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Li F, Liu J, Maldonado-Gómez MX, Frese SA, Gänzle MG, Walter J. Highly accurate and sensitive absolute quantification of bacterial strains in human fecal samples. MICROBIOME 2024; 12:168. [PMID: 39244633 PMCID: PMC11380787 DOI: 10.1186/s40168-024-01881-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 07/26/2024] [Indexed: 09/09/2024]
Abstract
BACKGROUND Next-generation sequencing (NGS) approaches have revolutionized gut microbiome research and can provide strain-level resolution, but these techniques have limitations in that they are only semi-quantitative, suffer from high detection limits, and generate data that is compositional. The present study aimed to systematically compare quantitative PCR (qPCR) and droplet digital PCR (ddPCR) for the absolute quantification of Limosilactobacillus reuteri strains in human fecal samples and to develop an optimized protocol for the absolute quantification of bacterial strains in fecal samples. RESULTS Using strain-specific PCR primers for L. reuteri 17938, ddPCR showed slightly better reproducibility, but qPCR was almost as reproducible and showed comparable sensitivity (limit of detection [LOD] around 104 cells/g feces) and linearity (R2 > 0.98) when kit-based DNA isolation methods were used. qPCR further had a wider dynamic range and is cheaper and faster. Based on these findings, we conclude that qPCR has advantages over ddPCR for the absolute quantification of bacterial strains in fecal samples. We provide an optimized and easy-to-follow step-by-step protocol for the design of strain-specific qPCR assays, starting from primer design from genome sequences to the calibration of the PCR system. Validation of this protocol to design PCR assays for two L. reuteri strains, PB-W1 and DSM 20016 T, resulted in a highly accurate qPCR with a detection limit in spiked fecal samples of around 103 cells/g feces. Applying our strain-specific qPCR assays to fecal samples collected from human subjects who received live L. reuteri PB-W1 or DSM 20016 T during a human trial demonstrated a highly accurate quantification and sensitive detection of these two strains, with a much lower LOD and a broader dynamic range compared to NGS approaches (16S rRNA gene sequencing and whole metagenome sequencing). CONCLUSIONS Based on our analyses, we consider qPCR with kit-based DNA extraction approaches the best approach to accurately quantify gut bacteria at the strain level in fecal samples. The provided step-by-step protocol will allow scientists to design highly sensitive strain-specific PCR systems for the accurate quantification of bacterial strains of not only L. reuteri but also other bacterial taxa in a broad range of applications and sample types. Video Abstract.
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Affiliation(s)
- Fuyong Li
- Department of Animal Science and Technology, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
| | - Junhong Liu
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | | | - Steven A Frese
- Department of Nutrition, University of Nevada, Reno, NV, 89557, USA
| | - Michael G Gänzle
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Jens Walter
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
- School of Microbiology, Department of Medicine, and APC Microbiome Ireland, University College Cork, Cork, T12 YT20, Ireland.
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Palumbo JD, Sarreal SBL, Kim JH. Simultaneous detection of mycotoxigenic Aspergillus species of sections Circumdati and Flavi using multiplex digital PCR. Lett Appl Microbiol 2023; 76:ovad142. [PMID: 38111225 DOI: 10.1093/lambio/ovad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/20/2023] [Accepted: 12/15/2023] [Indexed: 12/20/2023]
Abstract
Populations of ochratoxin-producing Aspergillus section Circumdati species and aflatoxin-producing Aspergillus section Flavi species frequently coexist in soil and are the main sources of mycotoxin contamination of tree nuts. Identification of mycotoxigenic Aspergillus species in these sections is difficult using traditional isolation and culture methods. We developed a multiplex digital PCR (dPCR) assay to detect and quantify Aspergillus ochraceus, Aspergillus westerdijkiae, and Aspergillus steynii (section Circumdati), as well as Aspergillus flavus and Aspergillus parasiticus (section Flavi), in environmental samples based on species-specific calmodulin gene sequences. Relative quantification of each species by dPCR of mixed-species templates correlated with corresponding DNA input ratios. Target species could be detected in soil inoculated with conidia from each species. Non-target species of sections Circumdati, Flavi, and Nigri were generally not detectable using this dPCR method. Detected non-target species (Aspergillus fresenii, Aspergillus melleus, Aspergillus sclerotiorum, and Aspergillus subramanianii) were discernible from A. ochraceus in dual-template dPCR reactions based on differential fluorescence intensity.
