NRL Dutch national programme studies VI/VII (2000) on bacteriological detection of Salmonella and pilot collaborative study I/II on detection of Campylobacter

In 2000, two bacteriological collaborative studies were organized by the Dutch National Reference Laboratory (NRL) for Salmonella among 23 laboratories participating in the Dutch national programme for control of Salmonella in the poultry sector. The main objective of these studies was to test the capacity of these laboratories to detect Salmonella in the presence of competitive micro-organisms. Reference capsules containing sublethally injured Salmonella Typhimurium had to be tested for the presence of Salmonella with and without the addition of chicken faeces. The method used in the studies was prescribed by the Product Boards for Livestock, Meat and Eggs. In this method the semi-solid medium MSRV had to be used as the selective enrichment medium. Depending on the results from previous collaborative studies, laboratories had to test 50 or 15 capsules. Only in the first study (study VI) one laboratory tested 50 capsules and this laboratory detected Salmonella from all Salmonella positive capsules. In this study VI 22 (of the 23) and in study VII 18 (of the 21) participating laboratores isolated Salmonella from all 10 Salmonella positive capsules. Additionally two pilot bacteriological collaborative studies on the detection methods of Campylobacter were organized. The main goal of these two pilot studies was that the participating laboratories could get experience with the detection of Campylobacter.In 2000 werden er twee bacteriologische ringonderzoeken voor de detectie van Salmonella in aanwezigheid van stoorflora georganiseerd door het Nationaal Referentie Laboratorium (NRL) voor Salmonella, waaraan werd deelgenomen door 23 laboratoria die betrokken zijn bij het plan van aanpak Salmonella en Campylobacter in de pluimveehouderij. Het belangrijkste doel van deze ringonderzoeken was te testen of de deelnemende laboratoria in staat waren om Salmonella te detecteren in aanwezigheid van stoorflora. Daarvoor werden referentiematerialen met Salmonella Typhimurium gebruikt die dienden te worden onderzocht met en zonder toevoeging van kippenfeces. De gebruikte methode was voorgeschreven door de Productschappen Vee, Vlees en Eieren (PVE). In deze methode moet het semi-solid medium MSRV gebruikt worden als selectief ophopingsmedium. Naar aanleiding van de resultaten die de deelnemende laboratoria in eerdere ringonderzoeken behaalden moesten 50 of 15 capsules onderzocht worden. Alleen in ringonderzoek VI (roz VI) moesten door een laboratorium 50 capsules worden onderzocht en dit laboratorium isoleerde Salmonella uit alle Salmonella positieve monsters. In roz VI isoleerden 22 (van de 23) en in roz VII 18 (van de 21) deelnemende laboratoria Salmonella uit alle 10 Salmonella positieve capsules. Daarnaast werden er voor de eerste keer pilot ringonderzoeken voor de bacteriologische detectie van Campylobacter georganiseerd met als doel laboratoria ervaring te laten opdoen met de detectie van Campylobacter

Surveillance of zoonotic bacteria in finishing pigs in The Netherlands

In The Netherlands, from 1998 till 2002, a surveillance programme for zoonotic bacteria in finishing pigs was conducted at herd level. In 2000-2002, the prevalence of Salmonella spp. approximated 30%, while a significantly decreasing trend was observed when standardizing data for herdsize, age and quarter of sampling. Serotype discrimination showed the predominance of S. Typhimurium with an increasing role for phage type DT104. Prevalence estimates for Campylobacter spp. were 97% in 1998 (4th quarter only) and 45% in 1999. For STEC O157, prevalence estimates were 2% and 0% in 1998 and 1999, respectively. By using the samples from this study, a comparison study was conducted in which three different selective enrichment media, i.e. RV, MSRV and DIASALM, were compared for the isolation of Salmonella spp. from pig feces. Both MSRV and DIASALM scored significantly better compared to RV. By using logistic regression analysis of farm and herd specific data, potential risk factors for Salmonella spp. in finishing pig herds were identified and quantified

Methods to assess the effect of meat processing on viability of Toxoplasma gondii: towards replacement of mouse bioassay by in vitro testing

