Diversity of Listeria monocytogenes strains of clinical and food chain origins in Belgium between 1985 and 2014

Listeriosis is a rare but severe disease, mainly caused by Listeria monocytogenes. This study shows the results of the laboratory-based surveillance of Listeriosis in Belgium over the period 1985-2014. Besides the incidence and some demographic data we present also more detailed microbiological and molecular characteristics of human strains isolated since 2000. The strains from the latter period were compared to food and animal strains from the same period. Our study shows that different food matrices were commonly contaminated with L. monocytogenes presenting the same PFGE profile as in patient's isolates. Since 1985, we observed a significant decrease in incidence of the Materno-Neonatal cases (from 0.15 to 0.04 cases /100,000 inhabitants-year), which is probably to be attributed to active prevention campaigns targeting pregnant women. Despite the strengthening of different control measures by the food industry, the incidence of non-Materno-Neonatal listeriosis increased in Belgium (from 0.3 to 0.7 cases /100,000 inhabitants-year), probably due to the rise of highly susceptible patients in an aging population. This significant increase found in non-Materno-Neonatal cases (slope coefficient 7.42%/year, P< 0.0001) can be attributed to significant increase in incidence of isolates belonging to serovars 1/2a (n = 393, slope coefficient 6.62%/year, P< 0.0001). Although resistance to antimicrobials is rare among L. monocytogenes isolates, a trend to increasing MIC values is evident with chloramphenicol, amoxicillin, tetracycline and ciprofloxacin. We show that fluoroquinolone resistance is not linked to chromosomal mutations, but caused by a variety of efflux pumps. Our study also shows that huge majority of known underlying pathologies (426 out of 785 cases) were cancers (185/426, 43.1%) and haematological malignancies (75/185, 40.5%). Moreover the risk population is susceptible to low levels of contamination in food stressing the need of prevention campaigns specifically targeting these persons

Outbreak of encephalitic listeriosis in red-legged partridges (Alectoris rufa)

An outbreak of neurological disease was investigated in red-legged partridges between 8 and 28 days of age. Clinical signs included torticollis, head tilt and incoordination and over an initial eight day period approximately 30–40 fatalities occurred per day. No significant gross post mortem findings were detected. Histopathological examination of the brain and bacterial cultures followed by partial sequencing confirmed a diagnosis of encephalitis due to Listeria monocytogenes. Further isolates were obtained from follow-up carcasses, environmental samples and pooled tissue samples of newly imported day-old chicks prior to placement on farm. These isolates had the same antibiotic resistance pattern as the isolate of the initial post mortem submission and belonged to the same fluorescent amplified fragment length polymorphism (fAFLP) subtype. This suggested that the isolates were very closely related or identical and that the pathogen had entered the farm with the imported day-old chicks, resulting in disease manifestation in partridges between 8 and 28 days of age. Reports of outbreaks of encephalitic listeriosis in avian species are rare and this is to the best of our knowledge the first reported outbreak in red-legged partridges

Inhibition of Listeria in cold-smoked salmon using liquid smoke and isoeugenol

Thesis (M.S.) University of Alaska Fairbanks, 2000Listeria monocytogenes is a foodborne pathogen, ubiquitous in nature and sometimes found in seafood. Cold-smoked salmon products have few barriers to inhibit pathogen growth. This study investigated the antilisterial effects of liquid smoke and the phenolic compound isoeugenol. Five commercial liquid smokes were tested 'in vitro' and the most inhibitory to Listeria monocytogenes ATCC 19115 and L. innocua ATCC 33090 was Charsol Supreme. Chum salmon samples (100-g each) were dipped for 15 seconds at varying concentrations of liquid smoke, processed, and analyzed for L. innocua. Liquid smoke concentrations of 60-100% reduced L. innocua by 3-logs in the final product. Dwell times of 15 seconds to 5 minutes using 60% liquid smoke gradually decreased listerial survival. Isoeugenol was antilisterial 'in vitro, ' but lacked synergism with liquid smoke in cold-smoked salmon. Charsol Supreme formed an antilisterial barrier in cold-smoked salmon, and may be a useful application to commercial products

Quantitative microbiological risk assessment as a tool to obtain useful information for risk managers - specific application to Listeria monocytogenes and ready-to-eat meat products

