Mortality risk factors for listeriosis – A 10 year review of non-pregnancy associated cases in England 2006–2015

Risk factors associated with food consumption and food-handling habits for sporadic listeriosis: a case-control study in China from 2013 to 2022

The prevalence of listeriosis in China has been increasing in recent years. Listeriosis primarily spreads through contaminated food. However, the resilient causative organism, Listeria monocytogenes, and its extended incubation period pose challenges in identifying risk factors associated with food consumption and food-handling habits. This study aimed to identify the risk factors associated with food consumption and food-handling habits for listeriosis in China. A matched case-control study (1:1 ratio) was conducted, which enrolled all eligible cases of listeriosis between 1 January 2013 and 31 December 2022 in China. Basic information and possible risk factors associated with food consumption and food-handling habits were collected. Overall, 359 patients were enrolled, including 208 perinatal and 151 non-perinatal cases. Univariate and multivariable logistic analyzes were performed for the perinatal group. For the perinatal and non-perinatal groups, ice cream and Chinese cold dishes were the high-risk foods for listeriosis (odds ratio (OR) 2.09 95% confidence interval (CI): 1.23-3.55; OR 3.17 95% CI: 1.29-7.81), respectively; consumption of leftovers and pet ownership were the high-risk food-handling habits (OR 1.92 95% CI: 1.03-3.59; OR 3.00 95% CI: 1.11-8.11), respectively. In both groups, separation of raw and cooked foods was a protective factor (OR 0.27 95% CI: 0.14-0.51; OR 0.35 95% CI: 0.14-0.89), while refrigerator cleaning reduced the infection risk by 64.94-70.41% only in the perinatal group. The identification of high-risk foods and food-handling habits for listeriosis is important for improving food safety guidelines for vulnerable populations.

Gentamicin combination treatment is associated with lower mortality in patients with invasive listeriosis: a retrospective analysis

PURPOSE

Listeria monocytogenes causes severe bacterial infections with the highest mortality rate among foodborne pathogens in Europe. Combination treatment with ampicillin and gentamicin is recommended for invasive manifestations. However, evidence to support this treatment approach remains limited due to a lack of randomised controlled trials. To explore this critical issue further, we conducted this retrospective, single-center study.

METHODS

We identified all patients hospitalized with invasive listeriosis at the University Medical Center Hamburg-Eppendorf between 2009 and 2020 and analyzed the effect of gentamicin combination treatment versus monotherapy on 90-day mortality.

RESULTS

In total, 36 patients with invasive listeriosis were included, of which 21 patients received gentamicin combination treatment and 15 received monotherapy. The mean age-adjusted Charlson Comorbidity Index (aaCCI) value was lower in the gentamicin combination treatment group (5.4 vs. 7.4). Neurolisteriosis was more common in the gentamicin group (81% vs. 20%). The 90-day mortality was with significantly lower in the gentamicin combination treatment group (10%) compared to the monotherapy group (60%). Multivariable cox regression analysis, adjusted for a propensity score computed based on neurolisteriosis, aaCCI and sex, revealed a significantly reduced hazard ratio of 0.07 (95% CI: 0.01-0.53, p = 0.01) for 90-day mortality for the gentamicin combination treatment.

CONCLUSION

This retrospective study highlights the benefit of gentamicin combination treatment in reducing the 90-day mortality rate among patients with invasive listeriosis. The high prevalence of monotherapy in this study cohort raises concerns about the adequacy of antibiotic therapy in clinical practice.

