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Koutsoumanis K, Allende A, Bolton D, Bover‐Cid S, Chemaly M, De Cesare A, Herman L, Hilbert F, Lindqvist R, Nauta M, Nonno R, Peixe L, Ru G, Simmons M, Skandamis P, Suffredini E, Fox E, Gosling R(B, Gil BM, Møretrø T, Stessl B, da Silva Felício MT, Messens W, Simon AC, Alvarez‐Ordóñez A. Persistence of microbiological hazards in food and feed production and processing environments. EFSA J 2024; 22:e8521. [PMID: 38250499 PMCID: PMC10797485 DOI: 10.2903/j.efsa.2024.8521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2024] Open
Abstract
Listeria monocytogenes (in the meat, fish and seafood, dairy and fruit and vegetable sectors), Salmonella enterica (in the feed, meat, egg and low moisture food sectors) and Cronobacter sakazakii (in the low moisture food sector) were identified as the bacterial food safety hazards most relevant to public health that are associated with persistence in the food and feed processing environment (FFPE). There is a wide range of subtypes of these hazards involved in persistence in the FFPE. While some specific subtypes are more commonly reported as persistent, it is currently not possible to identify universal markers (i.e. genetic determinants) for this trait. Common risk factors for persistence in the FFPE are inadequate zoning and hygiene barriers; lack of hygienic design of equipment and machines; and inadequate cleaning and disinfection. A well-designed environmental sampling and testing programme is the most effective strategy to identify contamination sources and detect potentially persistent hazards. The establishment of hygienic barriers and measures within the food safety management system, during implementation of hazard analysis and critical control points, is key to prevent and/or control bacterial persistence in the FFPE. Once persistence is suspected in a plant, a 'seek-and-destroy' approach is frequently recommended, including intensified monitoring, the introduction of control measures and the continuation of the intensified monitoring. Successful actions triggered by persistence of L. monocytogenes are described, as well as interventions with direct bactericidal activity. These interventions could be efficient if properly validated, correctly applied and verified under industrial conditions. Perspectives are provided for performing a risk assessment for relevant combinations of hazard and food sector to assess the relative public health risk that can be associated with persistence, based on bottom-up and top-down approaches. Knowledge gaps related to bacterial food safety hazards associated with persistence in the FFPE and priorities for future research are provided.
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2
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Daeschel D, Pettengill JB, Wang Y, Chen Y, Allard M, Snyder AB. Genomic analysis of Listeria monocytogenes from US food processing environments reveals a high prevalence of QAC efflux genes but limited evidence of their contribution to environmental persistence. BMC Genomics 2022; 23:488. [PMID: 35787787 PMCID: PMC9252043 DOI: 10.1186/s12864-022-08695-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/10/2022] [Indexed: 12/28/2022] Open
Abstract
Background Quaternary ammonium compound (QAC) efflux genes increase the minimum inhibitory concentration of Listeria monocytogenes (Lm) to benzalkonium chloride sanitizer, but the contribution of these genes to persistence in food processing environments is unclear. The goal of this study was to leverage genomic data and associated metadata for 4969 Lm isolates collected between 1999 and 2019 to: (1) evaluate the prevalence of QAC efflux genes among Lm isolates from diverse US food processors, (2) use comparative genomic analyses to assess confounding factors, such as clonal complex identity and stress tolerance genotypes, and (3) identify patterns in QAC efflux gene gain and loss among persistent clones within specific facilities over time. Results The QAC efflux gene cassette bcrABC was present in nearly half (46%) of all isolates. QAC efflux gene prevalence among isolates was associated with clonal complex (𝛘2 < 0.001) and clonal complex was associated with the facility type (𝛘2 < 0.001). Consequently, changes in the prevalence of QAC efflux genes within individual facilities were generally attributable to changes in the prevalence of specific clonal complexes. Additionally, a GWAS and targeted BLAST search revealed that clonal complexes with a high prevalence of QAC efflux genes commonly possessed other stress tolerance genes. For example, a high prevalence of bcrABC in a clonal complex was significantly associated with the presence of the SSI-1 gene cluster (p < 0.05). QAC efflux gene gain and loss were both observed among persistent populations of Lm in individual facilities, suggesting a limited direct role for QAC efflux genes as predictors of persistence. Conclusion This study suggests that although there is evidence that QAC efflux genes are part of a suite of adaptations common among Lm isolated from some food production environments, these genes may be neither sufficient nor necessary to enhance persistence. This is a crucial distinction for decision making in the food industry. For example, changes to sanitizer regimen targeting QAC tolerance would not address other contributing genetic or non-genetic factors, such as equipment hygienic design which physically mediates sanitizer exposure. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08695-2.