The presence of Listeria monocytogenes in a sliced cooked, cured ham-like meat product was quantitatively assessed. Sliced cooked, cured meat products are considered as high risk products. These ready-to-eat, RTE, products (no special preparation, e.g. thermal treatment, before eating is required), support growth of pathogens (high initial pH = 6.2–6.4 and water activity = 0.98–0.99) and has a relatively long period of storage at chilled temperatures with a shelf life equal to 60 days based on manufacturer's instructions. Therefore, in case of post-process contamination, even with low number of cells, the microorganism is able to reach unacceptable levels at the time of consumption. The aim of this study was to conduct a Quantitative Microbiological Risk Assessment (QMRA) on the risk of L. monocytogenes presence in RTE meat products. This may help risk managers to make decisions and apply control measures with ultimate objective the food safety assurance. Examples are given to illustrate the development of practical risk management strategies based on the results obtained from the QMRA model specifically developed for this pathogen/food product combinatio

Healthy Aging Update, August 1, 2006, Vol. 1, no. 5

This bimonthly electronic newsletter will provide information and resources on nutrition and health promotion and disease prevention. The Healthy Aging Update is produced for informal and educational purposes only. The newsletter will be distributed electronically and posted on the Department’s website at www.state.ia.us/elderaffairs

Prevalence, Pathogenicity, Virulence, Antibiotic Resistance, and Phylogenetic Analysis of Biofilm-Producing Listeria monocytogenes Isolated from Different Ecological Niches in Egypt: Food, Humans, Animals, and Environment

Serious outbreaks of foodborne disease have been caused by Listeria monocytogenes found in retail delicatessens and the severity of disease is significant, with high hospitalization and mortality rates. Little is understood about the formidable public health threat of L. monocytogenes in all four niches, humans, animals, food, and environment, in Egypt. This study analyzed the presence of L. monocytogenes collected from the four environmental niches and bioinformatics analysis was implemented to analyze and compare the data. PCR was used to detect virulence genes encoded by pathogenicity island (LIPI-1). prfA amino acid substation that causes constitutive expression of virulence was common in 77.7% of isolates. BLAST analysis did not match other isolates in the NCBI database, suggesting this may be a characteristic of the region associated with these isolates. A second group included the NH1 isolate originating in China, and BLAST analysis showed this prfA allele was shared with isolates from other global locations, such as Europe and North America. Identification of possible links and transmission pathways between the four niches helps to decrease the risk of disease in humans, to take more specific control measures in the context of disease prevention, to limit economic losses associated with food recalls, and highlights the need for treatment options

A protective role of gamma/delta T cells in primary infection with Listeria monocytogenes in mice.

We have previously reported that T cells bearing T cell receptors (TCRs) of gamma/delta type appear at a relatively early stage of primary infection with Listeria monocytogenes in mice. To characterize the early-appearing gamma/delta T cells during listeriosis, we analyzed the specificity and cytokine production of the gamma/delta T cells in the peritoneal cavity in mice inoculated intraperitoneally with a sublethal dose of L. monocytogenes. The early-appearing gamma/delta T cells, most of which were of CD4-CD8- phenotype, proliferated and secreted IFN-gamma and macrophage chemotactic factor in response to purified protein derivative from Mycobacterium tuberculosis, or recombinant 65-kD heat-shock protein derived from M. bovis but not to heat-killed Listeria. To further elucidate the potential role of the gamma/delta T cells in the host-defense mechanism against primary infection with Listeria, we examined the effects of in vivo administration of monoclonal antibodies (mAbs) against TCR-gamma/delta or TCR-alpha/beta on the bacterial eradication in mice infected with Listeria. Most of alpha/beta T cells or gamma/delta T cells were depleted in the peripheral lymphoid organs at least for 12 d after an intraperitoneal injection of 200 micrograms TCR-alpha/beta mAb or 200 micrograms TCR-gamma/delta mAb, respectively. An exaggerated bacterial multiplication was evident at the early stage of listerial infection in the gamma/delta T cells-depleted mice, whereas the alpha/beta T cell-depleted mice exhibited much the same resistance level as the control mice at this stage although the resistance was severely impaired at the late stage after listerial infection.(ABSTRACT TRUNCATED AT 250 WORDS