Genomic characterization of Listeria monocytogenes recovered from dairy facilities in British Columbia, Canada from 2007 to 2017

Listeria monocytogenes is a foodborne pathogen of concern in dairy processing facilities, with the potential to cause human illness and trigger regulatory actions if found in the product. Monitoring for Listeria spp. through environmental sampling is recommended to prevent establishment of these microorganisms in dairy processing environments, thereby reducing the risk of product contamination. To inform on L. monocytogenes diversity and transmission, we analyzed genome sequences of L. monocytogenes strains (n = 88) obtained through the British Columbia Dairy Inspection Program. Strains were recovered from five different dairy processing facilities over a 10 year period (2007-2017). Analysis of whole genome sequences (WGS) grouped the isolates into nine sequence types and 11 cgMLST types (CT). The majority of isolates (93%) belonged to lineage II. Within each CT, single nucleotide polymorphism (SNP) differences ranged from 0 to 237 between isolates. A highly similar (0-16 SNPs) cluster of over 60 isolates, collected over 9 years within one facility (#71), was identified suggesting a possible persistent population. Analyses of genome content revealed a low frequency of genes associated with stress tolerance, with the exception of widely disseminated cadmium resistance genes cadA1 and cadA2. The distribution of virulence genes and mutations within internalin genes varied across the isolates and facilities. Further studies are needed to elucidate their phenotypic effect on pathogenicity and stress response. These findings demonstrate the diversity of L. monocytogenes isolates across dairy facilities in the same region. Findings also showed the utility of using WGS to discern potential persistence events within a single facility over time.

Listeria monocytogenes bacteremia developed during treatment of COVID-19

Listeria monocytogenes is an important pathogen in older patients and immunosuppressed patients, often causing bacteremia. Complications resulting from infections other than COVID-19 must also be considered during COVID-19 treatment.

The Clinical Characteristics, Diagnostic Methods, Treatment, and Outcomes of Listeria monocytogenes Meningoencephalitis: A Case Series Study from China

Background

Listeria monocytogenes meningoencephalitis (LMM) is a rare but dangerous infection of the nervous system. This study intends to summarize and discuss the clinical features, diagnostic methods, treatment, and outcomes.

Methods

LMM patients treated in the First Affiliated Hospital of Zhengzhou University from June 2013 to December 2022 were retrospectively studied. The clinical data, magnetic resonance imaging (MRI), biochemical and hematological parameters, pathogen tests, treatments, and outcomes information were collected and summarized.

Results

Ten LMM patients were enrolled in this study. Three were female and seven were male, with a mean age of 54.5 years old. Seven (70%) of the patients had chronic conditions that either affected the liver (1 case), heart (1 case), or immune system (5 cases). The main clinical manifestations were fever (100%), headache, (60%), and disturbance of consciousness (60%). Out of the nine patients taken MRI, enhanced magnetic resonance imaging was observed with cerebral parenchyma and meningeal enhancement in 3 patients, whereas six patients showed non-specific abnormal signals and brain edema. Seven (70%) patients were positive for L. monocytogenes by bacterial culture and five patients were positive by further next-generation sequencing (NGS) test in CSF. All patients were treated with antibiotics based on antibiotic sensitivity tests or experience, with seven (70%) improved but three (30%) died within one month.

Conclusion

LMM patients have a high mortality rate. Considering the time and reliability of NGS reports, it would be better to identify L. monocytogenes infection in the CSF than bacterial culture. While, after diagnosis, giving timely and appropriate antibiotics would still be a challenge to achieve good outcomes.

Clinical Characteristics and Treatment of Listeria monocytogenes Infections in the Central Nervous System

Purpose

Listeria monocytogenes infections are rare in the central nervous system (CNS) and frequently difficult-to-diagnose. Our goal is to assess CNS listeriosis patients' clinical characteristics, diagnosis, treatment, and prognosis.

Patients and Methods

Patients with CNS listeriosis admitted to the Department of neurology, the first medical center of the Chinese PLA general hospital, were enrolled in this study from March 2018 to August 2022.

Results

This study analyzed eight adults, including five males and three females. The average age of onset was (50.25 ± 11.52) years. The clinical manifestations included fever, headache, altered mental status, vomiting, seizures, neck rigidity, hemiplegia and cranial nerve palsies. Cerebrospinal fluid (CSF) tests revealed intracranial hypertension, elevated cell count and protein concentration, and decreased glucose levels. The positive rates of blood and CSF culture were 40% and 28.57%, respectively. All patients underwent CSF metagenomic next-generation sequencing (mNGS), with a 100% positive rate and the specific read number 12-20394. Magnetic resonance imaging (MRI) exhibited leptomeningitis, meningoencephalitis, and brain abscess, and no specific changes were discovered in two patients. All patients received antibiotic treatment, seven were cured, and one died.

