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Objectives: To investigate the contribution to virulence of the surface protein internalin B (InlB) in the Listeria monocytogenes lineage I strain F2365, which caused a deadly listeriosis outbreak in California in 1985., Methods: The F2365 strain displays a point mutation that hampers expression of InlB. We rescued the expression of InlB in the L. monocytogenes lineage I strain F2365 by introducing a point mutation in the codon 34 (TAA to CAA). We investigated its importance for bacterial virulence using in vitro cell infection systems and a murine intravenous infection model., Results: In HeLa and JEG-3 cells, the F2365 InlB + strain expressing InlB was ≈9-fold and ≈1.5-fold more invasive than F2365, respectively. In livers and spleens of infected mice at 72 hours after infection, bacterial counts for F2365 InlB + were significantly higher compared to the F2365 strain (≈1 log more), and histopathologic assessment showed that the F2365 strain displayed a reduced number of necrotic foci compared to the F2365 InlB + strain (Mann-Whitney test)., Conclusions: InlB plays a critical role during infection of nonpregnant animals by a L. monocytogenes strain from lineage I. A spontaneous mutation in InlB could have prevented more severe human morbidity and mortality during the 1985 California listeriosis outbreak., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Listeria monocytogenes is the cause of listeriosis, an important foodborne disease. Contaminated ready-to-eat foods are common sources of L. monocytogenes, yet no global estimates exist for prevalence and levels in high-risk ready-to-eat foods. Our objective was to estimate the prevalence and levels of L. monocytogenes in deli meat, soft cheese, and packaged salad. We searched Medline, Web of Science, Agricola, Conference Proceedings Citation Index-Science, Science.gov, ScienceResearch.com , and OpenGREY for studies on L. monocytogenes prevalence and/or levels, with no restriction on publication date. We used a priori study selection, data extraction, and risk of biases processes. Results were synthesized with random-effects meta-analyses and meta-regressions to evaluate heterogeneity between studies. We included in the review 100 studies with a sample size restriction of ≥100, and we estimated L. monocytogenes prevalence in deli meat at 2.9% (95% confidence interval [CI], 2.3 to 3.6%), in soft cheese at 2.4% (95% CI, 1.6 to 3.6%), and in packaged salad at 2.0% (95% CI, 1.2 to 3.1%). High heterogeneity was present in all food groups, and meta-regressions did not reveal consistent explanations for heterogeneity. Pathogen level was not reported consistently or in the format required for synthesis, so meta-analyses of this variable were not performed. The high heterogeneity between studies indicates that use of global summary prevalence estimates for risk assessments are not advisable, but awareness of risk and the heterogeneity of the risk is relevant for education and further risk assessment.

Competing Interests: All authors have completed and submitted the ICMJE form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Listeria is ubiquitous in natural environments and can be isolated from animal hosts, including rodents. Listeria ivanovii and Listeria monocytogenes are the main pathogenic species that can cause serious listeriosis in animals and human. In this study, we investigated the prevalence of Listeria in wild rodents from six regions in China, and analyzed the molecular characteristics and antibiotics resistance of the L. ivanovii isolates. A total of 702 fecal samples of 25 different species of wild rodents were examined, and 75 were Listeria positive, including 26 L. ivanovii strains, 2 L. monocytogenes strains, and 47 Listeria innocus strains. The 26 L. ivanovii isolates (including 2 subspecies) were divided into 5 different sequence types by multilocus sequence typing with ST6 being the dominant type, and 5 different pulsotypes by pulsed-field gel electrophoresis. The results of antimicrobial susceptibility revealed that all L. ivanovii isolates were sensitive to rifampin, chloramphenicol, gentamicin, erythromycin, tetracycline, vancomycin, penicillin G, imipenem, trimethoprim-sulfamethoxazole, but some isolates (including ST1, ST7, and ST8) were resistant to clindamycin. The results suggest that the prevalence of L. ivanovii (3.7%, 26/702) in wild rodents was higher in some regions, and the genetic diversity of L. ivanovii isolates in the wild rodents is relatively low and most belong to one lineage. These wild rodents may act as the natural host for L. ivanovii and possibly transmit the pathogen between wild animals and humans.

The persuasiveness of genomic evidence has pressured scientific agencies to supplement or replace well-established methodologies to inform public health and food safety decision-making. This study of 52 epidemiologically defined Listeria monocytogenes isolates, collected between 1981 and 2011, including nine outbreaks, was undertaken (1) to characterize their phylogenetic relationship at finished genome-level resolution, (2) to elucidate the underlying genetic diversity within an endemic subtype, CC8, and (3) to re-evaluate the genetic relationship and epidemiology of a CC8-delimited outbreak in Canada in 2008. Genomes representing Canadian Listeria outbreaks between 1981 and 2010 were closed and manually annotated. Single nucleotide variants (SNVs) and horizontally acquired traits were used to generate phylogenomic models. Phylogenomic relationships were congruent with classical subtyping and epidemiology, except for CC8 outbreaks, wherein the distribution of SNV and prophages revealed multiple co-evolving lineages. Chronophyletic reconstruction of CC8 evolution indicates that prophage-related genetic changes among CC8 strains manifest as PFGE subtype reversions, obscuring the relationship between CC8 isolates, and complicating the public health interpretation of subtyping data, even at maximum genome resolution. The size of the shared genome interrogated did not change the genetic relationship measured between highly related isolates near the tips of the phylogenetic tree, illustrating the robustness of these approaches for routine public health applications where the focus is recent ancestry. The possibility exists for temporally and epidemiologically distinct events to appear related even at maximum genome resolution, highlighting the continued importance of epidemiological evidence.

This article describes the identification and investigation of two extended outbreaks of listeriosis in which crabmeat was identified as the vehicle of infection. Comparing contemporary and retrospective typing data of Listeria monocytogenes isolates from clinical cases and from food and food processing environments allowed the detection of cases going back several years. This information, combined with the analysis of routinely collected enhanced surveillance data, helped to direct the investigation and identify the vehicle of infection. Retrospective whole genome sequencing (WGS) analysis of isolates provided robust microbiological evidence of links between cases, foods, and the environments in which they were produced and demonstrated that for some cases and foods, identified by fluorescent amplified fragment length polymorphism, the molecular typing method in routine use at the time, were not part of the outbreak. WGS analysis also showed that the strains causing illness had persisted in two food production environments for many years and in one producer had evolved into two strains over a period of around 8 years. This article demonstrates the value of reviewing L. monocytogenes typing data from clinical cases together with that from foods as a means of identifying potential vehicles and sources of infection in outbreaks of listeriosis. It illustrates the importance of reviewing retrospective L. monocytogenes typing alongside enhanced surveillance data to characterize extended outbreaks and inform control measures. Also, this article highlights the advantages of WGS analysis for strain discrimination and clarification of evolutionary relationships that refine outbreak investigations and improve our understanding of L. monocytogenes in the food chain.

