Human Listeriosis Research Articles

Prevalence, virulence characterization, and genetic relatedness of Listeria monocytogenes isolated from chicken retail points and poultry slaughterhouses in Turkey.

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.

Listeria monocytogenes contamination in ready to eat foods

Listeria monocytogenes is a food-borne pathogen responsible for listeriosis, a sickness with a high mortality rate. Listeriosis is largely associated with ready-to-eat (RTE) foods. It is well established that foods that pose the greatest risk of foodborne listeriosis are those RTE foods that have intrinsic characteristics such as pH and water activity that support the growth of L. monocytogenes. RTE foods can also become re-contaminated during further processing and handling. Increased handling leads to a higher probability of contamination. Sources of contamination can be food contact surfaces, processing machinery and workers. In our research, L. monocytogenes was detected in a RTE salad. Food safety criteria for Listeria monocytogenes in RTE foods have been applied from 2006 (Commission Regulation (EC) 2073/2005). Still, human invasive listeriosis was reported to increase during 2009-2013 in the European Union and European Economic Area. Time series analysis for the 2008-2015 period in this area showed an increasing trend of the monthly notified incidence rate of confirmed human invasive listeriosis of the over 75 age groups and female age group between 25 and 44 years old (probably related to pregnancies).

A systematic review and meta-analysis on the prevalence of antibiotic-resistant Listeria species in food, animal and human specimens in Iran.

The aim of this study was to determine the antimicrobial resistance characteristics of Listeria species isolated from foods and food processing environments, animal and human specimens in Iran. A systematic review of the papers published in Persian and English languages up to 20th May 2019 and indexed in the Scientific Information Database, PubMed, Scopus and Google Scholar databases using related keywords was conducted. Eligible articles were selected based on the predefined inclusion and exclusion criteria, followed by data extraction and meta-analysis using random-effects or fixed-effects models. A total of 27 articles were found reporting antibiotic resistance patterns of different Listeria species using disk diffusion method. Among Listeria species, Listeria monocytogenes resistance to commonly used antibiotics i.e. penicillin, ampicillin and gentamicin was as follows: 34.5%, 26.4%, 8.9% in isolates from foods and food processing environments, 47.1%, 29.5%, 9.2% in isolates from animal specimens and 56.8%, 29.5%, 32.4% in human strains, respectively. A high prevalence of L. monocytogenes strains resistant to penicillin, ampicillin and gentamicin was observed in Iran. Our findings suggested that trimethoprim/sulfamethoxazole, vancomycin and ciprofloxacin can be used as alternatives in the treatment of human listeriosis in Iran due to their low resistance rates.

Broad host range phage vB-LmoM-SH3-3 reduces the risk of Listeria contamination in two types of ready-to-eat food

Listeria monocytogenes is a food borne pathogen causing listeriosis in humans and animals. L. monocytogenes can tolerate severe environments and food processing conditions by forming biofilms and becoming resistant to disinfectants. Thus, it is important to develop new strategies to control the contamination of L. monocytogenes and keep food safety. In the present study, a new L. monocytogenes phage vB-LmoM-SH3-3 (designated as phage SH3-3) was isolated from a food processing plant. The genome of phage SH3-3 shares homology with multiple non-Listeria phages, but shares low similarity with classical Listeria phages. Phage SH3-3 showed widely lytic activity to Listeria spp. including L. monocytogenes, L. innocua and L. welshimeri. With an efficient minimal inhibitory concentration, phage SH3-3 could also inhibit the formation of the dense and net-like structure of the L. monocytogenes biofilm. Moreover, phage SH3-3 showed high efficacy against L. monocytogenes in salmon meat and orange juice. Therefore, phage SH3-3 could be potentially used as a natural biocontrol preservative to reduce L. monocytogenes contamination in ready-to-eat food and during the processing stages of food production.

