern. It is the causative agent of Legionnaires’ disease (LD) and Pontiac fever and is ubiquitous in manufactured water systems, where protozoan hosts and complex microbial communities provide protection from disinfection procedures. This review collates the literature describing interactions between L. pneumophila and protozoan hosts in hospital and municipal potable water distribution systems. The effectiveness of currently available water disinfection protocols to control L. pneumophila and its protozoan hosts is explored. The studies identified in this systematic literature review demonstrated the failure of common disinfection procedures to achieve long term elimination of L. pneumophila and protozoan hosts from potable water. It has been demonstrated that protozoan hosts facilitate the intracellular replication and packaging of viable L. pneumophila in infectious vesicles; whereas, cyst-forming protozoans provide protection from prolonged environmental stress. Disinfection procedures and protozoan hosts also facilitate biogenesis of viable but non-culturable (VBNC) L. pneumophila which have been shown to be highly resistant to many water disinfection protocols. In conclusion, a better understanding of L. pneumophila-protozoan interactions and the structure of complex microbial biofilms is required for the improved management of L. pneumophila and the prevention of LD.
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Braun RS, Mendis N, Li L, Faucher SP. Quantification of Viable but Non-Culturable Cells of Legionella pneumophila. Methods Mol Biol 2019; 1921:45-53. [PMID: 30694484 DOI: 10.1007/978-1-4939-9048-1_3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Legionella pneumophila, among other bacteria, may enter a viable but non-culturable state as a means for survival in stressful conditions. Bacterial cells in the viable but non-culturable state cannot grow on standard medium; however, they continue to exhibit characteristics that are associated with live cells, such as respiration, transcription, and cell wall integrity. The present paper outlines a detailed protocol for the detection of viable but non-culturable L. pneumophila cells via Syto® 9 and propidium iodide staining coupled with flow cytometry.
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Affiliation(s)
- Rosalie S Braun
- New York University College of Dentistry, New York, NY, USA
- Faculty of Agricultural and Environmental Sciences, Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Nilmini Mendis
- Faculty of Agricultural and Environmental Sciences, Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Laam Li
- Faculty of Agricultural and Environmental Sciences, Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
- Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong
| | - Sebastien P Faucher
- Faculty of Agricultural and Environmental Sciences, Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada.
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Delafont V, Rodier MH, Maisonneuve E, Cateau E. Vermamoeba vermiformis: a Free-Living Amoeba of Interest. MICROBIAL ECOLOGY 2018; 76:991-1001. [PMID: 29737382 DOI: 10.1007/s00248-018-1199-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 04/30/2018] [Indexed: 05/22/2023]
Abstract
Free-living amoebae are protists that are widely distributed in the environment including water, soil, and air. Although the amoebae of the genus Acanthamoeba are still the most studied, other species, such as Vermamoeba vermiformis (formerly Hartmannella vermiformis), are the subject of increased interest. Found in natural or man-made aquatic environments, V. vermiformis can support the multiplication of other microorganisms and is able to harbor and potentially protect pathogenic bacteria or viruses. This feature is to be noted because of the presence of this thermotolerant amoeba in hospital water networks. As a consequence, this protist could be implicated in health concerns and be indirectly responsible for healthcare-related infections. This review highlights, among others, the consequences of V. vermiformis relationships with other microorganisms and shows that this free-living amoeba species is therefore of interest for public health.
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Affiliation(s)
- Vincent Delafont
- Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipe Microbiologie de l'Eau, Université de Poitiers, 1 rue Georges Bonnet, 86022, Poitiers Cedex, France
| | - Marie-Helene Rodier
- Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipe Microbiologie de l'Eau, Université de Poitiers, 1 rue Georges Bonnet, 86022, Poitiers Cedex, France
- Laboratoire de parasitologie et mycologie, CHU La Milètrie, 86021, Poitiers Cedex, France
| | - Elodie Maisonneuve
- Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipe Microbiologie de l'Eau, Université de Poitiers, 1 rue Georges Bonnet, 86022, Poitiers Cedex, France
| | - Estelle Cateau
- Ecologie et Biologie des Interactions, UMR CNRS 7267, Equipe Microbiologie de l'Eau, Université de Poitiers, 1 rue Georges Bonnet, 86022, Poitiers Cedex, France.
- Laboratoire de parasitologie et mycologie, CHU La Milètrie, 86021, Poitiers Cedex, France.