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Affiliation(s)
- Devin Daeschel
- Department of Food Science, Cornell University, Ithaca, NY, USA
| | - James B Pettengill
- Biostatistics and Bioinformatics Staff, Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, USA
| | - Yu Wang
- Biostatistics and Bioinformatics Staff, Office of Analytics and Outreach, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, USA
| | - Yi Chen
- Division of Microbiology, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, USA
| | - Marc Allard
- Division of Microbiology, Office of Regulatory Science, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD, USA
| | - Abigail B Snyder
- Department of Food Science, Cornell University, Ithaca, NY, USA.
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3
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Selection and characterization of lactic acid bacteria with activity against Listeria monocytogenes from traditional RTE ripened foods. Lebensm Wiss Technol 2022. [DOI: 10.1016/j.lwt.2022.113579] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Martín I, Alía A, Rodríguez A, Gómez F, Córdoba JJ. Growth and Expression of Virulence Genes of Listeria monocytogenes during the Processing of Dry-Cured Fermented "Salchichón" Manufactured with a Selected Lactilactobacillus sakei. BIOLOGY 2021; 10:1258. [PMID: 34943173 PMCID: PMC8698599 DOI: 10.3390/biology10121258] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/11/2021] [Accepted: 11/30/2021] [Indexed: 01/13/2023]
Abstract
The effect of the dry-cured fermented processing of "salchichón" inoculated with a selected strain of Lactilactobacillus sakei (205) on the growth and transcriptional response of three virulence genes (plcA, hly, and iap) of Listeria monocytogenes was evaluated. For this, three different batches of "salchichón" were analyzed: batch B (inoculated only with L. sakei), batch L (inoculated only with L. monocytogenes), and batch L + B (inoculated with both microorganisms). Sausages were ripened for 90 days according to a traditional industrial process. The processing of "salchichón" provoked a reduction in L. monocytogenes counts of around 2 log CFU/g. The downregulation of the expression of the three genes was found at the end of ripening when the water activity (aw) of "salchichón" was <0.85 aw. The combined effect on the reduction in L. monocytogenes counts together with the downregulation in the expression of the virulence genes throughout the "salchichón" processing could be of great interest to control the hazard caused by the presence of this pathogenic bacterium.
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Affiliation(s)
| | | | - Alicia Rodríguez
- Food Hygiene and Safety, Meat and Meat Products Research Institute, Faculty of Veterinary Science, University of Extremadura, Avda. de las Ciencias, s/n, 10003 Cáceres, Spain; (I.M.); (A.A.); (F.G.); (J.J.C.)
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5
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Alía A, Andrade MJ, Rodríguez A, Martín I, Pérez-Baltar A, Medina M, Córdoba JJ. Prevalence and characterization of Listeria monocytogenes in deboning and slicing areas of Spanish dry-cured ham processing. Lebensm Wiss Technol 2020. [DOI: 10.1016/j.lwt.2020.109498] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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6
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Antimicrobial activity of gaseous Citrus limon var pompia leaf essential oil against Listeria monocytogenes on ricotta salata cheese. Food Microbiol 2019; 87:103386. [PMID: 31948627 DOI: 10.1016/j.fm.2019.103386] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 10/03/2019] [Accepted: 11/19/2019] [Indexed: 12/20/2022]
Abstract
Contamination by Listeria monocytogenes is a particularly challenging problem in the food industry due to the ability of the bacterium to develop under conditions normally used for food preservation. Here, we show that the gaseous phase of Citrus limon var pompia leaf essential oil (hereafter PLEO) exerts specific anti-Listeria activity on ricotta salata cheese stored at 5 °C. The synergic effect of gaseous PLEO treatment and refrigeration was first confirmed in vitro on L. monocytogenes strains treated for 3 h with gaseous PLEO and then stored at 5 °C. Ricotta cheese was then inoculated with L. monocytogenes strains and subjected to hurdle technology with different concentrations of gaseous PLEO. Cell counts revealed gaseous PLEO to exert a bactericidal effect on L. monocytogenes 20600 DSMZ and a bacteriostatic effect on a mix of L. monocytogenes strains. Scanning and transmission electron microscopy analyses of L. monocytogenes cells suggested that gaseous PLEO targets the bacterial cell wall and plasma membrane. Chemical analyses of the liquid and vapor phases of PLEO indicated linalyl acetate to be the predominant compound, followed by limonene and the two isomers of citral, whereas EO composition analysis, although generally in line with previous findings, showed the presence of linalyl acetate for the first time. Solid-phase microextraction coupled with gas chromatography confirmed the presence of all crude oil components in the headspace of the box.