Consumption of meat containing viable tissue cysts is considered one of the main sources of human infection with Toxoplasma gondii. In contrast to fresh meat, raw meat products usually undergo processing, including salting and mixing with other additives such as sodium acetate and sodium lactate, which affects the viability of T. gondii. However, the experiments described in the literature are not always performed in line with the current processing methods applied in industry. It was our goal to study the effect of salting and additives according to the recipes used by industrial producers. Mouse or cat bioassay is the ‘gold standard’ to demonstrate the presence of viable T. gondii. However, it is costly, time consuming and for ethical reasons not preferred for large-scale studies. Therefore, we first aimed to develop an alternative for mouse bioassay that can be used to determine the effect of processing on the viability of T. gondii tissue cysts. The assays studied were (i) a cell culture method to determine the parasite’s ability to multiply, and (ii) a propidium monoazide (PMA) dye-based assay to selectively detect DNA from intact parasites. Processing experiments were performed with minced meat incubated for 20 h with low concentrations of NaCl, sodium lactate and sodium acetate. NaCl appeared to be the most effective ingredient with only one or two out of eight mice infected after inoculation with pepsin-digest of portions processed with 1.0, 1.2 and 1.6% NaCl. Results of preliminary experiments with the PMA-based method were inconsistent and did not sufficiently discriminate between live and dead parasites. In contrast, the cell culture method showed promising results, but further optimization is needed before it can replace or reduce the number of mouse bioassays needed. In future, standardised in vitro methods are necessary to allow more extensive testing of product-specific processing methods, thereby providing a better indication of the risk of T. gondii infection for consumers

The relationship between the presence of antibodies and direct detection of Toxoplasma gondii in slaughtered calves and cattle in four European countries

In cattle, antibodies to Toxoplasma gondii infection are frequently detected, but evidence for the presence of T. gondii tissue cysts in cattle is limited. To study the concordance between the presence of anti-T. gondii IgG and viable tissue cysts of T. gondii in cattle, serum, liver and diaphragm samples of 167 veal calves and 235 adult cattle were collected in Italy, the Netherlands, Romania and the United Kingdom. Serum samples were tested for anti-T. gondii IgG by the modified agglutination test and p30 immunoblot. Samples from liver were analyzed by mouse bioassay and PCR after trypsin digestion. In addition, all diaphragms of cattle that had tested T. gondii-positive (either in bioassay, by PCR on trypsin-digested liver or serologically by MAT) and a selection of diaphragms from cattle that had tested negative were analyzed by magnetic capture quantitative PCR (MC-PCR). Overall, 13 animals were considered positive by a direct detection method: seven out of 151 (4.6%) by MC-PCR and six out of 385 (1.6%) by bioassay, indicating the presence of viable parasites. As cattle that tested positive in the bioassay tested negative by MC-PCR and vice-versa, these results demonstrate a lack of concordance between the presence of viable parasites in liver and the detection of T. gondii DNA in diaphragm. In addition, the probability to detect T. gondii parasites or DNA in seropositive and seronegative cattle was comparable, demonstrating that serological testing by MAT or p30 immunoblot does not provide information about the presence of T. gondii parasites or DNA in cattle and therefore is not a reliable indicator of the risk for consumers

Development of prediction models for upper and lower respiratory and gastrointestinal tract infections using social network parameters in middle-aged and older persons -The Maastricht Study.

The ability to predict upper respiratory infections (URI), lower respiratory infections (LRI), and gastrointestinal tract infections (GI) in independently living older persons would greatly benefit population and individual health. Social network parameters have so far not been included in prediction models. Data were obtained from The Maastricht Study, a population-based cohort study (N = 3074, mean age (±s.d.) 59·8 ± 8·3, 48·8% women). We used multivariable logistic regression analysis to develop prediction models for self-reported symptomatic URI, LRI, and GI (past 2 months). We determined performance of the models by quantifying measures of discriminative ability and calibration. Overall, 953 individuals (31·0%) reported URI, 349 (11·4%) LRI, and 380 (12·4%) GI. The area under the curve was 64·7% (95% confidence interval (CI) 62·6-66·8%) for URI, 71·1% (95% CI 68·4-73·8) for LRI, and 64·2% (95% CI 61·3-67·1%) for GI. All models had good calibration (based on visual inspection of calibration plot, and Hosmer-Lemeshow goodness-of-fit test). Social network parameters were strong predictors for URI, LRI, and GI. Using social network parameters in prediction models for URI, LRI, and GI seems highly promising. Such parameters may be used as potential determinants that can be addressed in a practical intervention in older persons, or in a predictive tool to compute an individual's probability of infections

NRL Dutch national programme studies VI/VII (2000) on bacteriological detection of Salmonella and pilot collaborative study I/II on detection of Campylobacter