An outbreak with a remarkable Listeria monocytogenes clone causing 163 cases of non-invasive listeriosis occurred in Germany in 2015. Core genome multi locus sequence typing grouped non-invasive outbreak isolates and isolates obtained from related food samples into a single cluster, but clearly separated genetically close isolates obtained from invasive listeriosis cases. A comparative genomic approach identified a premature stop codon in the chiB gene, encoding one of the two L. monocytogenes chitinases, which clustered with disease outcome. Correction of this premature stop codon in one representative gastroenteritis outbreak isolate restored chitinase production, but effects in infection experiments were not found. While the exact role of chitinases in virulence of L. monocytogenes is still not fully understood, our results now clearly show that ChiB-derived activity is not required to establish L. monocytogenes gastroenteritis in humans. This limits a possible role of ChiB in human listeriosis to later steps of the infection.

Objectives: Listeria monocytogenes (Lm) is a foodborne human pathogen responsible for severe infections, including septicaemia, neurolisteriosis, and maternal-foetal and focal infections. Little is known about Lm-associated respiratory tract or lung infections., Methods: We conducted a retrospective study of culture-proven cases of Lm pleural infections and pneumonia reported to the French National Reference Centre for Listeria from January 1993 to August 2016., Results: Thirty-eight consecutive patients with pleural infection (n = 32), pneumonia (n = 5), or both (n = 1) were studied; 71% of these were men. Median age was 72 (range 29-90). Two patients presented with concomitant neurolisteriosis. All patients but one reported at least one immunosuppressive condition (97%), with a median number of 2 (range 0-5), including 29% (8/28) with current exposure to immunosuppressive therapy and 50% (17/34) with ongoing neoplasia; 75% (21/28) reported previous pleural or pulmonary disease. Antibiotic therapy mostly consisted in amoxicillin (72%) associated with aminoglycoside in 32%. Chest-tube drainage was performed in 7/19 patients with empyema (37%); 25% of the patients (7/30) required intensive care management. In-hospital mortality reached 35% and occurred after a median time interval of 4 days (range 1-33 days). Three patients had recurrence of empyema (time interval of 1 week to 4 months after treatment completion). Altogether, only 13/31 patients (42%) diagnosed with Lm respiratory infection experienced an uneventful outcome at 2-year follow-up., Conclusion: Lm is a rare but severe cause of pneumonia and pleural infection in older immunocompromised patients, requiring prompt diagnosis and adequate management and follow-up., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Background: A countrywide epidemic of Listeria monocytogenes (LM) in South Africa began in the first quarter of 2017, rapidly becoming the world's largest LM outbreak to date., Methods: We describe the clinical course of neonates with culture-confirmed LM infection admitted to a tertiary neonatal unit at Tygerberg Hospital, Cape Town (1 January 2017 - 31 January 2018). Current epidemic LM cases were compared with a historical cohort of sporadic neonatal LM cases at our institution (2006 - 2016). The global literature on epidemic neonatal LM outbreaks (1 January 1978 - 31 December 2017) was reviewed., Results: Twelve neonates (median gestational age 35 weeks, median birth weight 2 020 g) were treated for confirmed LM bacteraemia in 2017/18, presenting at a median age of 0.5 days. In 5 cases, neurolisteriosis was suspected. Three neonates died (25.0%) v. 8/13 neonatal deaths (61.6%) in the sporadic listeriosis cohort (2006 - 2016) (p=0.075). The institution's neonatal LM infection incidence increased significantly in 2017 from a historical rate of 0.17/1 000 live births to 1.4/1 000 (p<0.001). During the current LM epidemic, the crude neonatal fatality rate exceeded the average calculated global epidemic neonatal LM mortality (3/12 (25.0%) v. 50/290 (17.2%); p=0.448). Possible factors contributing to the high mortality rate in this epidemic LM neonatal cohort may include more virulent disease associated with sequence type 6 and the predominance of early-onset disease., Conclusions: Epidemic neonatal listeriosis at Tygerberg Hospital was associated with a predominance of bacteraemic, early-onset disease. Listeriosis-associated mortality rates were higher than previously published, but lower than the rate in a historical institutional cohort.

The classical definition of a disease outbreak is the occurrence of cases of disease in excess of what would normally be expected in a community, geographical area or time period. The establishment of an outbreak then starts with the identification of an incidence of cases above the normally expected threshold during a given time period. Subsequently, the cases are examined using a variety of subtyping methods to identify potential linkages. As listeriosis disease has a long incubation period, relating a single source or multiple sources of contaminated food to clinical disease is challenging and time consuming. The vast majority of human listeriosis cases are caused by three serotypes, 1/2a, 1/2b, and 4b. Thus serotyping of isolates from suspected foods and clinical samples, although useful for eliminating some food sources, has a very limited discriminatory power. The advent of faster and more affordable sequencing technology, coupled with increased computational power, has permitted comparisons of whole Listeria genome sequences from isolates recovered from clinical, food, and environmental sources. These analyses made it possible to identify outbreaks and the source much more accurately and faster, thus leading to a reduction in number of illnesses as well as a reduction in economic losses. Initial DNA sequence information also facilitated the development of a simple molecular serotype protocol which allowed for the identification of major disease causing serotypes of L. monocytogenes, including a clade of 4b variant (4bV) strains of L. monocytogenes involved in at least 3 more recent listeriosis outbreaks in the US. Furthermore, data generated using whole genome sequence (WGS) analyses was successfully utilized to develop a pan-genomic DNA microarray as well as a single nucleotide polymorphism (SNP) based analysis. Herein, we present and compare, the two recently developed sub-typing technologies and discuss how these methods are not only important in outbreak investigations, but could also shed light on possible adaptations to different foods and environments., (Published by Elsevier Ltd.)

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.

Background: Listeria monocytogenes is a widespread foodborne pathogen that can cause listeriosis, a potentially fatal infection. L. monocytogenes is subdivided into four phylogenetic lineages, with the highest incidence of listeriosis occurring within lineage I followed by lineage II. Strains of L. monocytogenes differ in their phenotypic characteristics, including virulence. However, the genetic bases for these observed differences are not well understood, and current efforts to monitor L. monocytogenes in food consider all strains to be equally virulent. We use a comparative genomics approach to identify genes and single nucleotide polymorphisms (SNPs) in 174 clinical and food isolates of L. monocytogenes that potentially contribute to virulence or the capacity to adapt to food environments., Results: No SNPs are significantly associated with food or clinical isolates. No genes are significantly associated with food or clinical isolates from lineage I, but eight genes consisting of multiple homologues are associated with lineage II food isolates. These include three genes which encode hypothetical proteins, the cadmium resistance genes cadA and cadC, the multi-drug resistance gene ebrB, a quaternary ammonium compound resistance gene qac, and a regulatory gene. All eight genes are plasmid-borne, and most closed L. monocytogenes plasmids carry at least five of the genes (24/27). In addition, plasmids are more frequently associated with lineage II food isolates than with lineage II clinical isolates., Conclusions: We identify eight genes that are significantly associated with food isolates in lineage II. Interestingly, the eight genes are virtually absent in lineage II outbreak isolates, are composed of homologues which show a nonrandom distribution among lineage I serotypes, and the sequences are highly conserved across 27 closed Listeria plasmids. The functions of these genes should be explored further and will contribute to our understanding of how L. monocytogenes adapts to the host and food environments. Moreover, these genes may also be useful as markers for risk assessment models of either pathogenicity or the ability to proliferate in food and the food processing environment.

