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Deciphering the virulence potential of Listeria monocytogenes in the Norwegian meat and salmon processing industry by combining whole genome sequencing and in vitro data. Int J Food Microbiol 2022; 383:109962. [DOI: 10.1016/j.ijfoodmicro.2022.109962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/28/2022] [Accepted: 09/29/2022] [Indexed: 11/05/2022]
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Schoder D, Guldimann C, Märtlbauer E. Asymptomatic Carriage of Listeria monocytogenes by Animals and Humans and Its Impact on the Food Chain. Foods 2022; 11:3472. [PMID: 36360084 PMCID: PMC9654558 DOI: 10.3390/foods11213472] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/11/2022] [Accepted: 10/26/2022] [Indexed: 07/30/2023] Open
Abstract
Humans and animals can become asymptomatic carriers of Listeria monocytogenes and introduce the pathogen into their environment with their feces. In turn, this environmental contamination can become the source of food- and feed-borne illnesses in humans and animals, with the food production chain representing a continuum between the farm environment and human populations that are susceptible to listeriosis. Here, we update a review from 2012 and summarize the current knowledge on the asymptomatic carrier statuses in humans and animals. The data on fecal shedding by species with an impact on the food chain are summarized, and the ways by which asymptomatic carriers contribute to the risk of listeriosis in humans and animals are reviewed.
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Affiliation(s)
- Dagmar Schoder
- Department of Veterinary Public Health and Food Science, Institute of Food Safety, University of Veterinary Medicine, 1210 Vienna, Austria
- Veterinarians without Borders Austria, 1210 Vienna, Austria
| | - Claudia Guldimann
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute of Food Safety and Analytics, Ludwig-Maximilians-University Munich, 85764 Oberschleißheim, Germany
| | - Erwin Märtlbauer
- Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute of Milk Hygiene, Ludwig-Maximilians-University Munich, 85764 Oberschleißheim, Germany
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Agostinho Davanzo EF, dos Santos RL, Castro VHDL, Palma JM, Pribul BR, Dallago BSL, Fuga B, Medeiros M, Titze de Almeida SS, da Costa HMB, Rodrigues DDP, Lincopan N, Perecmanis S, Santana AP. Molecular characterization of Salmonella spp. and Listeria monocytogenes strains from biofilms in cattle and poultry slaughterhouses located in the federal District and State of Goiás, Brazil. PLoS One 2021; 16:e0259687. [PMID: 34767604 PMCID: PMC8589217 DOI: 10.1371/journal.pone.0259687] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 10/23/2021] [Indexed: 10/26/2022] Open
Abstract
Listeria monocytogenes and Salmonella spp. are considered important foodborne pathogens that are commonly associated with foods of animal origin. The aim of this study was to perform molecular characterization of L. monocytogenes and Salmonella spp. isolated from biofilms of cattle and poultry slaughterhouses located in the Federal District and State of Goiás, Brazil. Fourteen L. monocytogenes isolates and one Salmonella sp. were detected in poultry slaughterhouses. No isolates were detected in cattle slaughterhouses. All L. monocytogenes isolates belonged to lineage II, and 11 different pulsotypes were detected. Pulsed-field gel electrophoresis analysis revealed the dissemination of two strains within one plant, in addition to the regional dissemination of one of them. The Salmonella isolate was identified via whole genome sequencing as Salmonella enterica serovar Minnesota ST548. In the sequence analysis, no premature stop codons were detected in the inlA gene of Listeria. All isolates demonstrated the ability to adhere to Caco-2 cells, while 50% were capable of invading them. Antimicrobial resistance was detected in 57.1% of the L. monocytogenes isolates, and resistance to sulfonamide was the most common feature. The tetC, ermB, and tetM genes were detected, and four isolates were classified as multidrug-resistant. Salmonella sp. was resistant to nine antimicrobials and was classified as multidrug-resistant. Resistance genes qnrB19, blaCMY-2, aac(6')-Iaa, sul2, and tetA, and a mutation in the parC gene were detected. The majority (78.5%) of the L. monocytogenes isolates were capable of forming biofilms after incubation at 37°C for 24 h, and 64.3% were capable of forming biofilms after incubation at 12°C for 168 h. There was no statistical difference in the biofilm-forming capacity under the different evaluated conditions. Salmonella sp. was capable of forming biofilms at both tested temperatures. Biofilm characterization was confirmed by collecting the samples consistently, at the same sampling points, and by assessing biofilm formation in vitro. These results highlight the potential risk of cross-contamination in poultry slaughterhouses and the importance of surveillance and pathogen control maintenance programs within the meat production industry.
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Affiliation(s)
| | | | | | - Joana Marchesini Palma
- Faculty of Agronomy and Veterinary Medicine, University of Brasília (UnB), Brasília, DF, Brazil
| | - Bruno Rocha Pribul
- National Reference Laboratory for Bacterial Enteric Infections, Oswaldo Cruz Institute, Manguinhos, Rio de Janeiro, RJ, Brazil
| | | | - Bruna Fuga
- Laboratory of Bacterial Resistance and Therapeutic Alternatives, Biomedical Sciences Institute, University of São Paulo, São Paulo, SP, Brazil
| | - Margareti Medeiros
- Faculty of Agronomy and Veterinary Medicine, University of Brasília (UnB), Brasília, DF, Brazil
| | | | | | - Dália dos Prazeres Rodrigues
- National Reference Laboratory for Bacterial Enteric Infections, Oswaldo Cruz Institute, Manguinhos, Rio de Janeiro, RJ, Brazil
| | - Nilton Lincopan
- Laboratory of Bacterial Resistance and Therapeutic Alternatives, Biomedical Sciences Institute, University of São Paulo, São Paulo, SP, Brazil
| | - Simone Perecmanis
- Faculty of Agronomy and Veterinary Medicine, University of Brasília (UnB), Brasília, DF, Brazil
| | - Angela Patrícia Santana
- Faculty of Agronomy and Veterinary Medicine, University of Brasília (UnB), Brasília, DF, Brazil
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Thomassen GMB, Krych L, Knøchel S, Mehli L. ON-rep-seq as a rapid and cost-effective alternative to whole-genome sequencing for species-level identification and strain-level discrimination of Listeria monocytogenes contamination in a salmon processing plant. Microbiologyopen 2021; 10:e1246. [PMID: 34964295 PMCID: PMC8591450 DOI: 10.1002/mbo3.1246] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 10/19/2021] [Indexed: 12/28/2022] Open
Abstract
Identification, source tracking, and surveillance of food pathogens are crucial factors for the food-producing industry. Over the last decade, the techniques used for this have moved from conventional enrichment methods, through species-specific detection by PCR to sequencing-based methods, whole-genome sequencing (WGS) being the ultimate method. However, using WGS requires the right infrastructure, high computational power, and bioinformatics expertise. Therefore, there is a need for faster, more cost-effective, and more user-friendly methods. A newly developed method, ON-rep-seq, combines the classical rep-PCR method with nanopore sequencing, resulting in a highly discriminating set of sequences that can be used for species identification and also strain discrimination. This study is essentially a real industry case from a salmon processing plant. Twenty Listeria monocytogenes isolates were analyzed both by ON-rep-seq and WGS to identify and differentiate putative L. monocytogenes from a routine sampling of processing equipment and products, and finally, compare the strain-level discriminatory power of ON-rep-seq to different analyzing levels delivered from the WGS data. The analyses revealed that among the isolates tested there were three different strains. The isolates of the most frequently detected strain (n = 15) were all detected in the problematic area in the processing plant. The strain level discrimination done by ON-rep-seq was in full accordance with the interpretation of WGS data. Our findings also demonstrate that ON-rep-seq may serve as a primary screening method alternative to WGS for identification and strain-level differentiation for surveillance of potential pathogens in a food-producing environment.
