Listeria Research Today is a free monthly online journal that collates and summarizes the latest research about Listeria, including details on listeria monocytogenes, listeriosis, symptoms, pregnancy, treatment, food safety.

Evidence for subpopulations of Listeria monocytogenes with enhanced invasion of cardiac cells.

Alonzo F, Bobo LD, Skiest DJ, Freitag NE

Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, USA.

Cardiac infections caused by the foodborne bacterium Listeria monocytogenes represent a significant but poorly studied facet of disease. It is not known whether L. monocytogenes cardiac infections stem solely from host susceptibility, or whether bacterial isolates exist that exhibit a tropism for cardiac tissue. Here we examine the cardio-invasive capacity of a recent L. monocytogenes cardiac case strain (07PF0776) as well as nine additional outbreak and clinical isolates. Mice infected with the cardiac isolate 07PF0776 had 10-fold more bacteria recovered from heart tissue than those infected with L. monocytogenes strain 10403S, a well-characterized clinical isolate originally obtained from a human skin lesion. Additional L. monocytogenes isolates exhibited varied capacities to colonize the hearts of mice; however, those with the highest efficiency of mouse cardiac invasion also demonstrated the highest levels of bacterial invasion in cultured myoblast cells. Our findings strongly suggest that subpopulations of L. monocytogenes strains have acquired an enhanced ability to target and invade the myocardium.

Published 17 March 2011 in J Med Microbiol, 60: 423-34.
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Articles on Listeria published 11 March 2011:

A bacterial protein targets the BAHD1 chromatin complex to stimulate type III interferon response.   Science, 331(6022): 1319-21.

Intracellular pathogens such as Listeria monocytogenes subvert cellular functions through the interaction of bacterial effectors with host components. Here we found that a secreted listerial virulence factor, LntA, could target the chromatin repressor BAHD1 in the host cell nucleus to activate interferon (IFN)-stimulated genes (ISGs). IFN-λ expression was induced in response to infection of epithelial cells with bacteria lacking LntA; however, the BAHD1-chromatin associated complex repressed ... [Abstract] [Full-text]

Articles on Listeria published 1 March 2011:

Transfer of Listeria innocua from contaminated compost and irrigation water to lettuce leaves.   Food Microbiol, 28(3): 590-6.

Many foodborne outbreaks of some pathogens such as Escherichia coli O157:H7, Salmonella or Listeria have been associated with the consumption of contaminated vegetables. Contaminated manure and polluted irrigation water are probable vehicles for the pathogens. The aim of this study was to determine the potential transfer of Listeria innocua from soil fertilized with contaminated compost or irrigated with contaminated water to the edible parts of lettuce grown on these soils together with its ... [Abstract] [Full-text]

Staphylococcus aureus and Listeria monocytogenes in Norwegian raw milk cheese production.   Food Microbiol, 28(3): 492-6.

The aim of this study was to survey the presence of Staphylococcus aureus and Listeria monocytogenes during the cheese making process in small-scale raw milk cheese production in Norway. The prevalence of S. aureus in bovine and caprine raw milk samples was 47.3% and 98.8%, respectively. An increase in contamination during the first 2-3 h resulted in a 73.6% prevalence of contamination in the bovine curd, and 23 out of 38 S. aureus-negative bovine milk samples gave rise to S. aureus-positive ... [Abstract] [Full-text]

Effects and interactions of sodium lactate, sodium diacetate, and pediocin on the thermal inactivation of starved Listeria monocytogenes on bologna.   Food Microbiol, 28(3): 440-6.

The effects and interactions of temperature (56.3-60 °C), sodium lactate (SL; 0-4.8%), sodium diacetate (SDA; 0-2.5%), and pediocin (0-10,000 AU) on starved Listeria monocytogenes (10(7) CFU/g) on bologna were investigated. Bologna slices containing SL and SDA in the formulation were dipped in pediocin, surface inoculated, and treated at various temperatures using combinations of parameters determined by central composite design. D-values were calculated. The observed D-values ranged from 2.8 ... [Abstract] [Full-text]

Resistance to benzalkonium chloride, peracetic acid and nisin during formation of mature biofilms by Listeria monocytogenes.   Food Microbiol, 28(3): 418-25.

Increase of resistance to the application of benzalkonium chloride (BAC), peracetic acid (PA) and nisin during biofilm formation at 25 °C by three strains of Listeria monocytogenes (CECT 911, CECT 4032, CECT 5873 and BAC-adapted CECT 5873) in different scenarios was compared. For this purpose, resistance after 4 and 11-days of biofilm formation was quantified in terms of lethal dose 90% values (LD(90)), determined according with a dose-response logistic mathematical model. Microscopic analyses ... [Abstract] [Full-text]

Growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham under refrigerated and temperature abuse conditions.   Food Microbiol, 28(3): 350-5.

This study examined the growth characteristics of Listeria monocytogenes as affected by a native microflora in cooked ham at refrigerated and abuse temperatures. A five-strain mixture of L. monocytogenes and a native microflora, consisting of Brochothrix spp., isolated from cooked meat were inoculated alone (monocultured) or co-inoculated (co-cultured) onto cooked ham slices. The growth characteristics, lag phase duration (LPD, h), growth rate (GR, log(10) cfu/h), and maximum population density ... [Abstract] [Full-text]

Articles on Listeria published 5 January 2011:

Single dose of anti-CTLA-4 enhances CD8+ T-cell memory formation, function, and maintenance.   Proc Natl Acad Sci U S A, 108(1): 266-71.

CTLA-4, an Ig superfamily molecule with homology to CD28, is one of the most potent negative regulators of T-cell responses. In vivo blockade of CTLA-4 exacerbates autoimmunity, enhances tumor-specific T-cell responses, and may inhibit the induction of T-cell anergy. Clinical trials of CTLA-4-blocking antibodies to augment T-cell responses to malignant melanoma are at an advanced stage; however, little is known about the effects of CTLA-4 blockade on memory CD8(+) T-cell responses and the ... [Abstract] [Full-text]

Articles on Listeria published 23 December 2010:

Heat shock factor 1 protects mice from rapid death during Listeria monocytogenes infection by regulating expression of tumor necrosis factor alpha during fever.   Infect Immun, 79(1): 177-84.

Heat shock factor 1 (HSF1) is a stress-induced transcription factor that promotes expression of genes that protect mammalian cells from the lethal effects of severely elevated temperatures (>42°C). However, we recently showed that HSF1 is activated at a lower temperature (39.5°C) in T cells, suggesting that HSF1 may be important for preserving T cell function during pathogen-induced fever responses. To test this, we examined the role of HSF1 in clearance of Listeria monocytogenes, an ... [Abstract] [Full-text]

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