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.

Retrospective analysis of a listeria monocytogenes contamination episode in raw milk goat cheese using quantitative microbial risk assessment tools.

In 2005, the Belgian authorities reported a Listeria monocytogenes contamination episode in cheese made from raw goat's milk. The presence of an asymptomatic shedder goat in the herd caused this contamination. On the basis of data collected at the time of the episode, a retrospective study was performed using an exposure assessment model covering the production chain from the milking of goats up to delivery of cheese to the market. Predictive microbiology models were used to simulate the growth of L. monocytogenes during the cheese process in relation with temperature, pH, and water activity. The model showed significant growth of L. monocytogenes during chilling and storage of the milk collected the day before the cheese production (median increase of 2.2 log CFU/ml) and during the addition of starter and rennet to milk (median increase of 1.2 log CFU/ml). The L. monocytogenes concentration in the fresh unripened cheese was estimated to be 3.8 log CFU/g (median). This result is consistent with the number of L. monocytogenes in the fresh cheese (3.6 log CFU/g) reported during the cheese contamination episode. A variance-based method sensitivity analysis identified the most important factors impacting the cheese contamination, and a scenario analysis then evaluated several options for risk mitigation. Thus, by using quantitative microbial risk assessment tools, this study provides reliable information to identify and control critical steps in a local production chain of cheese made from raw goat's milk.

Usefulness of the European Epidemic Intelligence Information System in the management of an outbreak of listeriosis, Belgium, 2011.

A cluster of time-linked cases and the identification of a clonal strain suggest the occurrence of an outbreak of listeriosis in Belgium in 2011, presumably due to the consumption of hard cheese made with pasteurised milk and produced by a Belgium manufacturer. The outbreak clone was identified as Listeria monocytogenes serovar 1/2a, sensitive to arsenic and cadmium and of multilocus sequence typing MLST-type 37. Food investigation of this outbreak was facilitated by the European Epidemic Intelligence Information System and data exchanged between French and Belgium listeriosis surveillance systems.

Microbiological and molecular investigation of an increase of human listeriosis in Belgium, 2006-2007.

In Belgium, the majority of cases of listeriosis are sporadic cases. In this study we present evidence for an episode of listeriosis: a time-linked cluster of cases that occurred in 2006 and 2007, and the identification of identical strains. The episode involved 11 patients, infected with Listeria monocytogenes of serovar 4b. The source of infection was not detected.

Sporadic case of listeriosis associated with the consumption of a Listeria monocytogenes-contaminated 'Camembert' cheese.

Listeria monocytogenes is an intracellular gram-positive organism responsible for severe infections in both humans and animals. Whereas the food-borne transmission of listeriosis was demonstrated in several outbreaks, most cases of listeriosis occur sporadically and are rarely linked with consumption of contaminated foods. In this paper a case of septicaemia with L. monocytogenes in a 73-year-old immunocompromised man is described. Evidence for the association of this case of listeriosis with the consumption of a contaminated 'Camembert' cheese is provided by serotyping, esterase typing, DNA macrorestriction patterns analysis and level of virulence of the isolated strains for mice.

[Serratia marcescens infections in a hospital: typing of isolated strains]. / Serratia marcescens infekties in een hospitaal: typering van de geïsoleerde stammen.

Ninety six strains of Serratia marcescens were isolated from one hospital. Strains originated from various sources: pressure transducer head (14), arterial catheter tip (4), blood (33), sputum (12), bronchial aspirate (10), urine (10), wound (8), miscellaneous (5). Most of the blood strains were isolated on the intensive care unit (ICU). Contaminated pressure transducer heads seemed to be involved in a nosocomial epidemic. All strains were characterized by serotyping, antibiotic resistance pattern, plasmid profile typing and biotyping. It was demonstrated that the epidemic strain was of serotype O14H4, biotype A5, carrying one plasmid coding for the resistance against gentamicin, streptomycin and sulfamethoxazole. The epidemic type was encountered with the majority of blood isolates (26/33) and with all the transducer head isolates from the ICU (11/11). Isolates from catheter tips (2/4), bronchial aspirate (3/10) and urine (1/10) belonged also to the epidemic type. Within the non-epidemic strains, the most prevalent serotypes were O14H12 (39%) and O14H4 (36%), corresponding well with the distribution of serotypes from a national survey study: O14H12 (36%), O14H4 (24%). Two biotypes were predominant within the non-epidemic strains: A5 (46%) and A8b (32%). Plasmid carriage was observed with 46% of the non-epidemic strains. A plasmid, similar to the epidemic plasmid, was detected in 7 strains, differentiating from the epidemic strain by the serotype and/or the biotype.

Performance of Several Enrichment Media in the Isolation of Salmonellae from Liquid Egg Products.

Ninety-seven samples of raw liquid whole egg and egg yolk were analyzed for the presence of Salmonella ; 51 samples (52%) were found positive. A comparative study was conducted on the performance of seven selective enrichment procedures in the isolation of Salmonella from liquid egg products: selenite-cystine broth incubated at 37°C and 43°C, Muller-Kauffmann tetrathionate broth at 43°C, modified Rappaport medium RIO/100 and RIO/10 also incubated at 43°C, the experimental broth of Greenwood et al. incubated at 37° and 43°C. The best results were obtained with tetrathionate broth which detected 96% of all positive samples. Differences in the rate of isolation by the tetrathionate broth, selenite-cystine broth, modified Rappaport medium RIO/100 and the experimental broth of Greenwood et al., all incubated at 43°C, were not significant as determined by paired χ2 test. Minor results were obtained with selenite-cystine broth and the experimental broth of Greenwood et al., both incubated at 37°C. Modified Rappaport medium RIO/100 proved to be more efficient than RIO/10.

In vitro interaction of aminobenzenesulfonic acids and their N-acetylated derivatives with rat liver glutathione S-transferase.

The in vitro interaction of the three aminobenzenesulfonic acids sulfanilic-, metanilic- and orthanilic acid, and their N-acetylated derivatives with rat liver glutathione S-transferase (GST) was studied. All inhibited the enzymatic conjugation of 1-chloro-2, 4-dinitro-benzene with glutathione. The sulfonate group and the benzene ring are molecular parts required for this inhibition. Each of the GST isoenzymes (AA, A, B, C, E and M) was inhibited, albeit at different degrees. Kinetic studies always revealed a mixed type function inhibition, towards glutathione and 1-chloro-2,4-dinitrobenzene as well. Conjugates of the six investigated compounds with glutathione were not formed. The results indicate that the aminobenzenesulfonic acids and their N-acetylates interact with GST by direct binding to this protein. It is suggested that the binding to GST of these compounds, from which several are metabolites of colors used in human food, could have a protective function against these dyes.

Binding of alkyl 1-thio-beta-D-galactopyranosides to beta-D-galactosidase from E. coli.

The binding of a series of alkyl 1-thio-beta-D-galactopyranosides to beta-D-galactosidase from E. coli has been investigated. The inhibition constants were compared to the partition coefficients for the transfer of these substrate-analogues from water to 1-octanol. The relationships between the observed binding-constants and the partition coefficients indicate that part of the aglycon group binds to a hydrophobic area that is limited in relation to the length of hydrocarbon chain that can be accomodated. Outside this area, the hydrocarbon chain is only partially desolvated. The main driving-force for binding of the aglycon group is the increase in entropy resulting from the return of water molecules from the more-organized layer around the solute molecule to the bulk-water phase.