Listeriosis in animals, its public health significance (food-borne zoonosis) and advances in diagnosis and control: a comprehensive review

Assessment of elimination efficacy on foodborne pathogenic microbes and foulant precipitates using phytic acid and sulfamic acid

This research investigated the comparative efficacy of sulfamic acid (SA) and phytic acid (PA), both individually and in combination, for treating potential foodborne pathogens and pre-formed foulants. Pathogens studied included Listeria monocytogenes, E. coli DH5α, Salmonella Typhimurium, Staphylococcus aureus, and vegetative Bacillus cereus, in suspended aqueous solutions, as well as Pseudomonas aeruginosa biofilm on quartz glass surfaces. Inactivation kinetics for Listeria monocytogenes revealed concentration-dependent rate constants (k) of 6.6(±0.2)×10-6 M and 2.8(±0.1)×10-8 M for single treatments of SA and PA, respectively, and ranged from 6.9(±0.3) to 50.7(±2.3)×10-6 M for combined treatments with PA pre-treatment concentrations of 75-758 μM. Observable cellular abnormalities in Listeria monocytogenes, such as membrane vesiculation, chelation, cellular disruption, biomolecule leakage, and lipid peroxidation, were identified after exposure to PA or SA, either individually or in combination. The optimized combined treatment of PA and SA achieved significant removal (i.e., >3-log; 99.9%) of potential foodborne pathogens under simulated food-washing process conditions. Additionally, over 90% descaling efficacy was observed for pre-formed foulants such as CaCO3 precipitates and Pseudomonas aeruginosa biofilm on quartz glass surfaces with the combined treatment. These findings provide novel insights into the versatile utility of PA and SA for optimizing combinational water disinfection systems and addressing (in)organic foulant scaling on surfaces in the food processing industry.

Complete genome of the Listeria monocytogenes strain AUF, used as a live listeriosis veterinary vaccine

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.

Antimicrobial Resistance of Listeria monocytogenes Strains Isolated in Food and Food-Processing Environments in Italy

Listeria monocytogenes, along with various other pathogenic bacteria, may show resistance against a broad spectrum of antibiotics. Evaluating the extent of resistance in harmful microorganisms like Listeria monocytogenes holds significant importance in crafting novel therapeutic strategies to mitigate or combat the rise of infections stemming from antibiotic-resistant bacteria. The present work aims to investigate the occurrence of antimicrobial resistance among Listeria monocytogenes strains in meat products (n = 173), seafood (n = 54), dairy products (n = 19), sauces (n = 2), confectionary products (n = 1), ready-to-eat rice dishes (n = 1), and food-processing environments (n = 19). A total of 269 Listeria monocytogenes strains belonging to eight different serovars were tested against 10 antimicrobials. In the classes of antibiotics, most of the strains were resistant antibiotics belonging to the family of β-lactams (92.94%). High proportions of L. monocytogenes isolates were resistant to oxacillin (88.48%), followed by fosfomycin (85.87%) and flumenique (78.44%). The lowest level of resistance was observed against gentamycin (1.49%). A total of 235 strains (n = 87.36%) showed a profile of multidrug resistance. In conclusion, a high occurrence of resistant and multidrug-resistant strains of Listeria monocytogenes was observed among the examined serotypes isolated from different food sources. This understanding enables the adoption of suitable measures to avert contamination and the spread of resistant bacteria via food.

Genomic Characterization of Listeria monocytogenes and Other Listeria Species Isolated from Sea Turtles

Listeria monocytogenes is a ubiquitous pathogen found both in the environment and food. It can cause listeriosis in a wide range of animals as well as in humans. Investigations on presence, spread and virulence are still limited to terrestrial and human environments. Embracing the One Health Approach, investigating the presence and spread of L. monocytogenes in marine ecosystems and among wildlife, would provide us with useful information for human health. This study investigated the presence of L. monocytogenes and Listeria spp. in two species of sea turtles common in the Mediterranean Sea (Caretta caretta and Chelonia mydas). A total of one hundred and sixty-four carcasses of sea turtles (C. caretta n = 161 and C. mydas n = 3) stranded along the Abruzzo, Molise, Campania, and Calabria coasts, were collected. Brain and fecal samples were taken, enriched, and cultured for the detection of Listeria spp. From the specimens collected, strains of L. monocytogenes (brain n = 1, brain and feces n = 1, multiorgan n = 1 and feces n = 1), L. innocua (feces n = 1 and brain n = 1), and L. ivanovii (brain n = 1) were isolated. Typical colonies were isolated for Whole Genome Sequencing (WGS). Virulence genes, disinfectants/metal resistance, and antimicrobial resistance were also investigated. L. monocytogenes, L. innocua, and L. ivanovii were detected in C. caretta, whilst only L. monocytogenes and L. innocua in C. mydas. Notable among the results is the lack of significant differences in gene distribution between human and sea turtle strains. Furthermore, potentially pathogenic strains of L. monocytogenes were found in sea turtles.

Unveiling a Listeria monocytogenes Outbreak in a Rabbit Farm: Clinical Manifestation, Antimicrobial Resistance, Genomic Insights and Environmental Investigation

Listeria monocytogenes poses a threat to both human and animal health. This work describes an L. monocytogenes outbreak in a Portuguese rabbit farm, detailing the isolates' clinical manifestations, necropsy findings, and phenotypic and genomic profiles. Clinical signs, exclusively observed in does, included lethargy and reproductive signs. Post-mortem examination of does revealed splenomegaly, hepatomegaly with a reticular pattern, pulmonary congestion, and haemorrhagic lesions in the uterus, with thickening of the uterine wall and purulent greyish exudates. Positive L. monocytogenes samples were identified in fattening and maternity units across different samples, encompassing does and environmental samples. Core-genome Multi Locus Sequence Typing (cgMLST) analysis confirmed the outbreak, with the 16 sequenced isolates (lineage II, CC31, and ST325) clustering within a ≤2 allelic difference (AD) threshold. Antimicrobial susceptibility testing for five antibiotics revealed that 15 out of 19 outbreak isolates were resistant to sulfamethoxazole-trimethoprim (SXT). Concordantly, all SXT-resistant sequenced isolates were found to exclusively harbour a plasmid containing a trimethoprim-resistance gene (dfrD), along with loci linked to resistance to lincosamides (lnuG), macrolides (mphB), and polyether ionophores (NarAB operon). All sequenced outbreak isolates carried the antibiotic resistance-related genes tetM, fosX, lin, norB, lmrB, sul, and mprF. The outbreak cluster comprises isolates from does and the environment, which underscores the ubiquitous presence of L. monocytogenes and emphasizes the importance of biosecurity measures. Despite limited data on listeriosis in rabbit farming, this outbreak reveals its significant impact on animal welfare and production.

LISTERIA MONOCYTOGENES INFECTION IN FREE-RANGING RED FOXES (VULPES VULPES) AND EURASIAN LYNX (LYNX LYNX) IN SWITZERLAND

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.

