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Silva AR, Melo LF, Keevil CW, Pereira A. Legionella colonization and 3D spatial location within a Pseudomonas biofilm. Sci Rep 2024; 14:16781. [PMID: 39039267 PMCID: PMC11263398 DOI: 10.1038/s41598-024-67712-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Accepted: 07/15/2024] [Indexed: 07/24/2024] Open
Abstract
Biofilms are known to be critical for Legionella settlement in engineered water systems and are often associated with Legionnaire's Disease events. One of the key features of biofilms is their heterogeneous three-dimensional structure which supports the establishment of microbial interactions and confers protection to microorganisms. This work addresses the impact of Legionella pneumophila colonization of a Pseudomonas fluorescens biofilm, as information about the interactions between Legionella and biofilm structures is scarce. It combines a set of meso- and microscale biofilm analyses (Optical Coherence Tomography, Episcopic Differential Interference Contrast coupled with Epifluorescence Microscopy and Confocal Laser Scanning Microscopy) with PNA-FISH labelled L. pneumophila to tackle the following questions: (a) does the biofilm structure change upon L. pneumophila biofilm colonization?; (b) what happens to L. pneumophila within the biofilm over time and (c) where is L. pneumophila preferentially located within the biofilm? Results showed that P. fluorescens structure did not significantly change upon L. pneumophila colonization, indicating the competitive advantage of the first colonizer. Imaging of PNA-labelled L. pneumophila showed that compared to standard culture recovery it colonized to a greater extent the 3-day-old P. fluorescens biofilms, presumably entering in VBNC state by the end of the experiment. L. pneumophila was mostly located in the bottom regions of the biofilm, which is consistent with the physiological requirements of both bacteria and confers enhanced Legionella protection against external aggressions. The present study provides an expedited methodological approach to address specific systematic laboratory studies concerning the interactions between L. pneumophila and biofilm structure that can provide, in the future, insights for public health Legionella management of water systems.
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Affiliation(s)
- Ana Rosa Silva
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
| | - Luis F Melo
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal
| | - C William Keevil
- School of Biological Sciences, University of Southampton, Southampton, UK
| | - Ana Pereira
- LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
- ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
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Niu H, Gu J, Zhang Y. Bacterial persisters: molecular mechanisms and therapeutic development. Signal Transduct Target Ther 2024; 9:174. [PMID: 39013893 PMCID: PMC11252167 DOI: 10.1038/s41392-024-01866-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 05/06/2024] [Accepted: 05/13/2024] [Indexed: 07/18/2024] Open
Abstract
Persisters refer to genetically drug susceptible quiescent (non-growing or slow growing) bacteria that survive in stress environments such as antibiotic exposure, acidic and starvation conditions. These cells can regrow after stress removal and remain susceptible to the same stress. Persisters are underlying the problems of treating chronic and persistent infections and relapse infections after treatment, drug resistance development, and biofilm infections, and pose significant challenges for effective treatments. Understanding the characteristics and the exact mechanisms of persister formation, especially the key molecules that affect the formation and survival of the persisters is critical to more effective treatment of chronic and persistent infections. Currently, genes related to persister formation and survival are being discovered and confirmed, but the mechanisms by which bacteria form persisters are very complex, and there are still many unanswered questions. This article comprehensively summarizes the historical background of bacterial persisters, details their complex characteristics and their relationship with antibiotic tolerant and resistant bacteria, systematically elucidates the interplay between various bacterial biological processes and the formation of persister cells, as well as consolidates the diverse anti-persister compounds and treatments. We hope to provide theoretical background for in-depth research on mechanisms of persisters and suggest new ideas for choosing strategies for more effective treatment of persistent infections.
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Affiliation(s)
- Hongxia Niu
- School of Basic Medical Science and Key Laboratory of Blood-stasis-toxin Syndrome of Zhejiang Province, Zhejiang Chinese Medical University, Hangzhou, 310053, Zhejiang, China
| | - Jiaying Gu
- School of Basic Medical Science and Key Laboratory of Blood-stasis-toxin Syndrome of Zhejiang Province, Zhejiang Chinese Medical University, Hangzhou, 310053, Zhejiang, China
| | - Ying Zhang
- State Key Laboratory for the Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, 310003, Zhejiang, China.
- Jinan Microecological Biomedicine Shandong Laboratory, Jinan, 250022, Shandong, China.
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Párraga-Niño N, Cortès-Tarragó R, Quero S, Garcia-Núñez M, Arqué E, Sabaté S, Ramirez D, Gavaldà L. Persistence of viable but nonculturable Legionella pneumophila state in hospital water systems: A hidden enemy? THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 927:172410. [PMID: 38608884 DOI: 10.1016/j.scitotenv.2024.172410] [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: 02/09/2024] [Revised: 04/09/2024] [Accepted: 04/09/2024] [Indexed: 04/14/2024]
Abstract
There is little evidence of the long-term consequences of maintaining sanitary hot water at high temperatures on the persistence of Legionella in the plumbing system. The aims of this study were to describe the persistence and genotypic variability of L. pneumophila in a hospital building with two entirely independent hot water distribution systems, and to estimate the thermotolerance of the genotypic variants by studying the quantity of VBNC L. pneumophila. Eighty isolates from 55 water samples obtained between the years 2012-2017 were analyzed. All isolates correspond to L. pneumophila serogroup 6. The isolates were discriminated in four restriction patterns by pulsed-field gel electrophoresis. In one installation, pattern A + Aa predominated, accounting for 75.8 % of samples, while the other installation exhibited pattern B as the most frequent (81.8 % of samples; p < 0.001). The mean temperature of the isolates was: 52.6 °C (pattern A + Aa) and 55.0 °C (pattern B), being significantly different. Nine strains were selected as representative among patterns to study their thermotolerance by flow-cytometry after 24 h of thermic treatment. VBNC bacteria were detected in all samples. After thermic treatment at 50 °C, 52.0 % of bacteria had an intact membrane, and after 55 °C this percentage decreased to 23.1 %. Each pattern exhibited varying levels of thermotolerance. These findings indicate that the same hospital building can be colonized with different predominant types of Legionella if it has independent hot water installations. Maintaining a minimum temperature of 50 °C at distal points of the system would allow the survival of replicative L. pneumophila. However, the presence of Legionella in hospital water networks is underestimated if culture is considered as the standard method for Legionella detection, because VBNC do not grow on culture plates. This phenomenon can carry implications for the Legionella risk management plans in hospitals that adjust their control measures based on the microbiological surveillance of water.
