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Tejeda C, Steuer P, Villegas M, Ulloa F, Hernández-Agudelo JM, Salgado M. Evidence of Homeostatic Regulation in Mycobacterium avium Subspecies paratuberculosis as an Adaptive Response to Copper Stress. Microorganisms 2023; 11:microorganisms11040898. [PMID: 37110321 PMCID: PMC10141397 DOI: 10.3390/microorganisms11040898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/22/2023] [Accepted: 03/25/2023] [Indexed: 04/03/2023] Open
Abstract
Background: Bacteria are capable of responding to various stressors, something which has been essential for their adaptation, evolution, and colonization of a wide range of environments. Of the many stressors affecting bacteria, we can highlight heavy metals, and amongst these, copper stands out for its great antibacterial capacity. Using Mycobacterium tuberculosis (Mtb) as a model, the action of proteins involved in copper homeostasis has been put forward as an explanation for the tolerance or adaptive response of this mycobacteria to the toxic action of copper. Therefore, the aim of this study was to confirm the presence and evaluate the expression of genes involved in copper homeostasis at the transcriptional level after challenging Mycobacterium avium subsp. paratuberculoisis (MAP) with copper ions. Methodology: Buffer inoculated with MAP was treated with two stressors, the presence of copper homeostasis genes was confirmed by bioinformatics and genomic analysis, and the response of these genes to the stressors was evaluated by gene expression analysis, using qPCR and the comparative ΔΔCt method. Results: Through bioinformatics and genomic analysis, we found that copper homeostasis genes were present in the MAP genome and were overexpressed when treated with copper ions, which was not the case with H2O2 treatment. Conclusion: These results suggest that genes in MAP that code for proteins involved in copper homeostasis trigger an adaptive response to copper ions.
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Affiliation(s)
- Carlos Tejeda
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
| | - Pamela Steuer
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
| | - Marcela Villegas
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
| | - Fernando Ulloa
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
- Escuela de Graduados, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
| | - José M. Hernández-Agudelo
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
- Escuela de Graduados, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
| | - Miguel Salgado
- Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia 5090000, Chile
- Correspondence: ; Tel.: +56-63-2-444358; Fax: +56-63-293-233
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Suter A, Schmitt S, Hübschke E, Kowalska M, Hartnack S, Pot S. The bactericidal effect of two photoactivated chromophore for keratitis-corneal crosslinking protocols (standard vs. accelerated) on bacterial isolates associated with infectious keratitis in companion animals. BMC Vet Res 2022; 18:317. [PMID: 35978428 PMCID: PMC9386977 DOI: 10.1186/s12917-022-03397-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 07/18/2022] [Indexed: 11/10/2022] Open
Abstract
Background Bacterial corneal infections are common and potentially blinding diseases in all species. As antibiotic resistance is a growing concern, alternative treatment methods are an important focus of research. Photoactivated chromophore for keratitis-corneal crosslinking (PACK-CXL) is a promising oxygen radical-mediated alternative to antibiotic treatment. The main goal of this study was to assess the anti-bactericidal efficacy on clinical bacterial isolates of the current standard and an accelerated PACK-CXL treatment protocol delivering the same energy dose (5.4 J/cm2). Methods Clinical bacterial isolates from 11 dogs, five horses, one cat and one guinea pig were cultured, brought into suspension with 0.1% riboflavin and subsequently irradiated. Irradiation was performed with a 365 nm UVA light source for 30 min at 3mW/cm2 (standard protocol) or for 5 min at 18mW/cm2 (accelerated protocol), respectively. After treatment, the samples were cultured and colony forming units (CFU’s) were counted and the weighted average mean of CFU’s per μl was calculated. Results were statistically compared between treated and control samples using a linear mixed effects model. Results Both PACK-CXL protocols demonstrated a significant bactericidal effect on all tested isolates when compared to untreated controls. No efficacy difference between the two PACK-CXL protocols was observed. Conclusion The accelerated PACK-CXL protocol can be recommended for empirical use in the treatment of bacterial corneal infections in veterinary patients while awaiting culture results. This will facilitate immediate treatment, the delivery of higher fluence PACK-CXL treatment within a reasonable time, and minimize the required anesthetic time or even obviate the need for general anesthesia.