Prediction of Persistence of Listeria monocytogenes ST451 in a Rabbit Meat Processing Plant in the Czech Republic

This study was focused on characterization of the genetic diversity of Listeria monocytogenes isolated from packed fresh rabbit meat obtained from one producer via retail outlets. The partial aim was to compare the characteristics of a suspect persistent strain with strains from human cases. The occurrence of L. monocytogenes in vacuum-packed rabbit meat was monitored during 2013 to 2016. All strains were characterized by serotyping, pulsed-field gel electrophoresis, and multilocus sequence typing (MLST). Selected strains, which represented each year, were analyzed using the whole genome sequencing method. L. monocytogenes was detected in 21 (38%) of 56 originally packed rabbit meat samples from one food producer during the whole monitored period. All strains showed the identical serotype (1/2a), AscI/ApaI pulsotype (735/2), and sequence type (ST451). The clonal similarity of strains from rabbit meat was also confirmed on the basis of core genome MLST (on 1,701 loci). This fact suggests the occurrence of a suspect persistent strain in the meat processing plant. Results of core genome MLST enabled us to unambiguously exclude rabbit meat as a source of listeriosis in humans caused by the indistinguishable AscI/ApaI pulsotype and sequence type, although all strains carried all genes important for the virulence of L. monocytogenes. No specific genes that may be associated with its persistence in the food processing environment were detected among the tested strains of ST451.

Listeria monocytogenes Biofilm Adaptation to Different Temperatures Seen Through Shotgun Proteomics.

Listeria monocytogenes is a foodborne pathogen that can cause invasive severe human illness (listeriosis) in susceptible patients. Most human listeriosis cases appear to be caused by consumption of refrigerated ready-to-eat foods. Although initial contamination levels in foods are usually low, the ability of these bacteria to survive and multiply at low temperatures allows it to reach levels high enough to cause disease. This study explores the set of proteins that might have an association with L. monocytogenes adaptation to different temperatures. Cultures were grown in biofilm, the most widespread mode of growth in natural and industrial realms. Protein extractions were performed from three different growth temperatures (10, 25, and 37°C) and two growth phases (early stage and mature biofilm). L. monocytogenes subproteomes were targeted using three extraction methods: trypsin-enzymatic shaving, biotin-labeling and cell fractionation. The different subproteomes obtained were separated and analyzed by shotgun proteomics using high-performance liquid chromatography combined with tandem mass spectrometry (LC-OrbiTrap LTQVelos, ThermoFisher Scientific). A total of 141 (biotinylation), 98 (shaving) and 910 (fractionation) proteins were identified. Throughout the 920 unique proteins identified, many are connected to basic cell functions, but some are linked with thermoregulation. We observed some noteworthy protein abundance shifts associated with the major adaptation to cold mechanisms present in L. monocytogenes, namely: the role of ribosomes and the stressosome with a higher abundance of the general stress protein Ctc (Rl25) and the general stress transcription factor sigma B (σB), changes in cell fluidity and motility seen by higher levels of foldase protein PrsA2 and flagellin (FlaA), the uptake of osmolytes with a higher abundance of glycine betaine (GbuB) and carnitine transporters (OpucA), and the relevance of the overexpression of chaperone proteins such as cold shock proteins (CspLA and Dps). As for 37°C, we observed a significantly higher percentage of proteins associated with transcriptional or translational activity present in higher abundance upon comparison with the colder settings. These contrasts of protein expression throughout several conditions will enrich databases and help to model the regulatory circuitry that drives adaptation of L. monocytogenes to environments.

Bio-Plex suspension array immuno-detection of Listeria monocytogenes from cantaloupe and packaged salad using virulence protein inducing activated charcoal enrichment media

Listeria monocytogenes, the causative agent of listeriosis in humans, is a Gram-positive bacterium that is contracted via the ingestion of contaminated foods. Two of the largest outbreaks of listeriosis occurred following consumption of tainted cantaloupe and packaged salads. Molecular methods and immuno-based techniques for detection of L. monocytogenes in these food matrices can be difficult due to the presence of assay inhibiting elements. In this study, we utilized a novel enrichment media containing activated charcoal as the key ingredient that induces hyperactive expression and secretion of L. monocytogenes virulence proteins. The Bio-Plex suspension array system, based on Luminex xMAP technology, was subsequently employed to specifically detect accumulated L. monocytogenes secreted and membrane bound proteins via paramagnetic microsphere-antibody complexes. Cantaloupe and packaged salad samples were treated with a dilution series of L. monocytogenes and incubated in activated charcoal media following a short pre-enrichment step in Buffered Listeria Enrichment Broth. Secreted L. monocytogenes lysteriolysin O was captured using magnetic microsphere-antibody conjugates and measured using the Bio-Ple×200 analyzer. As few as 100 CFU/g of L. monocytogenes was detected from both spiked cantaloupe and packaged salad samples. In addition, antibody conjugated microspheres targeting a membrane protein present on both pathogenic and nonpathogenic Listeria species was used to identify as few as 100 CFU/g of both pathogenic and nonpathogenic species in cantaloupe and packaged salad. This method presumptively identifies L. monocytogenes from cantaloupe and packaged salad in less than 24 h and non-pathogenic Listeria species within 22 h.