Purpose: From May 2015 to March 2016, an outbreak due to Listeria monocytogenes serotype 1/2a and clinical pulsotype never previously isolated in Europe occurred in central Italy, involving 24 confirmed clinical cases. The article provides a description of the outbreak and the investigation carried out by a multidisciplinary network., Methodology: Epidemiological and microbiological surveillance was conducted to confirm the outbreak and to detect the food vehicle of infection. The origin and destination of the implicated food and its ingredients were investigated by tracing-back and -forward investigation., Results: Next-generation sequencing confirmed the unique outbreak strain. On 4 January 2016, a L. monocytogenes strain with pulsotype indistinguishable from that isolated from clinical cases in the outbreak was detected in a sample of hog head cheese purchased from a retail supermarket by one of the patients. The hog head cheese was produced by a small meat processing plant in the Marche region, where microbiological investigation confirmed environmental and food contamination by the outbreak strain. Plant production was suspended and all contaminated batches of the hog head cheese were withdrawn from the market by 19 February by local health authority. We subsequently observed a sharp decline in clinical cases, the last being reported on 11 March 2016., Conclusion: The key factor in the timely conclusion of this investigation was intersectoral collaboration among epidemiologists, microbiologists, veterinarians, statisticians and health and food safety authorities at national, regional and local levels.

Background: Listeria monocytogenes as the main causative agent of human listeriosis is an intracellular bacterium that has the capability to infect a wide range of cell types. Human listeriosis is a sporadic foodborne disease, which is epidemiologically linked with consumption of contaminated food products. Listeriosis may range from mild and self-limiting diseases in healthy people to severe systemic infections in susceptible populations. This study aimed to investigate the prevalence of L. monocytogenes in food resources and human samples from Iran., Methods: A systematic search was performed by using electronic databases from papers that were published by Iranian authors Since January of 2000 to the end of April 2017. Then, 47 publications which met our inclusion criteria were selected for data extraction and analysis by Comprehensive Meta-Analysis Software., Results: The pooled prevalence of L. monocytogenes in human origin was 10% (95% CI: 7-12%) ranging from 0 to 28%. The prevalence of L. monocytogenes in animals was estimated at 7% (95% CI: 4-10%) ranging from 1 to 18%. Moreover, the pooled prevalence of L. monocytogenes in Iranian food samples was estimated at 4% (95% CI: 3-5%) ranging from 0 to 50%. From those 12 studies which reported the distribution of L. monocytogenes serotypes, it was concluded that 4b, 1/2a, and 1/2b were the most prevalent serotypes., Conclusions: The prevalence of L. monocytogenes and prevalent serotypes in Iran are comparable with other parts of the world. Although the overall prevalence of human cross-contamination origin was low, awareness about the source of contamination is very important because of the higher incidence of infections in susceptible groups.

A cluster of 34 human cases of listeriosis was traced to consumption of contaminated quargel cheese, a sour milk specialty sold in Austria, Germany and Czech Republic. Here, we try to assess how many portions were consumed by the Austrian population at a certain contamination level (CL). In total, 1623 cheese lots were produced during the outbreak period resulting in >3 million portions of cheese delivered to the market. From 650 sets of quality control data provided by the food business operator, we reconstructed the contamination scenario over time and identified 84 lots that were found to be positive. With regard to another sixteen lots, a CL was found ranging from one to 3,84 log 10  CFU L. monocytogenes/g, measured in product stored between one to 23 days after production. However the number of storage days at home before consumption is unknown. To resolve this issue, we modelled the theoretical CL of the product if consumed either 20, 30, 40 or 50 days post production. We found that 10 lots (approx. 27,350 portions) would have been contaminated at CLs higher than 3 log 10  CFU L. monocytogenes/g if all cheese had been consumed after 20 days of storage. This number shifts to 20 lots (approx. 54,700 portions) after 30 days of storage. If all cheese had been consumed at the end of shelf life (50 days of storage), theoretically 242,5 lots would have exceeded a CL of 6 log 10  CFU L. monocytogenes/g. We concluded that the extended shelf life given to the product was a driver of the outbreak scenario. It is stunning to note that so few cases were reported in spite of consumers' massive exposure to L. monocytogenes. We hypothesized that a low pathogenicity of both quargel outbreak clones (QOC1 and QOC2) could have contributed to this discrepancy. Our hypothesis was falsified since both strains QOC1 and QOC2 are fully virulent in an oral infection mouse model, showing even higher pathogenicity than the reference strain EGDe., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Since 2012-2016 an increased number of listeriosis cases, especially from one region of the Czech Republic, were observed. Most of them were caused by strains of serotype 1/2a, clonal complex 8, indistinguishable by pulsed-field gel electrophoresis. Twenty-six human cases were reported, including two neonatal cases in twins. Three cases were fatal. The typing of Listeria monocytogenes isolates from food enabled to confirm a turkey meat delicatessen as the vehicle of infection for this local outbreak in the Moravian-Silesian Region. The food strains belonging to identical pulsotype were isolated from ready-to-eat turkey meat products packaged by the same producer between 2012 and 2016. This fact confirms that the described L. monocytogenes outbreak strain probably persisted in the environment of the aforementioned food-processing plant over several years. Whole-genome sequencing confirmed a very close relationship (zero to seven different alleles) between isolates from humans, foods and swabs from the environment of the food-processing plant under investigation.

Background and aimThe trend in reported case counts of invasive Listeria monocytogenes ( Lm ), a potentially severe food-borne disease, has been increasing since 2008. In 2015, 2,224 cases were reported in the European Union/European Economic Area (EU/EEA). We aimed to validate the microbiological and epidemiological aspects of an envisaged EU/EEA-wide surveillance system enhanced by routine whole genome sequencing (WGS). Methods: WGS and core genome multilocus sequence typing (cgMLST) were performed on isolates from 2,726 cases from 27 EU/EEA countries from 2010-15. Results: Quality controls for contamination, mixed Lm cultures and sequence quality classified nearly all isolates with a minimum average coverage of the genome of 55x as acceptable for analysis. Assessment of the cgMLST variation between six different pipelines revealed slightly less variation associated with assembly-based analysis compared to reads-based analysis. Epidemiological concordance, based on 152 isolates from 19 confirmed outbreaks and a cluster cutoff of seven allelic differences, was good (sensitivity > 95% for two cgMLST schemes of 1,748 and 1,701 loci each; PPV 58‒68%). The proportion of sporadic cases was slightly below 50%. Of remaining isolates, around one third were in clusters involving more than one country, often spanning several years. Detection of multi-country clusters was on average several months earlier when pooling the data at EU/EEA level, compared with first detection at national level. Conclusions : These findings provide a good basis for comprehensive EU/EEA-wide, WGS-enhanced surveillance of listeriosis. Time limits should not be used for hypothesis generation during outbreak investigations, but should be for analytical studies.