Conclusion

Monitoring the proportion of monocytes in blood and mNGS results of CSF can play a crucial role in diagnosing pathogens. Early and sufficient application of two to three sensitive antibiotics with a BBB permeability of 20-30% for at least 2-3 months can significantly improve CNS listeriosis prognosis.

Cinnamaldehyde Targets the LytTR DNA-Binding Domain of the Response Regulator AgrA to Attenuate Biofilm Formation of Listeria monocytogenes

The Agr quorum sensing (QS) system is known to contribute to biofilm formation in Listeria monocytogenes. Cinnamaldehyde, a natural food preservative, is considered an inhibitor of Agr-mediated QS in L. monocytogenes. However, the exact mechanism by which cinnamaldehyde acts on Agr remains unclear. In this study, we assessed the effects of cinnamaldehyde on the histidine kinase AgrC and the response regulator AgrA in the Agr system. AgrC kinase activity was not influenced by cinnamaldehyde, and binding between AgrC and cinnamaldehyde was not observed when microscale thermophoresis (MST) was performed, indicating that AgrC was not the target of cinnamaldehyde. AgrA is specifically bound to the agr promoter (P2) to activate the transcription of the Agr system. However, AgrA-P2 binding was prevented by cinnamaldehyde. The interaction between cinnamaldehyde and AgrA was further confirmed with MST. Two conserved amino acids, Asn-178 and Arg-179, located in the LytTR DNA-binding domain of AgrA, were identified as the key sites for cinnamaldehyde-AgrA binding by alanine mutagenesis and MST. Coincidentally, Asn-178 was also involved in the AgrA-P2 interaction. Taken together, these results suggest that cinnamaldehyde acts as a competitive inhibitor of AgrA in AgrA-P2 binding, which leads to suppressed transcription of the Agr system and reduced biofilm formation in L. monocytogenes. IMPORTANCE Listeria monocytogenes can form biofilms on various food contact surfaces, posing a serious threat to food safety. Biofilm formation of L. monocytogenes is positively regulated by the Agr quorum sensing system. Thus, an alternative strategy for controlling L. monocytogenes biofilms is interfering with the Agr system. Cinnamaldehyde is considered an inhibitor of the L. monocytogenes Agr system; however, its exact mechanism of action is still unclear. Here, we found that AgrA (response regulator), rather than AgrC (histidine kinase), was the target of cinnamaldehyde. The conserved Asn-178 in the LytTR DNA-binding domain of AgrA was involved in cinnamaldehyde-AgrA and AgrA-P2 binding. Therefore, the occupation of Asn-178 by cinnamaldehyde suppressed transcription of the Agr system and reduced biofilm formation in L. monocytogenes. Our findings could provide a better understanding of the mechanism by which cinnamaldehyde inhibits L. monocytogenes biofilm formation.

Human Listeriosis

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that can cause severe invasive infections upon ingestion with contaminated food. Clinically, listerial disease, or listeriosis, most often presents as bacteremia, meningitis or meningoencephalitis, and pregnancy-associated infections manifesting as miscarriage or neonatal sepsis. Invasive listeriosis is life-threatening and a main cause of foodborne illness leading to hospital admissions in Western countries. Sources of contamination can be identified through international surveillance systems for foodborne bacteria and strains' genetic data sharing. Large-scale whole genome studies have increased our knowledge on the diversity and evolution of L. monocytogenes, while recent pathophysiological investigations have improved our mechanistic understanding of listeriosis. In this article, we present an overview of human listeriosis with particular focus on relevant features of the causative bacterium, epidemiology, risk groups, pathogenesis, clinical manifestations, and treatment and prevention.