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Affiliation(s)
- Jeffrey D Palumbo
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
| | - Siov Bouy L Sarreal
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
| | - Jong H Kim
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
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Colosi HA, Baciu AM, Costache C, Opris RV, Popp RA, Sabou M, Colosi IA. Prevalence of Azole-Resistant Aspergillus Section Fumigati Strains Isolated from Romanian Vineyard Soil Samples. Antibiotics (Basel) 2023; 12:1695. [PMID: 38136729 PMCID: PMC10741105 DOI: 10.3390/antibiotics12121695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 11/30/2023] [Accepted: 12/02/2023] [Indexed: 12/24/2023] Open
Abstract
The relationship between fungal species and their resistance patterns in vineyard soils has important implications for agriculture and medicine. This study explored the prevalence of Aspergillus section Fumigati species and their resistance to azole compounds in Romanian vineyard soils. METHODS A total of 265 soil samples from various Romanian vineyards were screened for fungi resistant to azoles. RESULTS Aspergillus section Fumigati isolates exhibited significant resistance to itraconazole and voriconazole, but no azole-resistant Aspergillus fumigatus strains were detected. Six percent of the samples were positive for Aspergillus section Fumigati strains, all of which were azole-resistant. The strains were mainly Aspergillus udagawae (93.75%) and Aspergillus lentulus (6.25%). The predominant azole-resistant Aspergillus species were Aspergillus section Nigri strains, which were found in 75 soil samples. CONCLUSIONS This study highlights the importance of understanding fungal resistance in vineyard soils for both the agricultural and clinical sectors. The presence of resistant strains may affect vine health and wine production while also constituting a challenge in the selection of effective treatments against severe and potentially fatal fungal infections in humans, stressing the importance of species-specific antifungal resistance knowledge.
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Affiliation(s)
- Horațiu Alexandru Colosi
- Department of Medical Education, Division of Medical Informatics and Biostatistics, Iuliu Hațieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania; (H.A.C.); (I.A.C.)
| | - Alina Mihaela Baciu
- Division of Microbiology, Iuliu Hațieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania
| | - Carmen Costache
- Division of Microbiology, Iuliu Hațieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania
| | - Razvan Vlad Opris
- Division of Microbiology, Iuliu Hațieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania
| | - Radu Anghel Popp
- Division of Medical Genetics, Iuliu Hatieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania
| | - Marcela Sabou
- Laboratoire de Parasitologie et Mycologie Médicale, Les Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France;
- Institut de Parasitologie et de Pathologie Tropicale, UR7292 Dynamique des Interactions hôte Pathogène, Fédération de Médecine Translationnelle, Université de Strasbourg, 67000 Strasbourg, France
| | - Ioana Alina Colosi
- Department of Medical Education, Division of Medical Informatics and Biostatistics, Iuliu Hațieganu University of Medicine and Pharmacy, 400349 Cluj-Napoca, Romania; (H.A.C.); (I.A.C.)
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Broccanello C, Ravi S, Deb S, Bolton M, Secor G, Richards C, Maretto L, Lucia MCD, Bertoldo G, Orsini E, Ronquillo-López MG, Concheri G, Campagna G, Squartini A, Stevanato P. Bacterial endophytes as indicators of susceptibility to Cercospora Leaf Spot (CLS) disease in Beta vulgaris L. Sci Rep 2022; 12:10719. [PMID: 35739218 PMCID: PMC9226160 DOI: 10.1038/s41598-022-14769-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 06/13/2022] [Indexed: 12/03/2022] Open
Abstract
The fungus Cercospora beticola causes Cercospora Leaf Spot (CLS) of sugar beet (Beta vulgaris L.). Despite the global importance of this disease, durable resistance to CLS has still not been obtained. Therefore, the breeding of tolerant hybrids is a major goal for the sugar beet sector. Although recent studies have suggested that the leaf microbiome composition can offer useful predictors to assist plant breeders, this is an untapped resource in sugar beet breeding efforts. Using Ion GeneStudio S5 technology to sequence amplicons from seven 16S rRNA hypervariable regions, the most recurring endophytes discriminating CLS-symptomatic and symptomless sea beets (Beta vulgaris L.ssp. maritima) were identified. This allowed the design of taxon-specific primer pairs to quantify the abundance of the most representative endophytic species in large naturally occurring populations of sea beet and subsequently in sugar beet breeding genotypes under either CLS symptomless or infection stages using qPCR. Among the screened bacterial genera, Methylobacterium and Mucilaginibacter were found to be significantly (p < 0.05) more abundant in symptomatic sea beets with respect to symptomless. In cultivated sugar beet material under CLS infection, the comparison between resistant and susceptible genotypes confirmed that the susceptible genotypes hosted higher contents of the above-mentioned bacterial genera. These results suggest that the abundance of these species can be correlated with increased sensitivity to CLS disease. This evidence can further prompt novel protocols to assist plant breeding of sugar beet in the pursuit of improved pathogen resistance.