Listeria monocytogenes, a ubiquitous bacterium in nature, can lead to human listeriosis through food consumption. Listeriosis is a rare, preventable, and treatable foodborne disease but can cause hospitalizations and fatalities. We reviewed the literature published in China to better understand the prevalence of L. monocytogenes in food products, incidence of human listeriosis, and characteristics of L. monocytogenes strains in China. The average prevalence of L. monocytogenes in Chinese food products in 28 provinces was 4.42%, with the highest prevalence of 8.91% in meat-poultry products, followed by aquatic animals, Chinese salad and salad, rice and flour products, and so on. Two hundred fifty-three invasive listeriosis cases were reported from 2011 to 2016 in 19 provinces, and the overall case-fatality rate was 25.7% with no deaths reported of pregnant women and children. L. monocytogenes strains were generally susceptible to most antibiotics, with ampicillin and penicillin G still effective in treatment. The predominant sequence types (STs) in food were ST9 and ST8, while clinically ST87 was most common ST in China. The national human listeriosis pilot surveillance started in 2013, and a total of 133 listeriosis cases have been collected until now. On the basis of the surveillance program, further research should be conducted to uncover the reason for the prevalence and pathogenic mechanism of the highly epidemiological hypervirulent ST87 strains in China.

Listeriosis is a foodborne disease with a high fatality rate, and infection is mostly transmitted through ready-to-eat (RTE) foods contaminated with Listeria monocytogenes, such as gravad/smoked fish, soft cheeses, and sliced processed delicatessen (deli) meat. Food products/dishes stored in vacuum or in modified atmospheres and with extended refrigerator shelf lives provide an opportunity for L. monocytogenes to multiply to large numbers toward the end of the shelf life. Elderly, pregnant women, neonates, and immunocompromised individuals are particularly susceptible to L. monocytogenes. Listeriosis in humans manifests primarily as septicemia, meningitis, encephalitis, gastrointestinal infection, and abortion. In the mid 1990s and early 2000s a shift from L. monocytogenes serovar 4b to serovar 1/2a causing human listeriosis occurred, and serovar 1/2a is becoming more frequently linked to outbreaks of listeriosis, particularly in Europe and Northern America. Consumer lifestyle has changed, and less time is available for food preparation. Modern lifestyle has markedly changed eating habits worldwide, with a consequent increased demand for RTE foods; therefore, more RTE and take away foods are consumed. There is a concern that many Listeria outbreaks are reported from hospitals. Therefore, it is vitally important that foods (especially cooked and chilled) delivered to hospitals and residential homes for senior citizens and elderly people are reheated to at least 72°C: cold food, such as turkey deli meat and cold-smoked and gravad salmon should be free from L. monocytogenes. Several countries have zero tolerance for RTE foods that support the growth of Listeria.

Listeriosis is a disease usually associated with the consumption of low-processed ready-to-eat food products contaminated by Listeria monocytogenes. In Italy, listeriosis has an incidence of 0.19-0.27 cases per 100000 persons. Since detailed information concerning the molecular characterization of listeriosis in the Italian Veneto region is currently lacking, we analyzed 36 L. monocytogenes clinical isolates collected between 2009 and 2014. Results show that the serotype 1/2a was the most represented among the tested samples. No antimicrobial resistance was detected in selected isolates representing the main pulsotypes.

Since 2006, the number of reported US listeriosis outbreaks associated with cheese made under unsanitary conditions has increased. Two-thirds were linked to Latin-style soft cheese, often affecting pregnant Hispanic women and their newborns. Adherence to pasteurization protocols and sanitation measures to avoid contamination after pasteurization can reduce future outbreaks.

Listeria monocytogenes causes foodborne outbreaks with high mortality. For improvement of outbreak cluster detection, the German consiliary laboratory for listeriosis implemented whole-genome sequencing (WGS) in 2015. A total of 424 human L. monocytogenes isolates collected in 2007 to 2017 were subjected to WGS and core-genome multilocus sequence typing (cgMLST). cgMLST grouped the isolates into 38 complexes, reflecting 4 known and 34 unknown disease clusters. Most of these complexes were confirmed by single nucleotide polymorphism (SNP) calling, but some were further differentiated. Interestingly, several cgMLST cluster types were further subtyped by pulsed-field gel electrophoresis, partly due to phage insertions in the accessory genome. Our results highlight the usefulness of cgMLST for routine cluster detection but also show that cgMLST complexes require validation by methods providing higher typing resolution. Twelve cgMLST clusters included recent cases, suggesting activity of the source. Therefore, the cgMLST nomenclature data presented here may support future public health actions., (Copyright © 2018 American Society for Microbiology.)

Unpasteurized dairy products are known to occasionally harbor Listeria monocytogenes and have been implicated in recent listeriosis outbreaks and numerous sporadic cases of listeriosis. However, the diversity and virulence profiles of L. monocytogenes isolates recovered from these products have not been fully described. Here we report a genomic analysis of 121 L. monocytogenes isolates recovered from milk, milk filters, and milking equipment collected from bovine dairy farms in 19 states over a 12-year period. In a multi-virulence-locus sequence typing (MVLST) analysis, 59 Virulence Types (VT) were identified, of which 25% were Epidemic Clones I, II, V, VI, VII, VIII, IX, or X, and 31 were novel VT. In a multi-locus sequence typing (MLST) analysis, 60 Sequence Types (ST) of 56 Clonal Complexes (CC) were identified. Within lineage I, CC5 and CC1 were among the most abundant, and within lineage II, CC7 and CC37 were the most abundant. Multiple CCs previously associated with central nervous system and maternal-neonatal infections were identified. A genomic analysis identified variable distribution of virulence markers, Listeria pathogenicity islands (LIPI) -1, -3, and -4, and stress survival island-1 (SSI-1). Of these, 14 virulence markers, including LIPI-3 and -4 were more frequently detected in one lineage (I or II) than the other. LIPI-3 and LIPI-4 were identified in 68% and 28% of lineage I CCs, respectively. Results of this analysis indicate that there is a high level of genetic diversity among the L. monocytogenes present in bulk tank milk in the United States with some strains being more frequently detected than others, and some being similar to those that have been isolated from previous non-dairy related outbreaks. Results of this study also demonstrate significant number of strains isolated from dairy farms encode virulence markers associated with severe human disease.

