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Ferrari DDDM, Lima SC, Teixeira RLF, Lopes MQP, Vaconcellos SEG, Machado ES, Suffys PN, Gomes HM. Genetic Diversity of Legionella pneumophila Isolates from Artificial Water Sources in Brazil. Curr Microbiol 2024; 81:165. [PMID: 38714565 PMCID: PMC11076386 DOI: 10.1007/s00284-024-03645-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 02/19/2024] [Indexed: 05/10/2024]
Abstract
Legionella pneumophila (Lp) is a Gram-negative bacterium found in natural and artificial aquatic environments and inhalation of contaminated aerosols can cause severe pneumonia known as Legionnaires' Disease (LD). In Brazil there is hardly any information about this pathogen, so we studied the genetic variation of forty Legionella spp. isolates obtained from hotels, malls, laboratories, retail centers, and companies after culturing in BCYE medium. These isolates were collected from various sources in nine Brazilian states. Molecular identification of the samples was carried out using Sequence-Based Typing (SBT), which consists of sequencing and analysis of seven genes (flaA, pilE, asd, mip, mompS, proA, and neuA) to define a Sequence Type (ST). Eleven STs were identified among 34/40 isolates, of which eight have been previously described (ST1, ST80, ST152, ST242, ST664, ST1185, ST1464, ST1642) and three were new STs (ST2960, ST2962, and ST2963), the former identified in five different cooling towers in the city of São Paulo. The ST1 that is widely distributed in many countries was also the most prevalent in this study. In addition, other STs that we observed have also been associated with legionellosis in other countries, reinforcing the potential of these isolates to cause LD in Brazil. Unfortunately, no human isolates could be characterized until presently, but our observations strongly suggest the need of surveillance implementation system and control measures of Legionella spp. in Brazil, including the use of more sensitive genotyping procedures besides ST.
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Affiliation(s)
- Dândrea Driely de Melo Ferrari
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil.
| | | | - Raquel Lima Figueiredo Teixeira
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil
| | - Marcia Quinhones Pires Lopes
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil
| | | | - Edson Silva Machado
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil
| | - Philip Noel Suffys
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil.
| | - Harrison Magdinier Gomes
- Laboratório de Biologia Molecular Aplicada a Micobactérias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, 21040-360, Brazil.
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Gleason JA, Newby R, Gaynor JJ, Lee LH, Chu T, Bliese AD, Taylor CW, Yoon P, DeLorenzo S, Pranitis D, Bella J. Legionella monitoring results by water quality characteristics in a large public water system. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:55974-55988. [PMID: 36913019 DOI: 10.1007/s11356-023-26198-9] [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: 06/29/2022] [Accepted: 02/25/2023] [Indexed: 06/18/2023]
Abstract
Legionella, the causative agent of Legionnaires' disease, is an emerging concern for water utilities. Passaic Valley Water Commission (PVWC) is a public drinking water supplier, which provides treated surface water to approximately 800,000 customers in New Jersey. To evaluate the occurrence of Legionella in the PVWC distribution system, swab, first draw, and flushed cold water samples were collected from total coliform sites (n = 58) during a summer and winter sampling event. Endpoint PCR detection methods were combined with culture for Legionella detection. Among 58 total coliform sites during the summer, 17.2% (10/58) of first draw samples were positive for 16S and mip Legionella DNA markers and 15.5% (9/58) in flushed samples. Across both summer and winter sampling, a total of four out of 58 sites had low-level culture detection of Legionella spp. (0.5-1.6 CFU/mL) among first draw samples. Only one site had both a first and flush draw detection (8.5 CFU/mL and 1.1 CFU/mL) for an estimated culture detection frequency of 0% in the summer and 1.7% in the winter among flushed draw samples. No L. pneumophila was detected by culture. Legionella DNA detection was significantly greater in the summer than in the winter, and detection was greater in samples collected from areas treated with phosphate. No statistical difference was found between first draw and flush sample detection. Total organic carbon, copper, and nitrate were significantly associated with Legionella DNA detection.