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Affiliation(s)
| | - Lukasz Krych
- Department of Food ScienceUniversity of CopenhagenFrederiksbergDenmark
| | - Susanne Knøchel
- Department of Food ScienceUniversity of CopenhagenFrederiksbergDenmark
| | - Lisbeth Mehli
- Department of Biotechnology and Food ScienceNorwegian University of Science and Technology (NTNU)TrondheimNorway
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Palaiodimou L, Fanning S, Fox EM. Genomic insights into persistence of Listeria species in the food processing environment. J Appl Microbiol 2021; 131:2082-2094. [PMID: 33768629 DOI: 10.1111/jam.15089] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/18/2021] [Accepted: 03/21/2021] [Indexed: 12/01/2022]
Abstract
AIMS Listeria species may colonize and persist in food processing facilities for prolonged periods of time, despite hygiene interventions in place. To understand the genetic factors contributing to persistence of Listeria strains, this study undertook a comparative analysis of seven persistent and six presumed non-persistent strains, isolated from a single food processing environment, to identify genetic markers correlating to promoting persistence of Listeria strains, through whole genome sequence analysis. METHODS AND RESULTS A diverse pool of genetic markers relevant to hygiene tolerance was identified, including disinfectant resistance markers qacH, emrC and the efflux cassette bcrABC. Both persistent and presumed non-persistent cohorts encoded a range of stress resistance markers, including heavy metal resistance, oxidative and pH stress, although trends were associated with each cohort (e.g., qacH and cadA1C resistance was more frequently found in persistent isolates). Persistent isolates were more likely to contain mutations associated with attenuated virulence, including a truncated InlA. Plasmids and transposons were widespread between cohorts. CONCLUSIONS Results suggest that no single genetic marker identified was universally responsible for a strain's ability to persist. Persistent strains were more likely to harbour mutation associated with hypovirulence. SIGNIFICANCE AND IMPACT OF THE STUDY This study provides additional insights into the distribution of genetic elements relevant to persistence across Listeria species, as well as strain virulence potential.
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Affiliation(s)
- L Palaiodimou
- Department of Applied Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - S Fanning
- UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland.,Institute for Global Food Security, Queen's University Belfast, Belfast, UK
| | - E M Fox
- Department of Applied Sciences, Northumbria University, Newcastle upon Tyne, UK
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Exploring Listeria monocytogenes Transcriptomes in Correlation with Divergence of Lineages and Virulence as Measured in Galleria mellonella. Appl Environ Microbiol 2019; 85:AEM.01370-19. [PMID: 31471303 DOI: 10.1128/aem.01370-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 08/25/2019] [Indexed: 12/24/2022] Open
Abstract
As for many opportunistic pathogens, the virulence potential of Listeria monocytogenes is highly heterogeneous between isolates and correlated, to some extent, with phylogeny and gene repertoires. In sharp contrast with copious data on intraspecies genome diversity, little is known about transcriptome diversity despite the role of complex genetic regulation in pathogenicity. The current study implemented RNA sequencing to characterize the transcriptome profiles of 33 isolates under optimal in vitro growth conditions. Transcript levels of conserved single-copy genes were comprehensively explored from several perspectives, including phylogeny, in silico-predicted virulence category based on epidemiological multilocus sequence typing (MLST) data, and in vivo virulence phenotype assessed in Galleria mellonella Comparing baseline transcriptomes between isolates was intrinsically more complex than standard genome comparison because of the inherent plasticity of gene expression in response to environmental conditions. We show that the relevance of correlation analyses and their statistical power can be enhanced by using principal-component analysis to remove the first level of irrelevant, highly coordinated changes linked to growth phase. Our results highlight the major contribution of transcription factors with key roles in virulence to the diversity of transcriptomes. Divergence in the basal transcript levels of a substantial fraction of the transcriptome was observed between lineages I and II, echoing previously reported epidemiological differences. Correlation analysis with in vivo virulence identified numerous sugar metabolism-related genes, suggesting that specific pathways might play roles in the onset of infection in G. mellonella IMPORTANCE Listeria monocytogenes is a multifaceted bacterium able to proliferate in a wide range of environments from soil to mammalian host cells. The accumulated genomic data underscore the contribution of intraspecies variations in gene repertoire to differential adaptation strategies between strains, including infection and stress resistance. It seems very likely that the fine-tuning of the transcriptional regulatory network is also a key component of the phenotypic diversity, albeit more difficult to investigate than genome content. Some studies reported incongruity in the basal transcriptome between isolates, suggesting a putative relationship with phenotypes, but small isolate numbers hampered proper correlation analyses with respect to their characteristics. The present study is the embodiment of the promising approach that consists of analyzing correlations between transcriptomes and various isolate characteristics. Statistically significant correlations were found with phylogenetic groups, epidemiological evidence of virulence potential, and virulence in Galleria mellonella larvae used as an in vivo model.