A comparative study on the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa

These cross-sectional studies reported the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa. A total of 328 samples (faeces, feeds, silage, and drinking water) were collected from 23 cattle farms (communal, cow-calf, and feedlot), and 262 samples (faeces, carcass swabs, and effluents) from 8 beef abattoirs (low throughput and high throughput) were processed using standard bacteriological and molecular methods to detect Listeria species. The factors associated with the prevalence of Listeria species were investigated, and multiplex polymerase chain reaction (mPCR) was used to determine Listeria species, the pathogenic serogroups, and the carriage of eight virulence-associated genes by Listeria monocytogenes. The overall prevalence of Listeria species in cattle farms was 14.6%, comprising Listeria innocua (11.3%), Listeria monocytogenes (3.4%), Listeria welshimeri (0.0%) compared with 11.1%, comprising Listeria innocua (5.7%), Listeria monocytogenes (4.6%), Listeria welshimeri (0.8%) for beef abattoirs. Of the three variables (area, type of farm/abattoir, and sample type) investigated, only the sample types at abattoirs had a significant (P < 0.001) effect on the prevalence of L. innocua and L. welshimeri. The frequency of distribution of the serogroups based on 11 L. monocytogenes isolated from farms was 72.7% and 27.3% for the serogroup 1/2a-3a and 4b-4d-4e, respectively, while for the 12 L. monocytogenes isolates recovered from abattoirs, it was 25%, 8.3%, 50% and 16.7% for the serogroup 1/2a-3a, 1/2b-3b, 1/2c-3c, and 4b-4d-4e respectively (P < 0.05). All (100%) isolates of L. monocytogenes from the farms and abattoirs were positive for seven virulence genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). The clinical and food safety significance of the findings cannot be ignored.

Genetic and Phenotypic Diversity of Listeria monocytogenes in Pig Slaughterhouses in Korea

Listeria monocytogenes is a foodborne pathogen that has variable subtypes associated with human listeriosis and occurs in food and processing environments. This study was conducted to provide the genetic and phenotypic characterization of L. monocytogenes in pig carcasses and environments of slaughterhouses in Korea. A total of 22 L. monocytogenes were isolated from eight of 26 pig slaughterhouses between 2020 and 2022, and the most common serotype was 1/2c (40.9%), followed by serotypes 1/2b (31.8%) and 1/2a (27.3%). The isolates showed a significantly high prevalence of virulence genes located in Listeria pathogenicity island-1 (LIPI-1) and internalins (90.9-100%; p < 0.05). However, the prevalence rates of llsX, ptsA, and stress survival islet-1 (SSI-1) located in LIPI-3, LIPI-4, and SSI were only 9.1%, 22.7%, and 31.8%, respectively. In addition, among the epidemic clones (EC), ECI, ECII, ECIII, and ECV, only one isolate was represented as ECV. Isolates identified from the same slaughterhouses were divided into two or more pulsotypes, except for two slaughterhouses. Furthermore, the seven STs were classified into seven clonal complexes (CCs) (CC8, CC9, CC37, CC87, CC121, CC155, and CC288), and all CCs belonged to lineages I (31.8%) and II (68.1%). Interestingly, the isolates showed a high prevalence of oxacillin resistance (59.1%), and most isolates of the serotypes 1/2a and 1/2b exhibited oxacillin resistance, whereas only one of nine serotype 1/2c isolates exhibited oxacillin resistance. These results provide the genetic diversity of L. monocytogenes in pig carcasses and environments of slaughterhouses, and continuous monitoring will be helpful in predicting food safety risks.

A review of the literature of Listeria monocytogenes in Africa highlights breast milk as an overlooked human source

According to the latest WHO estimates (2015) of the global burden of foodborne diseases, Listeria monocytogenes is responsible for one of the most serious foodborne infections and commonly results in severe clinical outcomes. The 2013 French MONALISA prospective cohort identified that women born in Africa has a 3-fold increase in the risk of maternal neonatal listeriosis. One of the largest L. monocytogenes outbreaks occurred in South Africa in 2017-2018 with over 1,000 cases. Moreover, recent findings identified L. monocytogenes in human breast milk in Mali and Senegal with its relative abundance positively correlated with severe acute malnutrition. These observations suggest that the carriage of L. monocytogenes in Africa should be further explored, starting with the existing literature. For that purpose, we searched the peer-reviewed and grey literature published dating back to 1926 to date using six databases. Ultimately, 225 articles were included in this review. We highlighted that L. monocytogenes is detected in various sample types including environmental samples, food samples as well as animal and human samples. These studies were mostly conducted in five east African countries, four west African countries, four north African countries, and two Southern African countries. Moreover, only ≈ 0.2% of the Listeria monocytogenes genomes available on NCBI were obtained from African samples, contracted with its detection. The pangenome resulting from the African Listeria monocytogenes samples revealed three clusters including two from South-African strains as well as one consisting of the strains isolated from breast milk in Mali and Senegal and, a vaginal post-miscarriage sample. This suggests there was a clonal complex circulating in Mali and Senegal. As this clone has not been associated to infections, further studies should be conducted to confirm its circulation in the region and explore its association with foodborne infections. Moreover, it is apparent that more resources should be allocated to the detection of L. monocytogenes as only 15/54 countries have reported its detection in the literature. It seems paramount to map the presence and carriage of L. monocytogenes in all African countries to prevent listeriosis outbreaks and the related miscarriages and confirm its association with severe acute malnutrition.

Structural basis for the unique molecular properties of broad-range phospholipase C from Listeria monocytogenes

Listeriosis is one of the most serious foodborne diseases caused by the intracellular bacterium Listeria monocytogenes. Its two major virulence factors, broad-range phospholipase C (LmPC-PLC) and the pore-forming toxin listeriolysin O (LLO), enable the bacterium to spread in the host by destroying cell membranes. Here, we determine the crystal structure of LmPC-PLC and complement it with the functional analysis of this enzyme. This reveals that LmPC-PLC has evolved several structural features to regulate its activity, including the invariant position of the N-terminal tryptophan (W1), the structurally plastic active site, Zn2+-dependent activity, and the tendency to form oligomers with impaired enzymatic activity. We demonstrate that the enzymatic activity of LmPC-PLC can be specifically inhibited by its propeptide added in trans. Furthermore, we show that the phospholipase activity of LmPC-PLC facilitates the pore-forming activity of LLO and affects the morphology of LLO oligomerization on lipid membranes, revealing the multifaceted synergy of the two virulence factors.

A comprehensive investigation of protein expression profiles in L. monocytogenes exposed to thermal abuse, mild acid, and salt stress conditions

Preventing L. monocytogenes infection is crucial for food safety, considering its widespread presence in the environment and its association with contaminated RTE foods. The pathogen's ability to persist under adverse conditions, for example, in food processing facilities, is linked to virulence and resistance mechanisms, including biofilm formation. In this study, the protein expression patterns of two L. monocytogenes 1/2a strains, grown under environmental stressors (mild acidic pH, thermal abuse, and high concentration of NaCl), were investigated. Protein identification and prediction were performed by nLC-ESI-MS/MS and nine different bioinformatic software programs, respectively. Gene enrichment analysis was carried out by STRING v11.05. A total of 1,215 proteins were identified, of which 335 were non-cytosolic proteins and 265 were immunogenic proteins. Proteomic analysis revealed differences in protein expression between L. monocytogenes strains in stressful conditions. The two strains exhibited unique protein expression profiles linked to stress response, virulence, and pathogenesis. Studying the proteomic profiles of such microorganisms provides information about adaptation and potential treatments, highlighting their genetic diversity and demonstrating the utility of bioinformatics and proteomics for a broader analysis of pathogens.

