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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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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

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Eggs or egg-based foods, either raw or undercooked, have been identified as vehicles of Salmonella outbreaks. The low numbers of Salmonella organisms in eggs makes it difficult to detect them in frequency studies. The nested-PCR (n-PCR) technique shows more sensitivity and specificity than bacteriological culture methods (BCMs). A preenrichment method followed by enrichment and n-PCR is a good alternative for the investigation of Salmonella and Listeria monocytogenes in eggs. A total of 2,650 chicken eggs representing five commercial brands were purchased from 10 grocery stores. Ten eggs of each brand were combined in order to obtain 265 pooled samples (53 per brand). The shells and yolks of 100 pooled samples were analyzed for Salmonella, while the shells of 65 pooled samples were analyzed for L. monocytogenes, using BCM and a combined method of enrichment and n-PCR (CM-n-PCR). Sixteen eggshell pooled samples tested positive for Salmonella by CM-n-PCR, compared with only two by BCM. Three egg yolk pooled samples tested positive for this pathogen by CM-n-PCR; none tested positive by BCM. Three eggshell pooled samples tested positive for L. monocytogenes by CM-n-PCR and none by BCM. In Mexico, as in other countries, official methods for detection of Salmonella and L. monocytogenes in foods are based on standard bacteriological culture techniques. The inclusion of more sensitive methods such as the one used in the present investigation would increase the probability of detecting positive samples, particularly in those foods in which a very low number of cells is expected.

Concepts: Egg, Type I and type II errors, Sensitivity and specificity, Chicken, Lutein, Listeria monocytogenes, Egg white, Egg yolk

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Abstract Ready-to-eat (RTE) muscle foods refer to a general category of meat and poultry products that are fully cooked and consumable without reheating. These products, including whole and sliced pork, beef, turkey, chicken, and variety meats, in the forms of ham, roast, rolls, sausage, and frankfurter, are widely available in the delicatessen section of retail stores or various food service outlets. However, difficulties in avoidance of contamination by foodborne pathogens, notably Listeria monocytogenes, during product post-lethality repackaging render RTE meats labile to outbreaks. Accordingly, the USDA-FSIS has established processing guidelines and regulations, which are constantly updated, to minimize foodborne pathogens in RTE products. Technologies that complement good manufacturing practice have been developed to control RTE meat safety. Among them, various antimicrobial product formulations, post-packaging pasteurization (thermal and nonthermal), and antimicrobial packaging, are being used. Through these efforts, outbreaks linked to RTE meat consumption have substantially reduced in recent years. However, the pervasive and virulent nature of L. monocytogenes and the possible presence of other cold-tolerant pathogens entail continuing developments of new intervention technologies. This review updates existing and emerging physical and chemical methods and their mode of action to inactivate or inhibit threatening microorganisms in RTE muscle foods.

Concepts: Nutrition, Microbiology, Beef, Meat, Listeria monocytogenes, Pork, Food safety, Sausage

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Nisin is a natural preservative for many food products. This bacteriocin is mainly used in dairy and meat products. Nisin inhibits pathogenic food borne bacteria such as Listeria monocytogenes and many other Gram-positive food spoilage microorganisms. Nisin can be used alone or in combination with other preservatives or also with several physical treatments. This article reviews physicochemical and biological properties of nisin, the main factors affecting its antimicrobial effectiveness, and its food applications as an additive directly incorporated into food matrices.

Concepts: Natural selection, Bacteria, Organism, Microbiology, Listeria monocytogenes, Listeria, Food preservation, Food additive