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Manso B, Melero B, Stessl B, Fernández-Natal I, Jaime I, Hernández M, Wagner M, Rovira J, Rodríguez-Lázaro D. Characterization of Virulence and Persistence Abilities of Listeria monocytogenes Strains Isolated from Food Processing Premises. J Food Prot 2019; 82:1922-1930. [PMID: 31633423 DOI: 10.4315/0362-028x.jfp-19-109] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We report the characterization of 15 Listeria monocytogenes strains isolated from various food processing plants by multivirulence locus sequence typing to determine virulence types (VTs) and epidemic clones. Molecular mechanisms involved in adaptation to food processing environments and related to virulence were also studied. Phenotypic behaviors associated with various antimicrobials, biofilm formations, and invasiveness were assessed. There were 11 VTs among the 15 L. monocytogenes strains. Strains belonging to six VTs were stress survival islet 1 (SSI-1) and one strain of VT94 was SSI-2. Tn6188 was found in VT6 and VT94 strains, and bcrABC cassette genes were identified in VT21, VT60, and VT63 strains. Only one strain, in VT20, showed llxS, whereas a full-size inlA was detected in strains belonging to VT8, VT20, VT21, and VT63. VT10, VT20, VT21, VT60, and VT63 strains were the most tolerant to studied disinfectants. A VT6 strain showed the strongest biofilm formation ability in polyvinyl chloride, and strains belonging to VT10, VT11, VT20, and VT94 had moderate abilities. Antimicrobial sensitivity tests showed that all the L. monocytogenes strains were multidrug resistant. F tests revealed that only strains of VT10, VT60, and VT94 were significantly noninvasive (P < 0.05) in Caco-2 cells. Our findings illustrate how L. monocytogenes isolates exploit diverse mechanisms to adapt to adverse conditions. Consequently, detailed characterization of L. monocytogenes isolates is required for comprehensive elimination of this pathogenic bacterium in food processing environments.
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Affiliation(s)
- Beatriz Manso
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.])
| | - Beatriz Melero
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.])
| | - Beatrix Stessl
- Institute of Milk Hygiene, Milk Technology and Food Science, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.,Christian Doppler Laboratory for Molecular Food Analytics, University of Veterinary Medicine, Vienna, Austria
| | - Isabel Fernández-Natal
- Complejo Asistencial, University of León, Leon, Spain.,Institute of Biomedicine (IBIOMED), University of León, Leon, Spain
| | - Isabel Jaime
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.])
| | - Marta Hernández
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.]).,Laboratory of Molecular Biology and Microbiology, Instituto Tecnológico Agrario de Castilla y León (ITACyL), Valladolid, Spain
| | - Martin Wagner
- Institute of Milk Hygiene, Milk Technology and Food Science, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.,Christian Doppler Laboratory for Molecular Food Analytics, University of Veterinary Medicine, Vienna, Austria
| | - Jordi Rovira
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.])
| | - David Rodríguez-Lázaro
- Department of Biotechnology and Food Science, Faculty of Sciences, University of Burgos, Burgos, Spain (ORCID. https://orcid.org/0000-0002-8795-854X [D.R.-L.])