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Relative Roles of Listeriolysin O, InlA, and InlB in Listeria monocytogenes Uptake by Host Cells. Infect Immun 2018; 86:IAI.00555-18. [PMID: 30061379 PMCID: PMC6204736 DOI: 10.1128/iai.00555-18] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 07/25/2018] [Indexed: 12/11/2022] Open
Abstract
Listeria monocytogenes is a facultative intracellular pathogen that infects a wide variety of cells, causing the life-threatening disease listeriosis. L. monocytogenes virulence factors include two surface invasins, InlA and InlB, known to promote bacterial uptake by host cells, and the secreted pore-forming toxin listeriolysin O (LLO), which disrupts the phagosome to allow bacterial proliferation in the cytosol. Listeria monocytogenes is a facultative intracellular pathogen that infects a wide variety of cells, causing the life-threatening disease listeriosis. L. monocytogenes virulence factors include two surface invasins, InlA and InlB, known to promote bacterial uptake by host cells, and the secreted pore-forming toxin listeriolysin O (LLO), which disrupts the phagosome to allow bacterial proliferation in the cytosol. In addition, plasma membrane perforation by LLO has been shown to facilitate L. monocytogenes internalization into epithelial cells. In this work, we tested the host cell range and importance of LLO-mediated L. monocytogenes internalization relative to the canonical invasins, InlA and InlB. We measured the efficiencies of L. monocytogenes association with and internalization into several human cell types (hepatocytes, cytotrophoblasts, and endothelial cells) using wild-type bacteria and isogenic single, double, and triple deletion mutants for the genes encoding InlA, InlB and LLO. No role for InlB was detected in any tested cells unless the InlB expression level was substantially enhanced, which was achieved by introducing a mutation (prfA*) in the gene encoding the transcription factor PrfA. In contrast, InlA and LLO were the most critical invasion factors, although they act in a different manner and in a cell-type-dependent fashion. As expected, InlA facilitates both bacterial attachment and internalization in cells that express its receptor, E-cadherin. LLO promotes L. monocytogenes internalization into hepatocytes, but not into cytotrophoblasts and endothelial cells. Finally, LLO and InlA cooperate to increase the efficiency of host cell invasion by L. monocytogenes.
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Tamburro M, Sammarco ML, Ripabelli G. High resolution melting analysis for the characterization of lineage II Listeria monocytogenes serovars 1/2a and 1/2c based on single nucleotide polymorphisms identification within the Listeria Pathogenicity Island-1 and inlAB operon: a novel approach for epidemiological surveillance. J Appl Microbiol 2018; 125:1920-1937. [PMID: 30187619 DOI: 10.1111/jam.14100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 07/02/2018] [Accepted: 08/18/2018] [Indexed: 01/16/2023]
Abstract
AIMS A high resolution melting (HRM) assay was developed for characterizing lineage II Listeria monocytogenes based on the amplification and the melting profiles analysis of 81 fragments targeting the region from the prs to ldh loci, including the Listeria Pathogenicity Island-1 (LIPI-1) genes and the inlAB operon. METHODS AND RESULTS Real-time PCR and HRM protocols were standardized using 10 replicate assays from L. monocytogenes EGD-e reference strain (serovar 1/2a). Twenty wild-type isolates of serovar 1/2a and two of serovar 1/2c were tested, and differences between EGD-e strain and the wild-type isolates were defined if the melting temperature (Tm ) of an amplicon was not within the lower and the upper limits calculated from replicate testing on EGD-e. The analysis revealed 17 and 19 HRM profiles with respect to prs/LIPI-1/ldh and inlAB target regions (Simpson's Index of Diversity 0·979 and 0·983) respectively. The 1/2c cultures showed 98·1% similarity to melting characteristics with EGD-e, whilst 1/2a isolates had the greatest heterogeneity that was related to inlA, inlB and actA genes. Sequencing of amplicons generating different Tm values from EGD-e confirmed the presence of point mutations. CONCLUSIONS This method was useful for L. monocytogenes subtyping based on single nucleotide polymorphisms detection through the melting behaviour analysis of main virulence genes. SIGNIFICANCE AND IMPACT OF THE STUDY The study underlines the effectiveness of HRM in differentiating L. monocytogenes strains with high discriminatory power, thus rendering it useful for epidemiological surveillance.
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Affiliation(s)
- M Tamburro
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
| | - M L Sammarco
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
| | - G Ripabelli
- Department of Medicine and Health Sciences "Vincenzo Tiberio", University of Molise, Campobasso, Italy
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Camargo AC, Woodward JJ, Nero LA. The Continuous Challenge of Characterizing the Foodborne Pathogen Listeria monocytogenes. Foodborne Pathog Dis 2016; 13:405-16. [PMID: 27120361 DOI: 10.1089/fpd.2015.2115] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Listeria monocytogenes is an important foodborne pathogen commonly isolated from food processing environments and food products. This organism can multiply at refrigeration temperatures, form biofilms on different materials and under various conditions, resist a range of environmental stresses, and contaminate food products by cross-contamination. L. monocytogenes is recognized as the causative agent of listeriosis, a serious disease that affects mainly individuals from high-risk groups, such as pregnant women, newborns, the elderly, and immunocompromised individuals. Listeriosis can be considered a disease that has emerged along with changing eating habits and large-scale industrial food processing. This disease causes losses of billions of dollars every year with recalls of contaminated foods and patient medical treatment expenses. In addition to the immune status of the host and the infecting dose, the virulence potential of each strain is crucial for the development of disease symptoms. While many isolates are naturally virulent, other isolates are avirulent and unable to cause disease; this may vary according to the presence of molecular determinants associated with virulence. In the last decade, the characterization of genetic profiles through the use of molecular methods has helped track and demonstrate the genetic diversity among L. monocytogenes isolates obtained from various sources. The purposes of this review were to summarize the main methods used for isolation, identification, and typing of L. monocytogenes and also describe its most relevant virulence characteristics.
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Affiliation(s)
- Anderson Carlos Camargo
- 1 Departamento de Veterinária, Universidade Federal de Viçosa , Viçosa, Minas Gerais, Brazil
| | | | - Luís Augusto Nero
- 1 Departamento de Veterinária, Universidade Federal de Viçosa , Viçosa, Minas Gerais, Brazil
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Tamburro M, Sammarco ML, Ammendolia MG, Fanelli I, Minelli F, Ripabelli G. Evaluation of transcription levels of inlA, inlB, hly, bsh and prfA genes in Listeria monocytogenes strains using quantitative reverse-transcription PCR and ability of invasion into human CaCo-2 cells. FEMS Microbiol Lett 2015; 362:fnv018. [PMID: 25673285 DOI: 10.1093/femsle/fnv018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Listeria monocytogenes virulence depends on the activity of well-characterized virulence factors. In this study, transcription levels of inlA, inlB, hly, bsh and prfA genes in L. monocytogenes strains, and the ability of invasion into CaCo-2 cells were investigated. Serotyping, multiplex-PCR for serovar identification and restriction fragment analysis of inlA were performed. Transcription levels and invasiveness were evaluated by quantitative reverse-transcription PCR and by in vitro assays, respectively. The isolates were of serovars 1/2a, 4b, 1/2c, 1/2b and 3a. Full-length inlA profiles were found for nine of ten clinical isolates, while five of seven cultures from foods showed truncated profile. The analysis of transcription levels of virulence factors encoding genes demonstrated a substantial inter-strain heterogeneity, with clinical strains showing higher levels for almost all genes than isolates from food. A correlation between transcription levels of inlA and inlB, as well as between bsh and prfA, was observed. Significant differences between clinical strains and food isolates in the invasion of CaCo-2 cells were found. Analysis of gene transcription and invasiveness of human cells suggests different virulence phenotypes among L. monocytogenes populations, and this characterization could be a useful tool for risk assessment purposes and for the development of public health strategies.