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Affiliation(s)
- Jessie A Gleason
- Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, 135 East State Street, P.O. Box 369, Trenton, NJ, 08625, USA.
| | - Robert Newby
- Division of Science, New Jersey Department of Environmental Protection, 428 East State Street, P.O. Box 420, Trenton, NJ, 08625, USA
| | - John J Gaynor
- Department of Biology, Montclair State University, Montclair, NJ, 07043, USA
| | - Lee H Lee
- Department of Biology, Montclair State University, Montclair, NJ, 07043, USA
| | - Tinchun Chu
- Department of Biological Sciences, Seton Hall University, 400 South Orange Ave, South Orange, NJ, 07076, USA
| | - Alorah D Bliese
- Department of Biology, Montclair State University, Montclair, NJ, 07043, USA
| | - Calvin W Taylor
- Department of Biology, Montclair State University, Montclair, NJ, 07043, USA
| | - Paul Yoon
- Department of Biological Sciences, Seton Hall University, 400 South Orange Ave, South Orange, NJ, 07076, USA
| | - Suzanne DeLorenzo
- Passaic Valley Water Commission, 1525 Main Avenue, Totowa, NJ, 07512, USA
| | - David Pranitis
- Passaic Valley Water Commission, 1525 Main Avenue, Totowa, NJ, 07512, USA
| | - Joe Bella
- Passaic Valley Water Commission, 1525 Main Avenue, Totowa, NJ, 07512, USA
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Matthews S, Trigui H, Grimard-Conea M, Vallarino Reyes E, Villiard G, Charron D, Bédard E, Faucher S, Prevost M. Detection of Diverse Sequence Types of Legionella pneumophila by Legiolert Enzymatic-Based Assay and the Development of a Long-Term Storage Protocol. Microbiol Spectr 2022; 10:e0211822. [PMID: 36314908 PMCID: PMC9769756 DOI: 10.1128/spectrum.02118-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
Legiolert is a rapid culture-based enzymatic method for the detection and quantification of Legionella pneumophila in potable and nonpotable water samples. We aimed to assess the ability of this assay to detect diverse sequence types and validated a simple method to preserve samples. We used this assay on 253 potable and 165 nonpotable cooling tower water samples from various buildings in Québec, Canada, and performed sequence-based typing on 96 isolates. Six sequence types were identified, including ST1, ST378, ST1427, ST2859, ST3054, and ST3069. Whole-genome sequencing revealed that ST2859 was a member of the L. pneumophila subspecies fraseri. Additional tests with pure isolates also found that subspecies Pascullei and Raphaeli could be detected via Legiolert. Eight storage methods, including the current recommendation to store Legiolert trays at 4°C, were evaluated for their ability to preserve viable cultures. Of those, storage of Legiolert culture with 10% glycerol at -80°C produced the best results, fully preserving culturable Legionella for at least 12.5 months. We incorporated these findings into a standard procedure for processing Legiolert packets. Overall, Legiolert captures a variety of common and new STs in addition to important L. pneumophila subspecies and can be easily stored, which allows the conservation of a population of isolates for later characterization. IMPORTANCE Legionnaires' disease is caused by the bacterium Legionella pneumophila, which can be found in a variety of water systems. When outbreaks of Legionnaires' disease occur, it is necessary to find the water systems transmitting the bacterium to humans. Access to historical isolates from water system samples is key for success in identifying sources but current regulations and isolation protocols mean very few isolates are obtained and stored long-term. We showed here that the Legiolert test could detect and produce isolates of a variety of L. pneumophila subspecies and types. In addition, the Legiolert test medium containing a representative population of isolates could be preserved for at least 12 months at -80°C with the addition of glycerol to the test medium. Therefore, we confirmed that the Legiolert method could be a useful tool for retrospective analysis of potential sources for an outbreak.
