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Vittal R, Raj JRM, Kumar BK, Karunasagar I. Advances in Environmental Detection and Clinical Diagnostic Tests for Legionella Species. JOURNAL OF HEALTH AND ALLIED SCIENCES NU 2021. [DOI: 10.1055/s-0041-1731863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Abstract
Legionella is a fastidious organism that is difficult to culture in the lab but is widely distributed in environmental, domestic, and hospital settings. The clinical manifestations due to Legionella infections range from mild fever to fatal pneumonia and multiorgan pathologies. Legionella outbreaks though prevalent globally are not reported in developing countries due to difficulties in isolating this organism and the lack of simple diagnostic protocols. Here, we review the literature from across countries to present various methods used to detect Legionella from environmental and clinical samples. We compare the sensitivity and the specificity of the conventional culture-based assays with the recent methods and discuss approaches to develop better detection and diagnostic tests. With better cost-effective detection techniques and regular monitoring of the susceptible sites, which may harbor Legionella colonies, most of the Legionella infections can be prevented. As a result, considerable burden, caused by Legionella infections, on the healthcare system, in especially economically weaker countries, can be mitigated.
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Affiliation(s)
- Rajeshwari Vittal
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Juliet Roshini Mohan Raj
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Ballamoole Krishna Kumar
- Division of Infectious Diseases, Nitte University Centre for Science Education and Research, Deralakatte, Mangaluru, Karnataka, India
| | - Indrani Karunasagar
- Nitte University Centre for Science Education and Research, Mangaluru, Karnataka, India
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Ahmed S, Liwak-Muir U, Walker D, Zoldowski A, Mears A, Golovan S, Mohr S, Lem P, Harder C. Validation and in-field testing of a new on-site qPCR system for quantification of Legionella pneumophila according to ISO/TS 12869:2012 in HVAC cooling towers. JOURNAL OF WATER AND HEALTH 2019; 17:237-253. [PMID: 30942774 DOI: 10.2166/wh.2019.252] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Legionella pneumophila, found in engineered water systems such as HVAC cooling towers, poses a significant public health risk. Culture, though routinely used to quantify L. pneumophila, has several disadvantages including long turnaround time, low sensitivity, and inter-laboratory variability. In this study, we validated the performance of an on-site quantitative polymerase chain reaction (qPCR) detection system for L. pneumophila in accordance with International Standards Organization Technical Specification 12869:2012. We evaluated specificity, limit of detection and quantification, and calibration curve linearity. Additionally, we evaluated whole system recovery and robustness using samples taken from taps and evaporative cooling towers. We then compared the system's performance against laboratory culture and laboratory qPCR across 53 cooling towers in a 12-week in-field study. We found that concordance between on-site qPCR and culture was both laboratory- and site/sample-dependent. Comparison of laboratory qPCR with on-site qPCR revealed that laboratory results were highly variable and showed little concordance. Some discordance may be explained by time delay between sample collection and testing ('shipping effect') which may lead to inaccurate reporting. Overall, our study highlights the value of on-site qPCR detection of L. pneumophila, demonstrates that laboratories are prone to misreporting results due to shipping effects, and reveals significant discordance between laboratory qPCR and culture.
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Affiliation(s)
- Shaimaa Ahmed
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Urszula Liwak-Muir
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Danielle Walker
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Agnes Zoldowski
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Alan Mears
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Sergey Golovan
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Steve Mohr
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Paul Lem
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
| | - Chris Harder
- Spartan Bioscience Inc., 2934 Baseline Road, Suite 500, Ottawa, ON K2H 1B2, Canada E-mail:
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Wu TY, Su YY, Shu WH, Mercado AT, Wang SK, Hsu LY, Tsai YF, Chen CY. A novel sensitive pathogen detection system based on Microbead Quantum Dot System. Biosens Bioelectron 2015; 78:37-44. [PMID: 26590701 DOI: 10.1016/j.bios.2015.11.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/04/2015] [Accepted: 11/06/2015] [Indexed: 10/22/2022]
Abstract
A fast and accurate detection system for pathogens can provide immediate measurements for the identification of infectious agents. Therefore, the Microbead Quantum-dots Detection System (MQDS) was developed to identify and measure target DNAs of pathogenic microorganisms and eliminated the need of PCR amplifications. This nanomaterial-based technique can detect different microorganisms by flow cytometry measurements. In MQDS, pathogen specific DNA probes were designed to form a hairpin structure and conjugated on microbeads. In the presence of the complementary target DNA sequence, the probes will compete for binding with the reporter probes but will not interfere with the binding between the probe and internal control DNA. To monitor the binding process by flow cytometry, both the reporter probes and internal control probes were conjugated with Quantum dots that fluoresce at different emission wavelengths using the click reaction. When MQDS was used to detect the pathogens in environmental samples, a high correlation coefficient (R=0.994) for Legionella spp., with a detection limit of 0.1 ng of the extracted DNAs and 10 CFU/test, can be achieved. Thus, this newly developed technique can also be applied to detect other pathogens, particularly viruses and other genetic diseases.
