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Listeria monocytogenes is an important foodborne pathogen known for causing listeriosis. To gain insights into the pathogenicity, genetic characterization, and evolution of various Listeria species, in vitro cell adhesion and invasion ability assays and whole-genome sequencing were performed using four Listeria strains isolated from livestock and poultry slaughterhouses. The four Listeria strains exhibited adhesion and invasion abilities in Caco-2 and RAW264.7 cells. Pathogenic Liv1-1 and Lm2-20 had higher adhesion ability, but non-pathogenic Lin4-99 was more invasive than Lm2-20 (p < 0.05). Genetic characterization revealed the presence of a single chromosome without plasmid across four strains with similar whole-genome sizes and G + C% content. Analysis of key pathogenic genes underscored the presence of multiple virulence genes among the four Listeria strains. In contrast, non-pathogenic Listeria lacked LIPI-1, LIPI-2, and LIPI-3 genes, which could possibly be the cause of their non-pathogenicity despite their in vitro cell adhesion and invasion abilities. Thus, genetic determinants of Listeria do not necessarily predict cell adhesion and/or invasive ability in vitro. This study presents a comprehensive comparative genome-wide analysis of four Listeria strains, offering invaluable insights into the pathogenesis of the Listeria genus., (© 2024. The Author(s).)

Background: Listeriosis is a global health threat to both animals and humans, especially in developing countries. This study was designed to isolate Listeria monocytogenes from faeces; environmental samples; and cow, sheep and goat milk, as well as human stool, to study its molecular characteristics and antibiotic sensitivity in the New Valley and Beheira Governorates, Egypt. The isolation and identification of L. monocytogenes were carried out using traditional culture and biochemical methods, followed by antibiography, genus confirmation of some isolates and detection and sequencing of InlB genes via PCR., Results: Out of 2097 examined samples, the prevalence of L. monocytogenes was 13.4% in animals; the prevalence was 9.2%, 2.4%, 25.4%, 4%, 42.4%, and 6.4% in cattle faeces, cattle milk, sheep faeces, sheep milk, goat faeces, and goat milk, respectively. However, the prevalence of L. monocytogenes was 8.3% in human samples. Both animal and human isolates showed 100% resistance to trimethoprim-sulfamethoxazole, and the isolates showed the highest sensitivity to flumequine (100%), amikacin (99.2%), gentamicin (97.6%), and levofloxacin (94.6%). Multidrug resistance (MDR) was detected in 86.9% of the tested isolates. The 16 S rRNA and inlB genes were detected in 100% of the randomly selected L. monocytogenes isolates. Phylogenetic analysis of three isolates based on the inlB gene showed 100% identity between faecal, milk and human stool isolates., Conclusions: Faeces and milk are major sources of listeriosis, and the high degree of genetic similarity between animal and human isolates suggests the possibility of zoonotic circulation. The high prevalence of MDR L. monocytogenes in both animal and human samples could negatively impact the success of prevention and treatments for animal and human diseases, thereby imposing serious risks to public health., (© 2024. The Author(s).)

Listeria monocytogenes (Lm) is a highly pathogenic bacterium that can cause listeriosis, a relatively rare food-borne infectious disease that affects farm, domestic, wild animals and humans as well. The infected livestock is the frequent sources of Lm. Vaccination is one of the methods of controlling listeriosis in target farm animals to prevent Lm-associated food contamination. Here we report the complete sequence of the Lm strain AUF attenuated from a fully-virulent Lm strain by ultraviolet irradiation, successfully used since the 1960s as a live whole-cell veterinary vaccine. The de novo assembled genome consists of a circular chromosome of 2,942,932 bp length, including more than 2,800 CDSs, 17 pseudogenes, 5 antibiotic resistance genes, and 56/92 virulence genes. Two wild Lm strains, the EGD and the 10403S that is also used in cancer Immunotherapy, were the closest homologs for the Lm strain AUF. Although all three strains belonged to different sequence types (ST), namely ST12, ST85, and ST1538, they were placed in the same genetic lineage II, CC7., (© 2024. The Author(s).)

Listeriosis is a zoonotic disease caused by Listeria monocytogenes and Listeria ivanovii. The genus Listeria currently includes 27 recognized species and is found throughout the environment. The number of systematic studies on antimicrobial resistance in L. monocytogenes isolates from domestic farms using antimicrobial substances is limited. Importantly, dairy ruminant farms are reservoir of hypervirulent lineage I L. monocytogenes isolates, previously associated with human clinical cases. Considering that the classes of antibiotics used in food-producing domestic animals are frequently the same or closely related to those used in human medicine, studies about the impact of antibiotic use on the acquisition of antibiotic resistance in Listeria spp. in domestic animal farms are, therefore, of high importance. Here, susceptibility to 25 antibiotics was determined. Eighty-one animal-related, 35 food and 21 human pathogenic Listeria spp. isolates and 114 animal-related non-pathogenic Listeria spp. isolates were tested. Whole genome sequencing data was used for molecular characterization. Regarding L. monocytogenes, 2 strains from the clinical-associated linage I showed resistance to erythromycin, both related to dairy ruminants. Acquired resistance to one antibiotic was exhibited in 1.5% of L. monocytogenes isolates compared with 14% of non-pathogenic Listeria spp. isolates. Resistance to tetracycline (7.9%), doxycycline (7.9%), penicillin (4.4%), and ampicillin (4.4%) were the most frequently observed in non-pathogenic Listeria spp. While resistance to two or more antibiotics (5.6%) was most common in Listeria spp., isolates, resistance to one antibiotic was also observed (1.6%). The present results show that non-pathogenic Listeria spp. harbour antimicrobial resistance genes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Listeria monocytogenes is an ubiquitous environmental saprophytic bacterium causing listeriosis in domestic animals, humans, and occasionally wildlife. In animals, this foodborne zoonotic disease mainly occurs in ruminants and it is rare in carnivores. Seven red foxes ( Vulpes vulpes ) and one Eurasian lynx ( Lynx lynx ) were diagnosed with listeriosis between 2010 and 2021 at the Institute for Fish and Wildlife Health, Bern, Switzerland. Necropsy and histopathology revealed meningitis (six of seven red foxes), hepatitis (six of seven red foxes), pneumonia (five of seven red foxes), splenitis (two of seven red foxes) and splenomegaly (the Eurasian lynx, two of seven red foxes). Listeria monocytogenes was isolated from either lung, spleen, liver, or kidney of all animals. Serotyping detected L. monocytogenes serotype 1/2a in five red foxes and the Eurasian lynx and serotype 4b in two red foxes. Six red foxes were positive for canine distemper virus (CDV) by polymerase chain reaction, whereas the Eurasian lynx and one red fox were negative. One red fox that was positive for CDV and listeriosis was also diagnosed with salmonellosis. The identified L. monocytogenes serotypes are among the three most frequently isolated serotypes (1/2a, 1/2b, and 4b) from food or the food production environment and those that cause most listeriosis cases in humans and animals. Coinfection with CDV in six red foxes questions the role of CDV as potential predisposing factor for septicemic listeriosis. The detection of listeriosis in the regionally endangered Eurasian lynx and in carnivores highly abundant in urban settings, such as red foxes, reinforces the importance of wildlife health surveillance in a One Health context and adds the Eurasian lynx to the list of carnivores susceptible to the disease. Further investigations are required to assess the prevalence and epidemiology of L. monocytogenes in free-ranging carnivores and its interaction with CDV.

Objective: To describe a unique presentation of systemic Listeria monocytogenes infection in a lactating adult Holstein cow., Animal: 3-year-old second-parity female Holstein, 200 days in milk., Clinical Presentation, Progression, and Procedures: A 3-year-old Holstein dairy cow was presented for decreased appetite, decreased milk production, and pyrexia. Blood work displayed marked abnormalities in liver-associated parameters. A diagnosis of L monocytogenes cholangiohepatitis was made following liver biopsy, histopathology, and bacterial culture., Treatment and Outcome: The cow was treated with systemic antimicrobial and antipyretic therapy. The cow was discharged to continue treatment on farm, and at time of last communication with the owner, the cow was doing very well, with full resolution of clinical signs., Clinical Relevance: This case report describes a novel presentation of L monocytogenes infection in an adult bovine. L monocytogenes cholangiohepatitis should be considered a rare differential diagnosis in cattle presenting with evidence of pyrexia and liver disease.