Mortality risk factors related to listeriosis - A meta-analysis

BACKGROUND

Relatively few studies have focused on mortality risk factors for listeriosis in the literature. Information on the mortality of populations with listeriosis is needed. We aimed to explore the mortality risk factors related to listeriosis in this meta-analysis.

METHODS

The studies were considered eligible for inclusion only if they directly compared the mortality risk factors for listeriosis between dead patients and surviving patients. The mortality risk factors included clinical predisposing factors and predisposing comorbidities.

RESULTS

Thirteen studies were included in this study. There were 12,265 listeriosis patients, including 2863 (23.3%) dead patients. The meta-analysis provided evidence that the mortality risk factors related to listeriosis were as follows: 1. Clinical predisposing factors included age ≥ 60 years, primary bacteremia and central nervous system involvement; 2. Predisposing comorbidities included non-hematological malignancies, alcoholism, chronic kidney disease, cardiovascular disease, and pulmonary disease. In addition, autoimmune disease comorbidity had a protective effect against listeriosis.

CONCLUSION

The presence of older patients, primary bacteremia, central nervous system involvement, non-hematological malignancies, alcoholism, chronic kidney disease, cardiovascular disease, and pulmonary disease should alert physicians to the higher risk of mortality.

Analysis of Clinical and Microbiological Features of Listeria monocytogenes Infection

Introduction

To analyze the demographics and clinical features of 59 cases of Listeria monocytogenes, and determine the predisposing conditions for severe meningitis infections for reference.

Materials and methods

A total of 59 cases isolated L. monocytogenes from 2009 to 2020 were enrolled. Electronic medical record data were used to determine the epidemiological and clinical characteristics of L. monocytogenes infection. Univariate and multifactorial logistic regression analyses were performed to predict risk factors for Listeria meningitis.

Results

A total of 59 cases (median age of 52 years, 30 females and 29 males) were enrolled. Twenty-five patients (42.37%) developed a neuroinvasive infection. The indexes of interleukin-6 (IL-6), CD3+T, CD4+T, and CD8+T cells in the study group were higher than those in the control group (P<0.05). In univariate analysis, the use of hormone drugs (odds ratio=3.21, P=0.000) and immunosuppressive agents (odds ratio=3.06, P=0.000) were relevant predictors of severe meningitis. 47 patients (79.66%) were treated with ampicillin (27.12%), carbapenems (18.64%), quinolones (11.86%), and β-lactamase inhibitors (11.86%) as the primary agents of antimicrobial therapy. Thirty-four patients (57.63%) showed clinical improvement, five patients (8.47%) had a poor prognosis, and two patients (3.39%) died.

Conclusion

Infection with Listeria changed the levels of IL-6, CD3+T, CD4+T, and CD8+T cells, and these analyzing items were significantly different between L. monocytogenes and other bacterial infections. Long-term use of immunosuppressants and hormones may be risk factors for severe adult forms of Listeria-related infections. Sensitive antibiotics, such as penicillins and carbapenems, should be added or replaced in the early empiric treatment of L. monocytogenes.

Listeria monocytogenes genes supporting growth under standard laboratory cultivation conditions and during macrophage infection

The Gram-positive bacterium Listeria monocytogenes occurs widespread in the environment and infects humans when ingested along with contaminated food. Such infections are particularly dangerous for risk group patients, for whom they represent a life-threatening disease. To invent novel strategies to control contamination and disease, it is important to identify those cellular processes that maintain pathogen growth inside and outside the host. Here, we have applied transposon insertion sequencing (Tn-Seq) to L. monocytogenes for the identification of such processes on a genome-wide scale. Our approach identified 394 open reading frames that are required for growth under standard laboratory conditions and 42 further genes, which become necessary during intracellular growth in macrophages. Most of these genes encode components of the translation machinery and act in chromosome-related processes, cell division, and biosynthesis of the cellular envelope. Several cofactor biosynthesis pathways and 29 genes with unknown functions are also required for growth, suggesting novel options for the development of antilisterial drugs. Among the genes specifically required during intracellular growth are known virulence factors, genes compensating intracellular auxotrophies, and several cell division genes. Our experiments also highlight the importance of PASTA kinase signaling for general viability and of glycine metabolism and chromosome segregation for efficient intracellular growth of L. monocytogenes.