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Affiliation(s)
- Manuela Tamburro
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
| | | | | | - Incoronata Fanelli
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
| | - Fabio Minelli
- European Reference Laboratory for Escherichia coli, Department of Veterinary Public Health and Food Safety, Istituto Superiore di Sanità, Rome, Italy
| | - Giancarlo Ripabelli
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
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Kyoui D, Takahashi H, Miya S, Kuda T, Kimura B. Comparison of the major virulence-related genes of Listeria monocytogenes in internalin A truncated strain 36-25-1 and a clinical wild-type strain. BMC Microbiol 2014; 14:15. [PMID: 24472083 PMCID: PMC3917698 DOI: 10.1186/1471-2180-14-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 01/21/2014] [Indexed: 01/12/2023] Open
Abstract
Background Internalin A (InlA) facilitates the invasion of Listeria monocytogenes into a host cell. Some strains of Listeria monocytogenes express truncated forms of InlA, which reduces invasiveness. However, few virulence-related genes other than inlA have been analyzed in InlA-truncated strains. In the present study, we sequenced the draft genome of strain 36-25-1, an InlA-truncated strain, with pyrosequencing and compared 36 major virulence-related genes in this strain and a clinical wild-type strain. Results Strain 36-25-1 possessed all of the virulence-related genes analyzed. Of the analyzed genes, only 4 genes (dltA, gtcA, iap, and inlA) differed when the nucleotide sequences of strain 36-25-1 and the clinical wild-type strain were compared. Analysis of the deduced amino acid sequences found no mutations that significantly influenced virulence in genes other than inlA. Conclusions The virulence-associated genes in strain 36-25-1 differ little from those of the clinical wild-type strain, indicating that a slight mutation in the nucleotide sequence determines the virulence of the InlA-truncated strain. In addition, the results suggest that, aside from InlA-mediated cell invasiveness, there is almost no difference between the virulence of strain 36-25-1 and that of the clinical wild-type strain.
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Affiliation(s)
| | - Hajime Takahashi
- Department of Food Science and Technology, Faculty of Marine Science, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato, Tokyo 108-8477, Japan.
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In vitro properties of a Listeria monocytogenes bacteriophage-resistant mutant predict its efficacy as a live oral vaccine strain. Infect Immun 2011; 79:5001-9. [PMID: 21930759 DOI: 10.1128/iai.05700-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A Listeria monocytogenes glcV mutation precludes the binding of certain listerial phages and produces a profound attenuation characterized by the absence of detectable mutants in the livers and spleens of orally inoculated mice. In vitro, we found that the mutant formed plaques on mouse enterocyte monolayers as efficiently as the parent but the plaques formed were smaller. Intracellular growth rate determinations and examination of infected enterocytes by light and fluorescence microscopy established that the mutant was impaired not in intracellular growth rate but in cell-to-cell spreading. Because this property is shared by other immunogenic mutants (e.g., actA mutants), our glcV mutant was tested for vaccine efficacy. Oral immunization with the mutant and subsequent oral challenge (22 days postvaccination) with the parent revealed a ca. 10,000-fold increase in protection afforded by the mutant compared to sham-vaccinated controls. The glcV mutant did not stimulate innate immunity under the dose and route employed for vaccination, and an infectivity index time course experiment revealed pronounced mutant persistence in Peyer's patches. The immunogenicity of the glcV mutant compared to an isogenic actA mutant reference strain was next tested in an experiment with a challenge given 52 days postvaccination. Both mutant strains showed scant vital organ infectivity and high levels of protection similar to those seen using the glcV mutant in the 22-day postvaccination challenge. Our results indicate that oral administration of a profoundly attenuated listerial mutant can safely elicit solid protective immunity.
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Ohk SH, Koo OK, Sen T, Yamamoto CM, Bhunia AK. Antibody-aptamer functionalized fibre-optic biosensor for specific detection of Listeria monocytogenes from food. J Appl Microbiol 2011; 109:808-17. [PMID: 20337767 DOI: 10.1111/j.1365-2672.2010.04709.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM To develop antibody-aptamer functionalized fibre-optic biosensor for specific detection of Listeria monocytogenes from food products. METHODS AND RESULTS Aptamer, a single-stranded oligonucleotide ligand that displays affinity for the target molecule, was used in the assay to provide sensor specificity. Aptamer-A8, specific for internalin A, an invasive protein of L. monocytogenes, was used in the fibre-optic sensor together with antibody in a sandwich format for detection of L. monocytogenes from food. Biotinylated polyclonal anti-Listeria antibody, P66, was immobilized on streptavidin-coated optical waveguide surface for capturing bacteria, and Alexa Fluor 647-conjugated A8 was used as a reporter. The biosensor was able to selectively detect pathogenic Listeria in pure culture and in mixture with other bacteria at a concentration of approx. 10(3) CFU ml(-1). This sensor also successfully detected L. monocytogenes cells from artificially contaminated (initial inoculation of 10(2) CFU 25 g(-1) ) ready-to-eat meat products such as sliced beef, chicken and turkey after 18 h of enrichment. CONCLUSION Based on the data presented in this study, the antibody-aptamer functionalized fibre-optic biosensor could be used as a detection tool for sensitive and specific detection of L. monocytogenes from foods. SIGNIFICANCE AND IMPACT OF THE STUDY The study demonstrates feasibility and novel application of aptamer on fibre-optic biosensor platform for the sensitive detection of L. monocytogenes from food products.
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Affiliation(s)
- S H Ohk
- Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, IN 47907-2009, USA
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Chen Y, Ross WH, Whiting RC, Van Stelten A, Nightingale KK, Wiedmann M, Scott VN. Variation in Listeria monocytogenes dose responses in relation to subtypes encoding a full-length or truncated internalin A. Appl Environ Microbiol 2011; 77:1171-80. [PMID: 21169442 PMCID: PMC3067222 DOI: 10.1128/aem.01564-10] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 12/07/2010] [Indexed: 11/20/2022] Open
Abstract
Internalin A (InlA; encoded by inlA) facilitates the crossing of the intestinal barrier by Listeria monocytogenes. Mutations leading to a premature stop codon (PMSC) in inlA and thus attenuated mammalian virulence have been reported. We recently characterized 502 L. monocytogenes food isolates from a retail survey and 507 human clinical isolates from multiple U.S. states with respect to the presence/absence of inlA mutations. The objective of this study was to investigate the hypothesis that dose responses for human listeriosis vary between L. monocytogenes strains with and those without a PMSC in inlA. Subtype-specific prevalence and concentration distributions in food, along with epidemiologic and consumption data, were input into established dose-response models to generate an r value (probability of a cell causing illness). Under the conservative assumption that L. monocytogenes levels at retail represent levels consumed, mean log(10) r values were -8.1 and -10.7 for L. monocytogenes subtypes with genes encoding a full-length and a truncated InlA, respectively. L. monocytogenes carrying a 5' frameshift mutation in a homopolymeric tract showed a mean log(10) r value of -12.1. Confidence intervals for the r values and their differences varied depending on subtypes. When the increase in concentration of L. monocytogenes subtypes between retail and consumption was considered, mean log(10) r values were reduced to -10.4, -13.8, and -12.8 for the subtypes with genes encoding a full-length InlA, for the subtypes carrying a PMSC in inlA, and for all L. monocytogenes isolates regardless of subtype, respectively. Our study provides further quantitative evidence that L. monocytogenes subtypes vary in abilities and relative likelihoods of causing human disease, which were mechanistically related to defined genetic markers.