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Affiliation(s)
- Noemí Párraga-Niño
- Clinical and environmental infectious diseases study group, Fundació Institut d'Investigació Germans Trias i Pujol, Carretera de Can Ruti, Camí de les Escoles s/n, 08916 Badalona, Barcelona, Spain; Fundació Lluita contra les Infeccions, Carretera de Can Ruti, 08916 Badalona, Barcelona, Spain.
| | - Roger Cortès-Tarragó
- Clinical and environmental infectious diseases study group, Fundació Institut d'Investigació Germans Trias i Pujol, Carretera de Can Ruti, Camí de les Escoles s/n, 08916 Badalona, Barcelona, Spain
| | - Sara Quero
- Clinical and environmental infectious diseases study group, Fundació Institut d'Investigació Germans Trias i Pujol, Carretera de Can Ruti, Camí de les Escoles s/n, 08916 Badalona, Barcelona, Spain; Fundació Lluita contra les Infeccions, Carretera de Can Ruti, 08916 Badalona, Barcelona, Spain; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Av. Monforte de Lemos, 3-5. Pabellón 11. Planta 0, 28029 Madrid, Spain; Parc Taulí Hospital Universitari, Institut d'Investigació i Innovació Parc Taulí (I3PT-CERCA), Universitat Autònoma de Barcelona, Plaça Torre de l'Aigua, s/n, 08208 Sabadell, Barcelona, Spain
| | - Marian Garcia-Núñez
- Clinical and environmental infectious diseases study group, Fundació Institut d'Investigació Germans Trias i Pujol, Carretera de Can Ruti, Camí de les Escoles s/n, 08916 Badalona, Barcelona, Spain
| | - Elisenda Arqué
- Clinical and environmental infectious diseases study group, Fundació Institut d'Investigació Germans Trias i Pujol, Carretera de Can Ruti, Camí de les Escoles s/n, 08916 Badalona, Barcelona, Spain
| | - Sara Sabaté
- Agència de Salut Pública de Barcelona (ASPB), Plaza Lesseps 1, 08023 Barcelona, Spain; Institut d'Investigació Biomèdica Sant Pau (IIB SANT PAU), Sant Quintí 77-79, 08041 Barcelona, Spain
| | - Dolors Ramirez
- Department of Preventive Medicine-Hospital Hygiene. Hospital Universitari de Bellvitge-IDIBELL, Barcelona, Spain
| | - Laura Gavaldà
- Department of Preventive Medicine-Hospital Hygiene. Hospital Universitari de Bellvitge-IDIBELL, Barcelona, Spain
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Liao L, Luo ZQ, Byeon JH, Park JH. Size-selective sampler combined with an immunochromatographic assay for the rapid detection of airborne Legionella pneumophila. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 927:172085. [PMID: 38554967 DOI: 10.1016/j.scitotenv.2024.172085] [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: 01/02/2024] [Revised: 03/04/2024] [Accepted: 03/27/2024] [Indexed: 04/02/2024]
Abstract
Airborne biological aerosols (also called bioaerosols) are found in various environmental and occupational settings. Among these, pathogenic bioaerosols can cause diseases such as legionellosis, influenza, measles, and tuberculosis. To prevent or minimize people's exposure to these pathogenic bioaerosols in the field, a rapid detection method is required. In this study, a size-selective bioaerosol (SSB) sampler was combined with the immunochromatographic assay (ICA). The SSB sampler can collect bioaerosols on the sampling swab and the lateral flow test kit used in ICA can rapidly detect the pathogens in bioaerosols collected on the swab. Before testing the combined method, the lower limit of detection (LOD) of the lateral flow test kit was determined. Legionella pneumophila (L. pneumophila) was used as a target pathogen. The results show that at least 1.3 × 103L. pneumophila cells are required to be detected by the lateral flow test kit. To test the developed method, L. pneumophila suspension was aerosolized in the sampling chamber and collected using two SSB samplers with different sampling times (10 and 20 min). The developed method could detect aerosolized L. pneumophila and also estimate the concentrations from the lower LOD, sampling time, and formation of a positive line on a test strip. When positive results were obtained from sampling for 10 min and 20 min, concentrations of respirable L. pneumophila were estimated ≥5.2 × 104 CFUresp/m3 and ≥2.6 × 104 CFUresp/m3, respectively. The conventional sampler Andersen impactor with colony counting was also used for comparison. In all cases, the estimated concentrations obtained by the developed method were higher than those obtained by the conventional method. These findings confirm that the developed method can overcome the limitations of conventional methods and eventually benefit environmental and occupational health by providing a better method for risk assessment.