Listeria monocytogenes Pathogenesis: The Role of Stress Adaptation

Adaptive stress tolerance responses are the driving force behind the survival ability of Listeria monocytogenes in different environmental niches, within foods, and ultimately, the ability to cause human infections. Although the bacterial stress adaptive responses are primarily a necessity for survival in foods and the environment, some aspects of the stress responses are linked to bacterial pathogenesis. Food stress-induced adaptive tolerance responses to acid and osmotic stresses can protect the pathogen against similar stresses in the gastrointestinal tract (GIT) and, thus, directly aid its virulence potential. Moreover, once in the GIT, the reprogramming of gene expression from the stress survival-related genes to virulence-related genes allows L. monocytogenes to switch from an avirulent to a virulent state. This transition is controlled by two overlapping and interlinked transcriptional networks for general stress response (regulated by Sigma factor B, (SigB)) and virulence (regulated by the positive regulatory factor A (PrfA)). This review explores the current knowledge on the molecular basis of the connection between stress tolerance responses and the pathogenesis of L. monocytogenes. The review gives a detailed background on the currently known mechanisms of pathogenesis and stress adaptation. Furthermore, the paper looks at the current literature and theories on the overlaps and connections between the regulatory networks for SigB and PrfA.

Kaempferol-Driven Inhibition of Listeriolysin O Pore Formation and Inflammation Suppresses Listeria monocytogenes Infection

Listeria monocytogenes remains a nonnegligible cause of foodborne infection, posing a critical threat to public health. Under the global antibiotic crisis, novel alternative approaches are urgently needed. The indispensable role of listeriolysin O (LLO) in the intracellular life cycle, barrier penetration, colonization, and systemic dissemination of L. monocytogenes renders it a potent drug target, which means curbing L. monocytogenes via interfering with LLO-associated pathogenic mechanisms. Here, we identified kaempferol, a natural small molecule compound, as an effective LLO inhibitor that engaged the residues Glu437, Ile468, and Tyr469 of LLO, thereby suppressing LLO-mediated membrane perforation and barrier disruption. Moreover, we found that kaempferol also suppressed host-derived inflammation in a distinct way independent of LLO inhibition. The in vivo study revealed that kaempferol treatment significantly reduced bacterial burden and cytokine burst in target organs, thereby effectively protecting mice from systemic L. monocytogenes infection. Our findings present kaempferol as a potential therapeutic application for L. monocytogenes infection, which is less likely to induce drug resistance than antibiotics because of its superiority of interfering with the pathogenesis process rather than exerting pressure on bacterial viability.

IMPORTANCE Currently, we are facing a global crisis of antibiotic resistance, and novel alternative approaches are urgently needed to curb L. monocytogenes infection. Our study demonstrated that kaempferol alleviated L. monocytogenes infection via suppressing LLO pore formation and inflammation response, which might represent a novel antimicrobial-independent strategy to curb listeriosis.

Contamination by Listeria monocytogenes in Latin American Meat Products and Its Consequences

Background and objective:

Listeria monocytogenes is one of the most important bacteria in food technology, causing listeriosis, a disease with high mortality rates, important especially in developing countries. Thus, the objective of this review was to gather recent work on the presence of L. monocytogenes in meat and meat products in Latin America, in addition to pointing out control methods and resistance genes that can be disseminated.

Methods:

Original research articles in Portuguese, Spanish and English published since 2017 were selected, reporting the presence of L. monocytogenes in meat and meat products in Latin American countries. Articles were also reviewed on innovative methods for controlling the bacteria in food, such as intelligent packaging and the use of essential oils, and on resistance genes found in L. monocytogenes, pointing out the possible implications of this occurrence.