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Zhang Y, Dong S, Chen H, Chen J, Zhang J, Zhang Z, Yang Y, Xu Z, Zhan L, Mei L. Prevalence, Genotypic Characteristics and Antibiotic Resistance of Listeria monocytogenes From Retail Foods in Bulk in Zhejiang Province, China. Front Microbiol 2019; 10:1710. [PMID: 31402906 PMCID: PMC6672743 DOI: 10.3389/fmicb.2019.01710] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 07/11/2019] [Indexed: 12/28/2022] Open
Abstract
Listeria monocytogenes is an important foodborne pathogen causing public concern. A total of 3354 retail foods in bulk were sampled and screened for L. monocytogenes. Seventy-three (2.2%) samples including 21 ready-to-eat (RTE) foods and 52 raw foods were confirmed positive for L. monocytogenes. Sushi and salmon sashimi occupied the top two slots in RTE foods with relatively high presence rate of 12.9 and 6.9%, respectively. Meanwhile, L. monocytogenes was found to be distributed unequally in raw foods; the presence rates in raw meat (3.5%) and poultry (3.8%) were significantly higher than that in raw seafood (1.3%). Notably, L. monocytogenes was not detected in raw freshwater food. The L. monocytogenes isolates belonged to four serotypes, 1/2a, 1/2b, 1/2c, and 4b, with the most prevalent serotype being 1/2a (47.9%). Eighteen sequence types (STs) and eighteen virulence types (VTs) containing four newly assigned VTs (VT180, VT181, VT182, and VT183) were determined via multilocus sequence typing (MLST) and multi-virulence-locus sequence typing (MVLST). Among the 73 L. monocytogenes isolates, 23 (31.5%) belonged to epidemic clones (ECs) including ECI, ECIV, ECV, ECVI, ECVIII and ECXI among which ECV was predominant. Antibiotic susceptibility tests revealed a high resistance rate (11.0%) to tetracycline. Moreover, we identified the distribution patterns of virulence genes of four Listeria pathogenicity islands (LIPI) in L. monocytogenes isolates. prfA, hly, plcA, plcB, mpl, actA genes in LIPI-1 and inlA, inlB, inlC, inlJ genes in LIPI-2 were detected in approximately all L. monocytogenes isolates. The distribution of both LIPI-3 genes and LIPI-4 genes exhibited association with lineage and ST. LIPI-4 genes were present exclusively in ST87 isolates. Relatedness analysis revealed the absence of distinct association between STs, ECs, LIPI-3 and LIPI-4 distribution and specific food groups. This study provided fundamental data for Chinese food safety authorities to grasp the contamination status of L. monocytogenes in foods, assess the potential risk of this pathogen and further address the safety issue of retail foods in bulk in China.
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Affiliation(s)
- Yunyi Zhang
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Shilei Dong
- Department of Clinical Laboratory, Zhejiang Hospital, Hangzhou, China
| | - Honghu Chen
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Jiancai Chen
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Junyan Zhang
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Zhen Zhang
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Yong Yang
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Ziyan Xu
- Department of Biotechnology, Wenzhou Medical University, Wenzhou, China
| | - Li Zhan
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
| | - Lingling Mei
- Department of Microbiology, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China
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Kuch A, Goc A, Belkiewicz K, Filipello V, Ronkiewicz P, Gołębiewska A, Wróbel I, Kiedrowska M, Waśko I, Hryniewicz W, Lomonaco S, Skoczyńska A. Molecular diversity and antimicrobial susceptibility of Listeria monocytogenes isolates from invasive infections in Poland (1997-2013). Sci Rep 2018; 8:14562. [PMID: 30267005 PMCID: PMC6162231 DOI: 10.1038/s41598-018-32574-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 09/11/2018] [Indexed: 11/24/2022] Open
Abstract
The epidemiology of invasive listeriosis in humans appears to be weakly characterized in Poland, the sixth most populous member state of the European Union. We obtained antimicrobial susceptibility data, PCR-serogroups and genotypic profiles for 344 invasive isolates of Listeria monocytogenes, collected between 1997 and 2013 in Poland. All isolates were susceptible to the 10 tested antimicrobials, except one that was resistant to tetracycline and minocycline and harbored the tet(M), tet(A) and tet(C) genes. Overall, no increasing MIC values were observed during the study period. Four PCR-serogroups were observed: IVb (55.8%), IIa (34.3%), IIb (8.1%) and IIc (1.8%). We identified clonal complexes (CCs) and epidemic clones (ECs) previously involved in outbreaks worldwide, with the most prevalent CCs/ECs being: CC6/ECII (32.6%), CC1/ECI (17.2%), CC8/ECV (6.1%) and CC2/ECIV (5.5%). The present study is the first extensive analysis of Polish L. monocytogenes isolates from invasive infections.