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Affiliation(s)
- Li Liao
- School of Health Sciences, Purdue University, West Lafayette, IN 47906, USA
| | - Zhao-Qing Luo
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47906, USA
| | - Jeong Hoon Byeon
- School of Mechanical Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea.
| | - Jae Hong Park
- School of Health Sciences, Purdue University, West Lafayette, IN 47906, USA.
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5
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İzgördü ÖK, Gurbanov R, Darcan C. Understanding the transition to viable but non-culturable state in Escherichia coli W3110: a comprehensive analysis of potential spectrochemical biomarkers. World J Microbiol Biotechnol 2024; 40:203. [PMID: 38753033 PMCID: PMC11098925 DOI: 10.1007/s11274-024-04019-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 05/09/2024] [Indexed: 05/19/2024]
Abstract
The viable but non-culturable (VBNC) state is considered a survival strategy employed by bacteria to endure stressful conditions, allowing them to stay alive. Bacteria in this state remain unnoticed in live cell counts as they cannot proliferate in standard culture media. VBNC cells pose a significant health risk because they retain their virulence and can revive when conditions normalize. Hence, it is crucial to develop fast, reliable, and cost-effective methods to detect bacteria in the VBNC state, particularly in the context of public health, food safety, and microbial control assessments. This research examined the biomolecular changes in Escherichia coli W3110 induced into the VBNC state in artificial seawater under three different stress conditions (temperature, metal, and antibiotic). Initially, confirmation of VBNC cells under various stresses was done using fluorescence microscopy and plate counts. Subsequently, lipid peroxidation was assessed through the TBARS assay, revealing a notable increase in peroxidation end-products in VBNC cells compared to controls. ATR-FTIR spectroscopy and chemomometrics were employed to analyze biomolecular changes, uncovering significant spectral differences in RNA, protein, and nucleic acid concentrations in VBNC cells compared to controls. Notably, RNA levels increased, while protein and nucleic acid amounts decreased. ROC analyses identified the 995 cm- 1 RNA band as a consistent marker across all studied stress conditions, suggesting its potential as a robust biomarker for detecting cells induced into the VBNC state under various stressors.
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Affiliation(s)
- Özge Kaygusuz İzgördü
- Biotechnology Application and Research Center, Bilecik Şeyh Edebali University, Bilecik, Turkey
- Department of Molecular Biology and Genetics, Institute of Graduate Education, Bilecik Şeyh Edebali University, Bilecik, Turkey
| | - Rafig Gurbanov
- Department of Bioengineering, Bilecik Şeyh Edebali University, Bilecik, Turkey.
- Central Research Laboratory, Bilecik Şeyh Edebali University, Bilecik, Turkey.
| | - Cihan Darcan
- Department of Molecular Biology and Genetics, Bilecik Şeyh Edebali University, Bilecik, Turkey
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Shi Y, Wen T, Zhao F, Hu J. Bacteriostasis of nisin against planktonic and biofilm bacteria: Its mechanism and application. J Food Sci 2024; 89:1894-1916. [PMID: 38477236 DOI: 10.1111/1750-3841.17001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 01/27/2024] [Accepted: 02/09/2024] [Indexed: 03/14/2024]
Abstract
Food safety incidents caused by bacterial contamination have always been one of the public safety issues of social concern. Planktonic cells, viable but non-culturable (VBNC) cells, and biofilm cells of bacteria can coexist in food or food processing, posing more serious challenges to public health and safety by increasing bacterial survival and difficulty in detection. As a non-toxic, no side effect, and highly effective bacteriostatic substance, nisin has received wide attention from researchers. In this review, we summarized the species and biosynthesis of nisin, the effects of nisin alone or in combination with other treatments on planktonic and biofilm cells, and its applications in the fields of food, feed, and medicine by consulting numerous studies. Meanwhile, the mechanism of nisin on planktonic and biofilm cells was proposed based on existing researches. Nisin not only has antibacterial activity against most G+ bacteria but also exhibits a bacteriostatic effect on G- bacteria when combined with other antibacterial treatments. In addition to planktonic cells, nisin also has significant effects on bacterial cells in biofilms by changing the thickness, density, and composition of biofilms. Based on the three action processes of nisin on biofilms, we summarized the changes of bacteria in biofilms, including the causes of bacterial death and the formation of the VBNC state. We consider that research on the relationship between nisin and VBNC state should be strengthened.