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Affiliation(s)
- Tzong-Yuan Wu
- Department of Bioscience Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan; Center for Nanotechnology and Center for Biomedical Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan; R&D Center of Membrane Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan
| | - Yi-Yu Su
- Department of Bioscience Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan
| | - Wei-Hsien Shu
- Department of Bioscience Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan
| | - Augustus T Mercado
- Department of Bioscience Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan; Department of Chemistry, Chung Yuan Christian University, Chung-Li 320, Taiwan
| | - Shi-Kwun Wang
- Environmental Analysis Laboratory, Environmental Protection Administration, Chung-Li 320, Taiwan
| | - Ling-Yi Hsu
- Environmental Analysis Laboratory, Environmental Protection Administration, Chung-Li 320, Taiwan
| | - Yow-Fu Tsai
- Department of Chemistry, Chung Yuan Christian University, Chung-Li 320, Taiwan
| | - Chung-Yung Chen
- Department of Bioscience Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan; Center for Nanotechnology and Center for Biomedical Technology, Chung Yuan Christian University, Chung-Li 320, Taiwan.
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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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Rafiee M, Jahangiri-rad M, Hajjaran H, Mesdaghinia A, Hajaghazadeh M. Detection and identification of Legionella species in hospital water supplies through Polymerase Chain Reaction (16S rRNA). JOURNAL OF ENVIRONMENTAL HEALTH SCIENCE & ENGINEERING 2014; 12:83. [PMID: 24860661 PMCID: PMC4032159 DOI: 10.1186/2052-336x-12-83] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 04/20/2014] [Indexed: 06/03/2023]
Abstract
Legionella spp. are important waterborne pathogens that are normally transmitted through aerosols. The present work was conducted to investigate the presence of Legionella spp. and its common species in hospital water supplies. Considering the limitations of culture method, polymerase chain reaction (PCR) assays were developed to detect the gene 16S rRNA irrespective of the bacterial serotype. Four well-established DNA extraction protocols (freeze & thaw and phenol-chloroform as two manual protocols and two commercial kits) were tested and evaluated to release DNA from bacterial cells. A total of 45 samples were collected from seven distinct hospitals' sites during a period of 10 months. The PCR assay was used to amplify a 654-bp fragment of the 16S rRNA gene. Legionella were detected in 13 samples (28.9%) by all of the methods applied for DNA extraction. Significant differences were noted in the yield of extracted nucleic acids. Legionella were not detected in any of the samples when DNA extraction by freeze & thaw was used. Excluding this method and comparing manual protocol with commercial kits, Kappa coefficient was calculated as 0.619 with p < 0.05. Although no meaningful differences were found between the kits, DNA extraction with Bioneer kit exhibited a higher sensitivity than classical Qiagen. Showerheads and cold-water taps were the most and least contaminated sources with 55.5 and 9 percent positive samples, respectively. Moreover two positive samples were identified for species by DNA sequencing and submitted to the Gene Bank database with accession Nos. FJ480932 and FJ480933. The results obtained showed that despite the advantages of molecular assays in Legionella tracing in environmental sources, the use of optimised DNA extraction methods is critical.
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Affiliation(s)
- Mohammad Rafiee
- Department of Environmental Health Engineering, School of Public Health, Alborz University of Medical Sciences, Alborz, Iran
| | - Mahsa Jahangiri-rad
- Department of Environmental Health Engineering, Islamic Azad University, Tehran Medical Sciences Branch, Tehran, Iran
| | - Homa Hajjaran
- Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Mesdaghinia
- Department of Environmental Health Engineering, School of Public Health, Center for Water Quality Research, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Hajaghazadeh
- Department of Occupational Health, Health Faculty, Urmia University of Medical Sciences, Urmia, Iran
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Ducret A, Chabalier M, Dukan S. Characterization and resuscitation of 'non-culturable' cells of Legionella pneumophila. BMC Microbiol 2014; 14:3. [PMID: 24383402 PMCID: PMC3882098 DOI: 10.1186/1471-2180-14-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 12/02/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Legionella pneumophila is a waterborne pathogen responsible for Legionnaires' disease, an infection which can lead to potentially fatal pneumonia. After disinfection, L. pneumophila has been detected, like many other bacteria, in a "viable but non culturable" state (VBNC). The physiological significance of the VBNC state is unclear and controversial: it could be an adaptive response favoring long-term survival; or the consequence of cellular deterioration which, despite maintenance of certain features of viable cells, leads to death; or an injured state leading to an artificial loss of culturability during the plating procedure. VBNC cells have been found to be resuscitated by contact with amoebae. RESULTS We used quantitative microscopic analysis, to investigate this "resuscitation" phenomenon in L. pneumophila in a model involving amending solid plating media with ROS scavengers (pyruvate or glutamate), and co-culture with amoebae. Our results suggest that the restoration observed in the presence of pyruvate and glutamate may be mostly due to the capacity of these molecules to help the injured cells to recover after a stress. We report evidence that this extracellular signal leads to a transition from a not-culturable form to a culturable form of L. pneumophila, providing a technique for recovering virulent and previously uncultivated forms of L. pneumophila. CONCLUSION These new media could be used to reduce the risk of underestimation of counts of virulent of L. pneumophila cells in environmental samples.