Objectives: The bacterium Listeria monocytogenes (Lm) is associated with adverse pregnancy outcomes. Infection occurs through consumption of contaminated food that is disseminated to the maternal-fetal interface. The influence on the gastrointestinal microbiome during Lm infection remains unexplored in pregnancy. The objective of this study was to determine the impact of listeriosis on the gut microbiota of pregnant macaques., Methods: A non-human primate model of listeriosis in pregnancy has been previously described. Both pregnant and non-pregnant cynomolgus macaques were inoculated with Lm and bacteremia and fecal shedding were monitored for 14 days. Non-pregnant animal tissues were collected at necropsy to determine bacterial burden, and fecal samples from both pregnant and non-pregnant animals were evaluated by 16S rRNA next-generation sequencing., Results: Unlike pregnant macaques, non-pregnant macaques did not exhibit bacteremia, fecal shedding, or tissue colonization by Lm. Dispersion of Lm during pregnancy was associated with a significant decrease in alpha diversity of the host gut microbiome, compared to non-pregnant counterparts. The combined effects of pregnancy and listeriosis were associated with a significant loss in microbial richness, although there were increases in some genera and decreases in others., Conclusions: Although pregnancy alone is not associated with gut microbiome disruption, we observed dysbiosis with listeriosis during pregnancy. The macaque model may provide an understanding of the roles that pregnancy and the gut microbiota play in the ability of Lm to establish intestinal infection and disseminate throughout the host, thereby contributing to adverse pregnancy outcomes and risk to the developing fetus., (© The Author(s) 2023. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The presence of significant areas used for pastures in Kazakhstan makes it relevant to study the epizootic situation in terms of the incidence of animals during their grazing. The most frequent and dangerous diseases during this period are clostridiosis and listeriosis, which cause significant damage to livestock. Monitoring studies of the dynamics of morbidity among animals for infectious diseases during the grazing period were carried out on the basis of veterinary reporting. Bacteriological studies were carried out in a state laboratory using generally accepted microbiological methods. Analytical and statistical methods were used during the work. Monitoring studies indicate a significant spread of clostridiosis in the territory of Kazakhstan. The highest incidence rate was characterised by emphysematous carbuncle infection, which was recorded throughout the country, with an average frequency of about 40 cases per year. The incidence of braxy and anaerobic enterotoxemia occurred much less frequently and mainly in the southern regions of the country. Listeriosis was also observed only in some regions, but at the same time, a stationary focus of the disease was recorded in the Utylaut region, where cases of the disease are recorded annually. Conducted research made it possible to form the dynamics of the incidence of animals in the pasture period for these diseases, to determine the regions of the country with different intensity of the epizootic situation, as well as to carry out bacteriological isolation of a pure culture of the pathogen from samples taken in the foci of the disease. The studies made it possible to collect information on the features and mechanisms of the occurrence of diseases in the conditions of different regions of Kazakhstan and to develop a multi-vector strategy for preventive measures to eliminate animal diseases during the grazing period., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Listeria monocytogenes (Lm) is a deadly foodborne pathogen that comprises 14 serotypes, among which, serotype 4b Lm is the primary cause of listeriosis outbreaks in humans and animals. Here, we evaluated the safety, immunogenicity, and protective efficacy of a serotype 4b vaccine candidate Lm NTSNΔactA/plcB/orfX in sheep. The infection dynamics, clinical features, and pathological observation verified that the triple genes deletion strain has adequate safety for sheep. Moreover, NTSNΔactA/plcB/orfX significantly stimulated humoral immune response and provided 78% immune protection to sheep against lethal wild-type strain challenge. Notably, the attenuated vaccine candidate could differentiate infected and vaccinated animals (DIVA) via serology determination of the antibody against listeriolysin O (LLO, encoded by hly) and phosphatidylinositol-specific phospholipase C (PI-PLC, encoded by plcB). These data suggest that the serotype 4b vaccine candidate has high efficacy, safety, and DIVA characteristics, and may be used to prevent Lm infection in sheep. Our study provides a theoretical basis for its future application in livestock and poultry breeding., Competing Interests: Declaration of competing interest The authors of this manuscript declare that they have no competing interests., (Copyright © 2023. Published by Elsevier Ltd.)

Whole-genome sequencing (WGS) has revolutionized surveillance of infectious diseases. Disease outbreaks can now be detected with high precision, and correct attribution of infection sources has been improved. Listeriosis, caused by the bacterium Listeria monocytogenes, is a foodborne disease with a high case fatality rate and a large proportion of outbreak-related cases. Timely recognition of listeriosis outbreaks and precise allocation of food sources are important to prevent further infections and to promote public health. We report the WGS-based identification of a large multinational listeriosis outbreak with 55 cases that affected Germany, Austria, Denmark, and Switzerland during 2020 and 2021. Clinical isolates formed a highly clonal cluster (called Ny9) based on core genome multilocus sequence typing (cgMLST). Routine and ad hoc investigations of food samples identified L. monocytogenes isolates from smoked rainbow trout filets from a Danish producer grouping with the Ny9 cluster. Patient interviews confirmed consumption of rainbow trout as the most likely infection source. The Ny9 cluster was caused by a MLST sequence type (ST) ST394 clone belonging to molecular serogroup IIa, forming a distinct clade within molecular serogroup IIa strains. Analysis of the Ny9 genome revealed clpY , dgcB , and recQ inactivating mutations, but phenotypic characterization of several virulence-associated traits of a representative Ny9 isolate showed that the outbreak strain had the same pathogenic potential as other serogroup IIa strains. Our report demonstrates that international food trade can cause multicountry outbreaks that necessitate cross-border outbreak collaboration. It also corroborates the relevance of ready-to-eat smoked fish products as causes for listeriosis. IMPORTANCE Listeriosis is a severe infectious disease in humans and characterized by an exceptionally high case fatality rate. The disease is transmitted through consumption of food contaminated by the bacterium Listeria monocytogenes. Outbreaks of listeriosis often occur but can be recognized and stopped through implementation of whole-genome sequencing-based pathogen surveillance systems. We here describe the detection and management of a large listeriosis outbreak in Germany and three neighboring countries. This outbreak was caused by rainbow trout filet, which was contaminated by a L. monocytogenes clone belonging to sequence type ST394. This work further expands our knowledge on the genetic diversity and transmission routes of an important foodborne pathogen., Competing Interests: The authors declare no conflict of interest.

Two 3-week-old goat kids from a herd of ~50 to 60 goats were examined by a veterinarian. The goats were in lateral recumbency with an inability to rise. Unilateral cranial nerve deficiencies included cervical rotation, nystagmus, ptosis, facial paralysis, and absence of palpebral reflex. One of the 2 kids had a fever. The kids died and necropsy examinations were performed. Histopathology findings were highly suggestive of Listeria monocytogenes infection, which was confirmed by bacterial culture. This case suggests that listeriosis should be included in the differential diagnosis for goats with neurological signs even if they are not fed silage or haylage and are kept in a clean barn., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)

