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Du Y, Yan Z, Song K, Jin J, Xiao L, Sun Z, Tan Y, Zhang P, Du Z, Yang R, Zhao Y, Song Y. Development and evaluation of a multiplex droplet digital polymerase chain reaction method for simultaneous detection of five biothreat pathogens. Front Microbiol 2022; 13:970973. [PMID: 35966705 PMCID: PMC9366144 DOI: 10.3389/fmicb.2022.970973] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 07/11/2022] [Indexed: 11/20/2022] Open
Abstract
Biothreat agents pose a huge threat to human and public health, necessitating the development of rapid and highly sensitive detection approaches. This study establishes a multiplex droplet digital polymerase chain reaction (ddPCR) method for simultaneously detecting five high-risk bacterial biothreats: Yersinia pestis, Bacillus anthracis, Brucella spp., Burkholderia pseudomallei, and Francisella tularensis. Unlike conventional multiplex real-time PCR (qPCR) methods, the multiplex ddPCR assay was developed using two types of probe fluorophores, allowing the assay to perform with a common two-color ddPCR system. After optimization, the assay performance was evaluated, showing a lower limit of detection (LOD) (0.1–1.0 pg/μL) and good selectivity for the five bacteria targets. The multiplex assay’s ability to simultaneously detect two or more kinds of targets in a sample was also demonstrated. The assay showed strong sample tolerance when testing simulated soil samples; the LOD for bacteria in soil was 2 × 102–2 × 103 colony-forming unit (CFU)/100 mg soil (around 5–50 CFU/reaction), which was 10-fold lower than that of the single-target qPCR method. When testing simulated soil samples at bacterial concentrations of 2 × 103–2 × 104 CFU/100 mg soil, the assay presented a higher sensitivity (100%, 35/35) than that of the qPCR method (65.71%, 23/35) and a good specificity (100%, 15/15). These results suggest that the developed 5-plex ddPCR method is more sensitive than conventional qPCR methods and is potentially suitable for rapidly detecting or screening the five selected bacterial biothreats in suspicious samples.
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Affiliation(s)
- Yipu Du
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
- The First Department, General Hospital of Northern Theater Command, Shenyang, China
| | - Ziheng Yan
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Kai Song
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Junyan Jin
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Liting Xiao
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
- School of Basic Medical Sciences, Anhui Medical University, Hefei, China
| | - Zhulin Sun
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Yafang Tan
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Pingping Zhang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Zongmin Du
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Ruifu Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
| | - Yong Zhao
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
- *Correspondence: Yong Zhao,
| | - Yajun Song
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Academy of Military Medical Sciences (AMMS), Beijing, China
- Yajun Song,
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Vetchinin SS, Shevyakov AG, Khomyakov AE, Mironova RI, Mokrievich AN, Biketov SF. Development of an immunoassay test system based on monoclonal antybodies and immunomagnetic particles for the detection of F. tularensis cells. Klin Lab Diagn 2021; 66:353-357. [PMID: 34105911 DOI: 10.51620/0869-2084-2021-66-6-353-357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Tularemia is an especially dangerous infection caused by the gram-negative bacterium Francisella tularensis. It belongs to natural focal infections, and therefore is under continuous control by quarantine services. When carrying out their activities they use a whole range of diagnostic tools. The objective of this research is to develop an enzyme immunoassay based on highly specific monoclonal antibodies and immunomagnetic particles for monitoring the tularemia pathogen. To produce hybridomas mice were immunized with cells of the vaccine strain F. tularensis subsp. holarctica 15 NIIEG. After cell fusion hybridomas were selected by a solid-phase enzyme immunoassay (ELISA) using lipopolysaccharide (LPS) of the tularemia microbe. As a result, two hybridomas, 1C2 and 3F5, were produced. MABs of the hybridomas were obtained by using BALB / c mice. The MABs were purified by sepharose A affinity chromatography and used for conjugation with magnetic particles, and for biotinylation followed by matching a pair for ELISA. The pair of IMPs and MABs 3F5 as well as biotinylated FB11-x MABs was the best in detecting tularemia cells. The use of this MAB pair in ELISA allowed the identification of 105 microbial cells/ml in a 4 ml sample and 5×103 microbial cells/ml in a 45ml sample. Interaction with F. tularensis subsp. novicida Utah112 cells was absent.