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Affiliation(s)
- Anja Suter
- Ophthalmology Section, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
| | - Sarah Schmitt
- Veterinary Bacteriology Section, Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Ella Hübschke
- Veterinary Bacteriology Section, Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Malwina Kowalska
- Epidemiology Section, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Sonja Hartnack
- Epidemiology Section, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Simon Pot
- Ophthalmology Section, Equine Department, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
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Stabel JR, Turner A, Walker M. An eco-friendly decontaminant to kill Mycobacterium avium subsp. paratuberculosis. J Microbiol Methods 2020; 176:106001. [PMID: 32653399 DOI: 10.1016/j.mimet.2020.106001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 10/23/2022]
Abstract
Mycobacteria are difficult to kill due to the complexity of their cell wall. Further, Mycobacterium avium subsp. paratuberculosis (MAP) has one of the more elaborate cell wall compositions of all the mycobacteria. As a working pathogen within a research laboratory setting or as an environmental contaminant shed in the manure from infected animals, MAP is highly resistant to typical disinfectants. In the past, the most successful disinfectants to kill mycobacteria were based upon phenolics, harsh compounds that can break down the lipids within the cell wall. New disinfectants have been developed that are less toxic to the environment, however, it is unknown how well they perform compared to more traditional disinfectants. In the present study, we present comparative data on the utility of a commercial eco-friendly disinfectant, Benefect®, compared to Amphyl®, a phenolic-based disinfectant, and Lysol®, a quaternary ammonium-based disinfectant, to kill MAP in pure culture, tissues, and manure. Results demonstrated that Benefect was highly effective with up to 100% kill of MAP within 30 min in all experiments, paralleling results obtained with Amphyl. Lysol performed the most poorly, requiring longer contact times to kill MAP. These results suggest that natural, nontoxic ingredients can be used to disinfect even hearty pathogens such as MAP effectively, both within the laboratory and on-farm.
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Affiliation(s)
- J R Stabel
- USDA-ARS-National Animal Disease Center, Ames, IA 50010, United States of America.
| | - A Turner
- USDA-ARS-National Animal Disease Center, Ames, IA 50010, United States of America
| | - M Walker
- USDA-ARS-National Animal Disease Center, Ames, IA 50010, United States of America
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Khammadov NI, Aleksandrova NM, Khammadova AV, Shuralev EA. Evaluation of the Effectiveness of Genetic Markers of Mycobacteria for Assessing the Disinfection Quality by Viability Real Time PCR. BioNanoSci 2019. [DOI: 10.1007/s12668-019-00654-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Rice JH, McDaniel MM, Holland A, Eda S. Modelling Bovine Granuloma Formation In Vitro upon Infection with Mycobacterium Avium Subspecies Paratuberculosis. Vet Sci 2019; 6:E80. [PMID: 31614819 DOI: 10.3390/vetsci6040080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 09/30/2019] [Accepted: 10/08/2019] [Indexed: 02/07/2023] Open
Abstract
Mycobacterium avium subspecies paratuberculosis (Map) causes chronic granulomatous disease in cattle and ruminant livestock, causing substantial economic losses. Current vaccines delay clinical signs but cannot train the immune system to fully eradicate latent Map. During latency, Map uses host defenses, cage-like macrophage clusters called granuloma, as incubators for months or years. We used an in vitro model to investigate the early coordination of macrophages into granuloma upon Map infection over ten days. We found that at multiplicities of infection (MOI; Map:macrophages) of 1:2 and below, the macrophages readily form clusters and evolve pro-inflammatory cytokines in keeping with a cell-mediated immune response. At higher MOIs, viability of host macrophages is negatively impacted. At 1:4 MOI, we quantified viable Map in our model and confirmed that intracellular Map reproduced over the first five days of infection. Host cells expressed Type 1-specific cytokines, and Map-infected macrophages displayed reduced motility compared to Map-exposed, uninfected macrophages, suggesting an important role for uninfected macrophages in the early aggregative response. Reported is the first in vitro JD granuloma model capturing Map and macrophage viability, size distribution of resulting clusters, motility of monocyte-derived macrophages, and cytokine response during clustering, allowing quantitative analysis of multiple parameters of the Map-specific granulomatous response.
