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Concept: Listeriosis


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


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


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


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


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


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


Listeria monocytogenes is a major foodborne pathogen that causes life-threatening illnesses in humans. With emergence of antibiotic resistance in L. monocytogenes, there is considerable interest in testing the efficacy of alternative therapies for controlling listeriosis in humans. This study investigated the efficacy of three phytochemicals, namely trans-cinnamaldehyde (TC), carvacrol (CR), and thymol (TY) in reducing L. monocytogenes virulence in the recently established invertebrate model, Galleria mellonella. In addition, the effect of phytochemicals on the transcription of antimicrobial peptide genes in G. mellonella (responsible for host defense) was investigated using real-time quantitative polymerase chain reaction. G. mellonella larvae were inoculated with L. monocytogenes (10(5) CFU/larvae) either with or without the subinhibitory concentration (chemical concentration not inhibiting bacterial growth) of phytochemicals. The larvae were incubated at 37 °C for 5 days, and their mortality was scored at 24-h intervals. The transcriptional response of the defense genes was studied in inoculated and uninoculated larvae at 6 h post challenge. The experiments were repeated at least six times with replicates. All phytochemicals enhanced the survival rates of G. mellonella infected with lethal doses of L. monocytogenes (P < 0.05). CR and TC at 0.01 % concentration were found to be the most effective treatments, and increased larval survival rates by 80 % and 50 %, respectively, on day 5 (P < 0.05). The phytochemicals also upregulated the expression of antimicrobial peptide genes in G. mellonella larvae challenged with L. monocytogenes (P < 0.05). Results suggest that TC, CR, and TY could potentially be used to control listeriosis. Further investigation in an appropriate mammalian model is warranted.

Concepts: DNA, Gene expression, Bacteria, Molecular biology, Microbiology, Listeria monocytogenes, Listeria, Listeriosis


Listeria monocytogenes 15G01, a strain belonging to the persistent pulsotype 5132, was isolated from a seafood processing plant in New Zealand. Simple monoculture assays using crystal violet staining showed good biofilm formation for this strain and it was therefore chosen to be further investigated in regard to its biofilm forming ability. To evaluate its behaviour in different conditions commonly encountered in food processing environments, biofilm assays and growth studies were performed using common laboratory media under a range of temperatures (20°C, 30°C and 37°C). Furthermore, the effects of incubation time and different environmental conditions including static, dynamic and anaerobic incubation on biofilm formation were investigated. Changes in the environmental conditions resulted in different biofilm phenotype of L. monocytogenes 15G01. We demonstrated that increasing temperature and incubation time led to a higher biofilm mass and that dynamic incubation has little effect on biofilm formation at 37°C but encourages biofilm formation at 30°C. Biofilm production at 20°C was minimal regardless of the medium used. We furthermore observed that anaerobic environment led to reduced biofilm mass at 30°C for all tested media but not at 37°C. Biofilm formation could not be narrowed down to one factor but was rather dependent on multiple factors with temperature and medium having the biggest effects.

Concepts: Microbiology, Environment, Natural environment, Listeria monocytogenes, Listeria, Listeriosis, Environmental science, Joseph Lister, 1st Baron Lister


Listeria monocytogenes infections are an important disease of ruminants worldwide, causing encephalitis, septicemia, and abortions. Ruminant listeriosis can also pose a food safety risk due to the potential for L. monocytogenes to enter the food supply via the farm environment. Data on the genetic diversity of L. monocytogenes from ruminant clinical cases in the United States is limited. Our goal was to assess the genetic diversity of clinical listeriosis isolates from ruminants in the Upper Great Plains states, a population not well-studied, and compare this population to isolates from ruminants in New York State. Multi-locus sequence typing (MLST) was used to classify and compare the genetic diversity of the isolates from the two regions. Loci sequences were compared to all known sequence types using the Pasteur Institute L. monocytogenes MLST database. Four novel sequence types (ST) were identified among the Upper Great Plains isolates, and four new STs were classified in the New York collection. Five STs were found to be common across the 2 geographical regions; ST 1, 7, 191, and 204. Strains of ST 7 were most frequently isolated (7/46 isolates). Strains of ST 91 were all associated with fetal infections from the Upper Great Plains. Our results demonstrate that while there are some subtypes commonly found between the two geographic regions, there are also subtypes distinct to each region.

Concepts: Agriculture, United States, Meningitis, Native Americans in the United States, Listeria monocytogenes, Listeria, Listeriosis, Great Plains


This study analyses the epidemiologic, clinical and molecular findings of all culture-confirmed cases of listeriosis notified from 2010 to 2015 in the Tel Aviv District, which is known to have high rates of listeriosis. All clinical isolates of Listeria monocytogenes were subtyped using two-enzyme pulsed-field gel electrophoresis. During the studied period, 102 cases of listeriosis were notified, including 23 pregnancy-associated cases (23%). Among 79 non-pregnancy-associated cases, 18 had neuro-invasive disease (21%). There were 26 deaths associated with the disease. Using molecular identification, we found a number of clusters of identical bacterial clones, which pointed to possible sources of infection. The high rates of morbidity and mortality resulting from listeriosis, as well as the diverse ways of infection demonstrated in this study, accentuate the need to boost public health actions, in order to raise awareness and better control high-risk contamination routes.

Concepts: Epidemiology, Disease, Molecular biology, Death, Listeria monocytogenes, Listeria, Listeriosis, Tel Aviv