Isolation, Potential Virulence, and Population Diversity of Listeria monocytogenes From Meat and Meat Products in China.

Listeria monocytogenes is a globally notorious foodborne pathogen. This study aimed to qualitatively and quantitatively detect L. monocytogenes from meat and meat products in China and to establish their virulence profiles and population diversity. From 1212 meat and meat product samples, 362 (29.9%) were positive for L. monocytogenes. Of these positive samples, 90.6% (328/362) had less than 10 MPN/g, 5.5% (20/364) samples had 10–110 MPN/g, and 3.9% (14/362) of the positive samples had over 110 MPN/g. Serogroup analysis showed that the most prevalent serogroup of L. monocytogenes was I.1 (1/2a-3a), which accounted for 45.0% (123/458) of the total, followed by serogroup I.2 (1/2c-3c) that comprised 26.9%, serogroup II.1 (4b-4d-4e) that comprised 4.8%, and serogroup II.2 (1/2b-3b-7) that comprised 23.3%. A total of 458 isolates were grouped into 35 sequence types (STs) that belonged to 25 clonal complexes (CCs) and one singleton (ST619) by multi-locus sequence typing. The most prevalent ST was ST9 (26.9%), followed by ST8 (17.9%), ST87 (15.3%), ST155 (9.4%), and ST121 (7.6%). Thirty-seven isolates harbored the llsX gene (representing LIPI-3), and they belonged to ST1/CC1, ST3/CC3, ST288/CC288, ST323/CC288, ST330/CC288, ST515/CC1, and ST619, among which ST323/CC288, ST330/CC288, and ST515/CC1 were newly reported to carry LIPI-3. Seventy-five isolates carried ptsA, and they belonged to ST87/CC87, ST88/CC88, and ST619, indicating that consumers may be exposed to potential hypervirulent L. monocytogenes. Antibiotics susceptibility tests revealed that over 90% of the isolates were susceptible to 11 antibiotics; however, 40.0% of the isolates exhibited resistance against ampicillin and 11.8% against tetracycline; further, 45.0 and 4.6% were intermediate resistant and resistant to ciprofloxacin, respectively. The rise of antibiotic resistance in L. monocytogenes suggests that stricter regulations should be formulated to restrict the use of antibiotic agents in human listeriosis treatment and livestock breeding.

Biotechnological method of preparation and characterization of recombinant antimicrobial peptide avicin a from Enterococcus avium

Avicin A is a bacteriocin from the gram-positive bacterium Enterococcus avium. It exhibits a high microbicidal activity against bacteria of the genus Listeria, a causative agent of the severe human infection listeriosis. We developed a biotechnological method for obtaining avicin A and characterized its structure and biological activity. We also proposed a possible mechanism of the antimicrobial action of avicin A.

Impact of Combined Acidic and Hyperosmotic Shock Conditions on the Proteome ofListeria monocytogenesATCC 19115 in a Time-Course Study

Listeria monocytogenescan cause listeriosis in humans through consumption of contaminated food and can adapt to and grow under a wide array of physiochemical stresses. Consequently, it causes persistent food safety issues and requires vigilant sanitation processes to be in place, especially for the manufacture of high-risk food products. In this study, the global proteomic responses of the food-borne pathogenL. monocytogenesstrain ATCC 19115 were determined when exposed to nonthermal inactivation. This process was examined in the early stationary growth phase with the strain placed under simultaneous exposure to low pH (pH 3.5) and high salinity (aw0.900, 14% NaCl). Proteomic responses, measured using iTRAQ techniques, were conducted over a time course (5 min, 30 min, and 1 h at 25°C). The enumeration results showed that, at 5 min, cells underwent initial rapid inactivation by 1.2 log units and 2.5 log units after 30 min, and after that, culturability remained stable when sampled at 1 h. From the iTRAQ results, the proteome level changes that occur rapidly during the inactivation process mainly affected prophage, cell defense/detoxification, carbohydrate-related metabolism, transporter proteins, phosphotransferase systems, cell wall biogenesis, and specific cell surface proteins. Pathway map analysis revealed that several pathways are affected including pentose and glucuronate interconversions, glycolysis/gluconeogenesis, pyruvate metabolism, valine, leucine and isoleucine biosynthesis, oxidative phosphorylation, and proteins associated with bacterial invasion of epithelial cells and host survival. Proteome profiling provided a better understanding of the physiological responses of this pathogen to adapt to lethal nonthermal environments and indicates the need to improve food processing and storage methods, especially for non- or minimally thermally processed foods.