Results and conclusion:

Some negligence was observed in determining the prevalence of this bacterium in several countries in Latin America. Although studies on L. monocytogenes have been found in milk and dairy products, demonstrating the existence of the necessary structure and knowledge for research development, studies on meat and meat products have not been found in most countries. In control methods developed against L. monocytogenes, the versatility of the approaches used stands out, enabling their use in different types of meat products, according to their technological characteristics. Several resistance genes have been determined to be carried and possibly disseminated by L. monocytogenes, which adds more importance in the establishment of methods for its control.

Molecular characterization and hematological analysis of Listeria monocytogenes infection in dairy cows in Punjab (Pakistan)

Listeriosis is an emerging bacterial disease of animals and humans worldwide, caused by Listeria monocytogenes. The infected dairy cows continuously shed the microbes in their milk, a human being's concern. This study was designed to molecular characterize the Listeria monocytogenes isolated from symptomatic cow's milk of tehsils Samundri, Gujar khan, and Alipur of Punjab. A total of 175 milk samples were collected, pre-enriched and cultured on PALCAM agar. The affirmation of the hlyA gene of Listeria monocytogenes was performed by polymerase chain reaction (PCR) and 3.43% of isolates were found positive. The phylogenetic analysis showed a resemblance of our isolates of Listeria monocytogenes with India (KP965733), the USA (DQ812484), and 3 of our isolates made a clade. The leucocytes and neutrophils count were found significantly increased in listeriosis affected cows. The Chi-square test showed a significant association between poor quality silage feeding and listeriosis. The presence of L.monocytogenes in cow's milk indicates a potential threat to humans. It is further recommended that it should be consistently monitored to ensure food safety.

Use of Focus Groups to Identify Food Safety Risks for Older Adults in the U.S

Older adults are vulnerable to foodborne illness; however, many do not follow safe food handling guidelines that would reduce their risk of infection. Virtual focus groups were used to explore older adults' food handling and consumption practices and to understand how to apply the Health Belief Model for food safety research with respect to older adults. Thirty-nine adults between the ages of 56 and 80 participated in the study. Most participants reported eating poultry and eggs, whereas few reported eating precut fruit or raw sprouts. The majority were not using a cooking thermometer for all types of poultry and did report washing raw poultry. Participants were generally resistant to the idea of heating deli meats. Most focus group participants did not perceive themselves as being personally susceptible to foodborne illness. They did, however, express food safety concerns related to specific foods, such as melons and bagged salads, and they reported taking precautions to limit health risks from these foods. Regarding the Health Belief Model, our results indicate that the construct of perceived susceptibility could be expanded to include perceived risk, which refers to an individual's belief about the likelihood that a food might be contaminated with a foodborne pathogen. These results should be confirmed among a nationally representative sample of older adults.

Performance of Scoring Systems in Predicting Clinical Outcomes in Patients with Bacteremia of Listeria monocytogenes: A 9-Year Hospital-Based Study

BACKGROUND

Listeria monocytogenes (LM) is a facultative anaerobe, Gram-positive bacillus which is widely distributed in nature, and can be separated from soil, water, and rotten vegetables. Immunocompetent people are less likely to suffer from LM infection or may only show gastrointestinal symptoms. However, immunocompromised elderly people, pregnant women, and newborns may develop life-threatening invasive infections. The mortality rate of LM infection is as high as 25-30%. The aim of this study is to investigate clinical scores of patients with bacteremia of LM confirmed by one or more blood cultures. We analyzed their demographics and laboratory findings in relation to their clinical outcomes.

MATERIALS AND METHODS

This was a hospital-based retrospective study on patients with bacteremia of LM. Data were collected from the electronic clinical database of Taichung Veterans General Hospital between January 2012 and December 2020. Bacteremia of LM was confirmed by at least one blood culture. Demographics, clinical characteristics, and laboratory data were collected for analysis. A variety of clinical scoring systems were used to predict the clinical outcome.