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Affiliation(s)
- Chiara Broccanello
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Samathmika Ravi
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Saptarathi Deb
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Melvin Bolton
- Northern Crop Science Laboratory, U.S. Dept. Agriculture, Fargo, ND, USA
| | - Gary Secor
- Plant Pathology Department, North Dakota State University, Fargo, ND, USA
| | | | - Laura Maretto
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Maria Cristina Della Lucia
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Giovanni Bertoldo
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Elena Orsini
- Strube Research GmbH & Co. KG, Söllingen, Germany
| | | | - Giuseppe Concheri
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | | | - Andrea Squartini
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy
| | - Piergiorgio Stevanato
- Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padua, Viale Dell'Università, Legnaro, PD, Italy.
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Digital PCR: What Relevance to Plant Studies? BIOLOGY 2020; 9:biology9120433. [PMID: 33266157 PMCID: PMC7760125 DOI: 10.3390/biology9120433] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 11/25/2020] [Accepted: 11/27/2020] [Indexed: 01/01/2023]
Abstract
Simple Summary Digital PCR is a third-generation technology based on the subdivision of the analytical sample into numerous partitions that are amplified individually. This review presents the major applications of digital PCR (dPCR) technology developed so far in the field of plant science. In greater detail, dPCR assays have been developed to trace genetically modified plant components, pathogenic and non-pathogenic microorganisms, and plant species. Other applications have concerned the study of the aspects of structural and functional genetics. Abstract Digital PCR (dPCR) is a breakthrough technology that able to provide sensitive and absolute nucleic acid quantification. It is a third-generation technology in the field of nucleic acid amplification. A unique feature of the technique is that of dividing the sample into numerous separate compartments, in each of which an independent amplification reaction takes place. Several instrumental platforms have been developed for this purpose, and different statistical approaches are available for reading the digital output data. The dPCR assays developed so far in the plant science sector were identified in the literature, and the major applications, advantages, disadvantages, and applicative perspectives of the technique are presented and discussed in this review.
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Maldonado-González MM, Del Pilar Martínez-Diz M, Andrés-Sodupe M, Bujanda R, Díaz-Losada E, Gramaje D. Quantification of Cadophora luteo-olivacea From Grapevine Nursery Stock and Vineyard Soil Using Droplet Digital PCR. PLANT DISEASE 2020; 104:2269-2274. [PMID: 32568630 DOI: 10.1094/pdis-09-19-2035-re] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cadophora luteo-olivacea is the most prevalent Cadophora species associated with Petri disease and esca of grapevine. Accurate, early, and specific detection and quantification of C. luteo-olivacea are essential to alert growers and nurseries to the presence of the pathogens in soil and to prevent the spread of this pathogen through grapevine planting material. The aim of this study was to develop molecular tools to detect and quantify C. luteo-olivacea inoculum from environmental samples. Species specific primers based on the β-tubulin gene and a TaqMan probe for droplet digital PCR (ddPCR) and quantitative PCR (qPCR) were first developed to detect and quantify purified DNA of the target fungus. Specificity tests showed that the primers were able to amplify the C. luteo-olivacea DNA (20 isolates) while none of the 29 nontarget fungal species (58 isolates) tested were amplified. The ddPCR was shown to be more sensitive compared with qPCR in the detection and quantification of C. luteo-olivacea at very low concentrations and was further selected to accurately detect and quantify the fungus from environmental samples. Twenty-five of the 94 grafting plants (26.6%) analyzed by ddPCR tested positive to C. luteo-olivacea DNA (>3 copies/µl). C. luteo-olivacea was barely detected from vineyard soils. The procedure employed in this study revealed the presence of the pathogen in symptomless vines, which makes implementation of this technique suitable for certification schemes of C. luteo-olivacea-free grapevine planting material.