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Ali ZI, Saudi AM, Albrecht R, Talaat AM. The inhibitory effect of nisin on Mycobacterium avium ssp. paratuberculosis and its effect on mycobacterial cell wall. J Dairy Sci 2019; 102:4935-4944. [PMID: 30981481 DOI: 10.3168/jds.2018-16106] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/08/2019] [Indexed: 11/19/2022]
Abstract
Infection with Mycobacterium avium ssp. paratuberculosis (M. paratuberculosis) is a widespread problem in the United States and worldwide, and it constitutes a significant health problem for dairy animals with a potential effect on human health. Mycobacterium paratuberculosis is easily transmitted through consumption of contaminated milk; therefore, finding safe methods to reduce the mycobacterial load in milk and other dairy products is important to the dairy industry. The main objective of the current study was to investigate the effect of natural products, such as bacteriocins designated as "generally regarded as safe" (GRAS), on the survival of M. paratuberculosis in milk. Commercially synthesized bacteriocin (nisin) was used to examine its effect on the survival of laboratory and field isolates of M. paratuberculosis and in contaminated milk. Surprisingly, nisin had a higher minimum inhibitory concentration (MIC) against the laboratory strain (M. paratuberculosis K10), at 500 U/mL, than against field isolates (e.g., M. paratuberculosis 4B and JTC 1281), at 15 U/mL. In milk, growth of M. paratuberculosis was inhibited after treatment with levels of nisin that are permissible in human food at 4°C and 37°C. Using both fluorescent and scanning electron microscopy, we were able to identify defects in the bacterial cell walls of treated cultures. Our analysis indicated that nisin reduced membrane integrity by forming pores in the mycobacterial cell wall, thereby decreasing survival of M. paratuberculosis. Thus, nisin treatment of milk could be implemented as a control measure to reduce M. paratuberculosis secreted in milk from infected herds. Nisin could also be used to reduce M. paratuberculosis in colostrum given to calves from infected animals, improving biosecurity control in dairy herds affected by Johne's disease.
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Affiliation(s)
- Zeinab I Ali
- Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Cairo University, Giza, 11221, Egypt
| | - Adel M Saudi
- Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Cairo University, Giza, 11221, Egypt
| | - Ralph Albrecht
- Department of Animal Science, University of Wisconsin, Madison 53706
| | - Adel M Talaat
- Department of Pathobiological Sciences, University of Wisconsin, Madison 53706.
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Kralik P, Babak V, Dziedzinska R. The Impact of the Antimicrobial Compounds Produced by Lactic Acid Bacteria on the Growth Performance of Mycobacterium avium subsp. paratuberculosis. Front Microbiol 2018; 9:638. [PMID: 29666620 PMCID: PMC5891613 DOI: 10.3389/fmicb.2018.00638] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 03/19/2018] [Indexed: 11/18/2022] Open
Abstract
Cell-free supernatants (CFSs) extracted from various lactic acid bacteria (LAB) cultures were applied to Mycobacterium avium subsp. paratuberculosis (MAP) cells to determine their effect on MAP viability. In addition, 5% lactic acid (LA; pH 3) and commercially synthetized nisin bacteriocin were also tested. This procedure was chosen in order to mimic the influence of LAB compounds during the production and storage of fermented milk products, which can be contaminated by MAP. Its presence in milk and milk products is of public concern due to the possible ingestion of MAP by consumers and the discussed role of MAP in Crohn’s disease. Propidium monoazide real-time PCR (PMA qPCR) was used for viability determination. Although all CFS showed significant effects on MAP viability, two distinct groups of CFS – effective and less effective – could be distinguished. The effective CFSs were extracted from various lactobacilli cultures, their pH values were mostly lower than 4.5, and their application resulted in >2 log10 reductions in MAP viability. The group of less effective CFS were filtered from Lactococcus and enterococci cultures, their pH values were higher than 4.5, and their effect on MAP viability was <2 log10. LA elicited a reduction in MAP viability that was similar to that of the group of less effective CFS. Almost no effect was found when using commercially synthetized nisin at concentrations of 0.1–1000 μg/ml. A combination of the influence of the type of bacteriocin, the length of its action, bacteriocin production strain, and pH are all probably required for a successful reduction in MAP viability. However, certain bacteriocins and their respective LAB strains (Lactobacillus sp.) appear to play a greater role in reducing the viability of MAP than pH.