Lactic acid bacteria secreted proteins as potential Listeria monocytogenes quorum sensing inhibitors

Listeria monocytogenes is an important human and animal pathogen able to cause an infection named listeriosis and is mainly transmitted through contaminated food. Among its virulence traits, the ability to form biofilms and to survive in harsh environments stand out and lead to the persistence of L. monocytogenes for long periods in food processing environments. Virulence and biofilm formation are phenotypes regulated by quorum sensing (QS) and, therefore, the control of L. monocytogenes through an anti-QS strategy is promising. This study aimed to identify, by in silico approaches, proteins secreted by lactic acid bacteria (LAB) potentially able to interfere with the agr QS system of L. monocytogenes. The genome mining of Lacticaseibacillus rhamnosus GG and Lactobacillus acidophilus NCFM revealed 151 predicted secreted proteins. Concomitantly, the three-dimensional (3D) structures of AgrB and AgrC proteins of L. monocytogenes were modeled and validated, and their active sites were predicted. Through protein-protein docking and molecular dynamic, Serine-type D-Ala-D-Ala carboxypeptidase and L,D-transpeptidase, potentially secreted by L. rhamnosus GG and L. acidophilus NCFM, respectively, were identified with high affinity to AgrB and AgrC proteins, respectively. By inhibiting the translocation of the cyclic autoinducer peptide (cyclic AIP) via AgrB, and its recognition in the active site of AgrC, these LAB proteins could disrupt L. monocytogenes communication by impairing the agr QS system. The application of the QS inhibitors predicted in this study can emerge as a promising strategy in controlling L. monocytogenes in food processing environment and as an adjunct to antibiotic therapy for the treatment of listeriosis.

Antibacterial and anti-biofilm activities of probiotic Lactobacillus plantarum against Listeria monocytogenes isolated from milk, chicken and pregnant women

Listeria monocytogenes (L. monocytogenes) is a foodborne pathogen that poses significant risks to public health and food safety. The present study aimed to identify the presence of Listeria spp. in various samples, including pasteurized milk, chicken fillets, and stool samples from pregnant women in Sharkia Governorate, Egypt. Additionally, the study identified the serotypes, virulence-associated genes, antimicrobial resistance patterns, and biofilm formation in L. monocytogenes isolates. Moreover, the antibacterial and anti-biofilm activity of Lactobacillus plantarum ATCC 14917 (L. plantarum) against L. monocytogenes isolates was investigated. A cross-sectional study was conducted from August 2021 to January 2022 to collect 300 samples of pasteurized milk, chicken fillets, and stool from pregnant women admitted to outpatient clinics of hospitals. The results showed that 32.7% of the samples were positive for Listeria spp., including L. innocua (48.9%), L. monocytogenes (26.5%), L. ivanovii (14.3%), L. grayi (5.1%), and L. welshimeri (5.1%). Among all L. monocytogenes isolates, hlyA, actA, inlC, and inlJ virulence-associated genes were detected. However, the virulence genes plcB, iap, and inlA were found in 10 (38.5%), 8 (30.8%), and 25 (96.2%) isolates, respectively. The L. monocytogenes isolates classified into four serotypes (1/2a, 1/2b, 1/2c, and 4b), with 1/2a and 4b each identified in 30.8% of the isolates, while 1/2b and 1/2c were identified in 19.2% of the isolates. All L. monocytogenes isolates showed 100% resistance to streptomycin, kanamycin, and nalidix acid, and 92.3% of isolates showed gentamicin resistance. However, all isolates were susceptible to ampicillin and ampicillin/sulbactam. Multidrug resistance (MDR) was observed in 20 (76.9%) L. monocytogenes isolates. The biofilm formation ability of 26 L. monocytogenes isolates was evaluated at different incubation temperatures. At 4°C, 25°C, and 37°C, 53.8, 69.2, and 80.8% of the isolates, respectively, were biofilm producers. Furthermore, 23.1% were strong biofilm producers at both 4°C and 25°C, while 34.6% were strong biofilm formers at 37°C. Treating L. monocytogenes isolates with L. plantarum cell-free supernatant (CFS) reduced the number of biofilm-producing isolates to 15.4, 42.3, and 53.8% at 4°C, 25°C, and 37°C, respectively. L. plantarum's CFS antibacterial activity was tested against six virulent, MDR, and biofilm-forming L. monocytogenes isolates. At a concentration of 5 μg/mL of L. plantarum CFS, none of the L. monocytogenes isolates exhibited an inhibition zone. However, an inhibition zone was observed against L. monocytogenes strains isolated from pasteurized milk and pregnant women's stools when using a concentration of 10 μg/mL. Transmission electron microscopy (TEM) revealed that L. plantarum CFS induced morphological and intracellular structural changes in L. monocytogenes. In conclusion, this study identified virulent MDR L. monocytogenes isolates with strong biofilm-forming abilities in food products in Egypt, posing significant risks to food safety. Monitoring the prevalence and antimicrobial resistance profile of L. monocytogenes in dairy and meat products is crucial to enhance their safety. Although L. plantarum CFS showed potential antibacterial and anti-biofilm effects against L. monocytogenes isolates, further research is needed to explore its full probiotic potential.

Risk factors associated with outcome in goats with encephalitic listeriosis: A retrospective study of 36 cases from 2008 to 2021

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.

Isoflavone glucoside genistin, an inhibitor targeting Sortase A and Listeriolysin O, attenuates the virulence of Listeria monocytogenes in vivo and in vitro

As a common intracellular facultative anaerobic Gram-positive bacterium, Listeria monocytogenes (L. monocytogenes) exhibits strong resistance to extreme environments, such as low temperature and a wide range of pH values, causing contamination in food production and processing. Sortase A (SrtA) and listeriolysin O (LLO), two crucial virulence factors of L. monocytogenes, are widely recognized as potential targets for the development of anti-L. monocytogenes infection drugs. In this study, we found that genistin simultaneously inhibits the peptidase activity of SrtA and the hemolytic activity of LLO without affecting the growth of L. monocytogenes, alleviating concerns about developing resistance. Furthermore, we demonstrated that genistin reduces L. monocytogenes biofilm formation and invasion of human colorectal cancer (Caco-2) cells. Subsequent mechanistic studies revealed that genistin inhibited LLO-mediated Caco-2 cell damage by blocking LLO oligomerization. Fluorescence quenching assay revealed the potential binding mode of SrtA and LLO to genistin. Genistin might bind to the active pocket of SrtA through residues Leu33, Asn29, and Met40, interacting with D1 domain of LLO involved in oligomerization and pore formation through residues Asn259. Studies in infection models revealed that genistin reduces mortality and pathological damage in mice infected with L. monocytogenes. These results indicate that genistin is a promising anti-virulence agent that could be considered an alternative candidate for the treatment of L. monocytogenes infection.

Bactericidal Action of Shrimp Shell Chitooligosaccharide Conjugated with Epigallocatechin Gallate (COS-EGCG) against Listeria monocytogenes

The antibacterial effect of chitooligosaccharide conjugated with five different polyphenols, including catechin (COS-CAT), epigallocatechin gallate (COS-EGCG), gallic acid (COS-GAL), caffeic acid (COS-CAF), and ferulic acid (COS-FER), against Listeria monocytogenes was investigated. Among all the conjugates tested, COS-EGCG showed the highest inhibition toward Listeria monocytogenes, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 1024 and 1024 µg/mL, respectively. The COS-EGCG conjugate also had a bactericidal effect on the environmental and clinical strains of L. monocytogenes. The low concentration of COS-EGCG conjugate augmented the formation of biofilm and the growth of L. monocytogenes. Nevertheless, the inhibition of biofilm formation and bacterial growth was achieved when treated with the COS-EGCG conjugate at 2 × MIC for 48 h. In addition, the COS-EGCG conjugate at 2 × MIC had the potential to inactivate the pre-biofilm, and it reduced the production of the extracellular polysaccharides of L. monocytogenes. The COS-EGCG conjugate at the MIC/4 effectively impeded the motility (the swimming and swarming) of L. monocytogenes, with an 85.7-94.3% inhibition, while 100% inhibition was achieved with the MIC. Based on scanning electron microscopic (SEM) images, cell wall damage with numerous pores on the cell surface was observed. Such cell distortion resulted in protein leakage. As a result, COS-EGCG could penetrate into the cell and bind with the DNA backbone. Therefore, the COS-EGCG conjugate could be further developed as a natural antimicrobial agent for inhibiting or controlling L. monocytogenes.