Listeria monocytogenes, a foodborne human and veterinary pathogen, is associated with high mortality rates in ruminants. However, no studies have investigated the antimicrobial resistance of L. monocytogenes isolates from clinical ruminant cases. This study aimed to determine the phenotypic and genotypic characteristics of L. monocytogenes isolates from clinical cases of Korean ruminants. We collected 24 L. monocytogenes isolates from aborted bovine fetuses and goats presenting with listeriosis-related symptoms. The isolates were subjected to PCR serogrouping, conventional serotyping, virulence gene detection, and antimicrobial susceptibility testing. Furthermore, pulsed-field gel electrophoresis and multilocus sequence typing were used to classify and compare genetic diversity among the isolates, including human L. monocytogenes isolates. The most prevalent L. monocytogenes serotypes were 4b (Ⅳ b ), 1/2a (Ⅱ a ; Ⅱ c ), and 1/2b (Ⅱ b ). All isolates harbored the virulence genes; however, llsX-encoding listeriolysin were identified only in serotypes 4b and 1/2b. All isolates, including two found in humans, formed three genetically diverse pulsed-field gel electrophoresis clusters according to serotype, lineage, and sequence type. The most prevalent sequence type was ST1, followed by ST365 and ST91. The isolates from ruminants with listeriosis were resistant to oxacillin and ceftriaxone and showed diverse lineage, serotype (serogroup), and sequence type characteristics. Considering that the atypical sequence types exhibited clinical manifestations and histopathological lesions, further study is needed to elucidate the pathogenicity of genetically diverse ruminant L. monocytogenes isolates. Furthermore, continuous monitoring of antimicrobial resistance is required to prevent the emergence of L. monocytogenes strains resistant to common antimicrobials., Competing Interests: Competing interests The authors declare that they have no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: There exists a scarcity of information on risk factors associated with case outcomes in goats diagnosed with encephalitic listeriosis., Objective: Evaluate risk factors associated with outcomes in 36 cases of suspected encephalitic listeriosis in goats presented to a referral hospital., Animals: Thirty-six goats (26 does, 7 bucks, and 3 wethers) were presented to Auburn University Large Animal Teaching Hospital between 2008 and 2021 for treatment of neurologic disease diagnosed as encephalitic listeriosis based on any combination of clinical signs, cerebral spinal fluid (CSF) analysis, or postmortem examination., Methods: Retrospective study. Data were analyzed as binary and under a proportional odds model. The medical records were searched for presumptive encephalitic listeriosis in goats between 2008 and 2021. Data collected included signalment (sex, age, and breed), history, clinical signs, temperature, and ability to stand at presentation. Final diagnosis, CSF results, all treatments, outcomes, and results of necropsy were also collected for analysis., Results: Male goats were 14 (95% CI: 1.98-166.0) times more likely to be a non-survivor compared to females despite being presented with similar history, clinical signs, and treatments. Animals presented with circling or a history of circling were 6.24 (95% CI: 1.40-23.21) times more likely to be a survivor than a non-survivor. Other risk factors evaluated were not significantly associated with outcomes., Conclusions and Clinical Importance: Few risk factors were associated with outcomes. Duration of clinical signs, antimicrobial or anti-inflammatory choices, or CSF results were not associated with outcome. Only sex and history or presence of circling were associated with case outcomes., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Two species of Listeria are pathogenic, Listeria monocytogenes and Listeria ivanovii. Although studies have shown that dairy ruminants shed Listeria spp. in feces, there is little information about ruminants that do not shed Listeria spp. in their feces but asymptomatically carry them in organs. We evidence that ruminants can asymptomatically carry L. ivanovii in udders and L. monocytogenes and L. ivanovii in tonsils without fecal shedding. Whole-genome sequence of L. monocytogenes and L. ivanovii contained known core genes involved in virulence and antibiotic resistance. This work highlights tonsils and udders as a Listeria intra-host site of colonization., Competing Interests: Declaration of competing interest Authors declare no conflict of interest., (Copyright © 2022 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Listeria monocytogenes causes the severe foodborne disease listeriosis. Several clonal groups of L. monocytogenes possess the pathogenicity islands Listeria pathogenicity island 3 (LIPI-3) and LIPI-4. Here, we investigated the prevalence and genetic diversity of LIPI-3 and LIPI-4 among 63 strains of seven nonpathogenic Listeria spp. from the natural environment, i.e., wildlife (black bears [ Ursus americanus ]) and surface water. Analysis of the whole-genome sequence data suggested that both islands were horizontally acquired but differed considerably in their incidence and genetic diversity. LIPI-3 was identified among half of the L. innocua strains in the same genomic location as in L. monocytogenes ( guaA hot spot) in a truncated form, with only three strains harboring full-length LIPI-3, and a highly divergent partial LIPI-3 was observed in three Listeria seeligeri strains, outside the guaA hot spot. Premature stop codons (PMSCs) and frameshifts were frequently noted in the LIPI-3 gene encoding listeriolysin S. On the other hand, full-length LIPI-4 without any PMSCs was found in all Listeria innocua strains, in the same genomic location as L. monocytogenes and with ~85% similarity to the L. monocytogenes counterpart. Our study provides intriguing examples of genetic changes that pathogenicity islands may undergo in nonpathogenic bacterial species, potentially in response to environmental pressures that promote either maintenance or degeneration of the islands. Investigations of the roles that LIPI-3 and LIPI-4 play in nonpathogenic Listeria spp. are warranted to further understand the differential evolution of genetic elements in pathogenic versus nonpathogenic hosts of the same genus. IMPORTANCE Listeria monocytogenes is a serious foodborne pathogen that can harbor the pathogenicity islands Listeria pathogenicity island 3 (LIPI-3) and LIPI-4. Intriguingly, these have also been reported in nonpathogenic L. innocua from food and farm environments, though limited information is available for strains from the natural environment. Here, we analyzed whole-genome sequence data of nonpathogenic Listeria spp. from wildlife and surface water to further elucidate the genetic diversity and evolution of LIPI-3 and LIPI-4 in Listeria . While the full-length islands were found only in L. innocua , LIPI-3 was uncommon and exhibited frequent truncation and genetic diversification, while LIPI-4 was remarkable in being ubiquitous, albeit diversified from L. monocytogenes. These contrasting features demonstrate that pathogenicity islands in nonpathogenic hosts can evolve along different trajectories, leading to either degeneration or maintenance, and highlight the need to examine their physiological roles in nonpathogenic hosts.

Ruminants are a well-known reservoir for Listeria monocytogenes. In addition to asymptomatic carriage of the pathogen, ruminants can also acquire listeriosis and develop clinical manifestations in the form of neurologic or fetal infections, similar to those occurring in humans. Genomic characterization of ruminant listeriosis cases in Europe have identified lineage 1 and 2 strains associated with infection, as well as clonal complexes (CCs) that are commonly isolated from human cases of listeriosis; however, there is little information on the diversity of L. monocytogenes from ruminant listeriosis in the United States. In this study, we characterized and compared 73 L. monocytogenes isolates from ruminant listeriosis cases from the Midwest and the Upper Great Plains collected from 2015 to 2020. Using whole-genome sequence data, we classified the isolates and identified key virulence factors, stress-associated genes, and mobile genetic elements within our data set. Our isolates belonged to three different lineages: 31% to lineage 1, 53% to lineage 2, and 15% to lineage 3. Lineage 1 and 3 isolates were associated with neurologic infections, while lineage 2 showed a greater frequency of fetal infections. Additionally, the presence of mobile elements, virulence-associated genes, and stress and antimicrobial resistance genes was evaluated. These genetic elements are responsible for most of the subgroup-specific features and may play a key role in the spread of hypervirulent clones, including the spread of hypervirulent CC1 clone commonly associated with disease in humans, and may explain the increased frequency of certain clones in the area. IMPORTANCE Listeria monocytogenes affects humans and animals, causing encephalitis, septicemia, and abortions, among other clinical outcomes. Ruminants such as cattle, goats, and sheep are the main carriers contributing to the maintenance and dispersal of this pathogen in the farm environment. Contamination of food products from farms is of concern not only because many L. monocytogenes genotypes found there are associated with human listeriosis but also as a cause of significant economic losses when livestock and food products are affected. Ruminant listeriosis has been characterized extensively in Europe; however, there is limited information about the genetic diversity of these cases in the United States. Identification of subgroups with a greater ability to spread may facilitate surveillance and management of listeriosis and contribute to a better understanding of the genome diversity of this pathogen, providing insights into the molecular epidemiology of ruminant listeriosis in the region.

Listeria monocytogenes is a bacterium that can cause disease in many species, including humans, livestock, and wildlife. Increased interactions via shared habitats may promote pathogen transmission among these groups. Our objectives were to evaluate the Southeastern Cooperative Wildlife Disease Study diagnostic data to characterize and compare L. monocytogenes -induced lesions and comorbidities in gray foxes and wild turkeys, and to describe cases of listeriosis in 2 cervids. From 1991-2020, 8 gray foxes, 8 wild turkeys, a neonatal elk, and a white-tailed deer fawn from several eastern states in the United States were diagnosed with listeriosis. All 8 foxes had hepatitis and/or hepatic necrosis with intralesional gram-positive bacilli, and concurrent canine distemper virus (CDV) infection; 2 of the foxes had been vaccinated recently for CDV. L. monocytogenes was cultured from the liver (6 of 8) or lung (2 of 8) of foxes. Lesions in wild turkeys included hepatocellular necrosis (3 of 8), heterophilic hepatitis (1 of 8), heterophilic granulomas (1 of 8), intrasinusoidal gram-positive bacilli without hepatic lesions (1 of 8), granulomatous dermatitis (1 of 8), and/or granulomatous myocarditis (2 of 8). Lymphoproliferative disease viral DNA was detected in 5 of 6 turkeys tested; reticuloendotheliosis viral DNA was detected in 2 of 3 turkeys tested. Both cervids had systemic listeriosis, with L. monocytogenes isolated from liver. Immunohistochemistry for Listeria spp. on select cases revealed immunolabeling in affected organs. Listeriosis was thus established as a cause of morbidity and mortality in 3 wildlife species, which often suffered from concurrent infections and likely immunosuppression.