Zoonoses are diseases transmitted from animals to humans, posing a great threat to the health and life of people all over the world. According to WHO estimations, 600 million cases of diseases caused by contaminated food were noted in 2010, including almost 350 million caused by pathogenic bacteria. Campylobacter , Salmonella , as well as Yersinia enterocolitica and Listeria monocytogenes may dwell in livestock (poultry, cattle, and swine) but are also found in wild animals, pets, fish, and rodents. Animals, often being asymptomatic carriers of pathogens, excrete them with faeces, thus delivering them to the environment. Therefore, pathogens may invade new individuals, as well as reside on vegetables and fruits. Pathogenic bacteria also penetrate food production areas and may remain there in the form of a biofilm covering the surfaces of machines and equipment. A common occurrence of microbes in food products, as well as their improper or careless processing, leads to common poisonings. Symptoms of foodborne infections may be mild, sometimes flu-like, but they also may be accompanied by severe complications, some even fatal. The aim of the paper is to summarize and provide information on campylobacteriosis, salmonellosis, yersiniosis, and listeriosis and the aetiological factors of those diseases, along with the general characteristics of pathogens, virulence factors, and reservoirs.

Biodiversity analysis of the foodborne pathogen Listeria monocytogenes recently revealed four serotype 4b major hypervirulent clonal complexes (CCs), i.e., CC1, CC2, CC4, and CC6. Hypervirulence was indicated by overrepresentation of these clones, and serotype 4b as a whole, among human clinical isolates in comparison to food. However, data on potential source-dependent partitioning among serotype 4b clones in diverse regions are sparse. We analyzed a panel of 347 serotype 4b isolates, primarily from North America, to determine the distribution of clones in humans, other animals, food, and water. CC1, CC2, CC4, and CC6 predominated, but surprisingly, only three clones, i.e., CC2 and the singleton sequence types (STs) ST382 and ST639, exhibited significant source-dependent associations, with higher propensity for food (CC2) or water (ST382 and ST639) than other sources. Pairwise comparisons between human and food isolates identified CC4 as the only serotype 4b clone significantly overrepresented among human isolates. Our analysis also revealed several serotype 4b clones emerging in North America. Two such emerging clones, ST382 (implicated in several outbreaks since 2014) and ST639, were primarily encountered among human and water isolates. Findings suggest that in spite of the ubiquity of CC1, CC2, CC4, and CC6, regional heterogeneity in serotype 4b is substantially larger than previously surmised. Analysis of even large strain panels from one region may not adequately predict clones unique to, and emerging in, other areas. Serotype 4b clonal complexes may differ in ecological niche preference, suggesting the need to further elucidate reservoirs and vehicles, especially for emerging clones. IMPORTANCE In Listeria monocytogenes , serotype 4b strains are leading contributors to human disease, but intraserotype distributions among different sources and regions remain poorly elucidated. Analysis of 347 serotype 4b isolates from four different sources, mostly from North America, confirmed the overall predominance of the major clones CC1, CC2, CC4, and CC6 but found that only CC4 was significantly associated with human disease, while CC2 was significantly associated with food. Remarkably, several emerging clones were identified among human isolates from North America, with some of these also exhibiting a propensity for surface water. The latter included the singleton clones ST382, implicated in several outbreaks in the United States since 2014, and ST639. These clones were noticeably underrepresented among much larger panels from other regions. Though associated with North America for the time being, they may eventually become globally disseminated through the food trade or other venues., (Copyright © 2018 Lee et al.)

In May 2016, two separate clusters of febrile gastroenteritis caused by Listeria monocytogenes were detected by the local health authority in Piedmont, in northern Italy. We carried out epidemiological, microbiological and traceback investigations to identify the source. The people affected were students and staff members from two different schools in two different villages located in the Province of Turin; five of them were hospitalised. The epidemiological investigation identified a cooked beef ham served at the school canteens as the source of the food-borne outbreak. L. monocytogenes was isolated from the food, the stools of the hospitalised pupils and the environment of the factory producing the cooked beef ham. All isolates except one were serotype 1/2a, shared an indistinguishable PFGE pattern and were 100% identical by whole genome sequencing (WGS). By combining a classical epidemiological approach with both molecular subtyping and WGS techniques, we were able to identify and confirm a Listeria gastroenteritis outbreak associated with consumption of sliced cold beef ham.

Background: Listeriosis caused by Listeria monocytogenes has a high case-fatality rate (CFR) of approximately 20% to 30%. An increasing incidence of listeriosis has been reported in many countries recently. We investigated the annual incidence, clinical characteristics, and outcomes of listeriosis at three different hospitals in Korea and evaluated the effects of appropriate empiric antimicrobial treatments on patient outcomes., Methods: We retrospectively collected the data of all culture-positive cases of human listeriosis from three hospitals of different sizes in Korea during 2006-2016 and calculated the annual number of cases and incidence per 100,000 admissions., Results: A total of 58 patients with L. monocytogenes were included in this study. The incidence of listeriosis was significantly higher in 2013-2016 than in 2006-2012 (RR 3.1; 95% CI 1.79-5.36; P<0.001), mainly because of an increase in patients over 60 years of age (RR 3.69; 95% CI 1.70-8.02; P<0.001). Multivariate analysis showed that healthcare-associated infection (adjusted OR, 12.15; 95% CI, 2.56-86.01; P=0.004) and empirical treatment with first-line antimicrobial agents (adjusted OR, 0.08; 95% CI, 0.00-0.63; P=0.044) were associated with CFR., Conclusions: Healthcare-associated infections caused by L. monocytogenes are associated with high CFR. Adequate initial empirical treatments could reduce CFR, suggesting that careful consideration of an empirical antimicrobial regimen is warranted for elderly or immunocompromised patients admitted to the hospital., Competing Interests: We declare that we have no conflicts of interest., (© The Korean Society for Laboratory Medicine)

Listeria monocytogenes infections are an important disease of ruminants worldwide, causing encephalitis, septicemia, and abortions. Ruminant listeriosis can also pose a food safety risk due to the potential for L. monocytogenes to enter the food supply via the farm environment. Data on the genetic diversity of L. monocytogenes from ruminant clinical cases in the United States is limited. Our goal was to assess the genetic diversity of clinical listeriosis isolates from ruminants in the Upper Great Plains states, a population not well-studied, and compare this population to isolates from ruminants in New York State. Multi-locus sequence typing (MLST) was used to classify and compare the genetic diversity of the isolates from the two regions. Loci sequences were compared to all known sequence types using the Pasteur Institute L. monocytogenes MLST database. Four novel sequence types (ST) were identified among the Upper Great Plains isolates, and four new STs were classified in the New York collection. Five STs were found to be common across the 2 geographical regions; ST 1, 7, 191, and 204. Strains of ST 7 were most frequently isolated (7/46 isolates). Strains of ST 91 were all associated with fetal infections from the Upper Great Plains. Our results demonstrate that while there are some subtypes commonly found between the two geographic regions, there are also subtypes distinct to each region., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This study analyses the epidemiologic, clinical and molecular findings of all culture-confirmed cases of listeriosis notified from 2010 to 2015 in the Tel Aviv District, which is known to have high rates of listeriosis. All clinical isolates of Listeria monocytogenes were subtyped using two-enzyme pulsed-field gel electrophoresis. During the studied period, 102 cases of listeriosis were notified, including 23 pregnancy-associated cases (23%). Among 79 non-pregnancy-associated cases, 18 had neuro-invasive disease (21%). There were 26 deaths associated with the disease. Using molecular identification, we found a number of clusters of identical bacterial clones, which pointed to possible sources of infection. The high rates of morbidity and mortality resulting from listeriosis, as well as the diverse ways of infection demonstrated in this study, accentuate the need to boost public health actions, in order to raise awareness and better control high-risk contamination routes.