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Affiliation(s)
- Adrien Ducret
- Aix Marseille Université, Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée - CNRS, 31, Chemin Joseph Aiguier, 13402 Marseille, France
- Present address: Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405 USA
| | - Maïalène Chabalier
- Aix Marseille Université, Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée - CNRS, 31, Chemin Joseph Aiguier, 13402 Marseille, France
| | - Sam Dukan
- Aix Marseille Université, Laboratoire de Chimie Bactérienne (UMR7283), Institut de Microbiologie de la Méditerranée - CNRS, 31, Chemin Joseph Aiguier, 13402 Marseille, France
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7
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Buse HY, Donohue MJ, Ashbolt NJ. Hartmannella vermiformis inhibition of Legionella pneumophila cultivability. MICROBIAL ECOLOGY 2013; 66:715-726. [PMID: 23764733 DOI: 10.1007/s00248-013-0250-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 05/27/2013] [Indexed: 06/02/2023]
Abstract
Hartmannella vermiformis and Acanthamoeba polyphaga are frequently isolated from drinking water and permissive to Legionella pneumophila parasitization. In this study, extracellular factor(s) produced by H. vermiformis and A. polyphaga were assessed for their effects on cultivability of L. pneumophila. Page's amoeba saline (PAS) was used as an encystment medium for H. vermiformis and A. polyphaga monolayers, and the culture supernatants (HvS and ApS, respectively) were assessed against L. pneumophila growth. Compared to PAS and ApS, HvS significantly inhibited L. pneumophila strain Philadelphia-1 (Ph-1) cultivability by 3 log(10) colony forming unit (CFU) mL(-1) after 3 days of exposure compared to <0.5 log(10) CFU mL(-1) reduction of strain Lp02 (P < 0.001). Flow cytometric analysis revealed changes in the percentage and cultivability of three bacterial subpopulations: intact/slightly damaged membrane (ISM), undefined membrane status (UD), and mixed type (MT). After 3 days of HvS exposure, the MT subpopulation decreased significantly (31.6 vs 67.2 %, respectively, P < 0.001), while the ISM and UD subpopulations increased (+26.7 and +6.9 %, respectively) with the ISM subpopulation appearing as viable but nonculturable (VBNC) cells. HvS was separated into two fractions based on molecular weight, with more than 99 % of the L. pneumophila inhibition arising from the <5 kDa fraction (P < 0.001). Liquid chromatography indicated the inhibitory molecule(s) are likely polar and elute from a Novapak C18 column between 6 and 15 min. These results demonstrate that H. vermiformis is capable of extracellular modulation of L. pneumophila cultivability and probably promote the VBNC state for this bacterium.
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Affiliation(s)
- Helen Y Buse
- Dynamac c/o US Environmental Protection Agency, 26 W Martin Luther King Dr, Cincinnati, OH, 45268, USA,
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8
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Detection and Quantification of Legionella pneumophila from Water Systems in Kuwait Residential Facilities. J Pathog 2012; 2012:138389. [PMID: 22888441 PMCID: PMC3409524 DOI: 10.1155/2012/138389] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 05/27/2012] [Accepted: 05/30/2012] [Indexed: 11/22/2022] Open
Abstract
The prevalence of Legionella pneumophilia in water systems of residential facilities in Kuwait was performed during the period from November 2007 to November 2011. A total of 204 water samples collected from faucets and showerheads in bathrooms (n = 82), taps in kitchens (n = 51), and water tanks (n = 71), from different locations of residential facilities in Kuwait were screened for Legionella pneumophila by the standard culture method and by real time polymerase chain reaction (RT-PCR). Out of the 204 samples, 89 (43.6%) samples were positive for Legionella spp., 48 (23.5%) samples were detected by the standard culture method, and 85 (41.7%) were detected by RT-PCR. Of the culture positive Legionella samples, counts ranged between 10 to 2250 CFU/L. Serological typing of 48 Legionella isolates revealed that 6 (12.5%) of these isolates belonged to Legionella pneumophila serogroup 1, 37 (77.1%) isolates to Legionella pneumophila serogroup 3, and 1 isolate each (2.1%) belonged to serogroups 4, 7, and 10. The minimum inhibitory concentration (MICs) of the 46 environmental L. pneumophila isolates against the 10 antimicrobials commonly used for Legionella infection treatments were determined. Rifampicin was found to be the most active against L. pneumophila serogroups isolates in vitro.
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Specific real-time PCR for simultaneous detection and identification of Legionella pneumophila serogroup 1 in water and clinical samples. Appl Environ Microbiol 2010; 77:1708-17. [PMID: 21193672 DOI: 10.1128/aem.02261-10] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Legionella pneumophila, a bacterium that replicates within aquatic amoebae and persists in the environment as a free-living microbe, is the causative agent of Legionnaires' disease. Among the many Legionella species described, L. pneumophila is associated with 90% of human disease, and within the 15 serogroups (Sg), L. pneumophila Sg1 causes more than 84% of Legionnaires' disease worldwide. Thus, rapid and specific identification of L. pneumophila Sg1 is of the utmost importance for evaluation of the contamination of collective water systems and the risk posed. Previously we had shown that about 20 kb of the 33-kb locus carrying the genes coding for the proteins involved in lipopolysaccharide biosynthesis (LPS gene cluster) by L. pneumophila was highly specific for Sg1 strains and that three genes (lpp0831, wzm, and wzt) may serve as genetic markers. Here we report the sequencing and comparative analyses of this specific region of the LPS gene cluster in L. pneumophila Sg6, -10, -12, -13, and -14. Indeed, the wzm and wzt genes were present only in the Sg1 LPS gene cluster, which showed a very specific gene content with respect to the other five serogroups investigated. Based on this observation, we designed primers and developed a classical and a real-time PCR method for the detection and simultaneous identification of L. pneumophila Sg1 in clinical and environmental isolates. Evaluation of the selected primers with 454 Legionella and 38 non-Legionella strains demonstrated 100% specificity. Sensitivity, specificity, and predictive values were further evaluated with 209 DNA extracts from water samples of hospital water supply systems and with 96 respiratory specimens. The results showed that the newly developed quantitative Sg1-specific PCR method is a highly specific and efficient tool for the surveillance and rapid detection of high-risk L. pneumophila Sg1 in water and clinical samples.