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Affiliation(s)
- Petr Kralik
- Veterinary Research Institute, Brno, Czechia
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More S, Bøtner A, Butterworth A, Calistri P, Depner K, Edwards S, Garin-Bastuji B, Good M, Gortázar Schmidt C, Michel V, Miranda MA, Nielsen SS, Raj M, Sihvonen L, Spoolder H, Stegeman JA, Thulke HH, Velarde A, Willeberg P, Winckler C, Baldinelli F, Broglia A, Zancanaro G, Beltrán-Beck B, Kohnle L, Morgado J, Bicout D. Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): paratuberculosis. EFSA J 2017; 15:e04960. [PMID: 32625604 PMCID: PMC7010113 DOI: 10.2903/j.efsa.2017.4960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Paratuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of paratuberculosis to be listed, Article 9 for the categorisation of paratuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to paratuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, paratuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria in Sections 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for paratuberculosis according to Article 8(3) criteria are several species of mammals and birds as susceptible species and some species of the families Bovidae, Cervidae and Leporidae as reservoirs.
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Weigel KM, Nguyen FK, Kearney MR, Meschke JS, Cangelosi GA. Molecular Viability Testing of UV-Inactivated Bacteria. Appl Environ Microbiol 2017; 83:e00331-17. [PMID: 28283525 DOI: 10.1128/AEM.00331-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 03/08/2017] [Indexed: 01/01/2023] Open
Abstract
PCR is effective in detecting bacterial DNA in samples, but it is unable to differentiate viable bacteria from inactivated cells or free DNA fragments. New PCR-based analytical strategies have been developed to address this limitation. Molecular viability testing (MVT) correlates bacterial viability with the ability to rapidly synthesize species-specific rRNA precursors (pre-rRNA) in response to brief nutritional stimulation. Previous studies demonstrated that MVT can assess bacterial inactivation by chlorine, serum, and low-temperature pasteurization. Here, we demonstrate that MVT can detect inactivation of Escherichia coli, Aeromonas hydrophila, and Enterococcus faecalis cells by UV irradiation. Some UV-inactivated E. coli cells transiently retained the ability to synthesize pre-rRNA postirradiation (generating false-positive MVT results), but this activity ceased within 1 h following UV exposure. Viable but transiently undetectable (by culture) E. coli cells were consistently detected by MVT. An alternative viability testing method, viability PCR (vPCR), correlates viability with cell envelope integrity. This method did not distinguish viable bacteria from UV-inactivated bacteria under some conditions, indicating that the inactivated cells retained intact cell envelopes. MVT holds promise as a means to rapidly assess microbial inactivation by UV treatment.IMPORTANCE UV irradiation is increasingly being used to disinfect water, food, and other materials for human use. Confirming the effectiveness of UV disinfection remains a challenging task. In particular, microbiological methods that rely on rapid detection of microbial DNA can yield misleading results, due to the detection of remnant DNA associated with dead microbial cells. This report describes a novel method that rapidly distinguishes living microbial cells from dead microbial cells after UV disinfection.
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Affiliation(s)
- William C Davis
- a Department of Microbiology and Pathology , Washington State University , Pullman , WA , USA
| | - J Todd Kuenstner
- b Clinical Laboratories and Clinical Pathology , Temple University Hospital , Philadelphia , PA , USA
| | - Shoor Vir Singh
- c Microbiology Laboratory, Animal Health Division , Central Institute for Research on Goats , Mathura , India
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Bull TJ, Munshi T, Mikkelsen H, Hartmann SB, Sørensen MR, Garcia JS, Lopez-Perez PM, Hofmann S, Hilpert K, Jungersen G. Improved Culture Medium (TiKa) for Mycobacterium avium Subspecies Paratuberculosis (MAP) Matches qPCR Sensitivity and Reveals Significant Proportions of Non-viable MAP in Lymphoid Tissue of Vaccinated MAP Challenged Animals. Front Microbiol 2017; 7:2112. [PMID: 28101082 PMCID: PMC5209360 DOI: 10.3389/fmicb.2016.02112] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Accepted: 12/14/2016] [Indexed: 11/13/2022] Open
Abstract
The quantitative detection of viable pathogen load is an important tool in determining the degree of infection in animals and contamination of foodstuffs. Current conventional culture methods are limited in their ability to determine these levels in Mycobacterium avium subspecies paratuberculosis (MAP) due to slow growth, clumping and low recoverability issues. The principle goal of this study was to evaluate a novel culturing process (TiKa) with unique ability to stimulate MAP growth from low sample loads and dilutions. We demonstrate it was able to stimulate a mean 29-fold increase in recoverability and an improved sensitivity of up to three logs when compared with conventional culture. Using TiKa culture, MAP clumping was minimal and produced visible colonies in half the time required by standard culture methods. Parallel quantitative evaluation of the TiKa culture approach and qPCR on MAP loads in tissue and gut mucosal samples from a MAP vaccine-challenge study, showed good correlations between colony counts (cfu) and qPCR derived genome equivalents (Geq) over a large range of loads with a 30% greater sensitivity for TiKa culture approach at low loads (two logs). Furthermore, the relative fold changes in Geq and cfu from the TiKa culture approach suggests that non-mucosal tissue loads from MAP infected animals contained a reduced proportion of non-viable MAP (mean 19-fold) which was reduced significantly further (mean 190-fold) in vaccinated “reactor” calves. This study shows TiKa culture equates well with qPCR and provides important evidence that accuracy in estimating viable MAP load using DNA tests alone may vary significantly between samples of mucosal and lymphatic origin.