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Affiliation(s)
- Yuhuan Chen
- Grocery Manufacturers Association, Washington, DC, USA.
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17
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Larsen MH, Koch AG, Ingmer H. Listeria monocytogenes efficiently invades Caco-2 cells after low-temperature storage in broth and on deli meat. Foodborne Pathog Dis 2010; 7:1013-8. [PMID: 20443727 DOI: 10.1089/fpd.2009.0470] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
The objective of this study was to investigate how various growth conditions influence the virulence of Listeria monocytogenes monitored by its ability to invade the epithelial cell lines Caco-2 and INT-407. The growth conditions examined were modified atmosphere-packaged deli meat and brain heart infusion broth (BHI) with and without salt. Five strains of L. monocytogenes were selected to investigate their invasiveness and all strains invaded Caco-2 cells at higher levels than INT-407 cells. Further, the clinical strains (3443 and 3734) were more invasive (p < 0.05) than the strains isolated from meat and food-processing environments (3008, 3126, and 4140) after grown in BHI at 30 degrees C. This attenuation could not be ascribed to a defective Internalin A as all strains encoded an intact inlA gene. To determine the influence of food products on virulence, the ability of L. monocytogenes to invade Caco-2 cells was compared after growth on a fermented sausage and on cured cooked ham to that of bacteria grown in BHI broth supplemented with salt. Samples were stored under chilling conditions for up to 4 weeks. The results showed no difference (p > 0.05) in invasiveness after 7 days at 10 degrees C in BHI broth or on sausage, whereas a slight increase (p < 0.05) was observed after incubation on ham for 2 and 4 weeks compared to that in BHI broth. Most importantly, our results show that L. monocytogenes efficiently invade Caco-2 cells even after 4 weeks of storage at chilled temperature. This is highly relevant for safety assessment of this organism in food as these conditions reflect storage of ready-to-eat food products in domestic refrigerators.
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Affiliation(s)
- Marianne Halberg Larsen
- Department of Veterinary Disease Biology, Centre for Advanced Food Studies, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark.
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Tamburro M, Ripabelli G, Fanelli I, Maria Grasso G, Lucia Sammarco M. Typing ofListeria monocytogenesstrains isolated in Italy byinlA gene characterization and evaluation of a new cost-effective approach to antisera selection for serotyping. J Appl Microbiol 2010; 108:1602-11. [DOI: 10.1111/j.1365-2672.2009.04555.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Risk of Listeria monocytogenes contamination of raw ready-to-eat seafood products available at retail outlets in Japan. Appl Environ Microbiol 2010; 76:3383-6. [PMID: 20348310 DOI: 10.1128/aem.01456-09] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Examination of Listeria monocytogenes prevalence among ready-to-eat foods in Japan revealed frequent (5.7 to 12.1%) contamination of minced tuna and fish roe products, and the isolates had the same virulence levels as clinical isolates in terms of invasion efficiency and infectivity in cell cultures and a murine infection model, respectively. Premature stop codons in inlA were infrequent (1 out of 39 isolates). Cell numbers of L. monocytogenes in minced tuna and salmon roe increased rapidly under inappropriate storage temperatures (from a most probable number [MPN] of 10(0) to 10(1)/g to an MPN of 10(3) to 10(4)/g over the course of 2 days at 10 degrees C). Thus, regulatory guidelines are needed for acceptable levels of L. monocytogenes in these foods.
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20
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Kerouanton A, Roche SM, Marault M, Velge P, Pourcher AM, Brisabois A, Federighi M, Garrec N. Characterization of isolates of Listeria monocytogenes from sludge using pulsed-field gel electrophoresis and virulence assays. J Appl Microbiol 2009; 108:1380-8. [PMID: 19796096 DOI: 10.1111/j.1365-2672.2009.04531.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
AIMS To study the diversity and virulence of Listeria monocytogenes isolated from sludge. METHODS AND RESULTS A total of 60 isolates of L. monocytogenes from sludge were characterized by serotyping, PFGE typing and using in vitro and in vivo virulence assays. The PFGE patterns were compared with those of food and human isolates to determine whether specific group clones are associated with environmental samples. The 60 isolates gave 44 different combined ApaI/AscI PFGE patterns. The PFGE patterns of most isolates were similar or very similar to those of epidemic isolates. The majority (93%) of isolates were found to be virulent by plaque-forming assay and by mouse virulence assay. CONCLUSIONS Our findings suggest that L. monocytogenes strains found in non-sanitized sludge are virulent and represent a potential health hazard. Although no case of listeriosis related to sludge spread onto agricultural land has been reported, particular attention to this pathogen is needed. SIGNIFICANCE AND IMPACT OF THE STUDY This is the first study dealing with the characterization of L. monocytogenes isolates from non-sanitized sludge samples by molecular typing methods and in vitro and in vivo virulence assays. Our findings provide relevant information for evaluating the health risks associated with spreading sludge onto agricultural land.
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Affiliation(s)
- A Kerouanton
- Unité Caractérisation et Epidémiologie Bactérienne, AFSSA LERQAP, 94706 Maisons-Alfort Cedex, France
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21
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Yu GX. Pathogenic Bacillus anthracis in the progressive gene losses and gains in adaptive evolution. BMC Bioinformatics 2009; 10 Suppl 1:S3. [PMID: 19208130 PMCID: PMC2648741 DOI: 10.1186/1471-2105-10-s1-s3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background Sequence mutations represent a driving force of adaptive evolution in bacterial pathogens. It is especially evident in reductive genome evolution where bacteria underwent lifestyles shifting from a free-living to a strictly intracellular or host-depending life. It resulted in loss-of-function mutations and/or the acquisition of virulence gene clusters. Bacillus anthracis shares a common soil bacterial ancestor with its closely related bacillus species but is the only obligate, causative agent of inhalation anthrax within the genus Bacillus. The anthrax-causing Bacillus anthracis experienced the similar lifestyle changes. We thus hypothesized that the bacterial pathogen would follow a compatible evolution path. Results In this study, a cluster-based evolution scheme was devised to analyze genes that are gained by or lost from B. anthracis. The study detected gene losses/gains at two separate evolutionary stages. The stage I is when B. anthracis and its sister species within the Bacillus cereus group diverged from other species in genus Bacillus. The stage II is when B. anthracis differentiated from its two closest relatives: B. cereus and B. thuringiensis. Many genes gained at these stages are homologues of known pathogenic factors such those for internalin, B. anthracis-specific toxins and large groups of surface proteins and lipoproteins. Conclusion The analysis presented here allowed us to portray a progressive evolutionary process during the lifestyle shift of B. anthracis, thus providing new insights into how B. anthracis had evolved and bore a promise of finding drug and vaccine targets for this strategically important pathogen.