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Affiliation(s)
- Ying Shi
- College of Food Science and Engineering, Jilin University, Changchun, P. R. China
| | - Tao Wen
- College of Food Science and Engineering, Jilin University, Changchun, P. R. China
| | - Feng Zhao
- College of Food Science and Engineering, Jilin University, Changchun, P. R. China
| | - Jia Hu
- College of Food Science and Engineering, Jilin University, Changchun, P. R. China
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Liang J, Cameron G, Faucher SP. Development of heat-shock resistance in Legionella pneumophila modeled by experimental evolution. Appl Environ Microbiol 2023; 89:e0066623. [PMID: 37668382 PMCID: PMC10537758 DOI: 10.1128/aem.00666-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 06/29/2023] [Indexed: 09/06/2023] Open
Abstract
Because it can grow in buildings with complex hot water distribution systems (HWDS), healthcare facilities recognize the waterborne bacterium Legionella pneumophila as a major nosocomial infection threat and often try to clear the systems with a pasteurization process known as superheat-and-flush. After this treatment, many facilities find that the contaminating populations slowly recover, suggesting the possibility of in situ evolution favoring increased survival in high-temperature conditions. To mimic this process in a controlled environment, an adaptive laboratory evolution model was used to select a wild-type strain of L. pneumophila for survival to transient exposures to temperatures characteristic of routine hot water use or failed pasteurization processes in HWDS. Over their evolution, these populations became insensitive to exposure to 55°C and developed the ability to survive short exposures to 59°C heat shock. Heat-adapted lineages maintained a higher expression of heat-shock genes during low-temperature incubation in freshwater, suggesting a pre-adaptation to heat stress. Although there were distinct mutation profiles in each of the heat-adapted lineages, each acquired multiple mutations in the DnaJ/DnaK/ClpB disaggregase complex, as well as mutations in chaperone htpG and protease clpX. These mutations were specific to heat-shock survival and were not seen in control lineages included in the experimental model without exposure to heat shock. This study supports in situ observations of adaptation to heat stress and demonstrates the potential of L. pneumophila to develop resistance to control measures. IMPORTANCE As a bacterium that thrives in warm water ecosystems, Legionella pneumophila is a key factor motivating regulations on hot water systems. Two major measures to control Legionella are high circulating temperatures intended to curtail growth and the use of superheat-and-flush pasteurization processes to eliminate established populations. Facilities often suffer recolonization of their hot water systems; hospitals are particularly at risk due to the severe nosocomial pneumoniae caused by Legionella. To understand these long-term survivors, we have used an adaptive laboratory evolution model to replicate this process. We find major differences between the mutational profiles of heat-adapted and heat-naïve L. pneumophila populations including mutations in major heat-shock genes like chaperones and proteases. This model demonstrates that well-validated treatment protocols are needed to clear contaminated systems and-in an analog to antibiotic resistance-the importance of complete eradication of the resident population to prevent selection for more persistent bacteria.
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Affiliation(s)
- Jeffrey Liang
- Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Québec, Canada
| | - Gillian Cameron
- Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Québec, Canada
| | - Sébastien P. Faucher
- Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, Québec, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada
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Tsai CM, Chen CH, Cheng WH, Stelma FF, Li SC, Lin WC. Homeostasis of cellular amino acids in Acanthamoeba castellanii exposed to different media under amoeba-bacteria coculture conditions. BMC Microbiol 2023; 23:198. [PMID: 37495951 PMCID: PMC10373360 DOI: 10.1186/s12866-023-02942-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 07/11/2023] [Indexed: 07/28/2023] Open
Abstract
BACKGROUND Acanthamoeba castellanii is a free-living protist that feeds on diverse bacteria. A. castellanii has frequently been utilized in studies on microbial interactions. Grazing bacteria also exhibit diverse effects on the physiological characteristics of amoebae, such as their growth, encystation, and cytotoxicity. Since the composition of amoebae amino acids is closely related to cellular activities, it can indicate the overall responses of A. castellanii to various stimuli. METHOD A. castellanii was exposed to different culture conditions in low-nutrient medium with heat-killed DH5α to clarify their effects. A targeted metabolomic technique was utilized to evaluate the concentration of cellular amino acids. The amino acid composition and pathways were analyzed by two web-based tools: MetaboAnalyst and Pathview. Then, long-term exposure to A. castellanii was investigated through in silico and in vitro methods to elucidate the homeostasis of amino acids and the growth of A. castellanii. RESULTS Under short-term exposure, all kinds of amino acids were enriched in all exposed groups. In contrast to the presence of heat-killed bacteria, the medium exhibited obvious effects on the amino acid composition of A. castellanii. After long-term exposure, the amino acid composition was more similar to that of the control group. A. castellanii may achieve amino acid homeostasis through pathways related to alanine, aspartate, citrulline, and serine. DISCUSSION Under short-term exposure, compared to the presence of bacteria, the type of medium exerted a more powerful effect on the amino acid composition of the amoeba. Previous studies focused on the interaction of the amoeba and bacteria with effective secretion systems and effectors. This may have caused the effects of low-nutrient environments to be overlooked. CONCLUSION When A. castellanii was stimulated in the coculture system through various methods, such as the presence of bacteria and a low-nutrient environment, it accumulated intracellular amino acids within a short period. However, different stimulations correspond to different amino acid compositions. After long-term exposure, A. castellanii achieved an amino acid equilibrium by downregulating the biosynthesis of several amino acids.
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Affiliation(s)
- Chih-Ming Tsai
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chun-Hsien Chen
- Department of Parasitology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Hung Cheng
- Department of Parasitology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Foekje F. Stelma
- Department of Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands
| | - Sung-Chou Li
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
- Department of Nursing, Meiho University, Pingtung, Taiwan
| | - Wei-Chen Lin
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Parasitology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Department of Microbiology and Immunology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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Farina C, Cacciabue E, Averara F, Ferri N, Vailati F, Del Castillo G, Serafini A, Fermi B, Doniselli N, Pezzoli F. Water Safety Plan, Monochloramine Disinfection and Extensive Environmental Sampling Effectively Control Legionella and Other Waterborne Pathogens in Nosocomial Settings: The Ten-Year Experience of an Italian Hospital. Microorganisms 2023; 11:1794. [PMID: 37512966 PMCID: PMC10384652 DOI: 10.3390/microorganisms11071794] [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: 05/24/2023] [Revised: 07/10/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Legionella contamination control is crucial in healthcare settings where patients suffer an increased risk of disease and fatal outcome. To ensure an effective management of this health hazard, the accurate application of a hospital-specific Water Safety Plan (WSP), the choice of a suitable water disinfection system and an extensive monitoring program are required. Here, the ten-year experience of an Italian hospital is reported: since its commissioning, Legionellosis risk management has been entrusted to a multi-disciplinary Working Group, applying the principles of the World Health Organization's WSP. The disinfection strategy to prevent Legionella and other waterborne pathogens relies on the treatment of domestic hot water with a system ensuring the in situ production and dosage of monochloramine. An average of 250 samples/year were collected and analyzed to allow an accurate assessment of the microbiological status of water network. With the aim of increasing the monitoring sensitivity, in addition to the standard culture method, an optimized MALDI-ToF MS-based strategy was applied, allowing the identification of Legionella species and other relevant opportunistic pathogens. Data collected so far confirmed the effectiveness of this multidisciplinary approach: the fraction of positive samples never overcame 1% on a yearly basis and Legionnaires' Disease cases never occurred.