This study aimed to investigate the prevalence and molecular characteristics of Listeria monocytogenes in cooked products in Zigong City, China. The overall occurrence of the L. monocytogenes in the ready-to-eat (RTE) shops and mutton restaurants surveyed was 16.2% (141/873). An occurrence of 13.5% was observed in RTE pork, 6.5% in RTE vegetables, and more than 24.0% in either cooked mutton or cooked haggis. Serotype 1/2b (45.4%), 1/2a (33.3%), and 1/2c (14.2%) were the predominant types. By comparing the clonal complexes (CCs) based on multilocus sequence typing (MLST) of the L. monocytogenes from cooked foods in Zigong City and 33 listeriosis cases from different districts of China, CC87, CC9, CC8, and CC3 were showed to be prevalent in cooked products and CC87 and CC3 were the first two frequent types in the 33 clinic-source strains. All CC87 stains harbored the newly reported Listeria pathogenicity island 4 (LIPI-4) gene fragment ptsA, and all CC3 strains possessed the Listeria pathogenicity island 3 (LIPI-3) gene fragment llsX. These may increase the occurrence of the strains belonging to CC87 and CC3 in listeriosis cases in China and also underline the risk of infection owing to the consumption of the cooked products from Zigong. ST619 (serotype 1/2b) harbored both llsX and ptsA, indicating a potential hypervirulent sequence type in Zigong.

The molecular epidemiology of Listeria monocytogenes was investigated in a longitudinal study of three Finnish dairy farms during 2013 to 2016. A total of 186 bulk tank milk (BTM), 224 milk filter sock (MFS), and 1,702 barn environment samples were analyzed, and isolates of L. monocytogenes were genotyped using pulsed-field gel electrophoresis. L. monocytogenes occurred throughout the year in all sample types, and the prevalence in MFS increased significantly during the indoor season. L. monocytogenes was more prevalent in MFS (29%) than in BTM (13%) samples. However, the prevalence of L. monocytogenes varied more between farms in samples of MFS (13 to 48%) than in BTM (10 to 16%). For each farm, the L. monocytogenes genotypes detected were classified by persistence (defined as persistent if isolated from ≥3 samples during ≥6 months) and predominance (defined as predominant if >5% prevalence on at least one farm visit). The prevalence of sporadic genotypes was 4 to 5% on all three farms. In contrast, the prevalence of persistent predominant genotypes varied between farms by 4% to 16%. The highest prevalence of persistent predominant genotypes was observed on the farm with the poorest production hygiene. Persistent predominant genotypes were most prevalent on feeding surfaces, water troughs, and floors. Genotypes isolated from the milking system or from cow udders had a greater relative risk of occurring in BTM and MFS than genotypes that only occurred elsewhere in the farm, supporting the hypothesis that L. monocytogene s is transmitted to milk from contamination on the udder surface or in the milking equipment. IMPORTANCE Listeria monocytogenes is a ubiquitous environmental bacterium and the causative agent of a serious foodborne illness, listeriosis. Dairy products are common vehicles of listeriosis, and dairy cattle farms harbor L. monocytogenes genotypes associated with human listeriosis outbreaks. Indeed, dairy cattle farms act as a reservoir of L. monocytogenes , and the organism is frequently detected in bulk tank milk (BTM) and in the feces of clinically healthy cows. The ecology of L. monocytogenes in the farm environment is complex and poorly understood. Isolates of the same L. monocytogenes genotype can occur in the farm for years, but the factors contributing to the persistence of genotypes on dairy farms are unknown. Knowledge of the persistence patterns and contamination routes of L. monocytogenes on dairy farms can improve management of the contamination pressure in the farm environment and aid in the development of focused control strategies to reduce BTM contamination., (Copyright © 2018 American Society for Microbiology.)

Listeria monocytogenes is among the most important foodborne pathogens, which can be isolated from bird feces. The aim of this study was to examine the prevalence, genotypes, virulence factors and drug-resistance characteristics of L. monocytogenes isolated from the black-headed gull in Kunming, China. Serotypes and virulence genes were identified by polymerase chain reaction. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) methods were used to describe the genetic characteristics of all positive isolates. Furthermore, all L. monocytogenes isolates were tested for antimicrobial susceptibility by disk diffusion method. All isolates were positive for inlA, inlB, plcB, prfA, iap, actA and hly genes. Serotyping showed the isolates belonged to serotype 1/2b (2/9, 22%), 1/2c (3/9, 33%), and 4a (4/9, 44%). PFGE showed 4 different pulsotypes (PTs), and MLST differentiated the 9 isolates into 4 sequence types (STs), ST3 (1), ST5 (1), ST35 (3) and ST201 (4). The result of antimicrobial susceptibility revealed that all isolates were naturally sensitive to most antibiotics. The L. monocytogenes isolates had pathogenic potential. There is a potential infection risk for people who come to frequent contact with black-headed gulls in Kunming. Hence, it is necessary to conduct surveillance of L. monocytogenes in the migratory black-headed gulls, which would be valuable to prevent listeriosis in local residents and tourists., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: To compare the symptomatology of pregnant women with suspected listeriosis to culture confirmed listeriosis., Study Design: All cases of suspected and culture confirmed pregnancy-associated listeriosis from a single center were retrospectively reviewed assessing demographics, clinical, laboratory and pathological findings, and maternal, fetal and neonatal outcomes., Results: Listeriosis was identified in seven patients, none of whom belonged to the 117 women with suspected listeriosis. Women with confirmed infection were more likely to exhibit fever (P=0.01), flu-like symptoms (P=0.006), threatened preterm labor (P=0.05) and inflammatory markers (P=0.02), but less likely to exhibit gastrointestinal complaints (P=0.004) in comparison with suspected non-confirmed cases. Confirmed cases resulted in preterm delivery (n=5) and stillbirth (n=2). Neonatal complications included meningitis, respiratory disease and sepsis. Maternal outcomes were favorable., Conclusion: Although 'febrile gastroenteritis' is a poor predictor of listeriosis in pregnancy, fever, premature contractions and inflammatory markers are important risk indices prompting workup and adequate empiric treatment.

In August 2017, an outbreak of six listeriosis cases in Denmark was traced to cold-smoked salmon, using epidemiological investigations and whole-genome sequencing (WGS) analyses. Exchange of genome sequences allowed identification in France of a food isolate from a salmon-derived product and a human isolate from 2016 within the same cgMLST cluster as the Danish isolates (L2-SL8-ST8-CT771). The salmon product came from a third European Union country. WGS can rapidly link human cases and food isolates across Europe.