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Affiliation(s)
- Alicja Kuch
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Anna Goc
- Nicolaus Copernicus University, Department of Genetics, Toruń, 87-100, Poland.
| | - Katarzyna Belkiewicz
- National Tuberculosis and Lung Diseases Research Institute, Department of Microbiology, Warsaw, 01-138, Poland
| | - Virginia Filipello
- University of Turin, Department of Veterinary Sciences, Grugliasco, 10095, Italy
- Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, 25124, Italy
| | - Patrycja Ronkiewicz
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Agnieszka Gołębiewska
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Izabela Wróbel
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Marlena Kiedrowska
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Izabela Waśko
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Waleria Hryniewicz
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
| | - Sara Lomonaco
- University of Turin, Department of Veterinary Sciences, Grugliasco, 10095, Italy
- US Food and Drug Administration, College Park, Maryland, 20740, USA
| | - Anna Skoczyńska
- National Medicines Institute, Department of Epidemiology and Clinical Microbiology, Warsaw, 00-725, Poland
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10
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Fox EM, Jiang Y, Gobius KS. Key pathogenic bacteria associated with dairy foods: On-farm ecology and products associated with foodborne pathogen transmission. Int Dairy J 2018. [DOI: 10.1016/j.idairyj.2018.03.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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11
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Amato E, Filipello V, Gori M, Lomonaco S, Losio MN, Parisi A, Huedo P, Knabel SJ, Pontello M. Identification of a major Listeria monocytogenes outbreak clone linked to soft cheese in Northern Italy - 2009-2011. BMC Infect Dis 2017; 17:342. [PMID: 28499357 PMCID: PMC5429568 DOI: 10.1186/s12879-017-2441-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 05/04/2017] [Indexed: 11/24/2022] Open
Abstract
Background Molecular subtyping and enhanced surveillance in Lombardy region identified a cluster of possibly related listeriosis cases from 2006 to 2010. This cluster grouped 31 isolates that belonged to serotype 1/2a and Sequence Type 38 (ST38) as defined by Multilocus Sequence Typing (MLST). Methods Our study expanded the previous investigation to include cases from 2011 to 2014 and used Multi-Virulence-Locus Sequence Typing (MVLST) on all ST38 isolates to better understand their epidemiology and possibly identify a common source outbreak. Results Out of 306 L. monocytogenes clinical isolates collected, 43 (14.1%) belonged to ST38 with cases occurring in nine out of twelve Lombardy provinces. The ST38 isolates were split by MVLST into two Virulence Types (VTs): VT80 (n = 12) and VT104 (n = 31). VT104 cases were concentrated between 2009 and 2011 in two provinces, Bergamo and Milan. An epidemiologic investigation was performed and in one case, a matching VT104 isolate was retrieved from a soft cheese sample from a patient’s refrigerator. Conclusions Our findings revealed a major listeriosis outbreak in Northern Italy linked to soft cheese in 2009–2011, which went undetected by local health authorities. Our study shows that integrating subtyping methods with conventional epidemiology can help identify the source of L. monocytogenes outbreak clones. Electronic supplementary material The online version of this article (doi:10.1186/s12879-017-2441-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ettore Amato
- Department of Health Sciences, University of Milan, Via di Rudinì, 8, 20142, Milan, Italy
| | - Virginia Filipello
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini, 2, 10095, Grugliasco, Italy.,Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Via A. Bianchi 9, 25124, Brescia, Italy
| | - Maria Gori
- Department of Health Sciences, University of Milan, Via di Rudinì, 8, 20142, Milan, Italy
| | - Sara Lomonaco
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini, 2, 10095, Grugliasco, Italy
| | - Marina Nadia Losio
- Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Via A. Bianchi 9, 25124, Brescia, Italy
| | - Antonio Parisi
- Istituto Zooprofilattico Sperimentale della Puglia e della Basilicata, Via Manfredonia 20, 71121, Foggia, Italy
| | - Pol Huedo
- Department of Health Sciences, University of Milan, Via di Rudinì, 8, 20142, Milan, Italy
| | - Stephen John Knabel
- Department of Food Science, The Pennsylvania State University, 405 Rodney A. Erickson Food Science Building, 16802 University Park, State College, PA, USA
| | - Mirella Pontello
- Department of Health Sciences, University of Milan, Via di Rudinì, 8, 20142, Milan, Italy. .,Coordinated Research Center "EpiSoMI", University of Milan, Via Carlo Pascal, 36, 20133, Milan, Italy.
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