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Affiliation(s)
- Claudio Farina
- Microbiology and Virology Laboratory, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
| | - Eleonora Cacciabue
- Health Care Coordination Offices, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
| | - Franca Averara
- Department of Health Care Professions, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
| | - Nadia Ferri
- Microbiology and Virology Laboratory, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
| | - Francesca Vailati
- Microbiology and Virology Laboratory, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
| | | | | | - Beatrice Fermi
- Sanipur S.p.A., 25020 Flero, Italy
- ESCMID Study Group for Legionella Infections (ESGLI), 4001 Basel, Switzerland
| | - Nicola Doniselli
- Sanipur S.p.A., 25020 Flero, Italy
- ESCMID Study Group for Legionella Infections (ESGLI), 4001 Basel, Switzerland
| | - Fabio Pezzoli
- Health Care Coordination Offices, ASST "Papa Giovanni XXIII", 24127 Bergamo, Italy
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10
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Nisar MA, Ross KE, Brown MH, Bentham R, Best G, Whiley H. Detection and quantification of viable but non-culturable Legionella pneumophila from water samples using flow cytometry-cell sorting and quantitative PCR. Front Microbiol 2023; 14:1094877. [PMID: 36793878 PMCID: PMC9922708 DOI: 10.3389/fmicb.2023.1094877] [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: 11/10/2022] [Accepted: 01/03/2023] [Indexed: 02/03/2023] Open
Abstract
Legionella pneumophila is a waterborne pathogen and, as the causative agent of Legionnaires' disease, a significant public health concern. Exposure to environmental stresses, and disinfection treatments, promotes the formation of resistant and potentially infectious viable but non-culturable (VBNC) Legionella. The management of engineered water systems to prevent Legionnaires' disease is hindered by the presence of VBNC Legionella that cannot be detected using the standard culture (ISO11731:2017-05) and quantitative polymerase reaction (ISO/TS12869:2019) methods. This study describes a novel method to quantify VBNC Legionella from environmental water samples using a "viability based flow cytometry-cell sorting and qPCR" (VFC + qPCR) assay. This protocol was then validated by quantifying the VBNC Legionella genomic load from hospital water samples. The VBNC cells were unable to be cultured on Buffered Charcoal Yeast Extract (BCYE) agar; however, their viability was confirmed through their ATP activity and ability to infect amoeba hosts. Subsequently, an assessment of the ISO11731:2017-05 pre-treatment procedure demonstrated that acid or heat treatment cause underestimation of alive Legionella population. Our results showed that these pre-treatment procedures induce culturable cells to enter a VBNC state. This may explain the observed insensitivity and lack of reproducibility often observed with the Legionella culture method. This study represents the first time that flow cytometry-cell sorting in conjunction with a qPCR assay has been used as a rapid and direct method to quantify VBNC Legionella from environmental sources. This will significantly improve future research evaluating Legionella risk management approaches for the control of Legionnaires' disease.
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Affiliation(s)
- Muhammad Atif Nisar
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Kirstin E. Ross
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Melissa H. Brown
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Richard Bentham
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Giles Best
- College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia,Flow Cytometry Facility, Flinders University, Bedford Park, SA, Australia
| | - Harriet Whiley
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia,*Correspondence: Harriet Whiley, ✉
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11
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Niculita-Hirzel H, Vanhove AS, Leclerc L, Girardot F, Pourchez J, Allegra S. Risk Exposure to Legionella pneumophila during Showering: The Difference between a Classical and a Water Saving Shower System. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19063285. [PMID: 35328980 PMCID: PMC8955837 DOI: 10.3390/ijerph19063285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/01/2022] [Accepted: 03/08/2022] [Indexed: 02/04/2023]
Abstract
The increase in legionellosis incidence in the general population in recent years calls for a better characterization of the sources of infection, such as showering. Water-efficient shower systems that use water-atomizing technology have been shown to emit slightly more inhalable particles in the range of bacterial sizes than the traditional systems; however, the actual rate of bacterial emission remains poorly documented. The aim of this study was to assess the aerosolisation rate of the opportunistic water pathogen Legionella pneumophila during showering with one shower system representative of each technology. To achieve this objective, we performed controlled experiments inside a glove box and determined the emitted dose and viability of airborne Legionella. The bioaerosols were sampled with a Coriolis® Delta air sampler and the total number of viable (cultivable and noncultivable) Legionella was determined by flow cytometry and culture. We found that the rate of viable and cultivable Legionella aerosolized from the water jet was similar between the two showerheads: the viable fraction represents 0.02% of the overall bacteria present in water, while the cultivable fraction corresponds to only 0.0005%. The two showerhead models emitted a similar ratio of airborne Legionella viable and cultivable per volume of water used. Therefore, the risk of exposure to Legionella is not expected to increase significantly with the new generation of water-efficient showerheads.