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Affiliation(s)
- María Mercedes Maldonado-González
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
| | - María Del Pilar Martínez-Diz
- Estación de Viticultura y Enología de Galicia (AGACAL-EVEGA), Ponte San Clodio s/n 32428-Leiro-Ourense, Spain
- Universidade da Coruña, Facultade de Ciencias, Zapateira, 15071, A Coruña, Spain
| | - Marcos Andrés-Sodupe
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
| | - Rebeca Bujanda
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
| | - Emilia Díaz-Losada
- Estación de Viticultura y Enología de Galicia (AGACAL-EVEGA), Ponte San Clodio s/n 32428-Leiro-Ourense, Spain
| | - David Gramaje
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
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Del Pilar Martínez-Diz M, Andrés-Sodupe M, Berbegal M, Bujanda R, Díaz-Losada E, Gramaje D. Droplet Digital PCR Technology for Detection of Ilyonectria liriodendri from Grapevine Environmental Samples. PLANT DISEASE 2020; 104:1144-1150. [PMID: 32053059 DOI: 10.1094/pdis-03-19-0529-re] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Black-foot disease is one of the most important soilborne diseases affecting planting material in grapevine nurseries and young vineyards. Accurate, early, and specific detection and quantification of black-foot disease causing fungi are essential to alert growers and nurseries to the presence of the pathogens in soil, and to prevent the spread of these pathogens through grapevines using certified pathogen-free planting material and development of resistance. We comparatively assessed the accuracy, efficiency, and specificity of droplet digital PCR (ddPCR) and real-time PCR (qPCR) techniques for the detection and quantification of Ilyonectria liriodendri in bulk and rhizosphere soils, as well as grapevine endorhizosphere. Fungal abundance was not affected by soil-plant fractions. Both techniques showed a high degree of correlation across the samples assessed (R2 = 0.95) with ddPCR being more sensitive to lower target concentrations. Roots of asymptomatic vines were found to be a microbial niche that is inhabited by black-foot disease fungi.
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Affiliation(s)
- María Del Pilar Martínez-Diz
- Estación de Viticultura y Enología de Galicia (AGACAL-EVEGA), Ponte San Clodio s/n 32428-Leiro-Ourense, Spain
- Universidade da Coruña, Facultade de Ciencias, Zapateira, 15071 A Coruña, Spain
| | - Marcos Andrés-Sodupe
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
| | - Mónica Berbegal
- Instituto Agroforestal Mediterráneo, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Rebeca Bujanda
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
| | - Emilia Díaz-Losada
- Estación de Viticultura y Enología de Galicia (AGACAL-EVEGA), Ponte San Clodio s/n 32428-Leiro-Ourense, Spain
| | - David Gramaje
- Instituto de Ciencias de la Vid y del Vino (ICVV), Consejo Superior de Investigaciones Científicas - Universidad de la Rioja - Gobierno de La Rioja, Ctra. de Burgos Km. 6, 26007 Logroño, Spain
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Jongman M, Carmichael PC, Bill M. Technological Advances in Phytopathogen Detection and Metagenome Profiling Techniques. Curr Microbiol 2020; 77:675-681. [PMID: 31960092 DOI: 10.1007/s00284-020-01881-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 01/09/2020] [Indexed: 12/11/2022]
Abstract
The use of advanced molecular methods in plant pathology and applied microbiology has necessitated for more accurate, rapid detection and identification of plant pathogens. This is particularly significant given accelerated emergence of virulence that leads to increased prevalence of plant pathogens. Thus, the capacity to contain plant pathogens and ultimately disease progression is key to ensuring crop biosecurity and overall food security. Of recent, research on pathogens utilizes a holistic approach focusing on elucidating growth dynamics within the entire biome rather than studying individual or closely related isolates in unison. This has advanced knowledge and information of microbial ecosystem within natural environments in the twenty first century. Applied technological platforms used for rapid detection and profiling microbial biomes in this regard include digital PCR, pyrosequencing, Illumina, DNA microarray and barcoding, Ion torrent, and nanopore. These technologies have been applied in various fields including human health and medicine, marine and animal biology, crop production and water quality research, to mention but a few. Although much has been done and achieved through the development of several technologies, more accuracy is required to circumvent the shortfalls still experienced. This includes integrating existing methods with new applications such as viability PCRs and microbial viability testing. Hence, this review provides critical analysis of some widely used latest technologies in rapid detection and identification of plant pathogens, and profiling plant associated microbiomes that reveal growth dynamics and population diversity. The advantages and limitations of the technologies are also discussed.