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Affiliation(s)
- G X Yu
- Dept, of Biological Science and Dept, of Computer Science, Boise State University, Boise, Idaho 83725, USA.
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Multilocus genotyping assays for single nucleotide polymorphism-based subtyping of Listeria monocytogenes isolates. Appl Environ Microbiol 2008; 74:7629-42. [PMID: 18931295 DOI: 10.1128/aem.01127-08] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Listeria monocytogenes is responsible for serious invasive illness associated with consumption of contaminated food and places a significant burden on public health and the agricultural economy. We recently developed a multilocus genotyping (MLGT) assay for high-throughput subtype determination of L. monocytogenes lineage I isolates based on interrogation of single nucleotide polymorphisms (SNPs) via multiplexed primer extension reactions. Here we report the development and validation of two additional MLGT assays that address the need for comprehensive DNA sequence-based subtyping of L. monocytogenes. The first of these novel MLGT assays targeted variation segregating within lineage II, while the second assay combined probes for lineage III strains with probes for strains representing a recently characterized fourth evolutionary lineage (IV) of L. monocytogenes. These assays were based on nucleotide variation identified in >3.8 Mb of comparative DNA sequence and consisted of 115 total probes that differentiated 93% of the 100 haplotypes defined by the multilocus sequence data. MLGT reproducibly typed the 173 isolates used in SNP discovery, and the 10,448 genotypes derived from MLGT analysis of these isolates were consistent with DNA sequence data. Application of the MLGT assays to assess subtype prevalence among isolates from ready-to-eat foods and food-processing facilities indicated a low frequency (6.3%) of epidemic clone subtypes and a substantial population of isolates (>30%) harboring mutations in inlA associated with attenuated virulence in cell culture and animal models. These mutations were restricted to serogroup 1/2 isolates, which may explain the overrepresentation of serotype 4b isolates in human listeriosis cases.
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inlA premature stop codons are common among Listeria monocytogenes isolates from foods and yield virulence-attenuated strains that confer protection against fully virulent strains. Appl Environ Microbiol 2008; 74:6570-83. [PMID: 18791029 DOI: 10.1128/aem.00997-08] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies showed that a considerable proportion of Listeria monocytogenes isolates obtained from foods carry a premature stop codon (PMSC) mutation in inlA that leads to production of a truncated and secreted InlA. To further elucidate the role these mutations play in virulence of L. monocytogenes, we created isogenic mutants, including (i) natural isolates where an inlA PMSC was reverted to a wild-type inlA allele (without a PMSC) and (ii) natural isolates where a PMSC mutation was introduced into a wild-type inlA allele; isogenic mutant sets were constructed to represent two distinct inlA PMSC mutations. Phenotypical and transcriptional analysis data showed that inlA PMSC mutations do not have a polar effect on the downstream inlB. Isogenic and natural strains carrying an inlA PMSC showed significantly reduced invasion efficiencies in Caco-2 and HepG2 cell lines as well as reduced virulence in oral guinea pig infections. Guinea pigs were also orally infected with a natural strain carrying the most common inlA PMSC mutation (vaccinated group), followed by challenge with a fully virulent L. monocytogenes strain 15 days postvaccination to probe potentially immunizing effects of exposure to L. monocytogenes with inlA PMSC mutations. Vaccinated guinea pigs showed reduced bacterial loads in internal organs and improved weight gain postchallenge, indicating reduced severity of infections in guinea pigs exposed to natural strains with inlA PMSC mutations. Our data support that (i) inlA PMSC mutations are causally associated with attenuated virulence in mammalian hosts and (ii) naturally occurring virulence-attenuated L. monocytogenes strains commonly found in food confer protective immunity.
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Témoin S, Roche SM, Grépinet O, Fardini Y, Velge P. Multiple point mutations in virulence genes explain the low virulence of Listeria monocytogenes field strains. MICROBIOLOGY-SGM 2008; 154:939-948. [PMID: 18310040 DOI: 10.1099/mic.0.2007/011106-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In order to understand the causes of the low virulence of Listeria monocytogenes field strains, five low-virulence strains were analysed. These five strains showed changes in relation to invasion, phosphatidyl-inositol phospholipase C (PI-PLC) activity, plaque formation and in vivo virulence. Molecular analyses revealed the same mutations in the plcA, inlA and inlB genes in all five strains. The Thr262Ala substitution in the PI-PLC protein was responsible for the absence of PI-PLC activity. This residue, conserved in certain L. monocytogenes species, is located at the outer rim of the active site pocket and could impair the cleavage activity of the enzyme. The low invasion rate of these strains was due to a nonsense codon leading to a lack of InlA protein synthesis, and to an Ala117Thr substitution in the leucine-rich repeat of InlB, which altered the interaction with the Met receptor. Single trans complementation with the inlA(EGDe), inlB(EGDe) or plcA(EGDe) genes restored the capacity of low-virulence strains either to enter epithelial and fibroblastic cells or to express PI-PLC activity. Complementation by allelic exchange of the plcA(EGDe) gene on the chromosome and trans complementation with either the inlA(EGDe) or the inlB(EGDe) gene restored the ability to form plaques, but only partly restored the in vivo virulence, suggesting that there were other gene mutation(s) with consequences that could mainly be observed in vivo. These results indicate that the low virulence of L. monocytogenes strains can be explained by point mutations in a number of virulence genes; these could therefore be important for detecting low-virulence strains. Moreover, the fact that all the strains had the same substitutions suggests that they have a common evolutionary pathway.