RESULTS

A total of 39 patients had confirmed bacteremia of LM. Among them, 1 neonatal patient was excluded. The remaining 38 patients were studied. They included 16 males (42.1%) and 22 females (57.9%), with a mean age of 59.9 ± 19.6 years. Their hospital stay averaged 23.3 ± 20.9 days. The in-hospital mortality rate was 36.8%. Mortality in Emergency Department Sepsis (MEDS) Score was 6.6 ± 4.0 for survivors and 12.4 ± 4.4 for non-survivors (P < 0.001). The National Early Warning Score (NEWS) was 3.9 ± 2.8 for survivors and 7.8 ± 3.1 for non-survivors (P = 0.001). Regarding the prediction of mortality risk, the AUC of ROC was 0.829 for MEDS and 0.815 for NEWS.

CONCLUSIONS

MEDS and NEWS were both good predictors of the clinical outcome in LM bacteremic patients. In those with higher scores of MEDS (≥10) and NEWS (≥8), we recommended an early goal-directed therapy and appropriate antibiotic treatment as early as possible to reduce mortality. Further large-scale studies are required to gain a deeper understanding of this disease and to ensure patient safety.

NF-κB/ROS and ERK pathways regulate NLRP3 inflammasome activation in Listeria monocytogenes infected BV2 microglia cells

Listeria monocytogenes is a food-borne pathogen responsible for neurolisteriosis, which is potentially lethal in immunocompromised individuals. Microglia are the main target cells for L. monocytogenes in central nervous system (CNS). However, the precise mechanisms by which they trigger neuroinflammatory processes remain unknown. The BV2 microglial cell line and a murine model of L. monocytogenes infection were used for experiments in this study. Listeria monocytogenes induced pyroptosis and nucleotide binding and oligomerization, leucine-rich repeat, pyrin domain-containing 3 (NLRP3) inflammasome activation in BV2. Pharmacological inhibition of the NLRP3 inflammasome attenuated L. monocytogenes-induced pyroptosis. Moreover, inhibition of nuclear factor kappa-B (NF-κB) and extracellular regulated protein kinases (ERK) pathways induced a decrease in caspase1 activation and mature IL-1β-17 secretion. Our collective findings support critical involvement of the NLRP3 inflammasome in L. monocytogenes-induced neuroinflammation and, to an extent, ROS production. In addition, ERK and NF-κB signaling play an important role in activation of the NLRP3 inflammasome, both in vitro and in vivo.

Clinical and molecular epidemiology of human listeriosis in Taiwan

OBJECTIVE

To determine serogroups, multilocus sequence typing (MLST) of Listeria monocytogenes isolates and analyze clinical characteristics of these clones focusing on non-perinatal cases.

METHODS

From 2000 to 2015, we analyzed 123 human listeriosis cases at a medical center in northern Taiwan using PCR serogrouping, MLST, and clinical presentations.

RESULTS

The annual incidence of listeriosis increased since 2005 with a peak in 2008 (0.2 per 1000 admission) and decreased thereafter. Of the 115 non-perinatal listeriosis cases, we found a male predominance (60%) with an average age of 63.9 years old (standard deviation: 15.3 years), and almost all patients had underlying conditions including malignancies (61.7%), steroid usage (39.1%), diabetes mellitus (31.3%), renal insufficiency (27.8%), and liver cirrhosis (17.4%). Clinical presentations included bacteremia (74.8%), neurolisteriosis (20.0%), and spontaneous bacterial peritonitis (5.2%). The most frequently identified serogroup-sequence types (ST) were IIB-ST87 (30.9%), followed by IIA-ST378 (16.3%) and IIA-ST155 (14.6%). The 30-day all-cause mortality of non-perinatal listeriosis was 25.2% and was associated with age (Hazard ratio: 1.04, 95% C.I. = 1.01-1.07, p = 0.021), steroid usage (Hazard ratio: 2.54, 95% C.I. = 1.06-6.11, p = 0.038) and respiratory distress at presentation (Hazard ratio: 2.59, 95% C.I. = 1.05-6.39, p = 0.038); while no association was found with serogroups (IIA, IIB, and IVB) or three major ST types by multivariable analysis. All 8 mothers of perinatal listeriosis patients survived and three neonates died (mortality, 37.5%), and IIB-ST87 was the major type (62.5%).