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Choi SH, Cho MK, Ahn SC, Lee JE, Lee JS, Kim DH, Xuan YH, Hong YC, Kong HH, Chung DI, Yu HS. Endosymbionts of Acanthamoeba isolated from domestic tap water in Korea. THE KOREAN JOURNAL OF PARASITOLOGY 2009; 47:337-44. [PMID: 19967080 DOI: 10.3347/kjp.2009.47.4.337] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 09/16/2009] [Accepted: 09/19/2009] [Indexed: 11/23/2022]
Abstract
In a previous study, we reported our discovery of Acanthamoeba contamination in domestic tap water; in that study, we determined that some Acanthamoeba strains harbor endosymbiotic bacteria, via our molecular characterization by mitochondrial DNA restriction fragment length polymorphism (Mt DNA RFLP). Five (29.4%) among 17 Acanthamoeba isolates contained endosymbionts in their cytoplasm, as demonstrated via orcein staining. In order to estimate their pathogenicity, we conducted a genetic characterization of the endosymbionts in Acanthamoeba isolated from domestic tap water via 16S rDNA sequencing. The endosymbionts of Acanthamoeba sp. KA/WP3 and KA/WP4 evidenced the highest level of similarity, at 97% of the recently published 16S rDNA sequence of the bacterium, Candidatus Amoebophilus asiaticus. The endosymbionts of Acanthamoeba sp. KA/WP8 and KA/WP12 shared a 97% sequence similarity with each other, and were also highly similar to Candidatus Odyssella thessalonicensis, a member of the alpha-proteobacteria. The endosymbiont of Acanthamoeba sp. KA/WP9 exhibits a high degree of similarity (85-95%) with genus Methylophilus, which is not yet known to harbor any endosymbionts. This is the first report, to the best of our knowledge, to show that Methylophilus spp. can live in the cytoplasm of Acanthamoeba.
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Affiliation(s)
- Seon Hee Choi
- Department of Parasitology, School of Medicine, Pusan National University, Busan, 602-739, Korea
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Storey MV, Winiecka-Krusnell J, Ashbolt NJ, Stenström TA. The Efficacy of Heat and Chlorine Treatment against Thermotolerant Acanthamoebae and Legionellae. ACTA ACUST UNITED AC 2009; 36:656-62. [PMID: 15370652 DOI: 10.1080/00365540410020785] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Free-living amoebae and Acanthamoebae are known to harbour a range of opportunistic microbial pathogens such as Legionellae, sequestering them from antimicrobial agents as well as environmental stresses. Less is known however of the interaction between the thermotolerant free-living amoebae and Legionellae. In the current study, such phenomena were investigated between an environmental and clinical thermotolerant Acanthamoebae isolate and 6 Legionellae; L. anisa, L. birminghamiensis, L. bozemanii, L. dumoffii, L. erythra and L. pneumophila. All Legionellae could be located within either Acanthamoeba isolate, with L. erythra, and L. pneumophila found located within vacuoles. At concentrations exceeding 2 mg/l, free chlorine was a better disinfectant than combined chlorine against Acanthamoebae-bound Legionellae, though thermal treatment was the most effective of the treatment types investigated. While the interaction with free-living Acanthamoebae increased the resistance of Legionellae to thermal treatment, it increased the sensitivity of Legionellae to free and combined chlorine. Interaction with biofilms did not affect the sensitivity of sessile and intracellular Legionellae to disinfection, caused in part by the thin coverage of biofilm on coupon surfaces. Acanthamoebae cysts remained viable after treatment with 100 mg/l chlorine (free and combined) for 10 min, as well as 80 degrees C, implying that conventional hyper-disinfection may be insufficient for long-term control of Acanthamoebae-bound Legionellae in water distribution systems.
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Affiliation(s)
- Michael V Storey
- Department of Parasitology, Mycology and Water Microbiology, Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden.