Isolation of Listeria monocytogenes from poultry red mite (Dermanyssus gallinae) infesting a backyard chicken farm in Greece

The poultry red mite (PRM), Dermanyssus gallinae, is arguably the most harmful, ubiquitous haematophagous ectoparasite infesting egg-laying hens. PRM is a vector of various microorganisms, with some being important for food microbiology and public health. The present study aimed to investigate the presence of specific pathogens, including Escherichia coli, Salmonella spp. and Listeria spp., carried by PRM infesting a chicken farm in Greece. Mites were caught using cardboard traps (Avivet), and 100 unwashed PRM were homogenized and used for microbiological cultures. Microbiological cultures were carried out on general and selective substrates to detect the above-mentioned bacteria. Specifically for Listeria spp., DNA was extracted from bacteria grown in Tryptone Soya Yeast Extract Agar using a commercial kit. The hly gene encoding the Listeriolysin O protein was amplified by PCR. Mites were identified as D. gallinae using morphological keys as well as by COI DNA barcoding. Microbiological cultures and PCR assays were positive for Listeria monocytogenes. No other bacteria were detected. The current study constitutes the first molecular isolation of L. monocytogenes from D. gallinae, confirming that PRM can carry this food-borne pathogen. PRM control measures and hygiene practices should be applied to minimize any possible contamination risk of poultry products with L. monocytogenes and safeguard public health.

Listeria monocytogenes-How This Pathogen Uses Its Virulence Mechanisms to Infect the Hosts

Listeriosis is a serious food-borne illness, especially in susceptible populations, including children, pregnant women, and elderlies. The disease can occur in two forms: non-invasive febrile gastroenteritis and severe invasive listeriosis with septicemia, meningoencephalitis, perinatal infections, and abortion. Expression of each symptom depends on various bacterial virulence factors, immunological status of the infected person, and the number of ingested bacteria. Internalins, mainly InlA and InlB, invasins (invasin A, LAP), and other surface adhesion proteins (InlP1, InlP4) are responsible for epithelial cell binding, whereas internalin C (InlC) and actin assembly-inducing protein (ActA) are involved in cell-to-cell bacterial spread. L. monocytogenes is able to disseminate through the blood and invade diverse host organs. In persons with impaired immunity, the elderly, and pregnant women, the pathogen can also cross the blood-brain and placental barriers, which results in the invasion of the central nervous system and fetus infection, respectively. The aim of this comprehensive review is to summarize the current knowledge on the epidemiology of listeriosis and L. monocytogenes virulence mechanisms that are involved in host infection, with a special focus on their molecular and cellular aspects. We believe that all this information is crucial for a better understanding of the pathogenesis of L. monocytogenes infection.

A systematic review and meta-analysis of the prevalence of Listeria monocytogenes in South-East Asia; a one-health approach of human-animal-food-environment

Listeria monocytogenes is an important foodborne intracellular pathogen. The pathogen is the primary cause of human Listeriosis. The main source of human Listeriosis is through consumption of contaminated food products. Other modes of transmission include zoonotic and vertical transmission. The disease often presents in a mild form, but severe and fatal cases, as well as outbreaks, may occur. Despite these challenges, there has been little attempt at enumerating the burden of the disease in countries of Southeast Asia (SEA) and some developing countries. Thus, this study investigated the prevalence of L. monocytogenes in SEA using one health approach through a systematic review and meta-analysis (SR&MA) of the existing literature. In accordance with the PRISMA guidelines, an a priori protocol for the SR&MA was developed and registered in PROSPERO (ID=CRD42021288903). A systematic search of four electronic databases was performed for relevant citations. The identified publications were screened, and 17 studies were included in the review from where data was extracted. The pooling of the prevalence estimate (with the 95% confidence interval [CI]) was done using the random effect model by employing the double transformed arcsine method using MetaXL software. The overall determined prevalence for L. monocytogenes in SEA (in food, animal, and environmental sources) was 16% (95% confidence interval [CI]: 10–23). Further subgroup analysis revealed ready-to-eat food of vegetable origin with the highest prevalence of 21% (CI: 6–41). Also, seven virulence genes were identified to be prevalent in the subregion. The commonest identification method was found to be the polymerase chain reaction (PCR). The knowledge of the high prevalence of L. monocytogenes in SEA is relevant for informed decision making by clinicians, public health practitioners, and policymakers. To achieve the goal of the effective control and prevention of the disease in the subregion.

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Using one-health approach, the prevalence of Listeria monocytogenes in the Southeast Asia was systematically evaluated.

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Estimate prevalence for food, environment and animal sources were pooled using the random effect model.

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L. monocytogenes was reported to be hyper-endemic in SEA with food being the predominant source.

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Prevalent L. monocytogenes virulent genes, high risk food sources, and commonly used detection methods were identified.

Retrospective Molecular Survey on Bacterial and Protozoan Abortive Agents in Roe Deer (Capreolus capreolus) from Central Italy

Bacterial and protozoan agents can determine abortion and other reproductive disorders in domestic ruminants, but data regarding their occurrence in wild ruminants are scanty worldwide, including in Italy. The aim of this retrospective study was to verify the occurrence of the main bacterial and protozoan abortive agents in 72 spleen samples previously collected from roe deer (Capreolus capreolus) living in mountain areas of Central Italy. All samples were collected and submitted to DNA extraction for other investigations. Molecular analyses were carried out on the DNA samples to detect Brucella spp., Chlamydia abortus, Coxiella burnetii, Salmonella enterica, Listeria monocytogenes, Neospora caninum, and Toxoplasma gondii. Three (4.16%) roe deer resulted PCR positive for C. burnetii and one (1.38%) for T. gondii. These findings suggest that roe deer living in the investigated areas do not act as important reservoirs of the searched agents. However, the tested animals lived in a closed area without contact with domestic animals that are usually involved in the epidemiology of the investigated pathogens. Monitoring of wild ruminants is pivotal to verify changes in the epidemiological scenario from a One Health perspective, too.

Recent Advances in the Application of Bacteriophages against Common Foodborne Pathogens

Bacteriophage potential in combating bacterial pathogens has been recognized nearly since the moment of discovery of these viruses at the beginning of the 20th century. Interest in phage application, which initially focused on medical treatments, rapidly spread throughout different biotechnological and industrial fields. This includes the food safety sector in which the presence of pathogens poses an explicit threat to consumers. This is also the field in which commercialization of phage-based products shows the greatest progress. Application of bacteriophages has gained special attention particularly in recent years, presumably due to the potential of conventional antibacterial strategies being exhausted. In this review, we present recent findings regarding phage application in fighting major foodborne pathogens, including Salmonella spp., Escherichia coli, Yersinia spp., Campylobacter jejuni and Listeria monocytogenes. We also discuss advantages of bacteriophage use and challenges facing phage-based antibacterial strategies, particularly in the context of their widespread application in food safety.

Probiotics in Poultry Nutrition as a Natural Alternative for Antibiotics

Since the early 1950s, antibiotics have been used in poultry for improving feed efficiency and growth performance. Nevertheless, various side effects have appeared, such as antibiotic resistance, antibiotic residues in eggs and meat, and imbalance of beneficial intestinal bacteria. Consequently, it is essential to find other alternatives that include probiotics that improve poultry production. Probiotics are live microorganisms administered in adequate doses and improve host health. Probiotics are available to be used as feed additives, increasing the availability of the nutrients for enhanced growth by digesting the feed properly. Immunity and meat and egg quality can be improved by supplementation of probiotics in poultry feed. Furthermore, the major reason for using probiotics as feed additives is that they can compete with various infectious diseases causing pathogens in poultry's gastrointestinal tract. Hence, this chapter focuses on the types and mechanisms of action of probiotics and their benefits, by feed supplementation, for poultry health and production.