In 2000 werden er twee bacteriologische ringonderzoeken voor de detectie van Salmonella in aanwezigheid van stoorflora georganiseerd door het Nationaal Referentie Laboratorium (NRL) voor Salmonella, waaraan werd deelgenomen door 23 laboratoria die betrokken zijn bij het plan van aanpak Salmonella en Campylobacter in de pluimveehouderij. Het belangrijkste doel van deze ringonderzoeken was te testen of de deelnemende laboratoria in staat waren om Salmonella te detecteren in aanwezigheid van stoorflora. Daarvoor werden referentiematerialen met Salmonella Typhimurium gebruikt die dienden te worden onderzocht met en zonder toevoeging van kippenfeces. De gebruikte methode was voorgeschreven door de Productschappen Vee, Vlees en Eieren (PVE). In deze methode moet het semi-solid medium MSRV gebruikt worden als selectief ophopingsmedium. Naar aanleiding van de resultaten die de deelnemende laboratoria in eerdere ringonderzoeken behaalden moesten 50 of 15 capsules onderzocht worden. Alleen in ringonderzoek VI (roz VI) moesten door een laboratorium 50 capsules worden onderzocht en dit laboratorium isoleerde Salmonella uit alle Salmonella positieve monsters. In roz VI isoleerden 22 (van de 23) en in roz VII 18 (van de 21) deelnemende laboratoria Salmonella uit alle 10 Salmonella positieve capsules. Daarnaast werden er voor de eerste keer pilot ringonderzoeken voor de bacteriologische detectie van Campylobacter georganiseerd met als doel laboratoria ervaring te laten opdoen met de detectie van Campylobacter.In 2000, two bacteriological collaborative studies were organized by the Dutch National Reference Laboratory (NRL) for Salmonella among 23 laboratories participating in the Dutch national programme for control of Salmonella in the poultry sector. The main objective of these studies was to test the capacity of these laboratories to detect Salmonella in the presence of competitive micro-organisms. Reference capsules containing sublethally injured Salmonella Typhimurium had to be tested for the presence of Salmonella with and without the addition of chicken faeces. The method used in the studies was prescribed by the Product Boards for Livestock, Meat and Eggs. In this method the semi-solid medium MSRV had to be used as the selective enrichment medium. Depending on the results from previous collaborative studies, laboratories had to test 50 or 15 capsules. Only in the first study (study VI) one laboratory tested 50 capsules and this laboratory detected Salmonella from all Salmonella positive capsules. In this study VI 22 (of the 23) and in study VII 18 (of the 21) participating laboratores isolated Salmonella from all 10 Salmonella positive capsules. Additionally two pilot bacteriological collaborative studies on the detection methods of Campylobacter were organized. The main goal of these two pilot studies was that the participating laboratories could get experience with the detection of Campylobacter.Keuringsdienst van Ware

Circulation of Group 2 Coronaviruses in a Bat Species Common to Urban Areas in Western Europe

Fecal samples of 211 bats representing 13 different bat species from 31 locations in the Netherlands were analyzed for the presence of coronaviruses (CoV) using a genus-wide reverse transcription (RT)-polymerase chain reaction. CoVs are known for their high potential for interspecies transmission, including zoonotic transmission with bats as reservoir hosts. For the first time, a group 2 CoV was found in a bat, Pipistrellus pipistrellus, in Europe. This is of particular interest for public health as the reservoir host is a species that is common to urban areas in most of Europe and notorious for its close interactions with humans. Four verspertilionid bat species were found to excrete group 1 CoVs, viz. Myotis daubentonii, M. dasycneme, P. pipistrellus, and Nyctalus noctula. The last species is a newly identified reservoir. The overall prevalence was 16.9% and positive bats were found at multiple widespread locations. The circulating group 1 CoV lineages were rather species associated than location associated

Experimental inoculation with Coxiella burnetii in male rats: successful infection, but no transmission to cage-mates

Beginning in 2007, the largest human Q fever outbreak ever described occurred in the Netherlands. Dairy goats from intensive farms were identified as the source, amplifying Coxiella burnetii during gestation and shedding large quantities during abortions. It has been postulated that wild rodents are reservoir hosts from which C. burnetii can be transmitted to domestic animals and humans. However, little is known about the infection dynamics of C. burnetii in wild rodents. The aim of this study was to investigate whether brown rats (Rattus norvegicus) can be experimentally infected with C. burnetii and whether transmission to a cage mates occurs. Fourteen male brown rats (wild type) were intratracheally or intranasally inoculated with a Dutch C. burnetii isolate obtained from a goat. At 3 days postinoculation, a contact rat was placed with each inoculated rat. The pairs were monitored using blood samples and rectal and throat swabs for 8 weeks, and after euthanasia the spleens were collected. Rats became infected by both inoculation routes, and detection of C. burnetii DNA in swabs suggests that excretion occurred. However, based on the negative spleens in PCR and the lack of seroconversion, none of the contact animals was considered infected; thus, no transmission was observed. The reproduction ratio R(0) was estimated to be 0 (95% confidence interval = 0 to 0.6), indicating that it is unlikely that rats act as reservoir host of C. burnetii through sustained transmission between male rats. Future research should focus on other transmission routes, such as vertical transmission or bacterial shedding during parturition