A 27-year-old female white-faced saki (Pithecia pithecia) died following an onset of vomiting and ptyalism. Necropsy revealed lesions of suppurative ventriculitis, choroid plexitis, periventricular encephalitis and meningitis with intralesional gram-positive coccobacilli and paired rods. The saki also had suppurative to mononuclear hepatitis, mild intestinal crypt necrosis, proliferative glomerulonephritis, aortic arteriosclerosis, pulmonary interstitial fibrosis, chronic mild epicarditis, ovarian medullary arteriopathy and a focal superficial cerebral fibrotic nodule with surrounding chronic mixed cell inflammation. Listeria monocytogenes was cultured from liver and spinal cord. Intralesional Listeria bacteria were immunolabelled in brain sections and real-time polymerase chain reaction of brain tissue detected L. monocytogenes. Whole genome multilocus sequence typing characterized the cultured bacterial isolates as sequence type 6 and clonal complex 6. A database search for related clinical and food listerial outbreaks identified genetically related isolates but, because these isolates were more than 20 alleles distant from the saki isolates, they were not a related cluster. Reports of listeriosis in non-human primates are infrequent, and when infections do occur, they tend to be haematogenous with the propensity to cause meningoencephalitis. This saki likely ingested environmental L. monocytogenes, which resulted in disease that may have been facilitated by pre-existing co-morbidities and age., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Listeria monocytogenes remains a significant public health threat, leading to invasive listeriosis with severe manifestations (i.e. septicemia, meningitis, and abortion) and up to 30% of fatal cases. Here, we aimed to investigate genotypic diversity, virulence profiles, antimicrobial resistance patterns from a large and integrated population of L. monocytogenes isolates in China (n = 369), including food (n = 326), livestock (n = 25), and hospitalized humans (n = 18) over the years (2002-2019). PCR-based serogrouping showed the dominance of serogroup 1/2a-3a (37.4%) in food, 4a-4c (76%) in livestock, and 1/2a-3a (44.4%) in humans. Phylogenetic lineage analysis revealed the dominance of lineage II (63.4%) in food, lineage III (76%) in livestock, and lineage II (55.5%) in humans. Altogether, 369 isolates were grouped into 55 sequence types (STs) via multi-locus sequence typing (MLST), which belonged to 26 clonal complexes (CCs) and 17 singletons. Among various STs, ST9 (26%) was the most abundant in food, ST202 (76%) in livestock, and ST8 (16.6%) in humans. Overall, ST4/CC4, ST218/CC218, and ST619 isolates harbored both LIPI-3 and LIPI-4 genes subsets indicating their hypervirulence potential. Additionally, a low resistance was observed towards tetracycline (5.1%), erythromycin (3.2%), cotrimoxazole (2.9%), chloramphenicol (2.7%), gentamicin (2.4%), and ampicillin (2.1%). Collectively, detection of hypervirulent determinants and antimicrobial-resistant phenotype among Chinese isolates poses an alarming threat to food safety and public health, which requires a continued and enhanced surveillance system for further prevention of human listeriosis., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Listeria monocytogenes is a ubiquitous environmental bacterium associated with a wide variety of natural and human-made environments, such as soil, vegetation, livestock, food processing environments, and urban areas. It is also among the deadliest foodborne pathogens, and knowledge about its presence and diversity in potential sources is crucial to effectively track and control it in the food chain. Isolation of L. monocytogenes from various rural and urban environments showed higher prevalence in agricultural and urban developments than in forest or mountain areas, and that detection was positively associated with rainfall. Whole-genome sequencing (WGS) was performed for the collected isolates and for L. monocytogenes from Norwegian dairy farms and slugs (218 isolates in total). The data were compared to available data sets from clinical and food-associated sources in Norway collected within the last decade. Multiple examples of clusters of isolates with 0 to 8 whole-genome multilocus sequence typing (wgMLST) allelic differences were collected over time in the same location, demonstrating persistence of L. monocytogenes in natural, urban, and farm environments. Furthermore, several clusters with 6 to 20 wgMLST allelic differences containing isolates collected across different locations, times, and habitats were identified, including nine clusters harboring clinical isolates. The most ubiquitous clones found in soil and other natural and animal ecosystems (CC91, CC11, and CC37) were distinct from clones predominating among both clinical (CC7, CC121, and CC1) and food (CC9, CC121, CC7, and CC8) isolates. The analyses indicated that ST91 was more prevalent in Norway than other countries and revealed a high proportion of the hypovirulent ST121 among Norwegian clinical cases. IMPORTANCE Listeria monocytogenes is a deadly foodborne pathogen that is widespread in the environment. For effective management, both public health authorities and food producers need reliable tools for source tracking, surveillance, and risk assessment. For this, whole-genome sequencing (WGS) is regarded as the present and future gold standard. In the current study, we use WGS to show that L. monocytogenes can persist for months and years in natural, urban, and dairy farm environments. Notably, clusters of almost identical isolates, with genetic distances within the thresholds often suggested for defining an outbreak cluster, can be collected from geographically and temporally unrelated sources. The work highlights the need for a greater knowledge of the genetic relationships between clinical isolates and isolates of L. monocytogenes from a wide range of environments, including natural, urban, agricultural, livestock, food production, and food processing environments, to correctly interpret and use results from WGS analyses.

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., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The bacterium Listeria monocytogenes ( Lm ) is widely distributed in the environment as a saprophyte, but may turn into a lethal intracellular pathogen upon ingestion. Invasive infections occur in numerous species worldwide, but most commonly in humans and farmed ruminants, and manifest as distinct forms. Of those, neuroinfection is remarkably threatening due to its high mortality. Lm is widely studied not only as a pathogen but also as an essential model for intracellular infections and host-pathogen interactions. Many aspects of its ecology and pathogenesis, however, remain unclear and are rarely addressed in its natural hosts. This review highlights the heterogeneity and adaptability of Lm by summarizing its association with the environment, farm animals, and disease. It also provides current knowledge on key features of the pathology and (molecular) pathogenesis of various listeriosis forms in naturally susceptible species with a special focus on ruminants and on the neuroinvasive form of the disease. Moreover, knowledge gaps on pathomechanisms of listerial infections and relevant unexplored topics in Lm pathogenesis research are highlighted.

Listeria monocytogenes is an important foodborne pathogen, and is ubiquitously distributed in the natural environment. Cattle and sheep, as natural hosts, can transmit L. monocytogenes to related meat and dairy products. In this study, the prevalence, distribution, and transmission characteristics of Listeria were analysed by investigating 5214 samples of cattle and sheep in farm and slaughtering environments in China. A low contamination incidence of L. monocytogenes (0.5%, 20/4430) was observed in farm environment, but there was a high contamination incidence in slaughtering environment (9.4%, 74/784). The incidence of L. innocua in cattle and sheep farm and slaughtering environments is more common and significantly higher (9.7%, 508/5214) than that of L. monocytogenes (1.8%, 94/5214). The distinct molecular and genetic characteristics of Listeria by PFGE and MLST indicated that L. monocytogenes and L. innocua were gradually transmitted from the farm and slaughtering environments to end products, such as beef and mutton along the slaughtering chain. The ST7, ST9, ST91, and ST155 found in our study were associated with the human listeriosis cases in China. In addition, the findings of virulence markers ( inlC , inlJ , LIPI-3 , LIPI-4, and ECIII) concerned with the pathogenesis of human listeriosis and antibiotics resistance of L. monocytogenes in this study implies a potential public health risk. This study fills the gap in the epidemiology of beef cattle and sheep that carry Listeria in farm and slaughtering environments in major cattle and sheep producing areas in China.