Phytochemicals as Alternatives to Antibiotics in Animal Production

Despite the continuous improvement of feed diets and recipes, animal health problems persist. For their treatment, antibiotics and chemotherapy have been shown to have side effects hard to control. The antibiotic residues in animal products may endanger human health. Since the antibiotics were restricted in animals’ diets, which were previously used to keep under control digestive and respiratory pathologies, as well as allergies, so the researchers began to search for natural alternatives. Thus, it was developed the concept of phytoadditives, and these natural plant extracts are gaining ground in animal farming. Since then, more and more animal breeders and farms are willing to use various types of phytoadditives. This chapter aims to present the most widely used phytochemicals in animal nutrition, their effects on animal production and health, and to make some recommendations on the use of phytochemicals in farm animals’ diets.

Listeria monocytogenes in foods-From culture identification to whole-genome characteristics

Listeria monocytogenes is an important foodborne pathogen, which is able to persist in the food production environments. The presence of these bacteria in different niches makes them a potential threat for public health. In the present review, the current information on the classical and alternative methods used for isolation and identification of L. monocytogenes in food have been described. Although these techniques are usually simple, standardized, inexpensive, and are routinely used in many food testing laboratories, several alternative molecular-based approaches for the bacteria detection in food and food production environments have been developed. They are characterized by the high sample throughput, a short time of analysis, and cost-effectiveness. However, these methods are important for the routine testing toward the presence and number of L. monocytogenes, but are not suitable for characteristics and typing of the bacterial isolates, which are crucial in the study of listeriosis infections. For these purposes, novel approaches, with a high discriminatory power to genetically distinguish the strains during epidemiological studies, have been developed, e.g., whole-genome sequence-based techniques such as NGS which provide an opportunity to perform comparison between strains of the same species. In the present review, we have shown a short description of the principles of microbiological, alternative, and modern methods of detection of L. monocytogenes in foods and characterization of the isolates for epidemiological purposes. According to our knowledge, similar comprehensive papers on such subject have not been recently published, and we hope that the current review may be interesting for research communities.

Modelling Neurological Diseases in Large Animals: Criteria for Model Selection and Clinical Assessment

Issue: The impact of neurological disorders is recognised globally, with one in six people affected in their lifetime and few treatments to slow or halt disease progression. This is due in part to the increasing ageing population, and is confounded by the high failure rate of translation from rodent-derived therapeutics to clinically effective human neurological interventions. Improved translation is demonstrated using higher order mammals with more complex/comparable neuroanatomy. These animals effectually span this translational disparity and increase confidence in factors including routes of administration/dosing and ability to scale, such that potential therapeutics will have successful outcomes when moving to patients. Coupled with advancements in genetic engineering to produce genetically tailored models, livestock are increasingly being used to bridge this translational gap. Approach: In order to aid in standardising characterisation of such models, we provide comprehensive neurological assessment protocols designed to inform on neuroanatomical dysfunction and/or lesion(s) for large animal species. We also describe the applicability of these exams in different large animals to help provide a better understanding of the practicalities of cross species neurological disease modelling. Recommendation: We would encourage the use of these assessments as a reference framework to help standardise neurological clinical scoring of large animal models.

Co-Infection of L. monocytogenes and Toxoplasma gondii in a Sheep Flock Causing Abortion and Lamb Deaths

Abortion in livestock is a public health burden, and the cause of economic losses for farmers. Abortion can be multifactorial, and a deep diagnostic investigation is important to reduce the spread of zoonotic disease and public health prevention. In our study, a multidisciplinary investigation was conducted to address the cause of increased abortion and lamb mortality on a farm, which detected a co-infection of Listeria monocytogenes and Toxoplasma gondii. Hence, it was possible to conclude that this was the reason for a reduced flock health status and the cause of an increased abortion rate. Furthermore, the investigation work and identification of the L. monocytogenes infection root allowed the reduction of economic loss.

Listeriosis with viral coinfections in 8 gray foxes, 8 wild turkeys, and 2 young cervids in the southeastern United States

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.

Listeria monocytogenes - How This Pathogen Survives in Food-Production Environments?

The foodborne pathogen Listeria monocytogenes is the causative agent of human listeriosis, a severe disease, especially dangerous for the elderly, pregnant women, and newborns. Although this infection is comparatively rare, it is often associated with a significant mortality rate of 20-30% worldwide. Therefore, this microorganism has an important impact on food safety. L. monocytogenes can adapt, survive and even grow over a wide range of food production environmental stress conditions such as temperatures, low and high pH, high salt concentration, ultraviolet lights, presence of biocides and heavy metals. Furthermore, this bacterium is also able to form biofilm structures on a variety of surfaces in food production environments which makes it difficult to remove and allows it to persist for a long time. This increases the risk of contamination of food production facilities and finally foods. The present review focuses on the key issues related to the molecular mechanisms of the pathogen survival and adaptation to adverse environmental conditions. Knowledge and understanding of the L. monocytogenes adaptation approaches to environmental stress factors will have a significant influence on the development of new, efficient, and cost-effective methods of the pathogen control in the food industry, which is critical to ensure food production safety.

Pathogen Screening for Possible Causes of Meningitis/Encephalitis in Wild Carnivores From Saxony-Anhalt

Inflammation in meninges and/or brain is regularly noticed in red foxes and other wild carnivores during rabies control programs. Despite negative rabies virus (RABV) results, the etiologies of these cases remain unknown. Thus, the aim of this study was to provide an overview of the occurrence of pathogens that may cause diseases in the brains of wild carnivores and pose a risk to humans and other animals. In addition to RABV and canine distemper virus (CDV), a variety of pathogens, including members of Flaviviridae, Bornaviridae, Herpesviridae, Circoviridae, as well as bacteria and parasites can also cause brain lesions. In 2016 and 2017, brain samples of 1,124 wild carnivores were examined by direct fluorescent antibody test for RABV as well as (reverse-transcriptase) quantitative polymerase chain reaction (PCR) for the presence of CDV as part of a monitoring program in Saxony-Anhalt, Germany. Here, we applied similar methods to specifically detect suid herpesvirus 1 (SuHV-1), West Nile virus (WNV), Borna disease virus 1 (BoDV-1), canid alphaherpesvirus 1 (CaHV-1), canine parvovirus type 2 (CPV-2), fox circovirus (FoxCV), and Neospora caninum (N. caninum). Further, bacteriogical examination for the existence of Listeria monocytogenes (L. monocytogenes) and immunohistochemistry of selected cases to detect Toxoplasma gondii (T. gondii) antigen were performed. Of all pathogens studied, CDV was found most frequently (31.05%), followed by FoxCV (6.80%), CPV-2 (6.41%), T. gondii (4/15; 26.67%), nematode larvae (1.51%), L. monocytogenes (0.3%), and various other bacterial pathogens (1.42%). In 68 of these cases (6.05%), multiple pathogen combinations were present simultaneously. However, RABV, WNV, BoDV-1, SuHV-1, CaHV-1, and N. caninum were not detected. The majority of the histopathological changes in 440 animals were inflammation (320/440; 72.73%), predominantly non-suppurative in character (280/320; 87.50%), and in many cases in combination with gliosis, satellitosis, neuronophagia, neuronal necrosis, and/or vacuolization/demyelination, or in single cases with malacia. Thus, it could be shown that wild carnivores in Saxony-Anhalt are carriers mainly for CDV and sometimes also for other, partly zoonotic pathogens. Therefore, the existing monitoring program should be expanded to assess the spill-over risk from wild carnivores to humans and other animals and to demonstrate the role of wild carnivores in the epidemiology of these zoonotic pathogens.