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Affiliation(s)
| | - Patricia C Carmichael
- Agricultural Research and Specialists, Department of Agriculture, Malkerns, Swaziland
| | - Malick Bill
- Plant Health and Food Safety Research, Department of Plant and Soil Sciences, University of Pretoria, Pretoria, 0002, South Africa
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Palumbo JD, O’Keeffe TL, Quejarro BJ, Yu A, Zhao A. Comparison of Aspergillus Section Nigri Species Populations in Conventional and Organic Raisin Vineyards. Curr Microbiol 2019; 76:848-854. [DOI: 10.1007/s00284-019-01697-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 04/26/2019] [Indexed: 10/26/2022]
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Xanthopoulou A, Ganopoulos I, Tryfinopoulou P, Panagou EZ, Osanthanunkul M, Madesis P, Kizis D. Rapid and accurate identification of black aspergilli from grapes using high-resolution melting (HRM) analysis. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2019; 99:309-314. [PMID: 29876941 DOI: 10.1002/jsfa.9189] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 06/04/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Aspergillus is a diverse genus of fungi with high economic and social impact. Various species that belong to section Nigri (black aspergilli) are common agents of grape spoilage and potent producers of ochratoxin A (OTA), a mycotoxin associated with various nephrotoxic and immunotoxic effects in humans. Black aspergilli are difficult to classify following only phenotypic criteria; thus chemotaxonomic and molecular methods are employed in parallel with phenotypic ones for species characterization. These approaches, though accurate and replicable, require more than one individual step and are to a certain extent laborious when a rapid identification of these species is required. RESULTS The aim of this study was to develop a high-resolution melting polymerase chain reaction (HRM-PCR) assay as a rapid method for identification of Aspergillus spp. section Nigri isolates and their detection in grape samples. Melt curve analysis of amplicons originating from the internal transcribed spacer 2 (ITS2) ribosomal region generated species-specific HRM curve profiles, enabling the accurate differentiation of the analyzed genotypes. Furthermore, the assay was able to identify A. carbonarius, A. tubingensis, A. niger, A. ibericus and A. japonicus in grape samples artificially inoculated with conidia of these fungi. CONCLUSION To our knowledge this is the first report on the development of an HRM-PCR assay for the identification of black Aspergillus species in grape samples. © 2018 Society of Chemical Industry.