Listeria monocytogenes and other Listeria species in raw milk and sausage in East Algeria

Listeria monocytogenes is a pathogenic bacterium that can cause Listeriosis in humans. The aim of this study is to isolate and enumerate L. monocytogenes and other Listeria species from raw milk and sausage samples collected in East Algeria. A total of 87 food samples were analyzed according to ISO 11290-1 and ISO 11290-2 methods. Of the samples examined, 10.34% were found to be positive for Listeria spp. Three species of Listeria were detected, in which L. innocua was the most commonly recovered species (66.67%) followed by L. seeligeri (22.22%) and L. monocytogenes (11.11%).The count for L. innocua ranged from 1.95 to 3.13 log10 (CFU g-1 or CFU ml-1), against 1.65 to 2.48 log10 (CFU g-1 or CFU ml-1) for L. seeligeri. L. monocytogenes contaminated sausage sample had enumeration results of 1.65 log10 (CFU g-1). The presence of Listeria in milk and sausage samples reflects the no control of hygienic practices.

Seasonal Changes in the Occurrence of Listeria Monocytogenes in Duhok Province

Listeria monocytogenes are Gram-positive bacilli cause listeriosis, associated with high rates of hospitalization and mortality. A total of 1362 samples were investigated included 647 clinical samples and 715 from food. This study investigated the differences in the seasonal occurrence of L. monocytogenes in Kurdistan region-Iraq. L. monocytogeneswas found in 48 samples (3.52%) out of 1362 samples. There were 7/642(1.09%) human clinical samples diagnosed with cold and moderate weather (November, December 2016, and January, February, April 2017). While 41/715(5.73%) of L. monocytogenesisolates were found among food samples, meat samples (n=37) and dairy samples (n=4). A total of 37/476 (7.77%) of the L. monocytogenes isolates in meat samplesweredetected during warm weather (from July through October 2016). In addition, L. monocytogenesin dairy products was found to be by 4/239 (1.68%), were isolated during the moderate season (October, November 2016, and April, May 2017). The study found that the incidence of meat contamination by L. monocytogenesincrease significantly during the warm season in comparison with other seasons. Furthermore, the cases of human Listeriosis caused correlated well with the seasonal levels of L. monocytogenesfound in dairy products. A statistically significant difference in the occurrence of L. monocytogenesisolates and seasons were identified in this study (P value= <0.05).

INDICATION OF LISTERIA MONOCYTOGENES IN MEAT AND MEAT PRODUCTS IN THE TERRITORY OF AGRICULTURAL PROVINCE

In recent decades, the majority of outbreaks of listeriosis with a high percentage of deaths was caused by the consumption of food products, including meat and meat products. One of the main principles of prevention of listeriosis in humans and animals is a constant quality control of food and feeds. The district of the Ussurisk city specializes mainly in the production of agricultural products. Meat production work on the raw materials of local origin, and the imported meat is also used. There was executed a study concerning the possibility of the contamination of meat products of Listeria monocytogenes on the territory of the agricultural province of the district of the Ussurisk city for the period from 2012 to 2015. A total of 21491 sample products were investigated according to rules “Common sanitary and epidemiological and hygienic requirements for goods subject to sanitary-and-epidemiologic supervision (control)” of the Customs Union (Chapter II, section 1) and the Technical Regulations of the Customs Union № 880 “About security of food “(Appendix 1). The presence of 45 positive cases of L. monocytogenes was revealed, at that the most of them have been found in meat products and poultry meat. Observations of the occurrence rate of L. monocytogenes in meat of the imported production for a number of years show these the pathogenic bacteria to be isolated every year in 40% - 66.6% of cases (of all positive cases of isolation from meat). This meat was imported mainly from countries such as Brazil, Paraguay, New Zealand, Austria, England, Uruguay. A large proportion of meat and meat products, contaminated by L. monocytogenes enters the territory of Primorsky Kray from Latin America. It is important to note that meat and meat products contaminated by these pathogens were also produced in the territory of the district of the city of Ussurisk. In connection with it there is obvious the need as for further continuation of monitoring products on the market, as a survey of agricultural animals of private and public farms in the district.