Lactic Acid Bacteria from Gamecock and Goat Originating from Phitsanulok, Thailand: Isolation, Identification, Technological Properties and Probiotic Potential

From independent swab samples of the cloaca of indigenous gamecocks (CIG), anus of healthy baby goats (AHG), and vagina of goats (VG) originating from Phitsanulok, Thailand, a total of 263 isolates of lactic acid bacteria (LAB) were collected. Only three isolates, designated C707, G502, and V202, isolated from CIG, AHG, and VG, respectively, exhibited an excellent inhibitory zone diameter against foodborne pathogenic bacteria when evaluated by agar spot test. Isolates C707 and G502 were identified as Enterococcus faecium, whereas V202 was identified as Pediococcus acidilactici, based on 16S rRNA sequence analysis. When foodborne pathogenic bacteria were co-cultured with chosen LAB in mixed BHI-MRS broth at 39°C, their growth was suppressed. These LAB were found to be capable of surviving in simulated stomach conditions. Only the isolate G502 was able to survive in the conditions of simulated intestinal juice. This research suggests that selected LAB could be used as a food/feed supplement to reduce foodborne pathogenic bacteria and improve the safety of animal-based food or feed.

Deep impact of the inactivation of the SecA2-only protein export pathway on the proteosurfaceome of Listeria monocytogenes

Listeria monocytogenes presents a dimorphism associated to the SecA2 activity with cells having a normal rod shape or a dysmorphic elongated filamentous form. Besides variation of the cell and colony morphotype, this cell differentiation has profound ecophysiological and physiopathological implications with collateral effects on virulence and pathogenicity, biotope colonisation, bacterial adhesion and biofilm formation. This suggests the SecA2-only protein export could influence the listerial cell surface, which was investigated first by characterising its properties in L. monocytogenes wt and ΔsecA2. The degree of hydrophilicity and Lewis acid-base properties appeared significantly affected upon SecA2 inactivation. As modification of electrostatic properties would owe to modification in the composition of cell-surface proteins, the proteosurfaceome was further investigated by shotgun label-free proteomic analysis with a comparative relative quantitative approach. Following secretomic analysis, the protein secretion routes of the identified proteins were mapped considering the cognate transport and post-translocational maturation systems, as well as protein categories and subcellular localisation. Differential protein abundance profiles coupled to network analysis revealed the SecA2 dependence of 48 proteins, including some related to cell envelope biogenesis, translation and protein export, which could account for modifications of adhesion and surface properties of L. monocytogenes upon SecA2 inactivation. This investigation unravelled the profound influence of SecA2 activity on the cell surface properties and proteosurfaceome of L. monocytogenes, which provides advanced insights about its ecophysiopathology. SIGNIFICANCE: L. monocytogenes is a foodborne zoonotic pathogen and etiological agent of human listeriosis. This species presents a cellular dimorphism associated to the SecA2 activity that has profound physiopathological and ecophysiological implications with collateral effects on bacterial virulence and colonisation. To explore the influence of the SecA2-only protein export on the listerial cell, the surface properties of L. monocytogenes expressing or depleted of SecA2 was characterised by microelectrophoresis, microbial affinity to solvents and contact angles analyses. As modifications of hydrophilicity and Lewis acid-base electrostatic properties would owe to modification in the composition of cell-surface proteins, the proteinaceous subset of the surfaceome, i.e. the proteosurfaceome, was investigated further by shotgun label-free proteomic analysis. This subproteome appeared quite impacted upon SecA2 inactivation with the identification of proteins accounting for modifications in the cell surface properties. The profound influence of SecA2 activity on the cell surface of L. monocytogenes was unravelled, which provides advanced insights about its ecophysiopathology.

Effect of Nanoencapsulated Alginate-Synbiotic on Gut Microflora Balance, Immunity, and Growth Performance of Growing Rabbits

A synbiotic comprising Saccharomyces cerevisiae yeast (SCY) and Moringa oleifera leaf extract (MOLE) has been encapsulated using nanotechnology. This duo is used as a dietary supplement for growing rabbits. Physicochemical analyses, in vitro antimicrobial activity, and gastrointestinal system evaluation were used to evaluate the quality of the nanofabricated synbiotic. The in vivo study was conducted using 40-day-old male growing rabbits (n = 16 rabbits/group) to evaluate the effect of the nanofabricated synbiotic on the health and growth performance of examined rabbits. Rabbits were equally allocated into four groups; (a) NCS, which received a basal diet supplemented with a noncapsulated 11 × 10¹² CFU SCY + 0.15 g MOLE/kg diet, (b) LCS: those receiving a nanoencapsulated 5.5 × 10¹² CFU SCY + 0.075 g MOLE/kg diet, (c) HCS: those receiving an 11 × 10¹² CFU SCY + 0.15 g MOLE/kg diet, and (d) CON: those receiving a basal diet without treatment (control). The treatments continued from day 40 to day 89 of age. During the experimental period, growth performance variables, including body weight (BW), feed consumption, BW gain, and feed conversion ratio were recorded weekly. Blood samples were collected on day 40 of age and immediately before the start of the treatments to confirm the homogeneity of rabbits among groups. On day 89 of age, blood samples, intestinal, and cecal samples were individually collected from eight randomly selected rabbits. The size and polydispersity index of the nanofabricated synbiotic were 51.38 nm and 0.177, respectively. Results revealed that the encapsulation process significantly improved yeast survival through the gastrointestinal tract, specifically in stomach acidic conditions, and significantly increased in vitro inhibitory activities against tested pathogens. Furthermore, treatments had no negative effects on hematobiochemical variables but significantly improved levels of blood plasma, total protein, and insulin-like growth factor-l. Compared to the CON, NCS, and LCS treatments, the HCS treatment increased the amount of intestinal and cecal yeast cells (p < 0.05) and Lactobacillus bacteria (p < 0.05) and decreased number of Salmonella (p < 0.05) and Coliform (p = 0.08) bacteria. Likewise, both LCS and HCS significantly improved the small intestine and cecum lengths compared to CON and NCS. The HCS treatment also significantly improved BW gain and feed conversion compared to CON treatment, whereas the NCS and LCS treatments showed intermediate values. Conclusively, the nanoencapsulation process improved the biological efficiency of the innovative synbiotic used in this study. A high dose of encapsulated synbiotic balanced the gut microflora, resulting in the growth of rabbits during the fattening period.

Myocarditis caused by Listeria monocytogenes in a dog

BACKGROUND

Canine myocarditis can result from infection with bacteria Listeria monocytogenes.

CASE REPORT

A 14-week-old female entire Staffordshire Bull Terrier was assessed for lethargy, inappetence and dyspnoea. Radiographs and echocardiography revealed fluid within the pericardial space, a plaque of marked hyperechogenicity within the right ventricular free wall, marked right atrial dilation and myocardial systolic dysfunction. Histopathology of the myocardium was consistent with severe pyogranulomatous myocarditis, with gram stain revealing gram-positive bacilli, consistent with a Listerial infection. Bacterial culture of the myocardium yielded a light growth of Listeria monocytogenes.