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Affiliation(s)
- Sara Matthews
- Department of Natural Resource Sciences, McGill University, Montréal, Québec, Canada
| | - Hana Trigui
- Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
| | - Marianne Grimard-Conea
- Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
| | | | - Gabriel Villiard
- Department of Natural Resource Sciences, McGill University, Montréal, Québec, Canada
| | - Dominique Charron
- Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
| | - Emilie Bédard
- Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
| | - Sébastien Faucher
- Department of Natural Resource Sciences, McGill University, Montréal, Québec, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Faculté de Médecine Vétérinaire, Université de Montréal, Montréal, Québec, Canada
| | - Michèle Prevost
- Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
- Industrial Chair on Drinking Water, Department of Civil, Geological and Mining Engineering, Polytechnique de Montréal, Montréal, Québec, Canada
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McLaren SJ, Sahli MW, Selig S, Masten SJ, Page WH. The drinking water crises of Flint and Havelock North: a failure of public health risk management. JOURNAL OF WATER AND HEALTH 2022; 20:1314-1328. [PMID: 36170188 DOI: 10.2166/wh.2022.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Between 2014 and 2016, there were two severe community water system (CWS) failures in Flint, Michigan (MI), USA and Havelock North, Hawkes Bay, New Zealand. These events had profound implications for public health in their respective countries. While the nature of both crises was different, certain aspects of the failings were strikingly similar. These included: failure of authorities to protect the integrity of their source water, 'wait-and-see approach' to address problems if and when they occurred, negligent approach to regulatory oversight and responsibility, substandard facilities and lack of knowledge and training of staff, failure of consultants and advisory services engaged by suppliers, and failure of government agencies to enforce regulations. The lessons from both incidents must be learned, or similar tragic events are likely to reoccur. The six principles identified in the Government Inquiry into the Havelock North outbreak are an essential first step. The next step is to implement them throughout the drinking water sector.
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Affiliation(s)
- S J McLaren
- College of Health, Massey University, Wellington, New Zealand
| | - M W Sahli
- Department of Public Health and Health Sciences, Coolege of Health Sciences, University of Michigan-Flint, Flint, MI, USA
| | - S Selig
- Department of Public Health and Health Sciences, Coolege of Health Sciences, University of Michigan-Flint, Flint, MI, USA
| | - S J Masten
- Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, USA E-mail:
| | - W H Page
- College of Health, Massey University, Wellington, New Zealand
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Pilot investigation on biostability of drinking water distribution systems under water source switching. Appl Microbiol Biotechnol 2022; 106:5273-5286. [PMID: 35794486 DOI: 10.1007/s00253-022-12050-6] [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: 02/23/2022] [Revised: 06/16/2022] [Accepted: 06/25/2022] [Indexed: 11/02/2022]
Abstract
Water quality deterioration of drinking water distribution systems (DWDSs) caused by water source switching has been reported previously. However, systematic investigation of the biostability of DWDS under water source switching is limited. Aged pipes, including three commonly used pipe materials dug out from a practical DWDS, were used to systematically investigate the biofilm stability mechanism of DWDS under water source switching to quality-improved water. An increase in adenosine triphosphate (ATP) concentration in the bulk water during the initial stage of the switching period was observed, indicating the risk of biofilm release through aged pipe surfaces after water source switching. Sloughing of biofilms might contribute to temporary instability. From day 35, the ATP concentration in the polyethylene (PE) and plastic stainless steel composite (PS) pipes were maintained at approximately 2.40 and 2.56 ng/L, respectively. In contrast, the ATP concentration in the ductile iron (DI) pipes was higher, at approximately 3.43 ng/L from day 42. The water quality variation could cause areas of the biofilm to slough and reduce the biomass of biofilm, causing partial alteration of the microbial community. 16S rRNA gene amplicon sequencing-based functional prediction revealed that the biofilm could increase the abundance of chlorine-resistant bacteria attributed to the increase in Pseudomonas and Methylobacterium after switching to quality-improved water. Moreover, the profiles of specific pathways linked to human diseases, antibiotic resistance, and antibiotic biosynthesis revealed that the safety of the biofilm could improve after switching to quality-improved water. KEY POINTS: • The PE and PS biofilm showed improved resistance to water quality perturbation. • Greater number of Methylobacterium was found in the biofilm after water source switching. • 3.16S gene-based metagenomics prediction revealed that the safety of the biofilm under water source switching.
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The Presence of Opportunistic Premise Plumbing Pathogens in Residential Buildings: A Literature Review. WATER 2022. [DOI: 10.3390/w14071129] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Opportunistic premise plumbing pathogens (OPPP) are microorganisms that are native to the plumbing environment and that present an emerging infectious disease problem. They share characteristics, such as disinfectant resistance, thermal tolerance, and biofilm formation. The colonisation of domestic water systems presents an elevated health risk for immune-compromised individuals who receive healthcare at home. The literature that has identified the previously described OPPPs (Aeromonas spp., Acinetobacter spp., Helicobacter spp., Legionella spp., Methylobacterium spp., Mycobacteria spp., Pseudomonas spp., and Stenotrophomonas spp.) in residential drinking water systems were systematically reviewed. By applying the Preferred reporting items for systematic reviews and meta-analyses guidelines, 214 studies were identified from the Scopus and Web of Science databases, which included 30 clinical case investigations. Tap components and showerheads were the most frequently identified sources of OPPPs. Sixty-four of these studies detected additional clinically relevant pathogens that are not classified as OPPPs in these reservoirs. There was considerable variation in the detection methods, which included traditional culturing and molecular approaches. These identified studies demonstrate that the current drinking water treatment methods are ineffective against many waterborne pathogens. It is critical that, as at-home healthcare services continue to be promoted, we understand the emergent risks that are posed by OPPPs in residential drinking water. Future research is needed in order to provide consistent data on the prevalence of OPPPs in residential water, and on the incidence of waterborne homecare-associated infections. This will enable the identification of the contributing risk factors, and the development of effective controls.
