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Concept: Listeria monocytogenes

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Listeria monocytogenes infection is most commonly recognized in ruminants, including cattle, sheep, and goats; but it is rarely diagnosed in poultry. This report describes an outbreak of L. monocytogenes in a backyard poultry flock. Also, it points out the importance of collaboration between veterinarians and public health departments and the possible implications of zoonotic diseases.

Concepts: Epidemiology, Listeria monocytogenes, Listeria, Listeriosis, Livestock, Goat, Joseph Lister, 1st Baron Lister, Herbivorous animals

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The objective of this study was to evaluate the susceptibility of 259 Listeria monocytogenes strains isolated from food and food-processing environments and patient samples in Germany to 14 antibiotics widely used in veterinary and human medicine. L. monocytogenes strains were isolated mainly from milk and milk products and classified according to their molecular serotypes IIa (n=112), IIb (n=41), IIc (n=36), IVa (n=1), IVb (n=66), and IVb-v1 (n=3).

Concepts: Medicine, Microbiology, Fungus, Antibiotic, Listeria monocytogenes, Listeria, Listeriosis, Joseph Lister, 1st Baron Lister

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Listeria monocytogenes can asymptomatically inhabit the human intestine as a commensal bacterium. However, the mechanism by which L. monocytogenes is able to inhabit the intestine without pathogenic symptoms remains unclear. Here, we compared the invasion efficiency of L. monocytogenes strains with the 268- and 385-bp-long actA gene. Clinical strains SMFM-CI-3 and SMFM-CI-6 with 268-bp actA isolated from patients with listeriosis and strains SMFM-SI-1 and SMFM-SI-2 with the 385-bp gene isolated from carcasses were used for inoculum preparation. The invasion efficiency of these strains was evaluated using Caco-2 cells (intestinal epithelial cell line), prepared as normal and healthy cells with tightened tight junctions and senescent cells with loose tight junctions, which were loosened by adriamycin treatment. The invasion efficiency of L. monocytogenes strains with the 268-bp-long actA gene was 1.12.6-times lower than that of the strains with the 385-bp-long gene in normal and healthy cells. However, the invasion efficiency of both types of strains did not differ in senescent cells. Thus, L. monocytogenes strains with the 268-bp-long actA gene can inhabit the intestine asymptomatically as a commensal bacterium, but they may invade the intestinal epithelial cells and cause listeriosis in senescent cells.

Concepts: Bacteria, Epithelium, Intestine, Meningitis, Listeria monocytogenes, Listeria, Listeriosis, Intestinal epithelium

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The microbiological safety of fresh produce is monitored almost exclusively by culture-based detection methods. However, bacterial food-borne pathogens are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses such as chlorine, which is commonly used for fresh produce decontamination. Here, complete VBNC induction of green fluorescent protein-tagged Listeria monocytogenes and Salmonella enterica serovar Thompson was achieved by exposure to 12 and 3 ppm chlorine, respectively. The pathogens were subjected to chlorine washing following incubation on spinach leaves. Culture data revealed that total viable L. monocytogenes and Salmonella Thompson populations became VBNC by 50 and 100 ppm chlorine, respectively, while enumeration by direct viable counting found that chlorine caused a <1-log reduction in viability. The pathogenicity of chlorine-induced VBNC L. monocytogenes and Salmonella Thompson was assessed by using Caenorhabditis elegans Ingestion of VBNC pathogens by C. elegans resulted in a significant life span reduction (P = 0.0064 and P < 0.0001), and no significant difference between the life span reductions caused by the VBNC and culturable L. monocytogenes treatments was observed. L. monocytogenes was visualized beyond the nematode intestinal lumen, indicating resuscitation and cell invasion. These data emphasize the risk that VBNC food-borne pathogens could pose to public health should they continue to go undetected.IMPORTANCE Many bacteria are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses. VBNC cells cannot be detected by standard laboratory culture techniques, presenting a problem for the food industry, which uses these techniques to detect pathogen contaminants. This study found that chlorine, a sanitizer commonly used for fresh produce, induces a VBNC state in the food-borne pathogens Listeria monocytogenes and Salmonella enterica It was also found that chlorine is ineffective at killing total populations of the pathogens. A life span reduction was observed in Caenorhabditis elegans that ingested these VBNC pathogens, with VBNC L. monocytogenes as infectious as its culturable counterpart. These data show that VBNC food-borne pathogens can both be generated and avoid detection by industrial practices while potentially retaining the ability to cause disease.