CONCLUSION

To the best of the authors' knowledge, this is the first case of canine myocarditis caused by Listeria monocytogenes to be described and should be included as a differential diagnosis of myocarditis. Further, it prompts the consideration of potential zoonotic risks for veterinarians treating dogs with pericardial effusions.

Ecology of Listeria monocytogenes and Listeria species in India: the occurrence, resistance to biocides, genomic landscape and biocontrol

Listeria monocytogenes, the causative agent of listeriosis, has been implicated in increasing foodborne outbreaks worldwide. The disease is manifested in various forms ranging from severe sepsis in immune-compromised individuals, febrile gastroenteritis, still birth, abortions and meningoencephalitis. In India, data from studies on the detection and molecular epidemiological analysis of L. monocytogenes are only recently emerging. The presence of Listeria in different ecological niches has been recorded from India, including foods, soil, vegetables, mangrove swamps, seafood, freshwater fishes, clinical cases, and also insects. The organism has also been isolated from women with spontaneous abortions, miscarriage or recurrent obstetric history, aborted foetuses, animal clinical cases and wildlife samples. A novel species of Listeria has also been characterized. Listeria monocytogenes strains isolated from clinical, environmental, and foods showed biofilm-forming abilities. Listeria monocytogenes serotype 4b isolates of ST328, a predominant and unique ST observed in India, was repeatedly isolated from different sources, times, and geographical locations. Here, we reviewed the occurrence of Listeria in different sources in India, its resistance to biocides, and provide epidemiological analysis on its genomic landscape.

Identification and serotyping of Listeria monocytogenes, isolated from various salmon products, sold in retail market in Lithuania

Cold smoked salmon products (belly flaps, pieces, fillet, and loin) obtained from the retail market in Lithuania were tested for the presence of L. monocytogenes. It was found that contamination of the cold smoked fish products with Listeria spp. depends on the type of the product. Contamination with listeria in salmon belly flaps was 7.5 times higher than in the loin (P<0.05), 1.8 times higher than in the pieces (P<0.05) and 30 times higher than in the fillet (P<0.05). Microbiological analysis showed that 32.5% (P<0.05) of the fish product samples were infected with L. monocytogenes, while multiplex PCR confirmed 31.25% positive samples (P<0.01). According to the study results, L. monocytogenes strains were divided into two serotypes: 4b (94.6%) and 1/2a (5.4%). High contamination of the products with Listeria spp. showed that cold smoked salmon products, sold in local market, can be a reason of human listeriosis in Lithuania.

Characterization and Genetic Diversity of Listeria monocytogenes Isolated from Cattle Abortions in Latvia, 2013-2018

Listeria monocytogenes can cause disease in humans and in a wide range of animal species, especially in farm ruminants. The aim of the study was to determine the prevalence and genetic diversity of L. monocytogenes related to 1185 cattle abortion cases in Latvia during 2013-2018. The prevalence of L. monocytogenes among cattle abortions was 16.1% (191/1185). The seasonality of L. monocytogenes abortions was observed with significantly higher occurrence (p < 0.01) in spring (March-May). In 61.0% of the cases, the affected cattle were under four years of age. L. monocytogenes abortions were observed during the third (64.6%) and second (33.3%) trimesters of gestation. Overall, 27 different sequence types (ST) were detected, and four of them, ST29 (clonal complex, CC29), ST37 (CC37), ST451 (CC11) and ST7 (CC7), covered more than half of the L. monocytogenes isolates. Key virulence factors like the prfA-dependent virulence cluster and inlA, inlB were observed in all the analyzed isolates, but lntA, inlF, inlJ, vip were associated with individual sequence types. Our results confirmed that L. monocytogenes is the most important causative agent of cattle abortions in Latvia and more than 20 different STs were observed in L. monocytogenes abortions in cattle.

Application and Future Prospective of Lactic Acid Bacteria as Natural Additives for Silage Production—A Review

Ensiling is one of the essential processes to preserve fodder with high nutrients and microbiological quality. The forages before ensiling have a limited number of bacteria associated with the controlled fermentation process. Undesirable microbes can grow in silages when there is not efficient fermentation. Such kinds of microbes might cause pathogenic or toxic compounds that affect animal and human health. Therefore, it is necessary to inoculate potent starter cultures. Lactic acid bacteria’s (LABs) have been considered the most prominent microbial additives used to improve the quality of silage. Currently, LABs have been used in modern and sustainable agriculture systems due to their biological potential. Recently, many scientists have increased their focus on developing nutrient-rich animal feed from forages with LAB. This current review focuses on issues related to forage preservation in the form of silages, how undesirable microbes affect the fermentation process, the critical role of LAB in silage production, and the selection of potent LABs to effectively control unwanted microbial growth and promote those which favor animal growth.

Expression of Acute Phase Protein, Glial Fibrillary Acidic Protein, Epithelial Cadherin, and S100 Protein in Brain Tissues from Natural Cases of Ovine Encephalitic Listeriosis

Listeriosis is a disease that is induced by infection with the Gram-positive bacterium Listeria monocytogenes. Much is still unknown about the pathogenesis of encephalitic listeriosis. We aimed to identify the contribution of glial fibrillary acidic protein (GFAP), epithelial cadherin (E-cadherin), S100, and acute-phase proteins (APPs) in pathogenesis, clinical and preclinical diagnosis of natural cases of encephalitic listeriosis. Of 1,325 Ossimi sheep, 64 were suspected of having listeriosis from 2018 to 2020. Prospective cohort evaluation of clinical and postmortem findings was performed, in addition to bacterial isolation, the measurement of APPs in serum and cerebrospinal fluid (CSF), and the histopathological and immunohistochemical evaluation of GFAP, S100, and E-cadherin. Infected sheep showed nervous symptoms ranging from neck stretching to complete paralysis. APPs were significantly increased in the CSF of both clinically and preclinically diseased animals; however, serum APPs were only significantly increased in clinically diseased animals. Histopathological evaluation revealed microabscesses, meningoencephalitis, and perivascular cuffing of the brainstem of infected sheep. Immunohistochemical investigations revealed strong expression of GFAP and S100 in necrotic areas and negative expression of E-cadherin. The measurement of CSF APPs could be useful in the preclinical diagnosis of sheep listeriosis. GFAP and S100 proteins could be involved in the pathogenesis of listeriosis; however, E-cadherin does not appear to be involved.

The molecular mechanisms of listeriolysin O-induced lipid membrane damage

Listeria monocytogenes is an intracellular food-borne pathogen that causes listeriosis, a severe and potentially life-threatening disease. Listeria uses a number of virulence factors to proliferate and spread to various cells and tissues. In this process, three bacterial virulence factors, the pore-forming protein listeriolysin O and phospholipases PlcA and PlcB, play a crucial role. Listeriolysin O belongs to a family of cholesterol-dependent cytolysins that are mostly expressed by gram-positive bacteria. Its unique structural features in an otherwise conserved three-dimensional fold, such as the acidic triad and proline-glutamate-serine-threonine-like sequence, enable the regulation of its intracellular activity as well as distinct extracellular functions. The stability of listeriolysin O is pH- and temperature-dependent, and this provides another layer of control of its activity in cells. Moreover, many recent studies have demonstrated a unique mechanism of pore formation by listeriolysin O, i.e., the formation of arc-shaped oligomers that can subsequently fuse to form membrane defects of various shapes and sizes. During listerial invasion of host cells, these membrane defects can disrupt phagosome membranes, allowing bacteria to escape into the cytosol and rapidly multiply. The activity of listeriolysin O is profoundly dependent on the amount and accessibility of cholesterol in the lipid membrane, which can be modulated by the phospholipase PlcB. All these prominent features of listeriolysin O play a role during different stages of the L. monocytogenes life cycle by promoting the proliferation of the pathogen while mitigating excessive damage to its replicative niche in the cytosol of the host cell.