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Gleason JA, Cohn PD. A review of legionnaires' disease and public water systems - Scientific considerations, uncertainties and recommendations. Int J Hyg Environ Health 2021; 240:113906. [PMID: 34923288 DOI: 10.1016/j.ijheh.2021.113906] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/02/2021] [Accepted: 12/13/2021] [Indexed: 11/17/2022]
Abstract
Legionella is an opportunistic premise plumbing pathogen and causative agent of a severe pneumonia called Legionnaires' Disease (LD). Cases of LD have been on the rise in the U.S. and globally. Although Legionella was first identified 45 years ago, it remains an 'emerging pathogen." Legionella is part of the normal ecology of a public water system and is frequently detected in regulatory-compliant drinking water. Drinking water utilities, regulators and public health alike are increasingly required to have a productive understanding of the evolving issues and complex discussions of the contribution of the public water utility to Legionella exposure and LD risk. This review provides a brief overview of scientific considerations important for understanding this complex topic, a review of findings from investigations of public water and LD, including data gaps, and recommendations for professionals interested in investigating public water utilities. Although the current literature is inconclusive in identifying a public water utility as a sole source of an LD outbreak, the evidence is clear that minimizing growth of Legionella in public water utilities through proper maintenance and sustained disinfectant residuals, throughout all sections of the water utility, will lead to a less conducive environment for growth of the bacteria in the system and the buildings they serve.
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Affiliation(s)
- Jessie A Gleason
- Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, 135 E. State Street, P.O. Box 369, Trenton, NJ, 08625, USA.
| | - Perry D Cohn
- Retired, Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, PO Box 369, Trenton, NJ, 08625, USA.
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A Legionnaires' Disease Cluster in a Private Building in Italy. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18136922. [PMID: 34203343 PMCID: PMC8297097 DOI: 10.3390/ijerph18136922] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 06/24/2021] [Accepted: 06/26/2021] [Indexed: 11/18/2022]
Abstract
Legionnaires’ disease (LD) is a severe pneumonia caused by bacteria belonging to the genus Legionella. This is a major public health concern and infections are steadily increasing worldwide. Several sources of infection have been identified, but they have not always been linked to human isolates by molecular match. The well-known Legionella contamination of private homes has rarely been associated with the acquisition of the disease, although some patients never left their homes during the incubation period. This study demonstrated by genomic matching between clinical and environmental Legionella isolates that the source of an LD cluster was a private building. Monoclonal antibodies and sequence-based typing were used to type the isolates, and the results clearly demonstrated the molecular relationship between the strains highlighting the risk of contracting LD at home. To contain this risk, the new European directive on the quality of water intended for human consumption has introduced for the first time Legionella as a microbiological parameter to be investigated in domestic water systems. This should lead to a greater attention to prevention and control measures for domestic Legionella contamination and, consequently, to a possible reduction in community acquired LD cases.