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12
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Viability PCR, a culture-independent method for rapid and selective quantification of viable Legionella pneumophila cells in environmental water samples. Appl Environ Microbiol 2009; 75:3502-12. [PMID: 19363080 DOI: 10.1128/aem.02878-08] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PCR-based methods have been developed to rapidly screen for Legionella pneumophila in water as an alternative to time-consuming culture techniques. However, these methods fail to discriminate between live and dead bacteria. Here, we report a viability assay (viability PCR [v-PCR]) for L. pneumophila that combines ethidium monoazide bromide with quantitative real-time PCR (qPCR). The ability of v-PCR to differentiate viable from nonviable L. pneumophila cells was confirmed with permeabilizing agents, toluene, or isopropanol. v-PCR suppressed more than 99.9% of the L. pneumophila PCR signal in nonviable cultures and was able to discriminate viable cells in mixed samples. A wide range of physiological states, from culturable to dead cells, was observed with 64 domestic hot-water samples after simultaneous quantification of L. pneumophila cells by v-PCR, conventional qPCR, and culture methods. v-PCR counts were equal to or higher than those obtained by culture and lower than or equal to conventional qPCR counts. v-PCR was used to successfully monitor in vitro the disinfection efficacy of heating to 70 degrees C and glutaraldehyde and chlorine curative treatments. The v-PCR method appears to be a promising and rapid technique for enumerating L. pneumophila bacteria in water and, in comparison with conventional qPCR techniques used to monitor Legionella, has the advantage of selectively amplifying only viable cells.
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13
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Lau HY, Ashbolt NJ. The role of biofilms and protozoa in Legionella pathogenesis: implications for drinking water. J Appl Microbiol 2009; 107:368-78. [PMID: 19302312 DOI: 10.1111/j.1365-2672.2009.04208.x] [Citation(s) in RCA: 186] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Current models to study Legionella pathogenesis include the use of primary macrophages and monocyte cell lines, various free-living protozoan species and murine models of pneumonia. However, there are very few studies of Legionella spp. pathogenesis aimed at associating the role of biofilm colonization and parasitization of biofilm microbiota and release of virulent bacterial cell/vacuoles in drinking water distribution systems. Moreover, the implications of these environmental niches for drinking water exposure to pathogenic legionellae are poorly understood. This review summarizes the known mechanisms of Legionella spp. proliferation within Acanthamoeba and mammalian cells and advocates the use of the amoeba model to study Legionella pathogenicity because of their close association with Legionella spp. in the aquatic environment. The putative role of biofilms and amoebae in the proliferation, development and dissemination of potentially pathogenic Legionella spp. is also discussed. Elucidating the mechanisms of Legionella pathogenicity development in our drinking water systems will aid in elimination strategies and procedural designs for drinking water systems and in controlling exposure to Legionella spp. and similar pathogens.
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Affiliation(s)
- H Y Lau
- National Exposure Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH 45268, USA.
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14
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Morio F, Corvec S, Caroff N, Le Gallou F, Drugeon H, Reynaud A. Real-time PCR assay for the detection and quantification of Legionella pneumophila in environmental water samples: utility for daily practice. Int J Hyg Environ Health 2007; 211:403-11. [PMID: 17720622 DOI: 10.1016/j.ijheh.2007.06.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 05/24/2007] [Accepted: 06/26/2007] [Indexed: 11/23/2022]
Abstract
We developed a quantitative real-time PCR assay targeting the mip gene of Legionella pneumophila for a prospective study from September 2004 to April 2005. It was compared with a standard culture method (French guideline AFNOR T90-431), analysing 120 water samples collected to monitor the risk related to Legionellae at Nantes hospital and to investigate a case of legionellosis acquired from hospital environment. Samples from six distinct water distribution systems were analysed by DNA extraction, amplification and detection with specific primers and FRET probes. The detection limit was 100 genomic units of L. pneumophila per liter (GU/l), the positivity threshold about 600 GU/l and the quantification limit 800 GU/l. PCR results were divided into three groups: negative (n=63), positive but non-quantifiable (n=22) or positive (n=35). PCR showed higher sensitivity than culture, whereas four culture-positive samples appeared negative by PCR (PCR inhibitor detected for two of them). Although no correlation was observed between both methods and real-time PCR cannot substitute for the reference method, it represents an interesting complement. Its sensitivity, reproducibility and rapidity appear particularly interesting in epidemic contexts in order to identify the source of contamination or to evaluate critical points of contamination in water distribution systems.
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Affiliation(s)
- Florent Morio
- Laboratoire de Bacteriologie-Virologie-Hygiene Hospitaliere, Institut de Biologie des Hopitaux de Nantes, 9 quai Moncousu, 44093 Nantes Cedex 01, France
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Delgado-Viscogliosi P, Simonart T, Parent V, Marchand G, Dobbelaere M, Pierlot E, Pierzo V, Menard-Szczebara F, Gaudard-Ferveur E, Delabre K, Delattre JM. Rapid method for enumeration of viable Legionella pneumophila and other Legionella spp. in water. Appl Environ Microbiol 2005; 71:4086-96. [PMID: 16000824 PMCID: PMC1169006 DOI: 10.1128/aem.71.7.4086-4096.2005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A sensitive and specific method has been developed to enumerate viable L. pneumophila and other Legionella spp. in water by epifluorescence microscopy in a short period of time (a few hours). This method allows the quantification of L. pneumophila or other Legionella spp. as well as the discrimination between viable and nonviable Legionella. It simultaneously combines the specific detection of Legionella cells using antibodies and a bacterial viability marker (ChemChrome V6), the enumeration being achieved by epifluorescence microscopy. The performance of this immunological double-staining (IDS) method was investigated in 38 natural filterable water samples from different aquatic sources, and the viable Legionella counts were compared with those obtained by the standard culture method. The recovery rate of the IDS method is similar to, or higher than, that of the conventional culture method. Under our experimental conditions, the limit of detection of the IDS method was <176 Legionella cells per liter. The examination of several samples in duplicates for the presence of L. pneumophila and other Legionella spp. indicated that the IDS method exhibits an excellent intralaboratory reproducibility, better than that of the standard culture method. This immunological approach allows rapid measurements in emergency situations, such as monitoring the efficacy of disinfection shock treatments. Although its field of application is as yet limited to filterable waters, the double-staining method may be an interesting alternative (not equivalent) to the conventional standard culture methods for enumerating viable Legionella when rapid detection is required.