MOLECULAR CHARACTERIZATION OF LISTERIA MONOCYTOGENES ISOLATED FROM SOME ABATTOIRS IN DAKAHLIA, EGYPT

A total of 400 samples were collected from 100 slaughtered carcasses (cattle, buffalo, sheep and goat, 25 of each). Four samples from each carcass representing: muscle, liver, kidney and heart were collected for detection of L. monocytogenes. Also, 100 environmental samples representing water used in abattoir, knife swabs and swabs from abattoir walls before and after cleaning, (25 for each) and 100 fecal swabs from abattoirs' workers were randomly collected from different abattoirs located at Dakahlia governorate, Egypt. The Prevalence rate of L. monocytogenes in cattle carcasses was 3 (12%), 2 (8%) and 1(4%) in examined liver, kidneys and heart samples out of 25 examined samples for each organ, respectively and couldn't be detected in any of muscle samples. Meanwhile, in buffalo carcasses, theprevalence rate was 4 (16%), 2 (8%),1 (4%) and 1 (4%) in examined liver, kidneys, heart and muscle samples out of 25 examined samples for each organ, respectively. Meanwhile, in sheep carcasses, the prevalence rate of L. monocytogenes was 3 (12%), 2 (8%), 2 (8%) and 2 (8%) in examined liver, kidneys, heart and muscle samples out of 25 examined samples for each organ, respectively. Meanwhile, in goat carcasses, the prevalence rate was 4 (12%), 2 (8%), 2 (8%) and 1(4%) in examined liver, kidneys, heart and muscle samples out of 25 examined samples for each organ, respectively. In environmental samples, the prevalence rate was 28% from examined wall swabs before cleaning, 4% from examined wall swabs after cleaning, 4% from examined knife swabs and 4% from fecal swabs from abattoirs workers. Meanwhile, no L. monocytogenes was detected in water samples. Regarding pathogenicity test, death of all inoculated wining rabbits (23) as following 60% on 3rd day, 30% on 4th day and 10% on 5th day and L. monocytogenes was isolated from their organs. The isolates of L. monocytogenes were found to be virulent by using PCR assay incorporating inlA, hlyA and prfA genes primers. The public health hazards as well as suggestive measures to reduce human listeriosis have been discussed.

Rhombencephalitis caused by Listeria monocytogenes with hydrocephalus and intracranial hemorrhage: A case report and review of the literature

BACKGROUNDListeria monocytogenes (L. monocytogenes), a Gram-positive facultatively intracellular bacterium, is the causative agent of human listeriosis. Listeria infection is usually found in immunocompromised patients, including elderly people, pregnant women, and newborns, whereas it is rare in healthy people. L. monocytogenes may cause meningitis, meningoencephalitis, and some very rare and severe complications, such as hydrocephalus and intracranial hemorrhage, which cause high mortality and morbidity worldwide. Up to now, reports on hydrocephalus and intracranial hemorrhage due to L. monocytogenes are few.CASE SUMMARYWe herein report a case of rhombencephalitis caused by L. monocytogenes in a 29-year-old man. He was admitted to the hospital with a 2-d history of headache and fever. He consumed unpasteurized cooked beef two days before appearance. His medical history included type 2 diabetes mellitus, and contaminated beef intake 2 d before onset. Cerebrospinal fluid analysis revealed Gram-positive rod infection, and blood culture was positive for L. monocytogenes. Magnetic resonance imaging findings suggested rhombencephalitis and hydrocephalus. Treatment was started empirically and then modified according to the blood culture results. Repeated CT images were suggestive of intracranial hemorrhage. Although the patient underwent aggressive external ventricular drainage, he died of a continuing deterioration of intracranial conditions.CONCLUSIONHydrocephalus, intracranial hemorrhage, and inappropriate antimicrobial treatment are the determinations of unfavorable outcomes.