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Affiliation(s)
- S S Vetchinin
- State Research Center of Applied Microbiology and Biotechnology
| | | | - A E Khomyakov
- State Research Center of Applied Microbiology and Biotechnology
| | - R I Mironova
- State Research Center of Applied Microbiology and Biotechnology
| | - A N Mokrievich
- State Research Center of Applied Microbiology and Biotechnology
| | - S F Biketov
- State Research Center of Applied Microbiology and Biotechnology
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Golovliov I, Bäckman S, Granberg M, Salomonsson E, Lundmark E, Näslund J, Busch JD, Birdsell D, Sahl JW, Wagner DM, Johansson A, Forsman M, Thelaus J. Long-Term Survival of Virulent Tularemia Pathogens outside a Host in Conditions That Mimic Natural Aquatic Environments. Appl Environ Microbiol 2021; 87:e02713-20. [PMID: 33397692 PMCID: PMC8104992 DOI: 10.1128/aem.02713-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 12/17/2020] [Indexed: 01/22/2023] Open
Abstract
Francisella tularensis, the causative agent of the zoonotic disease tularemia, can cause seasonal outbreaks of acute febrile illness in humans with disease peaks in late summer to autumn. Interestingly, its mechanisms for environmental persistence between outbreaks are poorly understood. One hypothesis is that F. tularensis forms biofilms in aquatic environments. We utilized two fully virulent wild-type strains: FSC200 (Francisella tularensis subsp. holarctica) and Schu S4 (Francisella tularensis subsp. tularensis) and three control strains, the attenuated live vaccine strain (LVS; F. tularensis subsp. holarctica), a Schu S4 ΔwbtI mutant that is documented to form biofilms, and the low-virulence strain U112 of the closely related species Francisella novicida Strains were incubated in saline solution (0.9% NaCl) microcosms for 24 weeks at both 4°C and 20°C, whereupon viability and biofilm formation were measured. These temperatures were selected to approximate winter and summer temperatures of fresh water in Scandinavia, respectively. U112 and Schu S4 ΔwbtI formed biofilms, but F. tularensis strains FSC200 and Schu S4 and the LVS did not. All strains exhibited prolonged viability at 4°C compared to 20°C. U112 and FSC200 displayed remarkable long-term persistence at 4°C, with only 1- and 2-fold log reductions, respectively, of viable cells after 24 weeks. Schu S4 exhibited lower survival, yielding no viable cells by week 20. At 24 weeks, cells from FSC200, but not from Schu S4, were still fully virulent in mice. Taken together, these results demonstrate biofilm-independent, long-term survival of pathogenic F. tularensis subsp. holarctica in conditions that mimic overwinter survival in aquatic environments.IMPORTANCE Tularemia, a disease caused by the environmental bacterium Francisella tularensis, is characterized by acute febrile illness. F. tularensis is highly infectious: as few as 10 organisms can cause human disease. Tularemia is not known to be spread from person to person. Rather, all human infections are independently acquired from the environment via the bite of blood-feeding arthropods, ingestion of infected food or water, or inhalation of aerosolized bacteria. Despite the environmental origins of human disease events, the ecological factors governing the long-term persistence of F. tularensis in nature between seasonal human outbreaks are poorly understood. The significance of our research is in identifying conditions that promote long-term survival of fully virulent F. tularensis outside a mammalian host or insect vector. These conditions are similar to those found in natural aquatic environments in winter and provide important new insights on how F. tularensis may persist long-term in the environment.
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Affiliation(s)
- Igor Golovliov
- Department of Clinical Microbiology, Umeå University, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Stina Bäckman
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Malin Granberg
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Emelie Salomonsson
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Eva Lundmark
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Jonas Näslund
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Joseph D Busch
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Dawn Birdsell
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Jason W Sahl
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - David M Wagner
- Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, Arizona, USA
| | - Anders Johansson
- Department of Clinical Microbiology, Umeå University, Umeå, Sweden
- Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Mats Forsman
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
| | - Johanna Thelaus
- Division of CBRN Defence and Security, Swedish Defence Research Agency FOI, Umeå, Sweden
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