Listeria monocytogenes widely exists in the natural environment and does great harm, which can cause worldwide public safety problem. Infection with L. monocytogenes can cause rapid death of Kupffer cell (KCs) in liver tissue and liver damage. American ginseng saponins is a natural compound in plants, which has great potential in inhibiting L. monocytogenes infection. Therefore, American ginseng stem-leaf saponins (AGS) and American ginseng heat-transformed saponins (HTS) were used as raw materials to study their bacteriostatic experiments in vivo and in vitro. In this experiment, female Kunming mice were randomly divided into five groups: control group, negative group, AGS group, HTS group (10 mg/kg/day in an equal volume via gastric administration) and penicillin group, each group containing six mice. Profiles AGS and HTS components were evaluated by high-performance liquid chromatography (HPLC) analysis. The bacteriostatic effect of AGS and HTS on L. monocytogenes was evaluated by inhibition zone test, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The bacteriostatic effect of AGS and HTS pretreatment on mice infected with L. monocytogenes were studies by animal experimental. The results showed that the content of polar saponins in AGS was 0.81 ± 0.003 mg/mg, less polar saponins was 0.08 ± 0.02 mg/mg, the content of polar saponins in HTS was 0.10 ± 0.01 mg/mg, less polar saponins was 0.76 ± 0.02 mg/mg. The in vitro bacteriostatic diameter of HTS (16.6 ± 0.8 mm) is large than that of AGS (10.2 ± 1.2 mm). AGS and HTS pretreatment could reduce the colony numbers in the livers of mice infected with Listeria monocytogenes. The levels of alanine aminotransferase (ALT), IL-1β, IL-6, TNF-α and IFN-γ in the livers of mice in the pretreatment group were significantly lower than those in the negative group. There were obvious leukoplakia, calcification and other liver damage on the liver surface in the negative control group, and obvious inflammatory cell infiltration in HE sections. AGS and HTS pretreatment can reduce liver injury caused by L. monocytogenes and protect the liver. Compared with AGS, HTS has higher content of less polar saponins and better bacteriostatic effect in vitro. The count of bacterial in liver tissue of HTS group was significantly lower, the survival rate was significantly higher than that of AGS group. Less polar saponins had better bacteriostatic effect. Collectively, less polar saponins pretreatment has a protective effect on mice infected with L. monocytogenes, to which alleviated liver damage, improved anti-inflammatory ability and immunity of the body, protected liver may contribute., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Listeria monocytogenes is a major human and animal foodborne pathogen. However, data from environmental reservoirs remain scarce. Here, we used whole-genome sequencing to characterize Listeria species isolates recovered over 1 year from wild animals in their natural habitats in Spain. Three different Listeria spp. ( L. monocytogenes [ n  = 19], Listeria ivanovii subsp. londoniensis [ n  = 4], and Listeria innocua [ n  = 3]) were detected in 23 animal tonsils (9 deer, 14 wild boars) and 2 feeding troughs. No Listeria species was detected in feces. L. monocytogenes was detected in tonsils of 44.4% (8 out of 18) of deer and 40.7% (11 out of 27) of wild boars. L. monocytogenes isolates belonged to 3 different core genome multilocus sequence typing (cgMLST) types (CTs) of 3 distinct sublineages (SL1, SL387, and SL155) from lineages I and II. While cgMLST type L1-SL1-ST1-CT5279 (IVb; clonal complex 1 [CC1]) occurred only in one animal, types L1-SL387-ST388-CT5239 (IVb; CC388) and L2-SL155-ST155-CT1170 (IIa; CC155) were retrieved from multiple animals. In addition, L1-SL387-ST388-CT5239 (IVb; CC388) isolates were collected 1 year apart, revealing their long-term occurrence within the animal population and/or environmental reservoir. The presence of identical L. monocytogenes strains in deer and wild boars suggests contamination from a common food or environmental source, although interhost transmission cannot be excluded. Pathogenicity islands LIPI-1, LIPI-3, and LIPI-4 were present in 100%, 5%, and 79% of the L. monocytogenes isolates, respectively, and all L. monocytogenes lineage II isolates ( n  = 3) carried SSI-1 stress islands. This study highlights the need for monitoring L. monocytogenes environmental contamination and the importance of tonsils as a possible L. monocytogenes intrahost reservoir. IMPORTANCE Listeria monocytogenes is a foodborne bacterial pathogen responsible for listeriosis. Whole-genome sequencing has been extensively used in public health and food industries to characterize circulating Listeria isolates, but genomic data on isolates occurring in natural environments and wild animals are still scarce. Here, we show that wild animals carry pathogenic Listeria and that the same genotypes can be found at different time points in different host species. This work highlights the need of Listeria species monitoring of environmental contamination and the importance of tonsils as a possible L. monocytogenes intrahost reservoir., (Copyright © 2021 American Society for Microbiology.)

The frequency of Listeria monocytogenes isolates collected from a total of 1150 samples including food (n = 300), livestock (n = 50), and human clinical (n = 800) was evaluated during 2008-2016. Antimicrobial resistance patterns, virulence factors, and molecular characteristics of these isolates were analyzed using disk diffusion method, sequencing, serotyping, and pulsed-field gel electrophoresis (PFGE). The analysis of 44 L. monocytogenes isolates showed that 72.7% (32 of 44) of all the isolates belonged to Serotype 1/2c, and 15.9% (7 of 44) belonged to Serotype 3c. All 44 isolates were resistant to one or more antimicrobial agents with the most frequent resistance to penicillin (75%) and tetracycline (47.7%). Of the 44 L. monocytogenes strains, 100, 69.2, and 62.5% of livestock, human, and food strains were resistant to penicillin, respectively. Using pulsed-field gel electrophoresis (PFGE) technique, the isolates' genetic diversity was determined, and 28 PFGE patterns with 8 common (CT) and 20 single types (ST) were identified. This study highlights the high prevalence of Serotype 1/2c in clinical and livestock samples, while different serotypes were observed in food samples. The presence of rare serotypes such as 4c, belonging to the Lineage III, as well as 4e and 1/2c which are infrequent in Iran indicates that paying attention to uncommon serotypes, especially 1/2c, during the listeriosis outbreaks is necessary.

Recent foodborne pathogen outbreaks associated with dry pet food and treats have focused the attention on these products as vehicles of pathogens for both pets and their owners. This study investigates the purchasing habits of dog owners and determines if and in what form pet snacks can be potentially dangerous for humans, especially for children. For these purposes, questionnaires collected from 406 dog owners were evaluated and microbiological analyses were performed on 120 dry pet snacks. The shape of the pet snack affects the purchase (median score, Mdn = 6.4) and the star bone was the preferred one (Mdn = 7.1). Most of the participants (76.0%; p  < 0.001) stated that snacks are attractive to their children and that the possibility for children to get in contact with pet snacks is rare, but not implausible (Mdn = 3.1). Indeed, more than 6% of respondents admitted that there had been incidents of involuntary ingestion of pet snacks, with fever and gastrointestinal manifestations. Microbiological analyses showed that 119 dry pet snacks analyzed of a total of 120 (99.2%) were in good sanitary condition except for one sample where the presence of Listeria ivanovii was confirmed. The upward trend in the presence of pets in households and the strong and continuous growth in value and volume of the pet food market led researchers to analyze possible public health issues. Children and infants in particular are the most exposed subjects as they are more likely to come into contact with pet snacks, attracted by a shape similar to that of a toy. For this reason, although our findings did not highlight important microbiological contamination of pet snacks, it would be useful to standardize food safety criteria with those for human food from a One Health perspective.

Herein we describe a rare case of systemic Listeria monocytogenes infection with concurrent pleural mesothelioma in a stray cat that was found dead and submitted for autopsy. Gross pathology changes consisted of thoracic clear yellow fluid admixed with suspended fibrin strands; clear-to-tan, variably sized, <3 mm diameter pulmonary nodules; and enlargement of the submandibular, retropharyngeal, and prescapular lymph nodes. Histologic changes consisted of extensive areas of suppurative inflammation and necrosis with mineralization that partially effaced the pulmonary parenchyma and lymph nodes. Random, distinct necrotic foci were present throughout the hepatic parenchyma. Extending from the pleura, within perinecrotic alveolar spaces, and infiltrating the submandibular, retropharyngeal, and prescapular lymph nodes were dense sheets of neoplastic epithelioid cells with moderate pleomorphism and occasional karyomegaly and multinucleation. Neoplastic cells exhibited immunolabeling for pancytokeratin AE1/AE3 and vimentin, consistent with pleural mesothelioma. Aerobic bacterial culture of lung yielded heavy growth of L. monocytogenes . Immunohistochemistry (IHC) for L. monocytogenes revealed clusters of bacteria in the lung, lymph node, and liver. Pathologic changes were consistent with systemic listeriosis, confirmed by bacterial culture and IHC, and concurrent pleural mesothelioma.