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Affiliation(s)
- Tim J Bull
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Tulika Munshi
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Heidi Mikkelsen
- National Veterinary Institute, Technical University of Denmark (DTU) Kongens Lyngby, Denmark
| | - Sofie B Hartmann
- National Veterinary Institute, Technical University of Denmark (DTU) Kongens Lyngby, Denmark
| | - Maria R Sørensen
- National Veterinary Institute, Technical University of Denmark (DTU) Kongens Lyngby, Denmark
| | - Joanna S Garcia
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Paula M Lopez-Perez
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Sven Hofmann
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Kai Hilpert
- Institute of Infection and Immunity, St George's University of London London, UK
| | - Gregers Jungersen
- National Veterinary Institute, Technical University of Denmark (DTU) Kongens Lyngby, Denmark
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Pooley HB, de Silva K, Purdie AC, Begg DJ, Whittington RJ, Plain KM. A Rapid Method for Quantifying Viable Mycobacterium avium subsp. paratuberculosis in Cellular Infection Assays. Appl Environ Microbiol 2016; 82:5553-62. [PMID: 27371585 DOI: 10.1128/AEM.01668-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 06/27/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Determining the viability of bacteria is a key outcome of in vitro cellular infection assays. Currently, this is done by culture, which is problematic for fastidious slow-growing bacteria such as Mycobacterium avium subsp. paratuberculosis, where it can take up to 4 months to confirm growth. This study aimed to identify an assay that can rapidly quantify the number of viable M. avium subsp. paratuberculosis cells in a cellular sample. Three commercially available bacterial viability assays along with a modified liquid culture method coupled with high-throughput quantitative PCR growth detection were assessed. Criteria for assessment included the ability of each assay to differentiate live and dead M. avium subsp. paratuberculosis organisms and their accuracy at low bacterial concentrations. Using the culture-based method, M. avium subsp. paratuberculosis growth was reliably detected and quantified within 2 weeks. There was a strong linear association between the 2-week growth rate and the initial inoculum concentration. The number of viable M. avium subsp. paratuberculosis cells in an unknown sample was quantified based on the growth rate, by using growth standards. In contrast, none of the commercially available viability assays were suitable for use with samples from in vitro cellular infection assays. IMPORTANCE Rapid quantification of the viability of Mycobacterium avium subsp. paratuberculosis in samples from in vitro cellular infection assays is important, as it allows these assays to be carried out on a large scale. In vitro cellular infection assays can function as a preliminary screening tool, for vaccine development or antimicrobial screening, and also to extend findings derived from experimental animal trials. Currently, by using culture, it takes up to 4 months to obtain quantifiable results regarding M. avium subsp. paratuberculosis viability after an in vitro infection assay; however, with the quantitative PCR and liquid culture method developed, reliable results can be obtained at 2 weeks. This method will be important for vaccine and antimicrobial screening work, as it will allow a greater number of candidates to be screened in the same amount of time, which will increase the likelihood that a favorable candidate will be found to be subjected to further testing.
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Lee ES, Lee MH, Kim BS. Evaluation of propidium monoazide-quantitative PCR to detect viable Mycobacterium fortuitum after chlorine, ozone, and ultraviolet disinfection. Int J Food Microbiol 2015; 210:143-8. [DOI: 10.1016/j.ijfoodmicro.2015.06.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 06/16/2015] [Accepted: 06/22/2015] [Indexed: 10/23/2022]
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