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Affiliation(s)
- S Témoin
- INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de Recherche de Tours, Nouzilly 37380, France
| | - S M Roche
- INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de Recherche de Tours, Nouzilly 37380, France
| | - O Grépinet
- INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de Recherche de Tours, Nouzilly 37380, France
| | - Y Fardini
- INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de Recherche de Tours, Nouzilly 37380, France
| | - P Velge
- INRA, UR1282, Infectiologie Animale et Santé Publique, Centre de Recherche de Tours, Nouzilly 37380, France
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Severino P, Dussurget O, Vêncio RZN, Dumas E, Garrido P, Padilla G, Piveteau P, Lemaître JP, Kunst F, Glaser P, Buchrieser C. Comparative transcriptome analysis of Listeria monocytogenes strains of the two major lineages reveals differences in virulence, cell wall, and stress response. Appl Environ Microbiol 2007; 73:6078-88. [PMID: 17704270 PMCID: PMC2075013 DOI: 10.1128/aem.02730-06] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Accepted: 08/06/2007] [Indexed: 01/02/2023] Open
Abstract
Listeria monocytogenes is a food-borne, opportunistic, bacterial pathogen causing a wide spectrum of diseases, including meningitis, septicemia, abortion, and gastroenteritis, in humans and animals. Among the 13 L. monocytogenes serovars described, human listeriosis is mostly associated with strains of serovars 4b, 1/2b, and 1/2a. Within the species L. monocytogenes, three phylogenetic lineages are described. Serovar 1/2a belongs to phylogenetic lineage I, while serovars 4b and 1/2b group in phylogenetic lineage II. To explore the role of gene expression in the adaptation of L. monocytogenes strains of these two major lineages to different environments, as well as in virulence, we performed whole-genome expression profiling of six L. monocytogenes isolates of serovars 4b, 1/2b, and 1/2a of distinct origins, using a newly constructed Listeria multigenome DNA array. Comparison of the global gene expression profiles revealed differences among strains. The expression profiles of two strains having distinct 50% lethal doses, as assessed in the mouse model, were further analyzed. Gene ontology term enrichment analysis of the differentially expressed genes identified differences in protein-, nucleic acid-, carbon metabolism-, and virulence-related gene expression. Comparison of the expression profiles of the core genomes of all strains revealed differences between the two lineages with respect to cell wall synthesis, the stress-related sigma B regulon and virulence-related genes. These findings suggest different patterns of interaction with host cells and the environment, key factors for host colonization and survival in the environment.
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Affiliation(s)
- Patricia Severino
- Unité de Génomique des Microorganismes Pathogènes, Institut Pasteur, 28 Rue du Dr. Roux, 75724 Paris Cedex 15, France
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Handa-Miya S, Kimura B, Takahashi H, Sato M, Ishikawa T, Igarashi K, Fujii T. Nonsense-mutated inlA and prfA not widely distributed in Listeria monocytogenes isolates from ready-to-eat seafood products in Japan. Int J Food Microbiol 2007; 117:312-8. [PMID: 17566579 DOI: 10.1016/j.ijfoodmicro.2007.05.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/15/2007] [Accepted: 05/09/2007] [Indexed: 11/29/2022]
Abstract
InlA is a surface protein participating in the entry of Listeria monocytogenes into mammalian non-phagocytic cells. PrfA is a positive regulatory factor that regulates the expression of a set of virulence genes. Recent studies revealed that some L. monocytogenes strains have a truncated form of these proteins because of nonsense mutations in their sequences, and these truncations contribute to the significant reduction in virulence of this pathogen. In this study, sequence analyses of inlA and prfA among L. monocytogenes isolated from ready-to-eat seafood revealed that only one out of 59 isolates had a nonsense-mutated inlA and all had non-mutated prfA. This indicated that these strains could be fully virulent based on the sizes of these proteins.
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Affiliation(s)
- Satoko Handa-Miya
- Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Japan
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27
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Felício MTS, Hogg T, Gibbs P, Teixeira P, Wiedmann M. Recurrent and sporadic Listeria monocytogenes contamination in alheiras represents considerable diversity, including virulence-attenuated isolates. Appl Environ Microbiol 2007; 73:3887-95. [PMID: 17449681 PMCID: PMC1932748 DOI: 10.1128/aem.02912-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microbiological characterization of alheiras, traditional smoked meat sausages produced in northern Portugal, had previously shown that more than 60% of the lots analyzed were contaminated with Listeria monocytogenes at levels higher than 100 CFU/g. In order to better understand L. monocytogenes contamination patterns in alheiras, we characterized 128 L. monocytogenes isolates from alheiras using a variety of subtyping techniques (i.e., molecular serotyping; arsenic, cadmium, and tetracycline resistance typing; and pulsed-field gel electrophoresis [PFGE]). Subtyping of isolates from products collected on two separate dates provided evidence for the persistence of specific L. monocytogenes PFGE types in the production and distribution chains of alheiras from four different processors. A subset of 21 isolates was further characterized using ribotyping and Caco-2 cell invasion assays to evaluate the pathogenic potential of L. monocytogenes present in alheiras. Caco-2 invasion assays revealed seven isolates with invasion efficiencies that were less than 20% of that of the control strain 10403S. All seven isolates had premature stop codons in inlA that represented three distinct mutations, which had previously been observed in isolates from the United States or France. Our findings indicate the need for a comprehensive approach to control L. monocytogenes in alheiras, including strategies to reduce persistence. The presence of considerable diversity in invasion phenotypes among L. monocytogenes strains present in alheiras, including the presence of subtypes likely to be virulence attenuated, may provide an opportunity to initially focus control strategies on the subtypes most likely to cause human disease.
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Affiliation(s)
- M T S Felício
- Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal
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28
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Ducey TF, Page B, Usgaard T, Borucki MK, Pupedis K, Ward TJ. A single-nucleotide-polymorphism-based multilocus genotyping assay for subtyping lineage I isolates of Listeria monocytogenes. Appl Environ Microbiol 2006; 73:133-47. [PMID: 17085705 PMCID: PMC1797101 DOI: 10.1128/aem.01453-06] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Listeria monocytogenes is a facultative intracellular pathogen responsible for food-borne disease with high mortality rates in humans and is the leading microbiological cause of food recalls. Lineage I isolates of L. monocytogenes are a particular public health concern because they are responsible for most sporadic cases of listeriosis and the vast majority of epidemic outbreaks. Rapid, reproducible, and sensitive methods for differentiating pathogens below the species level are required for effective pathogen control programs, and the CDC PulseNet Task Force has called for the development and validation of DNA sequence-based methods for subtyping food-borne pathogens. Therefore, we developed a multilocus genotyping (MLGT) assay for L. monocytogenes lineage I isolates based on nucleotide variation identified by sequencing 23,251 bp of DNA from 22 genes distributed across seven genomic regions in 65 L. monocytogenes isolates. This single-well assay of 60 allele-specific probes captured 100% of the haplotype information contained in approximately 1.5 Mb of comparative DNA sequence and was used to reproducibly type a total of 241 lineage I isolates. The MLGT assay provided high discriminatory power (Simpson's index value, 0.91), uniquely identified isolates from the eight listeriosis outbreaks examined, and differentiated serotypes 1/2b and 4b as well as epidemic clone I (ECI), ECIa, and ECII. In addition, the assay included probes for a previously characterized truncation mutation in inlA, providing for the identification of a specific virulence-attenuated subtype. These results demonstrate that MLGT represents a significant new tool for use in pathogen surveillance, outbreak detection, risk assessment, population analyses, and epidemiological investigations. DNA sequences were deposited in the GenBank database under accession numbers DQ 812146 to DQ 812517, DQ 843664 to DQ 844598, and AY 512391 to AY 512502.