Background: Listeria monocytogenes is a foodborne bacterial pathogen that causes listeriosis, an infectious disease in animals and people, with pigs acting as asymptomatic reservoirs. In August 2019 an outbreak associated with the consumption of pork meat caused 222 human cases of listeriosis in Spain. Determining the diversity as well as the virulence potential of strains from pigs is important to public health., Methods: The behaviour of 23 L monocytogenes strains recovered from pig tonsils, meat and skin was compared by studying (1) internalin A, internalin B, listeriolysin O, actin assembly-inducing protein and PrfA expression levels, and (2) their invasion and intracellular growth in eukaryotic cells., Results: Marked differences were found in the expression of the selected virulence factors and the invasion and intracellular replication phenotypes of L monocytogenes strains. Strains obtained from meat samples and belonging to serotype 1/2a did not have internalin A anchored to the peptidoglycan. Some strains expressed higher levels of the studied virulence factors and invaded and replicated intracellularly more efficiently than an epidemic L monocytogenes reference strain (F2365)., Conclusion: This study demonstrates the presence of virulent L monocytogenes strains with virulent potential in pigs, with valuable implications in veterinary medicine and food safety., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Listeria monocytogenes is a zoonotic food-borne pathogen that is associated with serious public health and economic implications. In animals, L. monocytogenes can be associated with clinical listeriosis, which is characterised by symptoms such as abortion, encephalitis and septicaemia. In human beings, listeriosis symptoms include encephalitis, septicaemia and meningitis. In addition, listeriosis may cause gastroenteric symptoms in human beings and still births or spontaneous abortions in pregnant women. In the last few years, a number of reported outbreaks and sporadic cases associated with consumption of contaminated meat and meat products with L. monocytogenes have increased in developing countries. A variety of virulence factors play a role in the pathogenicity of L. monocytogenes. This zoonotic pathogen can be diagnosed using both classical microbiological techniques and molecular-based methods. There is limited information about L. monocytogenes recovered from meat and meat products in African countries. This review strives to: (1) provide information on prevalence and control measures of L. monocytogenes along the meat value chain, (2) describe the epidemiology of L. monocytogenes (3) provide an overview of different methods for detection and typing of L. monocytogenes for epidemiological, regulatory and trading purposes and (4) discuss the pathogenicity, virulence traits and antimicrobial resistance profiles of L. monocytogenes.

Listeria monocytogenes strains were isolated from Cornu aspersum maxima snails from farm units experiencing high mortalities and were characterized by phenotypic, molecular and biochemical criteria. A high heterogeneity was observed in the pulsed-field gel electrophoresis (PFGE) pulsotypes as well as in the virulence (13-100% mortality) among the fifteen L. monocytogenes strains. One strain was characterized as non-virulent while three strains exhibited hypervirulent phenotype. Hypervirulence activity was associated with cell surface properties such as hydrophobicity, autoaggregation and biofilm formation, with increased tolerance to snail's gut barriers such as pedal mucus, gastric mucus, gastric juices, and acidic pH as well as with increased capacity to resist the antibacterial activity of snail haemolymph and modulate immune cell populations and functions such as chemotaxis and phagocytoses. L. monocytogenes dysbiosis was characterized by a clinicopathological phenotype including immobilization of snails' headfoot outside the shell, increased mucus-secreting cells in the intestinal epithelium and feces, alteration of intestinal ridges morphology and excessive increase of haemolymph immune cells and cell death. Rebiosis in L. monocytogenes SN3 strain infected snails was achieved by dietary supplementation of the snail-gut commensal probiotic L. plantarum Sgs14 strain by exhibiting anti-Listeria activity, reducing mortality and clinicopathological manifestations as well as exhibiting immunomodulatory activity., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

A 6-year-old female chinchilla from a small colony in residential housing was presented due to lethargy and anorexia. Besides a ketoacidosis diagnosed by urinalysis, sepsis was suspected. Symptomatic treatment did not lead to any improvement, in consequence the animal was euthanized. On the basis of histopathological, immunohistological, and bacteriological examinations an infection with Listeria monocytogenes was diagnosed. The pathogen was also detectable in the feces of 2 other animals of the herd, one of which died and the other survived. The herd was treated with antibiotics following microbiologic sensitivity testing. At the end of the 2-month observation period, 3 out of 7 chinchillas were still alive. The presented case report describes the detection of listeriosis in pet chinchillas, the pathogenesis of the disease, as well as the diagnostic options and therapy., Competing Interests: Die Autoren haben keine finanzielle Verbindung zu Unternehmen, deren Produkte in dieser Fallbeschreibung eine Rolle spielen oder die Konkurrenzprodukte zu den erwähnten Produkten herstellen oder vertreiben., (© Georg Thieme Verlag KG Stuttgart · New York.)

In 2018, a case of neural disease suspected of listeriosis was reported in a flock of sheep in Kosovo with the death of ewes and 5 lambs. Samples from the brain of only three dead animals were subjected to histopathological and bacteriological analysis. MALDI-TOF MS was applied to confirm suspected Listeria spp. isolates from culture and multiplex PCR was applied for molecular serotyping. All isolates were tested for antimicrobial susceptibility by microdilution broth method. The histopathological analysis of the brain specimens showed typical changes for Listeria monocytogenes. Listeria spp. was isolated in brain samples from all three animals, and all the isolates were confirmed using MALDI-TOF MS and PCR down to the species level (Listeria monocytogenes). The molecular characterisation using multiplex PCR revealed all isolates as Listeria monocytogenes serotype 4b. All L. monocytogenes isolates were found to be susceptible to penicillin, erythromycin, tetracycline, streptomycin, trimethoprim/sulfamethosazole, quinupristin/dalfopristin, kanamycin, vancomycin, and gentamicin but resistant to nitrofurantoin and lincomycin. This study shows the emergence of a highly virulent strain in sheep farms in Kosovo and a possible threat to public health.

The present study aimed to investigate the effect of probiotic Lactobacilli addition on Listeria monocytogenes load, inflammatory reaction, and virulence properties in broilers from 1 to 14 D of age. A total of 480 broiler chicks were randomly allocated to 4 treatments of 6 replicates each. All birds were infected with L. monocytogenes on the first day and supplemented an equal amount mixture of Lactobacillus acidophilus and Lactobacillus plantarum at doses of 0 (control), 10 6 , 10 8 , 10 10  cfu/kg of diet. The results showed that on 7 and 14 D after administration, Lactobacilli addition at the 3 doses decreased (P < 0.05) L. monocytogenes loads in the cecum, skin, liver, and spleen by 0.065 to 0.933 log 10  cfu, and the pathogen linearly reduced (P ≤ 0.015) with the increasing doses of probiotics in the skin. Serum cytokines including IL-1β, IL-6, tumor necrosis factor-α, and interferon-γ in probiotics treatments were decreased (P < 0.05) by 25.4 to 51.1%. Transcriptional levels of genes related to anti-inflammatory reactions including IL-10, hypoxia inducible factor 1 alpha (HIF1A), prostaglandin E receptor 2, and prostaglandin-endoperoxide synthase 2 in the intestinal mucosa were upregulated (P < 0.05) in Lactobacilli treatments, and linear and quadratic responses (P ≤ 0.019) were found on HIF1A. Furthermore, the probiotics attenuated (P < 0.05) listerial adhesion, pore-forming, and invasion properties by downregulating autolysin Ami, listeriolysin O, internalin A and B, and a linear (P = 0.006) dose response of probiotics was exhibited on flagellin. The findings indicate that dietary coadministration of L. acidophilus and L. plantarum can attenuate L. monocytogenes infection by depressing its intestinal inoculation, translocation, inflammatory reaction, and virulence property in broilers and suggest that the probiotics can be an alternative against listerial infection in broilers., (Copyright © 2020. Published by Elsevier Inc.)