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8
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Alqarni B, Colley B, Klebensberger J, McDougald D, Rice SA. Expression stability of 13 housekeeping genes during carbon starvation of Pseudomonas aeruginosa. J Microbiol Methods 2016; 127:182-187. [PMID: 27297333 DOI: 10.1016/j.mimet.2016.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 06/09/2016] [Accepted: 06/09/2016] [Indexed: 11/29/2022]
Abstract
Quantitative real-time polymerase chain reaction (qRT-PCR) is a reliable technique for quantifying mRNA levels when normalised by a stable reference gene/s. Many putative reference genes are known to be affected by physiological stresses, such as nutrient limitation and hence may not be suitable for normalisation. In this study of Pseudomonas aeruginosa, the expression of 13 commonly used reference genes, rpoS, proC, recA, rpsL, rho, oprL, anr, tipA, nadB, fabD, ampC, algD and gyrA, were analysed for changes in expression under carbon starvation and nutrient replete conditions. The results showed that rpoS was the only stably expressed housekeeping gene during carbon starvation. In contrast, other commonly used housekeeping genes were shown to vary by as much as 10-100 fold under starvation conditions. This study has identified a suitable reference gene for qRT-PCR in P. aeruginosa during carbon starvation. The results presented here highlight the need to validate housekeeping genes under the chosen experimental conditions.
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Affiliation(s)
- Budoor Alqarni
- Centre for Marine Bio-Innovation, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia; The School of Biotechnology and Biomolecular Sciences, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia
| | - Brendan Colley
- Centre for Marine Bio-Innovation, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia; The School of Biotechnology and Biomolecular Sciences, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia
| | - Janosch Klebensberger
- University of Stuttgart, Institute of Technical Biochemistry, Allmandring 31, D-70569 Stuttgart, Germany
| | - Diane McDougald
- The ithree Institute, The University of Technology Sydney, Australia; Singapore Centre for Environmental Life Sciences Engineering and the School of Biological Sciences, Nanyang Technological University, Singapore
| | - Scott A Rice
- Centre for Marine Bio-Innovation, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia; The School of Biological, Earth and Environmental Sciences, The University of New South Wales, Sydney, New South Wales, Australia; Singapore Centre for Environmental Life Sciences Engineering and the School of Biological Sciences, Nanyang Technological University, Singapore.
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9
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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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10
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Exposure to synthetic gray water inhibits amoeba encystation and alters expression of Legionella pneumophila virulence genes. Appl Environ Microbiol 2014; 81:630-9. [PMID: 25381242 DOI: 10.1128/aem.03394-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Water conservation efforts have focused on gray water (GW) usage, especially for applications that do not require potable water quality. However, there is a need to better understand environmental pathogens and their free-living amoeba (FLA) hosts within GW, given their growth potential in stored gray water. Using synthetic gray water (sGW) we examined three strains of the water-based pathogen Legionella pneumophila and its FLA hosts Acanthamoeba polyphaga, A. castellanii, and Vermamoeba vermiformis. Exposure to sGW for 72 h resulted in significant inhibition (P < 0.0001) of amoebal encystation versus control-treated cells, with the following percentages of cysts in sGW versus controls: A. polyphaga (0.6 versus 6%), A. castellanii (2 versus 62%), and V. vermiformis (1 versus 92%), suggesting sGW induced maintenance of the actively feeding trophozoite form. During sGW exposure, L. pneumophila culturability decreased as early as 5 h (1.3 to 2.9 log10 CFU, P < 0.001) compared to controls (Δ0 to 0.1 log10 CFU) with flow cytometric analysis revealing immediate changes in membrane permeability. Furthermore, reverse transcription-quantitative PCR was performed on total RNA isolated from L. pneumophila cells at 0 to 48 h after sGW incubation, and genes associated with virulence (gacA, lirR, csrA, pla, and sidF), the type IV secretion system (lvrB and lvrE), and metabolism (ccmF and lolA) were all shown to be differentially expressed. These results suggest that conditions within GW may promote interactions between water-based pathogens and FLA hosts, through amoebal encystment inhibition and alteration of bacterial gene expression, thus warranting further exploration into FLA and L. pneumophila behavior in GW systems.
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11
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Ramamurthy T, Ghosh A, Pazhani GP, Shinoda S. Current Perspectives on Viable but Non-Culturable (VBNC) Pathogenic Bacteria. Front Public Health 2014; 2:103. [PMID: 25133139 PMCID: PMC4116801 DOI: 10.3389/fpubh.2014.00103] [Citation(s) in RCA: 251] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 07/15/2014] [Indexed: 11/07/2022] Open
Abstract
Under stress conditions, many species of bacteria enter into starvation mode of metabolism or a physiologically viable but non-culturable (VBNC) state. Several human pathogenic bacteria have been reported to enter into the VBNC state under these conditions. The pathogenic VBNC bacteria cannot be grown using conventional culture media, although they continue to retain their viability and express their virulence. Though there have been debates on the VBNC concept in the past, several molecular studies have shown that not only can the VBNC state be induced under in vitro conditions but also that resuscitation from this state is possible under appropriate conditions. The most notable advance in resuscitating VBNC bacteria is the discovery of resuscitation-promoting factor (Rpf), which is a bacterial cytokines found in both Gram-positive and Gram-negative organisms. VBNC state is a survival strategy adopted by the bacteria, which has important implication in several fields, including environmental monitoring, food technology, and infectious disease management; and hence it is important to investigate the association of bacterial pathogens under VBNC state and the water/foodborne outbreaks. In this review, we describe various aspects of VBNC bacteria, which include their proteomic and genetic profiles under the VBNC state, conditions of resuscitation, methods of detection, antibiotic resistance, and observations on Rpf.