Occurrence, serotypes, and characteristics of Listeria monocytogenes in meat and meat products in South Africa between 2014 and 2016

AbstractListeria monocytogenes is an intracellular pathogen that causes life‐threatening disease called listeriosis. However, in South Africa (SA), there is a dearth of information concerning the potential role of meat and meat products as potential sources for human listeriosis. The aim of the study was to determine the occurrence and level of L. monocytogenes found in meat and meat products in SA and to characterize L. monocytogenes strains according to serogroups, antimicrobial resistance profiles and virulence genes. A total of 2,017 samples from imported and locally produced raw, processed and ready to eat meat were collected from 2014 to 2016 across nine provinces of SA. The samples for L. monocytogenes were isolated using microbiological techniques and real‐time polymerase chain reaction (PCR). Antimicrobial resistance profiles of the isolates were determined by testing 19 antimicrobial impregnated discs using Kirby–Bauer disc diffusion method. Characterization in terms of serogroup typing and virulence profiling was done using conventional PCR. The overall occurrence of L. monocytogenes was 14.7% (296/2,017), which varied between meat collected on the domestic market (15.0%; 264/1,758) and directly at the three ports of entries (12.4%; 32/259). The contamination level of the positive samples ranged from 1 to 3.7 log CFU/g and 1 to 4.1 log CFU/g for samples collected from the domestic and imported meat, respectively. All positive isolates were serotyped by multiplex PCR, of which majority of the isolates belonged to molecular serogroup ½a‐3a (45.5%), followed by 4b‐4d‐4e (24.2%), and ½c‐3c (15.2%). Most of the isolates harbored the inlJ (98.7%) and ipa (95.6%) genes. However, at least one of the other internalin genes (inlB, inlC, and inlA) was present in most of the isolates. All the tested isolates showed resistance to at least 3 of the 19 antibiotics, with 5 (1.7%) of them displaying resistance to 13 of the 19 antibiotics. Resistance to streptomycin (99.0%), clindamycin (97.3%), fusidic acids (95.6%), nitrofurantoin (79.7%), and gentamycin (74.4%) was observed while high rates of sensitivity were observed for ampicillin (85.6%), kanamycin (84.6%), amikacin (77.6%), vancomycin (74.2%), and tetracycline (62.5%). The presence of L. monocytogenes in various meat products in SA pose a risk to human health. Therefore, the present research provides valuable baseline information that will help in the development of policies and regulations for monitoring of L. monocytogenes in meat and meat products in SA.Practical applicationsThis study is extensive and involved analysis of meat and meat products from all the nine provinces of South Africa. Furthermore, the study involved analysis of imported meat (from the three major ports of entry) that was destined for the South African market. The findings that were obtained are significant from academic, policy, and practical points of view. The findings provide empirical evidence of the contamination of a proportion of raw intact, raw processed, and ready‐to‐eat meat and products that are available on the South African market. Furthermore, our findings illustrate the levels of contamination, which is important for providing guidelines with respect to L. monocytogenes contamination of meats. Information of the predominant L. monocytogenes serotypes from this study provide important epidemiological data of the strains that are circulating in meat and meat products. The antimicrobial resistance results are important for contributing to guidelines on antimicrobial use.

Antilisterial efficacy of Lactobacillus brevis MF179529 from cow: an in vivo evidence

BackgroundListeria monocytogenes is an opportunistic foodborne pathogen that causes human Listeriosis and high mortality particularly in immunocompromised individuals. Pregnant women are more prone to L. monocytogenes infection resulting in abortions.In the present study, antilisterial activity of Lactobacillus brevis (LB) MF179529, a probiotic bacterial strain, was investigated in a murine model.MethodsInitially a pilot study was conducted to determine the dose of L. monocytogenes required to cause symptomatic listeriosis. In the main trial, mice were divided into 4 groups. Group I was kept as negative control, group II was exposed to L. monocytogenes and maintained as positive control. Group III was fed with L. brevis only, while group IV received L. brevis for 3 days prior to L. monocytogenes infection. A volume of 200 μl of L. monocytogenes ATCC 19115 and L. brevis MF179529 bacterial suspension corresponding to cell density of 109CFU/ml were given to respective groups by intragastric route. Progress of infection was monitored for 7 days including general health scoring, listeria dispersion in organs, bacterial load in intestine and blood biochemistry were recorded on 3rd, 5th and 7th days post infection (dpi).ResultsClinical listeriosis was induced by 109CFU/ml of L. monocytogenes ATCC 19115 in mice.Animals of group IV displayed minor signs of infection. L. brevis supplementation resulted in significant reduction in dispersion and propagation of L. monocytogenes in liver, spleen and intestine. L. brevis MF179529 consumption led to a significant elevation of number of lactic acid bacteria and reduction of total plate count, anaerobic count and coliform population in intestine. Moreover, total leukocyte and neutrophil counts of treated animals were similar to the negative control while positive control group displayed higher number. Safety evaluation of L. brevis was performed by monitoring general health, hematological and serological parameters of L. brevis fed and negative control group (group III and I). No significant difference in feed intake, body temperature, body weight and blood picture could be detected in L. brevis supplemented and control groups.ConclusionOur results indicate ameliorative role of L. brevis in L. monocytogenes infection and suggest that L. brevis could be used for prophylactic measure.