This study characterized Listeria monocytogenes, Salmonella enterica, and E. coli O157:H7 by collecting rectoanal mucosal swabs and fecal samples from 518 imported beef cattle at Jordan's major abattoir. A unique 53 L. monocytogenes, 287 S. enterica, and 17 E. coli O157:H7 were isolated from 37, 120 and 9 different animals; respectively. The prevalence of S. enterica, L. monocytogenes and E. coli O157:H7 were 23.2 % (95 % CI, 19.7-27.0 %), 7.1 % (95 % CI, 5.2-9.7 %) and 1.7 % (95 % CI, 0.9-3.3 %); respectively. All L. monocytogenes, all E. coli O157:H7 and 93.0 % of S. enterica isolates resisted at least one antimicrobial class. All L. monocytogenes, 94.1 % of E. coli O157:H7 and 69.7 % of S. enterica isolates exhibited multidrug resistance (resistant to ≥3 antimicrobials classes). Moreover, high percentages of L. monocytogenes (98.1 %), E. coli O157:H7 (64.7 %) and S. enterica (45.3 %) isolates resisted ≥5 antimicrobial classes. More than 90 % of the L. monocytogenes isolates resisted ampicillin, penicillin and erythromycin and more than 75 % resisted vancomycin. S. enterica isolates resisted several treatment-of-choice antimicrobials such as nalidixic acid (85.4 %), ciprofloxacin (26.8 %) and ceftriaxone (19.5 %). Furthermore, greater than 50 % of the E. coli O157:H7 isolates resisted streptomycin, nalidixic acid, tetracycline, ampicillin, sulfamethoxazole-trimethoprim, kanamycin, chloramphenicol and ciprofloxacin. The high prevalence and the high resistance percentages of the studied pathogens toward clinically important antimicrobials is alarming. Thus, applying strict sanitation procedures at the abattoirs in Jordan is crucial to lower the risk of carcasses contamination., Competing Interests: Declaration of Competing Interest The author declares no conflict of interest., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Background: In a beef cattle facility an outbreak of abortions occurred over a 36-day period and included samples from two aborted (non-viable) fetuses and 21 post-abortion clinical cases. There are numerous etiologies, including clinical listeriosis. At the species level, Listeria monocytogenes is ubiquitous in cattle production environments, including soil, feed, and occasionally water sources, and is a common enteric resident of cattle and other mammals. There are four genetically distinct lineages of L. monocytogenes (I-IV), with most lineage III and IV isolates obtained from ruminants. Definitive diagnosis of L. monocytogenes as a causative agent in disease outbreaks relies upon case identification, appropriate sample collection, and laboratory confirmation. Furthermore, clearly establishing a relationship between a pathogen source and clinical disease is difficult., Results: Of the two fetal and 21 clinical case submissions, 19 were positive for L. monocytogenes. Subsequent culture for L. monocytogenes from water and silage sources identified both as potential origins of infection. Using whole-genome sequencing and phylogenetic analyses, clinical, water and silage L. monocytogenes strains grouped into two of four lineages. All water and silage strains, plus 11 clinical strains placed in lineage III, with identical or nearly identical genomic sequences. The remaining eight clinical strains placed in lineage I, with seven having nearly identical sequences and one distinctly different., Conclusion: Three genetically distinct strains within two lineages of L. monocytogenes caused the abortion outbreak. The etiology of abortion in 11 cases was directly linked to water and silage contamination from a lineage III L. monocytogenes strain. The source of infection for the remaining abortion cases with two different strains from lineage I is unknown. This is the first report of L. monocytogenes genomics being used as part of an outbreak investigation of cattle abortion.

Energy metabolism is a sensitive indicator of cellular disorders. Therefore, the objective of this study was to investigate changes in cardiac and hepatic energy metabolism during listeriosis using an experimental model. We divided gerbils into two groups: Control (n = 11) and orally Infected (n = 12) with 5 × 10 9  CFU/mL of Listeria monocytogenes. Euthanasia and sampling were performed on days 6 and 12 post-infection (PI). Histopathological lesions were not found in the heart; however, the liver showed pyogranuloma. In the hearts of infected animals, cytosolic creatine kinase activity was lower on day 6 and 12 PI; mitochondrial creatine kinase/pyruvate kinase (PK), and sodium potassium pump (Na + /K + -ATPase) activities were lower on day 12 PI. Hepatic PK and Na + /K + -ATPase activities were lower in the infected group on day 12 PI. Lipoperoxidation was higher in the livers and hearts of infected animals on day 12 PI, and antioxidant capacity against peroxyl radicals (ACAP) was also higher in this group. These data suggest that subclinical listeriosis alters hepatic and cardiac energy metabolism, possibly related to decreased activity of phosphotransferases and ATPase. Subsequent antioxidant responses are not sufficient to correct alterations in lipid peroxidation and bioenergetics, possibly leading to important cellular pathological mechanisms., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Listeria monocytogenes is the causative agent of listeriosis, a serious disease affecting both humans and animals. While listeriosis outbreaks in humans are commonly investigated in detail, routine typing of L. monocytogenes is generally not performed in animal outbreaks. Here, seven presumable listeriosis outbreaks in small ruminants were retrospectively identified based on the pulsed-field gel electrophoresis (PFGE) profiles. Outbreaks were further characterised using three different analytical approaches based on the whole-genome sequencing (WGS) data: core-genome multilocus sequence typing (cgMLST), whole-genome MLST (wgMLST) and whole-genome single nucleotide polymorphism (wgSNP) typing. A monoclonal pattern of all seven outbreaks was identified using all three approaches, indicating common-source outbreaks. The outbreak strains belonged to sequence types (STs) 1 (n = 3), ST18 (n = 1), ST21 (n = 2) and ST184 (n = 1). Two epidemiologically linked ST1 outbreaks with indistinguishable PFGE profiles showed a polyphyletic nature and differed in >78 SNPs; thus, they were classified as separate outbreaks according to WGS. In ST184, the outbreak strain was also found in faeces of apparently healthy ruminants, silage and water collected from the trough, which were the most likely source(s) of infection. The outbreak-associated isolates differed in 0-7 cgMLST alleles, 0-12 wgMLST alleles and 1-13 SNPs. The minimum genetic diversity between outbreak-associated isolates and epidemiologically unrelated isolates of the same ST was low in all analysed cases, approaching the maximum diversity within the outbreak cluster. The results suggest that a fixed threshold to define the outbreak cluster should only be considered as a guide and highlight the role of epidemiological data for outbreak confirmation. The identified cgMLST clusters may be further investigated by wgMLST and/or wgSNP typing to increase confidence during investigations of outbreaks caused by highly clonal L. monocytogenes groups. This study gives an overview of the inter- and intra-outbreak genetic diversity of L. monocytogenes strains involved in animal outbreaks, hence improving their investigation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Listeria monocytogenes is a promising therapeutic vaccine vector for cancer immunotherapy. Although highly attenuated, three cases of systemic listeriosis have been reported in people following treatment with Listeria-based therapeutic vaccines. This complication has thus far not been reported in canine patients., Case Presentation: A dog previously diagnosed with osteoblastic osteosarcoma was presented for care following administration of three doses of the Canine Osteosarcoma Vaccine-Live Listeria Vector. On routine staging chest radiographs, mild sternal lymphadenopathy and a right caudoventral thoracic mass effect were noted. Further evaluation of the mass effect with computed tomography and ultrasound revealed a cavitated mass associated with the 7th right rib. Aspirates of the mass cultured positive for Listeria monocytogenes. The mass and associated ribs were surgically removed. Histopathology was consistent with metastatic osteoblastic osteosarcoma. Treatment was continued with doxorubicin chemotherapy and at the time of publication, the dog was alive over 1 year following diagnosis with no evidence of further disease progression. Genotyping of the abscess-derived L. monocytogenes was consistent with the vaccine strain., Conclusions: This case represents the first veterinary case to describe development of a Listeria abscess following administration of a Listeria-based therapeutic vaccine.