First Detection of Listeria monocytogenes in a Buffalo Aborted Foetus in Campania Region (Southern Italy)

Listeria monocytogenes (LM) is the causative agent of listeriosis in both animals and humans, representing one of the most severe food-borne diseases in humans. Out of 13 serotypes, only three (i.e., 1/2a, 1/2b, and 4b) are responsible for 95% of human outbreaks of listeriosis. Ruminants have been hypothesised to represent the main natural reservoir for this pathogen and to be involved in the transmission of Listeria to humans. During pregnancy, listeriosis in ruminants cause various reproductive disorders as well as abortion. However, little is known about abortion due to LM in water buffaloes (Bubalus bubalis). In this study, we report for the first time the detection of LM in a water buffalo foetus in the region of Campania, Italy. Complete necropsy was performed, and samples and swabs from the abomasum, kidneys, liver, lungs, and spleen were collected. Microbiological and molecular analyses were carried out to detect bacterial, viral, and protozoarian abortive pathogens. The results revealed the presence of LM in the liver, lungs, and abomasum, and no other agent was detected. Isolation was confirmed by biochemical and molecular tests. Molecular serotype characterisation was performed, and serogroup IVb was identified. In conclusion, because of the zoonotic implications of our findings, this report highlights the importance of including LM in the diagnostic panel in cases of bubaline abortion.

Systemic Listeria monocytogenes infection and concurrent pleural mesothelioma in a cat

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.

A review of Listeria monocytogenes from meat and meat products: Epidemiology, virulence factors, antimicrobial resistance and diagnosis

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.

The Current Status of the Alternative Use to Antibiotics in Poultry Production: An African Perspective

Over the years the growth and health of food-producing animals have been enhanced by the use of antibiotics. These have helped reduce on-farm mortalities, lower incidences of diseases and more importantly improve productivity. Generally, the utilization of antibiotics in feed has been reevaluated since bacterial pathogens have established and shared a variety of antibiotic resistance mechanisms that can easily be spread within microbial communities. Multiple countries have introduced bans or severe restrictions on the non-therapeutic use of antibiotics. This has therefore warranted the urgent need for alternatives. Africa is facing its own challenges as it has been reported to be one of the continents with the highest number of foodborne diseases with approximately 91 million related diseases and 137,000 death per annum. Stakeholder and policy direction has been put in place to curb this escalation; however, the problem persists. The use of alternatives has been recommended and some successfully used in other countries as well as Africa, including pro- and prebiotics and phytochemicals. This then leads to the core aim of this review which is to (1) determine the extent to which antimicrobial-resistant pathogens have affected Africa, (2) assess the current measures put in place by Africa to reduces antimicrobial resistance and finally (3) explore the alternative use of antibiotics in poultry production. Improved sanitary conditions and farm biosecurity are important alternatives that could be adopted by farmers instead of depending on antibiotic drugs for disease control and prevention.

Listeriosis in a peri-urban area: Cultural and molecular characterization of Listeria monocytogenes isolated from encephalitic goats

Background and Aim:

Listeriosis in food animals bears a significant threat to human health. Detailed investigations into the cause facilitate proper management of the disease. This study reports the cultural, pathological, and molecular characterization of Listeria monocytogenes isolated from encephalitic goats from peri-urban Guwahati, Assam.

Materials and Methods:

Out of nine suspected samples, five positive isolates of L. monocytogenes were subjected to bacteriological, biochemical, and molecular tests. The genus and species-specific L. monocytogenes 16S rRNA and prs genes were amplified by polymerase chain reaction (PCR) to yield 1200 and 370 bp sized products, respectively. The encephalitic form of the disease was characterized by circling movement, high fever, and terminal recumbence.

Results:

All the five isolates were confirmed to be L. monocytogenes based on PCR amplification of genus and species-specific 16S rRNA and prs gene products. The isolates were sensitive to ciprofloxacin, oxytetracycline (OTC), and norfloxacin, but resistant to doxycycline and erythromycin. A high dose of OTC was used in a goat at the early stage of clinical symptom and the animal recovered clinically.

Conclusion:

Listeriosis in goats could pose a significant public health threat as the meat (occasionally milk) or meat products from goats are widely consumed by the people of Assam. Understanding the molecular epidemiological aspects of L. monocytogenes infections of food animal species should, therefore, be the priority in this part of the country.

Listeria monocytogenes induced dysbiosis in snails and rebiosis achieved by administration of the gut commensal Lactobacillus plantarum Sgs14 strain

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.

Multiple drug resistance of Listeria monocytogenes isolated from aborted women by using serological and molecular techniques in Diwaniyah city/Iraq

Background and Objectives:

The study was sought to detect the effect of Listeria monocytogenes on pregnant Iraqi women at Al-Diwaniya hospitals and determination of virulence genes and antimicrobial susceptibility of isolates.

Materials and Methods:

360 specimens including blood, urine, vaginal and endocervical were collected from 90 patients with spontaneous abortions. Blood samples were displayed to immunological study and remaining specimens were subjected to bacteriological diagnosis. PCR was used to determine the virulence factors and antimicrobial resistance genes.

Results:

Fifteen positive samples (16.6%) of patients and thirteen isolates (14.5%) from patients were recognized based on ELISA and PCR assay respectively. The general isolation of L. monocytogenes strains in cases of abortive women was 13/270 (4.8%). L. monocytogenes strains were highly virulent because of presence of virulence factors associated genes, namely actA, hlyA, plcA and prfA in all strains. Multiple drug resistance (MAR) index values of 15.4% of isolates were >0.2.

Conclusion:

It is necessary for conducting susceptibility testing and to select the suitable antibiotics and avoid the effects of these bacteria in pregnant women.

Review on Major Food-Borne Zoonotic Bacterial Pathogens

Food-borne microorganisms are major pathogens affecting food safety and cause human illness worldwide as a result of consumption of foodstuff, mainly animal products contaminated with vegetative pathogens or their toxins. Most of these microbes have zoonotic importance resulting in significant impact on both public health and economic sectors. Bacteria are the causative agents of two-thirds of human food-borne diseases worldwide with high burden in developing countries. Hence, the objectives of this review paper are to highlight the background of food-borne bacterial pathogens and to review common major food-borne zoonotic bacterial pathogens. Food animals are the major reservoirs of many food-borne zoonotic bacterial pathogens, and food products of animal origin are the main vehicles of transmission. Meat, dairy products, and eggs are the main ways by which people are exposed to zoonotic bacteria. S. aureus, Salmonella species, Campylobacter species, L. monocytogenes, and E. coli are the major zoonotic bacterial pathogens which are the causative agents of food-borne illness and death in the world associated with consumption of contaminated animal products. Production of toxins and structural virulent factors are responsible for the pathogenesis of these bacteria. These major zoonotic bacteria cause human infections which are characterized mainly by gastrointestinal symptoms including nausea, vomiting, diarrhea, abdominal cramps, and other agent-specific symptoms. Some bacteria may cause severe complications. Conventional (culturing), serological, and molecular techniques are important for detection of these common zoonotic bacteria and their toxins in food. Good hygiene, GMP, sanitation in operating procedures, and implementation of standardized HACCP and pasteurization procedures are effective methods for the control and prevention. Currently, the emergence of multidrug-resistant zoonotic bacteria associated with consumption of contaminated animal products is a great concern for the public health, and there should be coordinated surveillance and monitoring system for food-borne zoonotic bacterial pathogens particularly in developing countries including Ethiopia.