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Garner E, Davis BC, Milligan E, Blair MF, Keenum I, Maile-Moskowitz A, Pan J, Gnegy M, Liguori K, Gupta S, Prussin AJ, Marr LC, Heath LS, Vikesland PJ, Zhang L, Pruden A. Next generation sequencing approaches to evaluate water and wastewater quality. WATER RESEARCH 2021; 194:116907. [PMID: 33610927 DOI: 10.1016/j.watres.2021.116907] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/15/2021] [Accepted: 02/03/2021] [Indexed: 05/24/2023]
Abstract
The emergence of next generation sequencing (NGS) is revolutionizing the potential to address complex microbiological challenges in the water industry. NGS technologies can provide holistic insight into microbial communities and their functional capacities in water and wastewater systems, thus eliminating the need to develop a new assay for each target organism or gene. However, several barriers have hampered wide-scale adoption of NGS by the water industry, including cost, need for specialized expertise and equipment, challenges with data analysis and interpretation, lack of standardized methods, and the rapid pace of development of new technologies. In this critical review, we provide an overview of the current state of the science of NGS technologies as they apply to water, wastewater, and recycled water. In addition, a systematic literature review was conducted in which we identified over 600 peer-reviewed journal articles on this topic and summarized their contributions to six key areas relevant to the water and wastewater fields: taxonomic classification and pathogen detection, functional and catabolic gene characterization, antimicrobial resistance (AMR) profiling, bacterial toxicity characterization, Cyanobacteria and harmful algal bloom identification, and virus characterization. For each application, we have presented key trends, noteworthy advancements, and proposed future directions. Finally, key needs to advance NGS technologies for broader application in water and wastewater fields are assessed.
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Affiliation(s)
- Emily Garner
- Wadsworth Department of Civil and Environmental Engineering, West Virginia University, 1306 Evansdale Drive, Morgantown, WV 26505, United States.
| | - Benjamin C Davis
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Erin Milligan
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Matthew Forrest Blair
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Ishi Keenum
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Ayella Maile-Moskowitz
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Jin Pan
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Mariah Gnegy
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Krista Liguori
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Suraj Gupta
- The Interdisciplinary PhD Program in Genetics, Bioinformatics, and Computational Biology, Virginia Tech, Blacksburg, VA 24061, United States
| | - Aaron J Prussin
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Linsey C Marr
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Lenwood S Heath
- Department of Computer Science, Virginia Tech, 225 Stranger Street, Blacksburg, VA 24061, United States
| | - Peter J Vikesland
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States
| | - Liqing Zhang
- Department of Computer Science, Virginia Tech, 225 Stranger Street, Blacksburg, VA 24061, United States
| | - Amy Pruden
- Charles E. Via, Jr. Department of Civil and Environmental Engineering, Virginia Tech, 1145 Perry Street, Blacksburg, VA 24061, United States.
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Whole genome sequence analysis reveals the broad distribution of the RtxA type 1 secretion system and four novel putative type 1 secretion systems throughout the Legionella genus. PLoS One 2020; 15:e0223033. [PMID: 31935215 PMCID: PMC6959600 DOI: 10.1371/journal.pone.0223033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 12/17/2019] [Indexed: 01/18/2023] Open
Abstract
Type 1 secretion systems (T1SSs) are broadly distributed among bacteria and translocate effectors with diverse function across the bacterial cell membrane. Legionella pneumophila, the species most commonly associated with Legionellosis, encodes a T1SS at the lssXYZABD locus which is responsible for the secretion of the virulence factor RtxA. Many investigations have failed to detect lssD, the gene encoding the membrane fusion protein of the RtxA T1SS, in non-pneumophila Legionella, which has led to the assumption that this system is a virulence factor exclusively possessed by L. pneumophila. Here we discovered RtxA and its associated T1SS in a novel Legionella taurinensis strain, leading us to question whether this system may be more widespread than previously thought. Through a bioinformatic analysis of publicly available data, we classified and determined the distribution of four T1SSs including the RtxA T1SS and four novel T1SSs among diverse Legionella spp. The ABC transporter of the novel Legionella T1SS Legionella repeat protein secretion system shares structural similarity to those of diverse T1SS families, including the alkaline protease T1SS in Pseudomonas aeruginosa. The Legionella bacteriocin (1-3) secretion systems T1SSs are novel putative bacteriocin transporting T1SSs as their ABC transporters include C-39 peptidase domains in their N-terminal regions, with LB2SS and LB3SS likely constituting a nitrile hydratase leader peptide transport T1SSs. The LB1SS is more closely related to the colicin V T1SS in Escherichia coli. Of 45 Legionella spp. whole genomes examined, 19 (42%) were determined to possess lssB and lssD homologs. Of these 19, only 7 (37%) are known pathogens. There was no difference in the proportions of disease associated and non-disease associated species that possessed the RtxA T1SS (p = 0.4), contrary to the current consensus regarding the RtxA T1SS. These results draw into question the nature of RtxA and its T1SS as a singular virulence factor. Future studies should investigate mechanistic explanations for the association of RtxA with virulence.
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