Background: Listeria monocytogenes is the causative agent of listeriosis, a serious disease affecting both animals and humans. Here, multilocus sequence typing (MLST) was used to characterize the genetic diversity of Listeria monocytogenes strains isolated from the natural environment and animal clinical cases in Europe. The prevalence of clonal complexes (CCs) obtained was compared according to (i) the origin of isolation - clinical cases vs. natural environment - and (ii) the clinical form of animal listeriosis - rhombencephalitis vs. abortion. To this aim, two datasets were constructed. The clinical dataset consisted of 350 animal clinical isolates originating from France and Slovenia and supplemented with isolates from Switzerland and Great Britain. The natural environment dataset consisted of 253 isolates from the natural environment originating from Slovenia and supplemented with isolates from nine other European countries., Results: For the clinical cases, CC1, CC4-CC217 and CC412 were the most prevalent in rhombencephalitis and CC1, CC37 and CC4-CC217 in abortion. The hypervirulent CC1 and CC4-CC217 prevailed in both datasets. These results indicated that livestock is constantly exposed to hypervirulent CCs. CC1 was significantly associated with a clinical origin, whereas CC9, CC29 and CC14 were associated with the natural environment. CC1 was predominant among rhombencephalitis cases both in cattle and small ruminants, and its prevalence did not differ significantly between these two groups. A novel association of CC37 and CC6 with abortion cases was revealed., Conclusions: Here, we show that CC1 and CC4-CC217 are prevalent in isolates of environmental and animal clinical origin, suggesting that ruminants are frequently exposed to hypervirulent CCs. The presence of CC4 in two mastitis cases calls for further attention due to direct threat to the consumer. We showed several associations between CCs and the origin of isolation or clinical form of listeriosis, e.g. CC37 and CC6 with abortion. This study improves our understanding of the population structure of L. monocytogenes isolates from the natural environment and animal clinical cases. Moreover, it provides a basis for future studies aiming to determine the underlying mechanisms of phenotypic traits of interest.

Regulatory T cells (Treg) are key players in the maintenance of peripheral tolerance, preventing autoimmune diseases and restraining chronic inflammatory diseases. Evidence suggests Treg cells and NK cells have important roles in feline immunodeficiency virus (FIV) pathogenesis; however, in vivo studies investigating the interplay between these two cell populations are lacking. We previously described innate immune defects in FIV-infected cats characterized by cytokine deficits and impaired natural killer cell (NK) and NK T cell (NKT) functions. In this study, we investigated whether in vivo Treg depletion by treatment with an anti-feline CD25 monoclonal antibody would improve the innate immune response against subcutaneous challenge with Listeria monocytogenes (Lm). Treg depletion resulted in an increased overall number of cells in Lm-draining lymph nodes and increased proliferation of NK and NKT cells in FIV-infected cats. Treg depletion did not normalize expression of perforin or granzyme A by NK and NKT cells, nor did Treg depletion result in improved clearance of Lm. Thus, despite the quantitative improvements in the NK and NKT cell responses to Lm, there was no functional improvement in the early control of Lm. CD1a+ dendritic cell percentages in the lymph nodes of FIV-infected cats were lower than in specific-pathogen-free control cats and failed to upregulate CD80 even when Treg were depleted. Taken together, Treg depletion failed to improve the innate immune response of FIV-infected cats against Lm and this may be due to dendritic cell dysfunction., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Listeria monocytogenes is one of the most important foodborne pathogens and is a causal agent of listeriosis in humans and animals. The aim of this study was to determine the prevalence, serogroups, antibiotic susceptibility, virulence factor genes, and genetic relatedness of L. monocytogenes strains isolated from 500 poultry samples in Turkey. The isolation sources of 103 L. monocytogenes strains were retail markets (n = 100) and slaughterhouses (n = 3). L. monocytogenes strains were identified as serogroups 1/2a-3a (75.7%, lineage I), 1/2c-3c (14.56%, lineage I), 1/2b-3b-7 (5.82%, lineage II), 4a-4c (2.91%, lineage III), and 4b-4d-4e (0.97%, lineage III). Most of the L. monocytogenes strains (93.2%) were susceptible to the antibiotics tested. PCR analysis indicated that the majority of the strains (95% to 100%) contained most of the virulence genes (hylA, plcA, plcB, prfA, mpl, actA, dltA, fri, flaA inlA, inlC, and inlJ). Pulsed-field gel electrophoresis (PFGE) demonstrated that there were 18 pulsotypes grouped at a similarity of > 90% among the strains. These results indicate that it is necessary to prevent the presence of L. monocytogenes in the poultry-processing environments to help prevent outbreaks of listeriosis and protect public health.

Bacterial infections require special care since the indiscriminate use of antibiotics to treat them has been linked to the emergence of resistant strains. In this sense, phytoterapeutic alternatives such as curcumin and its nanocapsules have emerged as a promising supplement in optimizing availability of bioactives and reducing the development of antimicrobial resistance. Thus, the aim of this study was to verify the effects of pure and nanoencapsulated curcumin in the treatment of experimental listeriosis in gerbils regarding many aspects including antibacterial effect, antioxidant mechanisms involved and the energetic metabolism. Four groups were used containing 6 animals each: T0 (control), T1 (infected), T2 (infected and treated with free curcumin - dose of 30 mg/kg/day) and T3 (infected and treated with nanocapsules containing curcumin - a dose of 3 mg/kg/day). Treated animals received curcumin for 6 consecutive days starting 24 h after Listeria monocytogenes infection. All animals were euthanized on the 12th day after L. monocytogenes infection. Quantitative polymerase chain reaction (qPCR) identified L. monocytogenes DNA in the spleens of all animals of the T1 group, as well as T2 (2 out of 6) and T3 (5 out of 6). The weight of the spleens confirmed the infection, since it was larger in the T1 group, differing statistically from T0, and similarly to T2 and T3. Hepatic histopathological examination showed mild infiltration of neutrophils and macrophages, except for the T3 group (only 1/6). In the liver, the pyruvate kinase activity was higher in T1 and T2 compared to T0 and T3. The adenylate kinase activity did not differ between groups. The Na + /K + ATPase activity was lower in T1 group compared to T0 and T3. Lipoperoxidation was lower in the T3 group compared to groups T0, T1 and T2. The antioxidant capacity against peroxyl radicals was higher in T1, T2 and T3 groups compared to T0. In conclusion, free curcumin showed potent antibacterial effects; however, the nanoencapsulated form was able to minimize the effects caused by L. monocytogenes regarding tissue injury, changes on enzymes of the energetic metabolism, in addition to an antioxidant effect against lipoperoxidation., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Listeria monocytogenes is a ubiquitous Gram-positive bacterium responsible for a severe foodborne disease in humans, and contaminated dairy products can be an important source of infection. Typically, infected dairy ruminants show clinical manifestations including encephalitis, septicemia, abortion, and diarrhea, but may also become asymptomatic carriers and shed L. monocytogenes in the feces acting as an important source of viable bacteria. Isolation from individual goat milk has been documented very rarely, and chronic, asymptomatic intramammary infection by L. monocytogenes with continuous milk shedding of viable bacteria has never been described in this dairy species., Case Presentation: At the routine controls, cheese and bulk milk were positive for L. monocytogenes in a herd of 200 lactating Alpine goats, but none showed clinical signs of listeriosis. Individual milk was subjected to bacterial culture and a clinically healthy goat was identified as affected by a chronic intramammary infection (IMI) by L. monocytogenes. The goat had never shown clinical signs of mastitis or other diseases. Her right half-udder milk was positive to L. monocytogenes in two consecutive samples collected one week apart, as demonstrated by bacterial culture and molecular analysis. Mammary tissues collected after culling were also positive to L. monocytogenes by culture. Histological examination highlighted a chronic interstitial mastitis with leukocyte infiltration, atrophy of the alveoli and presence of corpora amylacea. Immunohistochemistry (IHC) and immunofluorescence (IF) confirmed the presence of high numbers of bacteria in the lumen of mammary alveoli, with intracellular bacteria mainly located in macrophages, but also present in neutrophils and epithelial cells. After culling of the positive goat, bulk tank milk tested negative to L. monocytogenes at the following controls., Conclusion: This study demonstrates that L. monocytogenes can establish a chronic, subclinical IMI in goats with high numbers of bacteria shed in milk, representing a source of contamination for the herd and its dairy products. This underscores the importance of frequently monitoring all dairy herds that sell directly milk and/or fresh cheese and indicates that a chronic L. monocytogenes IMI should also be considered as source of bacteria when bulk tank milk contamination is detected in a dairy goat farm.