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Söderberg MA, Rossier O, Cianciotto NP. The type II protein secretion system of Legionella pneumophila promotes growth at low temperatures. J Bacteriol 2004; 186:3712-20. [PMID: 15175284 PMCID: PMC419956 DOI: 10.1128/jb.186.12.3712-3720.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gram-negative bacterium Legionella pneumophila grows in both natural and man-made water systems and in the mammalian lung as a facultative intracellular parasite. The PilD prepilin peptidase of L. pneumophila promotes type IV pilus biogenesis and type II protein secretion. Whereas pili enhance adherence, Legionella type II secretion is critical for intracellular growth and virulence. Previously, we observed that pilD transcript levels are greater in legionellae grown at 30 versus 37 degrees C. Using a new pilD::lacZ fusion strain, we now show that pilD transcriptional initiation increases progressively as L. pneumophila is grown at 30, 25, and 17 degrees C. Legionella pilD mutants also had a dramatically reduced ability to grow in broth and to form colonies on agar at the lower temperatures. Whereas strains specifically lacking type IV pili were not defective for low-temperature growth, mutations in type II secretion (lsp) genes greatly impaired the capacity of L. pneumophila to form colonies at 25, 17, and 12 degrees C. Indeed, the lsp mutants were completely unable to grow at 12 degrees C. The growth defect of the pilD and lsp mutants was complemented by reintroduction of the corresponding intact gene. Interestingly, the lsp mutants displayed improved growth at 25 degrees C when plated next to a streak of wild-type but not mutant bacteria, implying that a secreted, diffusible factor promotes low-temperature growth. Mutants lacking either the known secreted acid phosphatases, lipases, phospholipase C, lysophospholipase A, or protease grew normally at 25 degrees C, suggesting the existence of a critical, yet-to-be-defined exoprotein(s). In summary, these data document, for the first time, that L. pneumophila replicates at temperatures below 20 degrees C and that a bacterial type II protein secretion system facilitates growth at low temperatures.
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Affiliation(s)
- Maria A Söderberg
- Department of Microbiology and Immunology, Northwestern University Medical School, 320 East Superior St., Chicago, IL 60611, USA
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Nwachuku N, Gerba CP. Health effects of Acanthamoeba spp. and its potential for waterborne transmission. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2004; 180:93-131. [PMID: 14561077 DOI: 10.1007/0-387-21729-0_2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Risk from Acanthamoeba keratitis is complex, depending upon the virulence of the particular strain, exposure, trauma, or other stress to the eye, and host immune response. Bacterial endosymbionts may also play a factor in the pathogenicity of Acanthamoeba. Which factor(s) may be the most important is not clear. The ability of the host to produce IgA antibodies in tears may be a significant factor. The immune response of the host is a significant risk factor for GAE infection. If so, then a certain subpopulation with an inability to produce IgA in the tears may be at greatest risk. There was no sufficient data on the occurrence or types of Acanthamoeba in tapwater in the U.S. Published work on amoebal presence in tapwater does not provide information on the type of treatment the water received or the level of residual chlorine. Assessment of the pathogenicity by cell culture and molecular methods of Acanthamoeba in tapwater would also be useful in the risk assessment process for drinking water. The possibility that Acanthamoeba spp. might serve as vectors for bacterial infections from water sources also should be explored. The bacterial endosymbionts include an interesting array of pathogens such as Vibrio cholerae and Legionella pneumophila, both of which are well recognized waterborne/water-based pathogens. Work is needed to determine if control of Acanthamoeba spp. is needed to control water-based pathogens in water supplies.
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Affiliation(s)
- Nena Nwachuku
- Office of Science and Technology, Office of Water, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave. N.W., Mc 4304T, Washington, DC 20460, USA
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Greub G, La Scola B, Raoult D. Parachlamydia acanthamoeba is endosymbiotic or lytic for Acanthamoeba polyphaga depending on the incubation temperature. Ann N Y Acad Sci 2003; 990:628-34. [PMID: 12860700 DOI: 10.1111/j.1749-6632.2003.tb07437.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Parachlamydiaceae are potential emerging pathogens that naturally infect free-living amoebae. We investigated the affects of incubation temperature on the growth and cytopathic effect of P. acanthamoeba in Acanthamoeba polyphaga. A. polyphaga were infected with P. acanthamoeba and incubated at different temperatures for ten days. Bacterial growth was quantified by real-time PCR. Cytopathic effects were determined by counting the number of cysts and viable amoebae (unstained with trypan blue) in Nageotte counting chambers. Uninfected amoebae cultures were used as negative control. At 32, 35, and 37 degrees C, we observed a significant decrease in the number of viable A. polyphaga that contrasted with the delayed and smaller decrease in the number of living A. polyphaga observed at 25, 28, and 30 degrees C. Higher incubation temperature, which is associated with amoebal lysis, surprisingly was not associated with increased growth rate. P. acanthamoeba is lytic for A. polyphaga at 32-37 degrees C but endosymbiotic at 25-30 degrees C. This suggests that A. polyphaga may be a reservoir of endosymbionts at the lower temperature of the nasal mucosa, which may be liberated by lysis at higher temperature, for instance, when the amoeba is inhaled and reaches the lower respiratory tract.