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Affiliation(s)
| | - Ioannis Ganopoulos
- Institute of Plant Breeding and Genetic Resources ELGO-DEMETER, Thessaloniki, Greece
| | - Paschalitsa Tryfinopoulou
- Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Efstathios Z Panagou
- Laboratory of Food Microbiology and Biotechnology, Department of Food Science and Human Nutrition, Agricultural University of Athens, Athens, Greece
| | - Maslin Osanthanunkul
- Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
- Center of Excellence in Bioresources for Agriculture, Industry and Medicine, Chiang Mai University, Chiang Mai, Thailand
| | | | - Dimosthenis Kizis
- Laboratory of Mycology, Department of Phytopathology, Benaki Phytopathological Institute, Athens, Greece
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Development of a sensitive and reliable reverse transcription droplet digital PCR assay for the detection of citrus yellow vein clearing virus. Arch Virol 2018; 164:691-697. [DOI: 10.1007/s00705-018-04123-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 11/15/2018] [Indexed: 10/27/2022]
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Development of a droplet digital PCR assay for population analysis of aflatoxigenic and atoxigenic Aspergillus flavus mixtures in soil. Mycotoxin Res 2018; 34:187-194. [PMID: 29582253 DOI: 10.1007/s12550-018-0313-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 03/08/2018] [Accepted: 03/13/2018] [Indexed: 10/17/2022]
Abstract
Aflatoxin B1 is a potent hepatotoxin and carcinogen that poses a serious safety hazard to both humans and animals. Aspergillus flavus is the most common aflatoxin-producing species on corn, cotton, peanuts, and tree nuts. Application of atoxigenic strains to compete against aflatoxigenic strains of A. flavus has emerged as one of the most practical strategies for ameliorating aflatoxin contamination in food. Genes directly involved in aflatoxin biosynthesis are clustered on an 82-kb region of the genome. Three atoxigenic strains (CA12, M34, and AF123) were each paired with each of four aflatoxigenic strains (CA28, CA42, CA90, and M52), inoculated into soil and incubated at 28 °C for 2 weeks and 1 month. TaqMan probes, omtA-FAM, and norA-HEX were designed for developing a droplet digital PCR (ddPCR) assay to analyze the soil population of mixtures of A. flavus strains. DNA was extracted from each soil sample and used for ddPCR assays. The data indicated that competition between atoxigenic and aflatoxigenic was strain dependent. Variation in competitive ability among different strains of A. flavus influenced the population reduction of the aflatoxigenic strain by the atoxigenic strain. Higher ratios of atoxigenic to aflatoxigenic strains increased soil population of atoxigenic strains. This is the first study to demonstrate the utility of ddPCR to quantify mixtures of both atoxigenic and aflatoxigenic A. flavus strains in soil and allows for rapid and accurate determination of population sizes of atoxigenic and aflatoxigenic strains. This method eliminates the need for isolation and identification of individual fungal isolates from experimental soil samples.
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Palumbo JD, O'Keeffe TL, Ho YS, Fidelibus MW. Population Dynamics of Aspergillus Section Nigri Species on Vineyard Samples of Grapes and Raisins. J Food Prot 2016; 79:448-53. [PMID: 26939655 DOI: 10.4315/0362-028x.jfp-15-437] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Several species of Aspergillus section Nigri, including potential mycotoxin producers, are common residents of grape vineyards, but the relative population size of individual species throughout the growing season is difficult to determine using traditional isolation and identification methods. Using a quantitative droplet digital PCR (ddPCR) method in combination with dilution plating, total Aspergillus section Nigri populations and relative proportions of A. niger, A. welwitschiae, A. carbonarius, and A. tubingensis were measured from vineyard samples without the need for identifying individual fungal isolates. Grapes were sampled from two raisin vineyards (vineyards A and B) at berry set, veraison, harvest, and raisin stages in two consecutive years. Plate counts showed that the total population of Aspergillus section Nigri present on the fruit increased from berry set to raisin and became a larger component of the total recovered fungal population in both vineyards in both years. Results from ddPCR analysis showed that the relative proportion of A. carbonarius among the four species assayed increased later in the season (harvest and raisin) in comparison to earlier in the season (berry set and veraison). Total fungal and Aspergillus section Nigri plate counts were not significantly different between vineyards in either year. However, vineyard A generally showed higher proportions of A. carbonarius in harvest and raisin samples than vineyard B. This coincided with higher incidence and levels of ochratoxin A in vineyard A harvest and raisin fruit than in vineyard B fruit. This work demonstrates that this ddPCR method is a useful tool for culture-independent monitoring of populations of mycotoxigenic Aspergillus species during grape and raisin production.
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Affiliation(s)
- Jeffrey D Palumbo
- Foodborne Toxin Detection and Prevention Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 800 Buchanan Street, Albany, California 94710, USA.
| | - Teresa L O'Keeffe
- Foodborne Toxin Detection and Prevention Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 800 Buchanan Street, Albany, California 94710, USA
| | - Yvonne S Ho
- Foodborne Toxin Detection and Prevention Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 800 Buchanan Street, Albany, California 94710, USA
| | - Matthew W Fidelibus
- University of California, Kearney Agricultural Research & Extension Center, 9240 South Riverbend Avenue, Parlier, California 93648, USA
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