CONCLUSION

Predominant strains in Taiwan could cause significant morbidity and mortality. Further disease monitoring and source surveillance are warranted despite a declining trend of human listeriosis in Taiwan.

An outbreak of human listeriosis associated with frozen sweet corn consumption: Investigations in the UK

The use of Whole genome sequencing (WGS) identified a multi-country outbreak of human listeriosis associated with consumption of frozen sweet corn produced in Hungary. The purpose of this report was to summarise information on the cases occurring in the UK which were part of this outbreak and outline investigations on the presence of Listeria monocytogenes in the affected food chain. Prior to the international recall of this product in 2018, 12 UK cases of listeriosis were identified as infected by the outbreak strain between 2015 and 18. Epidemiological and microbiological investigations confirmed these cases as belonging to the outbreak. A further case occurred in 2019 and a contaminated frozen pack from one of the implicated batches of sweet corn was recovered from the patient's domestic freezer. The outbreak strain was also detected in products from a sandwich manufacturer in 2018 which added frozen sweet corn directly to sandwich fillings. The sandwich manufacturer's sweet corn was supplied by a distributor in England which obtained frozen products from the Hungarian manufacturer implicated in the outbreak. Within the distributor's premises, 208 food and environmental samples were taken: L. monocytogenes was detected in 44% of 70 samples of frozen sweet corn and 5% of 79 other foods. The outbreak strain was detected in the frozen sweet corn, in one other frozen food (mixed vegetables) and in the factory environment. The outbreak strain was also recovered from frozen beans on retail sale in the first four months of 2019. Five other L. monocytogenes strains together with two other Listeria species were detected in samples from the importer's premises. One of the L. monocytogenes strains in the importer's factory, which was distinct from the outbreak strain, was also recovered from sweet corn collected from the sandwich manufacturer, sweet corn tested in England in 2013 and 2016 and the blood of two cases of human listeriosis which occurred in England in 2014. This report shows how analysis by WGS provides evidence to understand complex food chains. This report also highlights risks for transmission of human listeriosis from frozen sweet corn and the potential for misuse of this food as a ready-to-eat product.

Listeria monocytogenes infections: Analysis of 41 patients

OBJECTIVE

We describe and analyze Listeria-related demographics and clinical features to determine the predisposing conditions for severe infections.

METHODS

We performed a retrospective study using positive isolation of Listeria monocytogenes from blood, cerebrospinal fluid, and other organic fluids. Electronic health records were used to determine the epidemiological and clinical features of infections caused by L. monocytogenes. Mortality and sepsis were considered dependent variables in the statistical analyses.

RESULTS

We included 41 patients in an observation period of 15 years (2003-2018), with an annual incidence rate of 1.3 cases per 100,000 population. Three main population profiles were identified: newborns, pregnant women, and other adults (17.1%, 12.2%, and 82.9%, respectively). Neuroinvasive infection was present in 17 patients (41.5%). In both univariate and multivariate analyses, neurological infections, whether meningoencephalitis, rhombencephalitis, or brain abscesses, were the main risk factors for severe forms of Listeria-related infections (odds ratio 1.8, 95% CI 1.52-2.14, p=0.01). Malignancies, whether solid tumors or hematological neoplasms, immunosuppression, and chronic diseases were not related to either mortality or severe clinical syndromes.

CONCLUSION

Infections caused by L. monocytogenes were uncommon but could cause severe sepsis and mortality, especially in susceptible populations. Our study focused on neurological involvement and severe invasive forms of listeriosis. Neuroinvasive forms were the most important risk factors for severe illness but not for mortality.