Concepts: Bacteria, Microbiology, Caenorhabditis elegans, Caenorhabditis, Salmonella enterica, Salmonella, Listeria monocytogenes, 1984 Rajneeshee bioterror attack

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A 2014 multistate listeriosis outbreak was linked to consumption of caramel-coated apples, an unexpected and previously unreported vehicle for Listeria monocytogenes. This outbreak was unanticipated because both the pH of apples (<4.0) and the water activity of the caramel coating (<0.80) are too low to support Listeria growth. In this study, Granny Smith apples were inoculated with approximately 4 log10 CFU of L. monocytogenes (a cocktail of serotype 4b strains associated with the outbreak) on each apple's skin, stem, and calyx. Half of the apples had sticks inserted into the core, while the remaining apples were left intact. Apples were dipped into hot caramel and stored at either 7°C or 25°C for up to 11 or 28 days, respectively. Data revealed that apples with inserted sticks supported significantly more L. monocytogenes growth than apples without sticks under both storage conditions. Within 3 days at 25°C, L. monocytogenes populations increased >3 log10 in apples with sticks, whereas only a 1-log10 increase was observed even after 1 week for caramel-coated apples without sticks. When stored at 7°C, apples with sticks exhibited an approximately 1.5-log10 increase in L. monocytogenes levels at 28 days, whereas no growth was observed in apples without sticks. We infer that insertion of a stick into the apple accelerates the transfer of juice from the interior of the apple to its surface, creating a microenvironment at the apple-caramel interface where L. monocytogenes can rapidly grow to levels sufficient to cause disease when stored at room temperature.

Concepts: Listeria monocytogenes, Listeria, Listeriosis, Apple, Granny Smith, Apple Records, Eastwood, New South Wales

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The food-borne pathogen Listeria (L) monocytogenes is able to survive a variety of stress conditions leading to the colonization of different niches like the food processing environment. This study focuses on the hypervariable genetic hotspot lmo0443-lmo0449 haboring three inserts: the stress survival islet 1 (SSI-1), the single-gene insert LMOf2365_0481 and two homologous genes of the non-pathogenic species L. innocua: lin0464, a putative transcriptional regulator and lin0465, an intracellular PfpI protease. Our prevalence study revealed a different distribution of the inserts between human and food-associated isolates. The lin0464-lin0465 insert was predominantly found in food-associated strains of sequence type (ST) 121. Functional characterization of this insert showed that the putative PfpI protease Lin0465 is involved in alkaline and oxidative stress response, but not in acidic, gastric, heat, cold, osmotic and antibiotic stress. In parallel, deletion of lin0464 decreased the survival under alkaline and oxidative stress. The expression of both genes increased significantly under oxidative stress conditions independently of the alternative sigma factor σ(B) Furthermore, we showed that the expression of the protease lin0465 is regulated by the transcription factor lin0464 under stress conditions, suggesting that lin0464 and lin0465 form a functional unit.In conclusion, we identified a novel stress survival islet 2 (SSI-2), predominantly present in L. monocytogenes ST121 strains, beneficial for survival under alkaline and oxidative stress, potentially supporting adaptation and persistence of L. monocytogenes in food processing environments.IMPORTANCEListeria (L.) monocytogenes strains of ST121 are known to persist for months and even years in food processing environments, thereby increasing the risk of food contamination and listeriosis. However, the molecular mechanism underlying this remarkable niche-specific adaptation is still unknown. Here, we demonstrate that the genomic islet SSI-2, predominantly present in L. monocytogenes ST121 strains, is beneficial for survival under alkaline and oxidative stress conditions, which are routinely encountered in food processing environments. Our findings suggest that SSI-2 is part of a diverse set of molecular determinants contributing to niche-specific adaptation and persistence of L. monocytogenes ST121 strains in food processing environments.