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Affiliation(s)
- Thomas F Ducey
- Microbial Genomics and Bioprocessing Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604, USA
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Andersen JB, Roldgaard BB, Lindner AB, Christensen BB, Licht TR. Construction of a multiple fluorescence labelling system for use in co-invasion studies of Listeria monocytogenes. BMC Microbiol 2006; 6:86. [PMID: 17014739 PMCID: PMC1599739 DOI: 10.1186/1471-2180-6-86] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2006] [Accepted: 10/03/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Existing virulence models are often difficult to apply for quantitative comparison of invasion potentials of Listeria monocytogenes. Well-to-well variation between cell-line based in vitro assays is practically unavoidable, and variation between individual animals is the cause of large deviations in the observed capacity for infection when animal models are used. One way to circumvent this problem is to carry out virulence studies as competition assays between 2 or more strains. This, however, requires invasion-neutral markers that enable easy discrimination between the different strains. RESULTS A fluorescent marker system, allowing visualization and identification of single L. monocytogenes cells as well as colonies in a non-destructive manner, was developed. Five different fluorescent labels are available, and allowed simultaneous visual discrimination between three differently labelled strains at the single cell level by use of fluorescence microscopy. More than 90% of the L. monocytogenes host cells maintained the fluorescence tags for 40 generations. The fluorescence tags did not alter the invasive capacity of the L. monocytogenes cells in a traditional Caco-2 cell invasion assay, and visual discrimination between invaded bacteria carrying different fluorescent labels inside the cells was possible. CONCLUSION The constructed fluorescent marker system is stable, easy to use, does not affect the virulence of L. monocytogenes in Caco-2 cell assays, and allows discrimination between differently labelled bacteria after internalization in these cells.
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Affiliation(s)
- Jens B Andersen
- Danish Institute for Food and Veterinary Research, Department of Microbiological Food Safety, Mørkhøj Bygade 19, 2860 Søborg, Denmark
| | - Bent B Roldgaard
- Danish Institute for Food and Veterinary Research, Department of Microbiological Food Safety, Mørkhøj Bygade 19, 2860 Søborg, Denmark
| | - Ariel B Lindner
- Molecular, Evolution and Medical Genetics Laboratory, INSERM U571, Necker-Enfants Malades Faculty of Medicine, René Decartes – Paris V University, 156 Rue de Vaugirard, 75730 Paris Cedex 15, France
| | - Bjarke B Christensen
- Danish Institute for Food and Veterinary Research, Department of Microbiological Food Safety, Mørkhøj Bygade 19, 2860 Søborg, Denmark
| | - Tine R Licht
- Danish Institute for Food and Veterinary Research, Department of Microbiological Food Safety, Mørkhøj Bygade 19, 2860 Søborg, Denmark
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Chatterjee SS, Otten S, Hain T, Lingnau A, Carl UD, Wehland J, Domann E, Chakraborty T. Invasiveness is a variable and heterogeneous phenotype in Listeria monocytogenes serotype strains. Int J Med Microbiol 2006; 296:277-86. [PMID: 16527541 DOI: 10.1016/j.ijmm.2005.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2004] [Revised: 10/31/2005] [Accepted: 10/31/2005] [Indexed: 11/20/2022] Open
Abstract
The ability of Listeria monocytogenes to breach mucosal and endothelial barriers of the host during infection is a hallmark property mediated by the internalins (Inl) A and B. We examined the invasive property of several L. monocytogenes strains representing 13 serotypes. We found that invasiveness is a heterogeneous phenotype amongst L. monocytogenes serotype strains. Despite this, many of the poorly invasive and non-invasive strains of L. monocytogenes express internalins at levels comparable to those of invasive isolates. Introduction of the inlAB locus from EGD-e into several poorly invasive strains had no effect on their invasive properties. A strain from serotype 4b that exhibits highly invasive properties was further examined. Deletion of the inlAB locus abrogated invasion of this strain while reintroduction of the inlAB locus into this strain restored invasiveness. An analysis of regions flanking the inlAB locus revealed considerable differences in the strains studied. Our results suggest that efficacious entry of L. monocytogenes into eukaryotic cells is complex and requires additional factors apart from internalins. Data presented here also suggest that the inlAB locus was introduced into L. monocytogenes by horizontal gene transfer with subsequent deletion and rearrangements occurring during evolution of this species.
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Affiliation(s)
- Som S Chatterjee
- Institute for Medical Microbiology, Justus-Liebig-University, Frankfurter Str. 107, D-35392 Giessen, Germany
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Nightingale KK, Windham K, Martin KE, Yeung M, Wiedmann M. Select Listeria monocytogenes subtypes commonly found in foods carry distinct nonsense mutations in inlA, leading to expression of truncated and secreted internalin A, and are associated with a reduced invasion phenotype for human intestinal epithelial cells. Appl Environ Microbiol 2006; 71:8764-72. [PMID: 16332872 PMCID: PMC1317312 DOI: 10.1128/aem.71.12.8764-8772.2005] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The surface protein internalin A (InlA) contributes to the invasion of human intestinal epithelial cells by Listeria monocytogenes. Screening of L. monocytogenes strains isolated from human clinical cases (n=46), foods (n=118), and healthy animals (n=58) in the United States revealed mutations in inlA leading to premature stop codons (PMSCs) in L. monocytogenes ribotypes DUP-1052A and DUP-16635A (PMSC mutation type 1), DUP-1025A and DUP-1031A (PMSC mutation type 2), and DUP-1046B and DUP-1062A (PMSC mutation type 3). While all DUP-1046B, DUP-1062A, DUP-16635A, and DUP-1031A isolates (n=76) contained inlA PMSCs, ribotypes DUP-1052A and DUP-1025A (n=72) contained isolates with and without inlA PMSCs. Western immunoblotting showed that all three inlA PMSCs result in the production of truncated and secreted InlA. Searches of the Pathogen Tracker database, which contains subtype and source information for more than 5,000 L. monocytogenes isolates, revealed that the six ribotypes shown to contain isolates with inlA PMSCs were overall more commonly isolated from foods than from human listeriosis cases. L. monocytogenes strains carrying inlA PMSCs also showed significantly (P=0.0004) reduced invasion of Caco-2 cells compared to isolates with homologous 3' inlA sequences without PMSCs. Invasion assays with an isogenic PMSC mutant further supported the observation that inlA PMSCs lead to reduced invasion of Caco-2 cells. Our data show that specific L. monocytogenes subtypes which are common among U.S. food isolates but rare among human listeriosis isolates carry inlA mutations that are associated with, and possibly at least partially responsible for, an attenuated invasion phenotype.
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Affiliation(s)
- K K Nightingale
- Cornell University, Department of Food Science, 412 Stocking Hall, Ithaca, NY 14853.
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