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Affiliation(s)
- Hélène Niculita-Hirzel
- Department Work, Heath & Environment, Center for Primary Care and Public Health (Unisanté), University of Lausanne, Route de la Corniche 2, CH-1066 Epalinges-Lausanne, Switzerland
- Correspondence:
| | - Audrey S. Vanhove
- EVS-ISTHME UMR 5600, CNRS, University Jean Monnet of Saint-Etienne, F-42023 Saint-Etienne, France; (A.S.V.); (F.G.); (S.A.)
| | - Lara Leclerc
- Mines Saint-Etienne, University of Lyon, University Jean Monnet of Saint-Etienne, INSERM, U 1059 Sainbiose, Centre CIS, F-42023 Saint-Etienne, France; (L.L.); (J.P.)
| | - Françoise Girardot
- EVS-ISTHME UMR 5600, CNRS, University Jean Monnet of Saint-Etienne, F-42023 Saint-Etienne, France; (A.S.V.); (F.G.); (S.A.)
| | - Jérémie Pourchez
- Mines Saint-Etienne, University of Lyon, University Jean Monnet of Saint-Etienne, INSERM, U 1059 Sainbiose, Centre CIS, F-42023 Saint-Etienne, France; (L.L.); (J.P.)
| | - Séverine Allegra
- EVS-ISTHME UMR 5600, CNRS, University Jean Monnet of Saint-Etienne, F-42023 Saint-Etienne, France; (A.S.V.); (F.G.); (S.A.)
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12
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Cazals M, Bédard E, Doberva M, Faucher S, Prévost M. Compromised Effectiveness of Thermal Inactivation of Legionella pneumophila in Water Heater Sediments and Water, and Influence of the Presence of Vermamoeba vermiformis. Microorganisms 2022; 10:microorganisms10020443. [PMID: 35208896 PMCID: PMC8874534 DOI: 10.3390/microorganisms10020443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/04/2022] [Accepted: 02/09/2022] [Indexed: 11/21/2022] Open
Abstract
Intermittent reduction of temperature set-points and periodic shutdowns of water heaters have been proposed to reduce energy consumption in buildings. However, the consequences of such measures on the occurrence and proliferation of Legionella pneumophila (Lp) in hot water systems have not been documented. The impact of single and repeated heat shocks was investigated using an environmental strain of L. pneumophila and a reference strain of V. vermiformis. Heat shocks at temperatures ranging from 50 °C to 70 °C were applied for 1 h and 4 h in water and water heaters loose deposits (sludge). The regrowth potential of heat-treated culturable L. pneumophila in presence of V. vermiformis in water heaters sludges was evaluated. A 2.5-log loss of culturability of L. pneumophila was observed in simulated drinking water at 60 °C while a 4-log reduction was reached in water heaters loose deposits. Persistence of Lp after 4 h at 55 °C was shown and the presence of V. vermiformis in water heater’s loose deposits resulted in a drastic amplification (5-log). Results show that thermal inactivation by heat shock is only efficient at elevated temperatures (50 °C) in both water and loose deposits. The few remaining organisms can rapidly proliferate during storage at lower temperature in the presence of hosts.
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Affiliation(s)
- Margot Cazals
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada; (E.B.); (M.D.); (M.P.)
- Correspondence:
| | - Emilie Bédard
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada; (E.B.); (M.D.); (M.P.)
| | - Margot Doberva
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada; (E.B.); (M.D.); (M.P.)
| | - Sébastien Faucher
- Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada;
| | - Michèle Prévost
- Department of Civil Engineering, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada; (E.B.); (M.D.); (M.P.)
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13
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Molina JJ, Bennassar M, Palacio E, Crespi S. Low Efficacy of Periodical Thermal Shock for Long-Term Control of Legionella spp. in Hot Water System of Hotels. Pathogens 2022; 11:pathogens11020152. [PMID: 35215095 PMCID: PMC8875211 DOI: 10.3390/pathogens11020152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/21/2022] [Accepted: 01/21/2022] [Indexed: 02/04/2023] Open
Abstract
Different guidelines and regulations for the prevention of legionellosis in public facilities include the recommendation of a periodical thermal shock in the hot water system. The purpose of this study was to assess the efficacy of periodical thermal shocks along a 1-year period on the presence of Legionella spp. in the domestic hot water system of hotels. The Legionella testing results from the period January–December 2019 coming from a group of 77 hotel facilities in the Balearic Islands (Spain) conducting periodical thermal shocks were analyzed. A second group of 44 hotels operating without periodical thermal shocks was used for a comparative analysis. In the facilities where the periodical thermal shock was performed, 16.0% of the results (429 hot water samples collected) were positive for Legionella spp., compared to 21.1% (298 samples), where periodical thermal shock was not performed. Overall, in the thermal shock group, 32.5% of the sites presented at least 1 positive sample along the period of study versus 45.5% in the control group. None of these differences was statistically significant (p-value > 0.05). These findings suggest that the efficacy of regular thermal shock for long-term control of Legionella spp. in domestic hot water systems of hotels is low.
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Affiliation(s)
- Jhon J. Molina
- Biolinea Int., 07007 Palma, Spain; (J.J.M.); (M.B.)
- Environmental Analytical Chemistry Group, University of the Balearic Islands, 07122 Palma, Spain;
| | | | - Edwin Palacio
- Environmental Analytical Chemistry Group, University of the Balearic Islands, 07122 Palma, Spain;
| | - Sebastian Crespi
- Biolinea Int., 07007 Palma, Spain; (J.J.M.); (M.B.)