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Affiliation(s)
- Gilbert Greub
- Unité des Rickettsies, CNRS UPRESA 6020, Faculté de Médecine, Université de la Méditerranée, 13385 Marseilles Cedex 05, France
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Ohno A, Kato N, Yamada K, Yamaguchi K. Factors influencing survival of Legionella pneumophila serotype 1 in hot spring water and tap water. Appl Environ Microbiol 2003; 69:2540-7. [PMID: 12732519 PMCID: PMC154533 DOI: 10.1128/aem.69.5.2540-2547.2003] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The factors involved in the survival of Legionella pneumophila in the microcosms of both hot spring water and tap water were studied by examining cultivability and metabolic activity. L. pneumophila could survive by maintaining metabolic activity but was noncultivable in all microcosms at 42 degrees C, except for one microcosm with a pH of <2.0. Lower temperatures supported survival without loss of cultivability. The cultivability declined with increasing temperature, although metabolic activity was observed at temperatures of up to 45 degrees C. The optimal range of pH for survival was between 6.0 and 8. The metabolic activity could be maintained for long periods even in microcosms with high concentrations of salt. The cultivability of organisms in the post-exponential phase in a tap water microcosm with a low inoculum size was more rapidly reduced than that of organisms in the exponential phase. In contrast, the loss of cultivability in microcosms of a high inoculum size was significant in the exponential phase. Random(ly) amplified polymorphic DNA analysis of microcosms where cultivability was lost but metabolic activity was retained showed no change compared to cells grown freshly, although an effect on the amplified DNA band pattern by production of stress proteins was expected. Resuscitation by the addition of Acanthamoeba castellanii to the microcosm in which cultivability was completely lost but metabolic activity was maintained was observed only in part of the cell population. Our results suggest that L. pneumophila cell populations can potentially survive as free organisms for long periods by maintaining metabolic activity but temporarily losing cultivability under strict environments and requiring resuscitation by ingestion by amoebas.
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Affiliation(s)
- Akira Ohno
- Department of Microbiology, Toho University School of Medicine, 5-21-16 Omori-Nishi, Ota-Ku, Tokyo 143-8540, Japan.
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Abstract
Parachlamydiaceae, which naturally infect amoebae, form a sister taxon to the Chlamydiaceae on the basis of the Chlamydia-like cycle of replication and 80% to 90% homology of ribosomal RNA genes. Because intra-amoebal growth could increase the virulence of some intracellular bacteria, Parachlamydiaceae may be pathogenic. Arguments supporting a pathogenic role are that Chlamydia pneumoniae, a well-recognized agent of pneumonia, was shown to infect free-living amoebae and that another member of the Chlamydiales, Simkania negevensis, which has 88% homology with Parachlamydia acanthamoebae, has caused pneumonia in adults and acute bronchiolitis in infants. The recent identification of a 16S rRNA gene sequence of a Parachlamydiaceae from bronchoalveolar lavage is additional evidence supporting potential for pathogenicity.
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Affiliation(s)
- Gilbert Greub
- Unité des Rickettsies, Université de la Méditerranée, Marseille, France
| | - Didier Raoult
- Unité des Rickettsies, Université de la Méditerranée, Marseille, France
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21
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Greub G, Raoult D. Crescent bodies of Parachlamydia acanthamoeba and its life cycle within Acanthamoeba polyphaga: an electron micrograph study. Appl Environ Microbiol 2002; 68:3076-84. [PMID: 12039769 PMCID: PMC123927 DOI: 10.1128/aem.68.6.3076-3084.2002] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Parachlamydiaceae are endosymbionts of free-living amoeba first identified in 1997. Two developmental stages, elementary and reticulate bodies, were observed; however, their localization and proportions according to culture condition and duration remain unknown. The life cycle of Parachlamydia acanthamoeba within Acanthamoeba polyphaga was studied by transmission electron microscopy of 8-, 36-, and 144-h coculture. Morphometry and quantification were performed using SAMBA software. The elementary body, the predominant stage within the amoebae, was located mainly within their vacuoles. The multiplication of Parachlamydia bacteria by binary fission of reticulate bodies was independently associated with culture in PYG broth (odds ratio [OR] = 4.4; 95% confidence interval [CI], 1.55 to 12.46) and with the presence of reticulate bodies within the amoebae (OR = 2.10; 95% CI, 1.53 to 2.89). A third developmental stage was observed, the crescent body. Its presence outside and inside the amoebae was associated mainly with prolonged incubation time (OR = 3.98; 95% CI, 1.49 to 10.68, and OR = 5.98; 95% CI, 1.75 to 20.4, respectively). Elementary and crescent bodies were released into the extracellular medium within vesicles or after amoebal lysis. For both, phagocytosis was their mode of entry. This electron micrograph study revealed another infective developmental stage, the crescent body, and provided quantitative analysis of the life cycle of P. acanthamoeba within A. polyphaga.