Preliminary results on prevalence and persistence of Listeria monocytogenes in different dairy and meat processing plants in Central Italy

Purpose: Listeria monocytogenes is a relevant food - borne pathogen able to cause severe and fatal infections in humans. Understanding correlations among different Listeria monocytogenes strains and evaluating Listeria monocytogenes isolates capacity to persist in processing plant environments is an essential tool for food surveillance. Most outbreaks of human listeriosis seem to be linked to strains able to persist in the environment and to replicate in foods. The aim of this study was to investigate prevalence and persistence of Listeria monocytogenes strains subtypes in different dairy and meat processing plants in the Abruzzo and Molise Region. Methods & Materials: Totally 14 food processing plants have been selected for the study (7 for dairy products – DP - and 7 for meat products - MP). Sampling was performed in 4 session from March to October 2017, from 30 to 35 environmental sampling have been sampled in all the division of the plants, both from food contact surfaces (FCS) and non food contact surfaces (NFCS). Sampling sites were selected as niches for Listeria monocytogenes presence. Samples were tested with FSIS MLG8-10:2017 method. Listeria monocytogenes strains were serotyped using the method described in the U.S. FDA Bacteriological Analytical Manual (Bennett and Weaver, 2001). PFGE subtyping was performed according to the PulseNet protocol (Pulsenet USA, 2013) and macrorestriction patterns were analyzed using the BioNumerics 7.6 (Applied Maths, Kortrijk, Belgium). Results: Results are based on 1772 environmental samples tested, 135 (7.6%) samples were found positive for Listeria monocytogenes (94 NFCS and 41 FCS) in 4 DP and 6 MP. PFGE showed indistinguishable persistent strains in 2 DP and 3 MP in all sampling sessions and in one MP in 3 sampling sessions. Conclusion: The persistence of Listeria monocytogenes underlines the ability to persist in food producing plants, in favourable niches inside the processing environment. To reduce Listeria monocytogenes prevalence, Good Manufacturing Practices and Good Hygiene Practices are needed. Analysis are still ongoing to model the contamination path, NGS on isolated strains will be carried out to confirm the persistence of the strains and to find the presence of gene devoted to resistance and persistence.

Influence of agronomic practices and pre-harvest conditions on the attachment and development of Listeria monocytogenes in vegetables

Interest in fresh vegetables is on the increase due to their protective effects against several diseases. Listeria monocytogenes is a human pathogen easily found in vegetables. The purpose of this review article is to analyse the influence of the agricultural practices applied in pre-harvest, the environmental biotic and abiotic factors characterising the cultivation field, as well as the handling procedures at harvest that might greatly influence the presence and the levels of L. monocytogenes in fresh produce. This review article describes the routes of L. monocytogenes infections in relation to the agricultural practices commonly applied during vegetable cultivation. It also analyses the influence of the different cultivation systems as well as the main environmental factors and compares the effects of manual and mechanical harvest retrieving data from literature. Even though post-harvest sanitising is a common practice, fresh produce is still responsible for foodborne diseases. In the last years, the number of cases of human listeriosis is on the increase, and the consumption of fresh vegetables is being more frequently associated with these events. While still relatively rare, human listeriosis is one of the most serious food-borne diseases and continues to be one of the more lethal foodborne pathogens associated with vegetables. Seed decontamination represents an efficient operation to reduce microbial plant internalisation and diffusion. Since L. monocytogenes persists in soil for long periods, the hydroponic systems have been found to reduce its contamination of vegetables.

Biotechnological Method of Preparation and Characterization of Recombinant Antimicrobial Peptide Avicin A from Enterococcus avium.

Avicin A is a bacteriocin from the gram-positive bacterium Enterococcus avium. It exhibits a high microbicidal activity against bacteria of the genus Listeria, a causative agent of the severe human infection listeriosis. We developed a biotechnological method for obtaining avicin A and characterized its structure and biological activity. We also proposed a possible mechanism of the antimicrobial action of avicin A.