- Correspondence: ; Tel.: +34-971724701
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14
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Pereira A, Silva AR, Melo LF. Legionella and Biofilms-Integrated Surveillance to Bridge Science and Real-Field Demands. Microorganisms 2021; 9:microorganisms9061212. [PMID: 34205095 PMCID: PMC8228026 DOI: 10.3390/microorganisms9061212] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/28/2021] [Accepted: 05/31/2021] [Indexed: 11/16/2022] Open
Abstract
Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy.
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15
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Causes, Factors, and Control Measures of Opportunistic Premise Plumbing Pathogens—A Critical Review. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11104474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review critically analyses the chemical and physical parameters that influence the occurrence of opportunistic pathogens in the drinking water distribution system, specifically in premise plumbing. A comprehensive literature review reveals significant impacts of water age, disinfectant residual (type and concentration), temperature, pH, and pipe materials. Evidence suggests that there is substantial interplay between these parameters; however, the dynamics of such relationships is yet to be elucidated. There is a correlation between premise plumbing system characteristics, including those featuring water and energy conservation measures, and increased water quality issues and public health concerns. Other interconnected issues exacerbated by high water age, such as disinfectant decay and reduced corrosion control efficiency, deserve closer attention. Some common features and trends in the occurrence of opportunistic pathogens have been identified through a thorough analysis of the available literature. It is proposed that the efforts to reduce or eliminate their incidence might best focus on these common features.
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16
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Jia Y, Yu C, Fan J, Fu Y, Ye Z, Guo X, Xu Y, Shen C. Alterations in the Cell Wall of Rhodococcus biphenylivorans Under Norfloxacin Stress. Front Microbiol 2020; 11:554957. [PMID: 33123102 PMCID: PMC7573542 DOI: 10.3389/fmicb.2020.554957] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 09/14/2020] [Indexed: 01/20/2023] Open
Abstract
Many microorganisms can enter a viable but non-culturable (VBNC) state under various environmental stresses, while they can also resuscitate when the surroundings turn to suitable conditions. Cell walls play a vital role in maintaining cellular integrity and protecting cells from ambient threats. Here, we investigated the alterations in the cell wall of Rhodococcus biphenylivorans TG9 at VBNC state under norfloxacin stress and then at resuscitated state in fresh lysogeny broth medium. Electron microscopy analyses presented that TG9 in the VBNC state had a thicker and rougher cell wall than that in exponential phase or resuscitated state. Meanwhile, the results from infrared spectroscopy also showed that its VBNC state has different peptidoglycan structures in the cell wall. Moreover, in the VBNC cells the gene expressions related to cell wall synthesis and remodeling maintain a relatively high level. It indicates that the morphological variations of TG9 at the VBNC state might result from kinetic changes in the cell wall synthesis and remodeling. As a consequence, the alterations in the cell wall of VBNC TG9 may somewhat account for its tolerance mechanisms to antibiotic treatment.
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Affiliation(s)
- Yangyang Jia
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Chungui Yu
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Jiahui Fan
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Yulong Fu
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Zhe Ye
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Xiaoguang Guo
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
| | - Ying Xu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Chaofeng Shen
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory for Water Pollution Control and Environmental Safety, Hangzhou, China
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17
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Fu Y, Jia Y, Fan J, Yu C, Yu C, Shen C. Induction of Escherichia coli O157:H7 into a viable but non-culturable state by high temperature and its resuscitation. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:568-577. [PMID: 32783384 DOI: 10.1111/1758-2229.12877] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/09/2020] [Indexed: 06/11/2023]
Abstract
Escherichia coli O157:H7, a causative agent of haemolytic uremic syndrome, can enter into a viable but non-culturable (VBNC) state in response to harsh stress. Bacteria in this state can retain membrane integrity, metabolic activity and virulence expression, which may present health risks. However, virulence expression and resuscitation ability of the VBNC state are not well understood. Here, we induced E. coli O157:H7 into a VBNC state by high temperature, which is commonly used to prevent the proliferation of pathogens in process of soil solarization, composting and anaerobic digestion of organic wastes. The virulence genes were highly expressed in the VBNC state and resuscitated daughter cells. The resuscitation of VBNC cells occurred after the removal of heat stress in Luria-Bertani medium. In addition, E. coli O157: H7 cells can leave the VBNC state and resuscitate with the clearance of protein aggregates. Notably, with the accumulation of protein aggregation and increased levels of reactive oxygen species, cells lost their ability to resuscitate. The results of this study not only can facilitate a better understanding of the health risks associated with the VBNC state but also have the potential to provide a theoretical basis for thermal disinfection processing.