Concepts: DNA, Genetics, Gene expression, Transcription, Oxidative stress, Listeria monocytogenes, Listeria, Listeriosis

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To calculate the shear stress needed to remove sessile Listeria monocytogenes cells from stainless steel (SS) and polytetrafluoroethylene (PTFE) surfaces.

Concepts: Molybdenum, Force, Steel, Austenite, Listeria monocytogenes, Stainless steel, Corrosion, Cutlery

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PURPOSE: To study the incidence and clinical characteristics of delayed cerebral thrombosis in bacterial meningitis patients. METHODS: We assessed the incidence and clinical characteristics of delayed cerebral thrombosis in adults with cerebrospinal fluid (CSF) culture-proven community-acquired bacterial meningitis included in a prospective nationwide study in The Netherlands performed from 2006 to 2012. RESULTS: Delayed cerebral thrombosis occurred in 11 of 1,032 episodes (1.1 %). CSF culture yielded Streptococcus pneumoniae in ten patients and Listeria monocytogenes in one. Adjunctive dexamethasone therapy was administered before or with the first dose of antibiotics in 9 of 11 patients; two patients were initially not treated with dexamethasone. All patients made good initial recovery, followed by sudden deterioration after 7-42 days. Cranial imaging studies showed multiple cerebral infarctions in all patients. The outcome was unfavorable in all but one patient. In an explorative analysis, patients with delayed cerebral thrombosis had eightfold higher complement C5a CSF concentrations on the diagnostic lumbar puncture as compared in those without delayed cerebral thrombosis (p = 0.04). CONCLUSION: Delayed cerebral thrombosis is a rare but devastating complication of bacterial meningitis. Adjunctive dexamethasone therapy seems to predispose patients with bacterial meningitis to this complication. We found some evidence that this thrombotic complication is associated with activation of the complement system.

Concepts: Bacteria, Streptococcus pneumoniae, Cerebrospinal fluid, Meningitis, Listeria monocytogenes, Listeriosis, Tuberculous meningitis, Lumbar puncture

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The usefulness of electron beam (E-beam) irradiation to increase the shelf life of whole fresh pork loin stored at 4°C has been studied. The shelf life was extended from 5 to 11 and 20 days after the application of 1 and 2 kGy, respectively. If a temperature abuse situation were to occur during product distribution (e.g., increase to 8°C), the shelf life would be extended from 3 to 8 and 15 days, respectively, after application of the same doses. When considering Listeria monocytogenes from a public health point of view, the irradiated whole fresh loin may be marketable for periods longer than 2 weeks, thus guaranteeing a practically Listeria-free product. Irradiation produced no important changes in the rheological characteristics of the meat. Although the sensory quality of irradiated meat was scored lower than the control immediately after irradiation, after 5 days in storage, irradiated meat scored higher than or not different from the control.

Concepts: Listeria monocytogenes, Shelf life

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Contact with animals and their environment is an important, and often preventable, route of transmission for enteric pathogens. This study estimated the annual burden of illness attributable to animal contact for 7 groups of pathogens: Campylobacter species, Cryptosporidium species, Shiga toxin-producing Escherichia coli (STEC) O157, STEC non-O157, Listeria monocytogenes, nontyphoidal Salmonella species, and Yersinia enterocolitica.

Concepts: Microbiology, United States, Escherichia coli, Enterobacteriaceae, Listeria monocytogenes, Diarrhea, Foodborne illness, Enterobacteria