Listeria monocytogenes raises major food safety and public health concerns due to its potential for severe foodborne disease and persistent colonization of food processing facilities. Copper is often employed to control pathogens in agriculture and is increasingly used in healthcare facilities, but mechanisms mediating tolerance of L. monocytogenes to copper remain poorly understood. A mariner-based mutant library of L. monocytogenes 2011L-2858, implicated in the 2011 listeriosis outbreak via whole cantaloupe, was screened for growth at sublethal levels of copper yielding mutant G2B4 with decreased copper tolerance. The transposon was localized in pbp4 (lmo2229 homolog), encoding a penicillin-binding protein (PBP). In addition to reduced copper tolerance, G2B4 exhibited increased susceptibility to β-lactam antibiotics, reduced biofilm formation and reduced virulence in the Galleria mellonella model. Mutant phenotypes were fully restored upon genetic complementation of G2B4 with intact pbp4. Findings provide the first evidence for the role of a PBP in copper tolerance of L. monocytogenes and suggest that pbp4 may be a suitable target to enable the use of lower levels of copper or enhance the effectiveness of levels currently in use. Given the wide distribution of PBPs and their highly conserved nature, this could have profound impacts in regard to ecology and control of L. monocytogenes and other microorganisms., (© FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Listeria monocytogenes is a foodborne pathogen that contaminates food-processing environments and persists within biofilms on equipment, utensils, floors, and drains, ultimately reaching final products by cross-contamination. This pathogen grows even under high salt conditions or refrigeration temperatures, remaining viable in various food products until the end of their shelf life. While the estimated incidence of listeriosis is lower than other enteric illnesses, infections caused by L. monocytogenes are more likely to lead to hospitalizations and fatalities. Despite the description of L. monocytogenes occurrence in Brazilian food-processing facilities and foods, there is a lack of consistent data regarding listeriosis cases and outbreaks directly associated with food consumption. Listeriosis requires rapid treatment with antibiotics and most drugs suitable for Gram-positive bacteria are effective against L. monocytogenes. Only a minority of clinical antibiotic-resistant L. monocytogenes strains have been described so far; whereas many strains recovered from food-processing facilities and foods exhibited resistance to antimicrobials not suitable against listeriosis. L. monocytogenes control in food industries is a challenge, demanding proper cleaning and application of sanitization procedures to eliminate this foodborne pathogen from the food-processing environment and ensure food safety. This review focuses on presenting the L. monocytogenes distribution in food-processing environment, food contamination, and control in the food industry, as well as the consequences of listeriosis to human health, providing a comparison of the current Brazilian situation with the international scenario.

Objective: To analyze the clinical characteristics and perinatal outcomes of listeriosis during pregnancy. Methods: From July 2010 to April 2017, 70 131 women delivered in West China Second University Hospital. Nineteen cases were confirmed as listeriosis. The clinical symptoms, laboratory results, pathogens, placenta pathology and perinatal outcomes were analyzed retrospectively. Results: The median age of the 19 cases was 29.7 (19.0-42.0) years old. The median time before diagnosis was 4.8(0.5-19.0) days. The main clinical symptoms at first visits were high fever (17/19), increased white blood cells (18/19), abdominal pain (12/19). Listeria was found in samples of mother's blood (11/19), vaginal secretions (15/19), placenta (1/19), neonatal blood (4/19), neonatal phlegm (5/19) and neonatal ear secretions (1/19), respectively. Inflammation of placenta was identified in all 19 cases. Among the 19 cases, 1 was grade Ⅰ chorioamnionitis, 4 was grade Ⅱ, 5 was grade Ⅲ and 9 was grade Ⅵ. Only 4 newborn survived after therapy, and others suffered perinatal death, including 8 cases of intrauterine death, 3 cases of miscarriage and 6 cases of treatment failure. Conclusions: Listeriosis has characteristics of acute onset, quick development and high morbidity during pregnancy. The empiric use of antibiotics might not cover listeria. The understanding of listeriosis should be improved.

A total of 765 samples were collected from beef carcasses, knives, cutting table surfaces, beef, hands, air, and water from four cattle slaughterhouses of Kerala, South India, to determine the occurrence and antibiotic susceptibility of Listeria species and Staphylococcus aureus. Listeria spp. were isolated from beef carcasses (2.0%), knives (3.7%), cutting table surfaces (1.9%), beef (0.7%), and water (1.3%). The identified species were Listeria monocytogenes (0.1%), Listeria innocua (0.9%), and Listeria ivanovii (0.4%). Most of the Listeria spp. were susceptible to majority of the antibiotics tested. The virulence genes were not detected in Listeria spp. However, all the L. innocua isolates were found to harbor the iap gene. The overall occurrence of S. aureus in slaughterhouses was 50.8%. The highest occurrence was observed on hands of abattoir workers (79.6%) and beef carcasses (59.9%). The isolates were commonly resistant to penicillin (38.0%), followed by ceftriaxone (31.9%), ampicillin (29.0%), amoxicillin (28.8%), tetracycline (24.4%), and chloramphenicol (23.9%). Overall, 53.0% of S. aureus isolates were resistant to three or more antibiotics. Vancomycin and methicillin resistance were observed in 8.5% and 5.4% of S. aureus isolates, respectively. Eight methicillin-resistant S. aureus isolates were found to harbor the mecA gene. In conclusion, Listeria spp. was only rarely found in the slaughterhouse environment and on beef. Nevertheless, the recovery of L. monocytogenes from a water reservoir containing sea water that was used to wash carcasses indicates the potential risk of contamination of the carcasses with L. monocytogenes when using sea water. S. aureus was frequently isolated from abattoir workers and beef carcasses, and the occurrence of S. aureus differed significantly between slaughterhouses. The high occurrence of S. aureus, which were often resistant toward different antibiotics, represents a significant public health concern.

We investigated 543 Listeria monocytogenes isolates from food having a temporal and spatial distribution compatible with that of the invasive listeriosis outbreak occurring 2012-2016 in southern Germany. Using forensic microbiology, we identified several products from 1 manufacturer contaminated with the outbreak genotype. Continuous molecular surveillance of food isolates could prevent such outbreaks.