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Affiliation(s)
| | - Amit Ghosh
- National Institute of Cholera and Enteric Diseases (NICED) , Kolkata , India
| | - Gururaja P Pazhani
- National Institute of Cholera and Enteric Diseases (NICED) , Kolkata , India
| | - Sumio Shinoda
- Collaborative Research Center of Okayama University for Infectious Diseases in India, NICED , Kolkata , India
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12
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Li L, Mendis N, Trigui H, Oliver JD, Faucher SP. The importance of the viable but non-culturable state in human bacterial pathogens. Front Microbiol 2014; 5:258. [PMID: 24917854 PMCID: PMC4040921 DOI: 10.3389/fmicb.2014.00258] [Citation(s) in RCA: 546] [Impact Index Per Article: 54.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 05/12/2014] [Indexed: 12/12/2022] Open
Abstract
Many bacterial species have been found to exist in a viable but non-culturable (VBNC) state since its discovery in 1982. VBNC cells are characterized by a loss of culturability on routine agar, which impairs their detection by conventional plate count techniques. This leads to an underestimation of total viable cells in environmental or clinical samples, and thus poses a risk to public health. In this review, we present recent findings on the VBNC state of human bacterial pathogens. The characteristics of VBNC cells, including the similarities and differences to viable, culturable cells and dead cells, and different detection methods are discussed. Exposure to various stresses can induce the VBNC state, and VBNC cells may be resuscitated back to culturable cells under suitable stimuli. The conditions that trigger the induction of the VBNC state and resuscitation from it are summarized and the mechanisms underlying these two processes are discussed. Last but not least, the significance of VBNC cells and their potential influence on human health are also reviewed.
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Affiliation(s)
- Laam Li
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University Ste-Anne-de-Bellevue, QC, Canada
| | - Nilmini Mendis
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University Ste-Anne-de-Bellevue, QC, Canada
| | - Hana Trigui
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University Ste-Anne-de-Bellevue, QC, Canada
| | - James D Oliver
- Department of Biology, University of North Carolina at Charlotte Charlotte, NC, USA
| | - Sebastien P Faucher
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University Ste-Anne-de-Bellevue, QC, Canada
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13
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Buse HY, Lu J, Lu X, Mou X, Ashbolt NJ. Microbial diversities (16S and 18S rRNA gene pyrosequencing) and environmental pathogens within drinking water biofilms grown on the common premise plumbing materials unplasticized polyvinylchloride and copper. FEMS Microbiol Ecol 2014; 88:280-95. [PMID: 24490699 DOI: 10.1111/1574-6941.12294] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 01/08/2014] [Accepted: 01/23/2014] [Indexed: 11/29/2022] Open
Abstract
Drinking water (DW) biofilm communities influence the survival of opportunistic pathogens, yet knowledge about the microbial composition of DW biofilms developed on common in-premise plumbing material is limited. Utilizing 16S and 18S rRNA gene pyrosequencing, this study characterized the microbial community structure within DW biofilms established on unplasticized polyvinyl chloride (uPVC) and copper (Cu) surfaces and the impact of introducing Legionella pneumophila (Lp) and Acanthamoeba polyphaga. Mature (> 1 year old) biofilms were developed before inoculation with sterilized DW (control, Con), Lp, or Lp and A. polyphaga (LpAp). Comparison of uPVC and Cu biofilms indicated significant differences between bacterial (P = 0.001) and eukaryotic (P < 0.01) members attributable to the unique presence of several family taxa: Burkholderiaceae, Characeae, Epistylidae, Goniomonadaceae, Paramoebidae, Plasmodiophoridae, Plectidae, Sphenomonadidae, and Toxariaceae within uPVC biofilms; and Enterobacteriaceae, Erythrobacteraceae, Methylophilaceae, Acanthamoebidae, and Chlamydomonadaceae within Cu biofilms. Introduction of Lp alone or with A. polyphaga had no effect on bacterial community profiles (P > 0.05) but did affect eukaryotic members (uPVC, P < 0.01; Cu, P = 0.001). Thus, established DW biofilms host complex communities that may vary based on substratum matrix and maintain consistent bacterial communities despite introduction of Lp, an environmental pathogen.
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