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Affiliation(s)
- Gilbert Greub
- Unité des Rickettsies, Faculté de Médecine, Université de la Méditerranée, Marseille, France
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Ballard AL, Fry NK, Chan L, Surman SB, Lee JV, Harrison TG, Towner KJ. Detection of Legionella pneumophila using a real-time PCR hybridization assay. J Clin Microbiol 2000; 38:4215-8. [PMID: 11060093 PMCID: PMC87566 DOI: 10.1128/jcm.38.11.4215-4218.2000] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2000] [Accepted: 08/18/2000] [Indexed: 11/20/2022] Open
Abstract
A real-time PCR hybridization assay for Legionella pneumophila is described; the assay uses LightCycler (Idaho Technology) methodology to specifically detect 2.5 CFU/reaction, equivalent to 1,000 CFU/liter of starting water sample. The assay, including DNA extraction and confirmation of product identity, is completed within 90 min of receipt of a sample.
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Affiliation(s)
- A L Ballard
- Department of Microbiology and PHLS Laboratory, University Hospital, Nottingham NG7 2UH, United Kingdom
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Abstract
Studies on Legionella show a continuum from environment to human disease. Legionellosis is caused by Legionella species acquired from environmental sources, principally water sources such as cooling towers, where Legionella grows intracellularly in protozoa within biofilms. Aquatic biofilms, which are widespread not only in nature, but also in medical and dental devices, are ecological niches in which Legionella survives and proliferates and the ultimate sources to which outbreaks of legionellosis can be traced. Invasion and intracellular replication of L. pneumophila within protozoa in the environment play a major role in the transmission of Legionnaires' disease. Protozoa provide the habitats for the environmental survival and reproduction of Legionella species. L. pneumophila proliferates intracellularly in various species of protozoa within vacuoles studded with ribosomes, as it also does within macrophages. Growth within protozoa enhances the environmental survival capability and the pathogenicity (virulence) of Legionella. The growth requirements of Legionella, the ability of Legionella to enter a viable non-culturable state, the association of Legionella with protozoa and the occurrence of Legionella within biofilms complicates the detection of Legionella and epidemiological investigations of legionellosis. Polymerase chain reaction (PCR) methods have been developed for the molecular detection of Legionella and used in environmental and epidemiological studies. Various physical and chemical disinfection methods have been developed to eliminate Legionella from environmental sources, but gaining control of Legionella in environmental waters, where they are protected from disinfection by growing within protozoa and biofilms, remains a challenge, and one that must be overcome in order to eliminate sporadic outbreaks of legionellosis.
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Affiliation(s)
- R M Atlas
- Department of Biology, University of Louisville, KY 40292, USA.
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Liles MR, Edelstein PH, Cianciotto NP. The prepilin peptidase is required for protein secretion by and the virulence of the intracellular pathogen Legionella pneumophila. Mol Microbiol 1999; 31:959-70. [PMID: 10048038 DOI: 10.1046/j.1365-2958.1999.01239.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prepilin peptidases cleave, among other substrates, the leader sequences from prepilin-like proteins that are required for type II protein secretion in Gram-negative bacteria. To begin to assess the importance of type II secretion for the virulence of an intracellular pathogen, we examined the effect of inactivating the prepilin peptidase (pilD) gene of Legionella pneumophila. Although the pilD mutant and its parent grew similarly in bacteriological media, they did differ in colony attributes and recoverability from late stationary phase. Moreover, at least three proteins were absent from the mutant's supernatant, indicating that PilD is necessary for the secretion of Legionella proteins. The absence of both the major secreted protein and a haemolytic activity from the mutant signalled that the L. pneumophila zinc metalloprotease is excreted via type II secretion. Most interestingly, the pilD mutant was greatly impaired in its ability to grow within Hartmannella vermiformis amoebae and the human macrophage-like U937 cells. As reintroduction of pilD into the mutant restored inefectivity and as a mutant lacking type IV pilin replicated like wild type, these data suggested that the intracellular growth of L. pneumophila is promoted by proteins secreted via a type II pathway. Intratracheal inoculation of guinea pigs revealed that the LD50 for the pilD mutant is at least 100-fold greater than that for its parent, and the culturing of bacteria from infected animals showed a rapid clearance of the mutant from the lungs. This is the first study to indicate a role for PilD and type II secretion in intracellular parasitism.
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Affiliation(s)
- M R Liles
- Department of Microbiology-Immunology, Northwestern University, Chicago, IL 60611, USA
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Hamilton E, Seal DV, Hay J. Comparison of chlorine and chlorine dioxide disinfection for control of Legionella in a hospital potable water supply. J Hosp Infect 1996; 32:156-60. [PMID: 8666767 DOI: 10.1016/s0195-6701(96)90058-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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