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Affiliation(s)
- Yulong Fu
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Yangyang Jia
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Jiahui Fan
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Chunna Yu
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, 310036, China
| | - Chungui Yu
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Chaofeng Shen
- Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China
- Zhejiang Provincial Key Laboratory for Water Pollution Control and Environmental Safety, Hangzhou, 310058, China
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18
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Cervero-Aragó S. MUW researcher of the month. Wien Klin Wochenschr 2020; 132:412-413. [DOI: 10.1007/s00508-020-01716-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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19
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Huang C, Shen Y, Smith RL, Dong S, Nguyen TH. Effect of disinfectant residuals on infection risks from Legionella pneumophila released by biofilms grown under simulated premise plumbing conditions. ENVIRONMENT INTERNATIONAL 2020; 137:105561. [PMID: 32088542 DOI: 10.1016/j.envint.2020.105561] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 02/05/2020] [Accepted: 02/06/2020] [Indexed: 06/10/2023]
Abstract
The ubiquitous presence of biofilms in premise plumbing and stagnation, which commonly occurs in premise plumbing, can exacerbate the decay of chlorine residual in drinking water. Using biofilms grown in a simulated premise plumbing setup fed directly with freshly treated water at two full-scale water treatment plants, we previously determined the mass transfer coefficients for chlorine decay in premise plumbing. These coefficients coupled with inactivation kinetics of L. pneumophila released from biofilms reported previously were integrated into a Monte Carlo framework to estimate the infection risk of biofilm-derived L. pneumophila from 1 to 48 h of stagnation. The annual infection risk was significantly higher when water stayed stagnant for up to 48 h in pipes covered internally with biofilms, compared to clean pipes without biofilms. The decay of residual chlorine due to biofilms during 48-hour stagnation led to up to 6 times increase in the annual infection risk compared to the case where biofilms was absent. Global sensitivity analysis revealed that the rate of L. pneumophila detachment from biofilms and the decay of chlorine residual during stagnation are the two most important factors influencing the infection risks. Stagnation caused by water use patterns and water-saving devices in the premise plumbing can lead to increased infection risk by biofilm-derived L. pneumophila. Overall, this study's findings suggested that biofilms could induce chlorine decay and consequently increase L. pneumophila infection risk. Thus, reducing stagnation, maintaining residual chlorine, and suppressing biofilm growth could contribute to better management of L. pneumophila infection risk.
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Affiliation(s)
- Conghui Huang
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Yun Shen
- Department of Chemical and Environmental Engineering, The University of California, Riverside, Riverside, CA 92521, United States
| | - Rebecca L Smith
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States
| | - Shengkun Dong
- Guangdong Engineering Technology Research Center of Water Security Regulation and Control for Southern China, Key Laboratory of Water Cycle and Water Security in Southern China of Guangdong Higher Education Institute, School of Civil Engineering, Sun Yat-sen University, Guangzhou, Guangdong 510275, China.
| | - Thanh H Nguyen
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
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20
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Allegra S, Riffard S, Leclerc L, Girardot F, Stauffert M, Forest V, Pourchez J. A valuable experimental setup to model exposure to Legionella's aerosols generated by shower-like systems. WATER RESEARCH 2020; 172:115496. [PMID: 31972415 DOI: 10.1016/j.watres.2020.115496] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Revised: 01/07/2020] [Accepted: 01/08/2020] [Indexed: 06/10/2023]
Abstract
The mechanism underlying Legionella aerosolization and entry into the respiratory tract remains poorly documented. In previous studies, we characterized the aerodynamic behaviour of Legionella aerosols and assessed their regional deposition within the respiratory tract using a human-like anatomical model. The aim of this study was to assess whether this experimental setup could mimic the exposure to bioaerosols generated by showers. To achieve this objective we performed experiments to measure the mass median aerodynamic diameter (MMAD) as well as the emitted dose and the physiological state of the airborne bacteria generated by a shower and two nebulizers (vibrating-mesh and jet nebulizers). The MMADs of the dispersed bioaerosols were characterized using a 12-stage cascade low-pressure impactor. The amount of dispersed airborne bacteria from a shower was quantified using a Coriolis® Delta air sampler and compared to the airborne bacteria reaching the thoracic region in the experimental setup. The physiological state and concentration of airborne Legionella were assessed by qPCR for total cells, culture for viable and cultivable Legionella (VC), and flow cytometry for viable but non-cultivable Legionella (VBNC). In summary, the experimental setup developed appears to mimic the bioaerosol emission of a shower in terms of aerodynamic size distribution. Compared to the specific case of a shower used as a reference in this study, the experimental setup developed underestimates by 2 times (when the jet nebulizer is used) or overestimates by 43 times (when the vibrating-mesh nebulizer is used) the total emitted dose of airborne bacteria. To our knowledge, this report is the first showing that an experimental model mimics so closely an exposure to Legionella aerosols produced by showers to assess human lung deposition and infection in well-controlled and safe conditions.
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Affiliation(s)
- Séverine Allegra
- University of Lyon, University Jean Monnet of Saint-Etienne, CNRS, EVS-ISTHME UMR 5600, F-42023, Saint-Etienne, France.
| | - Serge Riffard
- University of Lyon, University Jean Monnet of Saint-Etienne, CNRS, EVS-ISTHME UMR 5600, F-42023, Saint-Etienne, France
| | - Lara Leclerc
- Mines Saint-Etienne, University of Lyon, University Jean Monnet of Saint-Etienne, INSERM, U 1059 Sainbiose, Centre CIS, F-42023, Saint-Etienne, France
| | - Françoise Girardot
- University of Lyon, University Jean Monnet of Saint-Etienne, CNRS, EVS-ISTHME UMR 5600, F-42023, Saint-Etienne, France
| | - Magalie Stauffert
- University of Lyon, University Jean Monnet of Saint-Etienne, CNRS, EVS-ISTHME UMR 5600, F-42023, Saint-Etienne, France
| | - Valérie Forest
- Mines Saint-Etienne, University of Lyon, University Jean Monnet of Saint-Etienne, INSERM, U 1059 Sainbiose, Centre CIS, F-42023, Saint-Etienne, France
| | - Jérémie Pourchez
- Mines Saint-Etienne, University of Lyon, University Jean Monnet of Saint-Etienne, INSERM, U 1059 Sainbiose, Centre CIS, F-42023, Saint-Etienne, France
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