Salmonella and Listeria monocytogenes are important human pathogens that can be isolated from the faeces of ruminants, and constitute potential sources of human infection via contamination of food and water or contact (direct or indirect) between humans and animals. A cross-sectional survey including 301 herds was carried out to estimate the prevalence of cattle herds (beef and dairy) and sheep flocks positive for these zoonotic organisms in ruminants in the Basque Country (Northern Spain). The proportion of herds where Salmonella shedding was detected was 5.8% for beef cattle, 3.7% for dairy cattle and 6.1% for sheep flocks. Apart from a multi-drug resistant (ASuT) monophasic variant of S. Typhimurium (4,[5],12:i:-) isolated from a beef cattle herd, the remaining 11 serotypes of S. enterica identified were not among the common causes of non-typhoidal salmonellosis in humans. L. monocytogenes was isolated from 42.3% of beef cattle herds, 46.3% of dairy cattle herds, and a significantly lower proportion of sheep flocks (23.5%). Presence of other animal species in the farm and geographical location were associated with herd risk of L. monocytogenes shedding. A total of 65.8% of the isolates of L. monocytogenes harboured the virulence gene, llsX, as determined by real-time PCR. In conclusion, ruminant herds in the Basque Country did not seem to pose a high risk for Salmonella serotypes commonly associated to human clinical cases of salmonellosis entering the food chain. Conversely, potentially pathogenic L. monocytogenes strains were widespread in ruminant farms, mostly in cattle., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Salmonellosis, campylobacteriosis and listeriosis are food-borne diseases. We estimated and forecasted the number of cases of these three diseases in Belgium from 2012 to 2020, and calculated the corresponding number of disability-adjusted life years (DALYs). The salmonellosis time series was fitted with a Bai and Perron two-breakpoint model, while a dynamic linear model was used for campylobacteriosis and a Poisson autoregressive model for listeriosis. The average monthly number of cases of salmonellosis was 264 (standard deviation (SD): 86) in 2012 and predicted to be 212 (SD: 87) in 2020; campylobacteriosis case numbers were 633 (SD: 81) and 1,081 (SD: 311); listeriosis case numbers were 5 (SD: 2) in 2012 and 6 (SD: 3) in 2014. After applying correction factors, the estimated DALYs for salmonellosis were 102 (95% uncertainty interval (UI): 8-376) in 2012 and predicted to be 82 (95% UI: 6-310) in 2020; campylobacteriosis DALYs were 1,019 (95% UI: 137-3,181) and 1,736 (95% UI: 178-5,874); listeriosis DALYs were 208 (95% UI: 192-226) in 2012 and 252 (95% UI: 200-307) in 2014. New actions are needed to reduce the risk of food-borne infection with Campylobacter spp. because campylobacteriosis incidence may almost double through 2020., (This article is copyright of The Authors, 2017.)

Listeria monocytogenes is an important cause of foodborne illness hospitalization, fetal loss, and death in the United States. Listeriosis incidence rate varies significantly among population subgroups with pregnant women, older persons, and the Hispanic population having increased relative risks compared with the other subpopulations. Using estimated rates of listeriosis per subpopulation based on FoodNet data from 2004 to 2009, we evaluate the expected number of cases and incidence rates of listeriosis in the US population and the pregnant women subpopulation as the demographic composition changes over time with respect to ethnicity, pregnancy status, and age distribution. If the incidence rate per subpopulation is held constant, the overall US population listeriosis incidence rate would increase from 0.25 per 100,000 (95% confidence interval [CI]: 0.19-0.34) in 2010 to 0.28 (95% CI: 0.22-0.38) in 2020 and 0.32 (95% CI: 0.25-0.43) in 2030, because of the changes in the population structure. Similarly, the pregnancy-associated incidence rate is expected to increase from 4.0 per 100,000 pregnant women (95% CI: 2.5-6.5) in 2010 to 4.1 (95% CI: 2.6-6.7) in 2020 and 4.4 (95% CI: 2.7-7.2) in 2030 as the proportion of Hispanic pregnant women increases. We further estimate that a reduction of 12% in the exposure of the US population to L. monocytogenes would be needed to maintain a constant incidence rate from 2010 to 2020 (current trend), assuming infectivity (strain virulence distribution and individual susceptibility) is unchanged. To reduce the overall US population incidence rate by one-third (Healthy People 2020 goal) would require a reduction in exposure (or infectivity) to L. monocytogenes of 48% over the same time period. Reduction/elimination in exposure of pregnant and Hispanic subpopulations alone could not meet this target. This information may be useful in setting public health targets, developing risk management options, and in interpreting trends in the public health burden of foodborne listeriosis in the United States.

Listeria monocytogenes is a Gram-positive bacillus and facultative intracellular bacterium whose transmission occurs mainly through the consumption of contaminated food. Listeriosis has an incidence estimated at around three-six cases per million per year and the most common forms of the infection are neurolisteriosis, bacteraemia, and maternal-neonatal infection. Those affected by listeriosis are at the extremes age of the life or report specific risk factors, such as malignancies, causing a defect of cellular immunity. Patients with L. monocytogenes meningitis present with signs and symptoms similar to those reported in the general population with community-acquired bacterial meningitis, but can experience a longer prodromal phase. Instead, patients with bacteraemia present generally with a febrile illness without focal symptoms, or with influenza-like symptoms and diarrhoea. These aspecific findings make the diagnosis difficult in the population of patients at the highest risk such as cirrhotics or those receiving chemotherapy. Mortality rate is estimated around 20% with a significant increase among those reporting a delay in diagnosis and treatment and in those with severe comorbidity. A number of antibiotics have been demonstrated to be active against L. monocytogenes, but penicillin, amoxicillin, and ampicillin are those used with the highest frequency and suggested by current guidelines and expert opinions. These antibiotics bind to PBP-3 with high affinity and are stored in the cytosol when taken up by cells. Although amoxicillin appears to have a better activity than ampicillin on the basis of in vitro studies, ampicillin is currently the drug of choice for the treatment of listeriosis. Cotrimoxazole could be administered as an alternative treatment; its use is associated with a favourable outcome probably due to the favourable penetration with brain. Quinolones have an excellent tissue and cell penetration and are rapidly bactericidal, but their clinical activity is not as high as we can predict on the basis of experimental model. Linezolid offers a number of advantages in the empiric treatment of meningitis due to its favourable penetration of CSF and the absence of bacteriolytic effect on S. pneumoniae as confirmed by a number of case-series highlighting its use as rescue therapy of pneumococcal meningitis, but data are currently limited particularly if we consider neurolisteriosis. Combination therapies have been proposed to enhance the activity of penicillins against Listeria in an attempt to achieve complete killing and decrease mortality. Steroids use is ineffective.

During 2015-2016, we evaluated the performance of whole-genome sequencing (WGS) as a routine typing tool. Its added value for microbiological and epidemiologic surveillance of listeriosis was compared with that for pulsed-field gel electrophoresis (PFGE), the current standard method. A total of 2,743 Listeria monocytogenes isolates collected as part of routine surveillance were characterized in parallel by PFGE and core genome multilocus sequence typing (cgMLST) extracted from WGS. We investigated PFGE and cgMLST clusters containing human isolates. Discrimination of isolates was significantly higher by cgMLST than by PFGE (p<0.001). cgMLST discriminated unrelated isolates that shared identical PFGE profiles and phylogenetically closely related isolates with distinct PFGE profiles. This procedure also refined epidemiologic investigations to include only phylogenetically closely related isolates, improved source identification, and facilitated epidemiologic investigations, enabling identification of more outbreaks at earlier stages. WGS-based typing should replace PFGE as the primary typing method for L. monocytogenes.