Boxman, Ingeborg L A; Tilburg, Jeroen J H C; Loeke, Nathalie A J M te; Vennema, Harry; Jonker, Klaas; Boer, Enne de; Koopmans, Marion (2006-05-01)
Shellfish from oyster farms in the Netherlands and imported from other European countries were examined for viral contamination. A method that allows sequence matching between noroviruses from human cases and shellfish was used. The samples of shellfish (n = 42) were analyzed using a semi-nested RT-PCR that had been optimized for detection of norovirus in shellfish (SR primer sets). In addition, a different genome region was targeted using a second primer set which is routinely used for diagnosis of norovirus infection in humans (JV12Y/JV13I). To improve the detection limit for this RT-PCR a semi-nested test format was developed (NV primer sets). One of 21 oyster samples (4.8%) from Dutch farms was norovirus positive, whereas norovirus was detected in 1 out of 8 oyster samples (12.5%) and 5 out of 13 mussel samples (38.5%) collected directly after importation in the Netherlands. RNA from samples associated with an outbreak of gastro-enteritis in the Netherlands in 2001 was re-analyzed using the NV primer sets. At least one identical sequence (142/142 nt) was found in three fecal and in two oyster samples related to this outbreak. Further surveillance of norovirus by detection and typing of viruses from patients with gastroenteritis and shellfish is warranted to clarify the causes of future outbreaks.
Wijnands, L M; Dufrenne, J B; Zwietering, M H; Leusden, F M van (2006-11-01)
The species Bacillus cereus, known for its ability to cause food borne disease, consists of a large variety of strains. An important property for discrimination of strains is their growth temperature range. Psychrotrophic strains can grow well at refrigerator temperatures but grow at 37 degrees C with difficulty. Mesophilic strains on the other hand are unable to grow below 10 degrees C, but grow well at 37 degrees C. Spores of six psychrotrophic and six mesophilic strains were investigated for their ability to survive and grow in simulated gastro-intestinal fluids, mimicking the conditions in the gastro-intestinal tract. The germination potential of psychrotrophic and mesophilic spores in simulated intestinal fluid does not differ much. Under conditions simulating the gastro-intestinal passage, 5 out of 6 mesophilic strains showed growth, and only 2 out of 6 psychrotrophic strains. Temperature (37 degrees C) and simulated gastro-intestinal conditions together influenced germination and growth.
Schuit, Albertine J; Wendel-Vos, Gerrie C W; Verschuren, Wilhelmina M M; Ronckers, Emma T; Ament, Andre; Assema, Patricia van; Ree, Jan van; Ruland, Erik C (2006-03-01)
BACKGROUND: A widely advocated strategy in public health is community-based health promotion. The aim of this study was to investigate the net effect of a cardiovascular disease prevention program (Hartslag Limburg) on cardiovascular risk factors after 5 years of intervention. DESIGN: Cohort study comparing 5-year mean change in risk factors between the intervention and reference area. The statistical analyses for the study were performed in 2005. SETTING/PARTICIPANTS: In 1998, 3000 subjects (aged 25 to 70) from the intervention area and 895 subjects from a reference area participated in the baseline measurement. Of these, 2414 intervention subjects and 758 reference subjects completed the follow-up measurement in 2003. INTERVENTION: Hartslag Limburg is an integrative community-based cardiovascular disease prevention program promoting a healthy lifestyle. MAIN OUTCOME MEASURES: Body mass index (BMI), waist circumference, blood pressure, serum glucose (nonfasting), and serum total and high-density lipoprotein (HDL) cholesterol. RESULTS: During the 5-year follow-up, risk factors changed unfavorably in the reference group, whereas changes were less pronounced or absent in the intervention group. The adjusted difference in mean change in risk factors between intervention and reference group was significant (p<0.05) for BMI: -0.36 kg/m(2) in men and -0.25 kg/m(2) in women; waist circumference -2.9 cm in men and -2.1 cm in women; systolic blood pressure: -7.8 mmHg in men and -5.5 mmHg in women; total cholesterol 0.11 mmol/L in women and finally serum glucose -0.23 mmol/L in women. CONCLUSIONS: Hartslag Limburg succeeded in reducing-and in some cases, preventing-age- and time-related increase in BMI, waist circumference, blood pressure, and, in women, nonfasting glucose concentration.
Amersfoorth, S C M van; Schouls, L M; Heide, H G J van der; Advani, A; Hallander, H O; Bondeson, K; König, C H W von; Riffelmann, M; Vahrenholz, C; Guiso, N; et al. (2005-06-01)
Despite the widespread use of pertussis vaccines during the last decades, pertussis has remained an endemic disease with frequent epidemic outbreaks. Currently two types of vaccines are used: whole-cell vaccines (WCVs) and recently developed acellular vaccines (ACVs). The long-term aim of our studies is to assess the effect of different vaccination policies on the population structure of Bordetella pertussis and ultimately on the disease burden in Europe. In the present study, a total of 102 B. pertussis isolates from the period 1998 to 2001 from five European countries (Finland, Sweden, Germany, The Netherlands, and France) were characterized. The isolates were analyzed by typing based on variable number of tandem repeats (VNTR); by sequencing of polymorphic genes encoding the surface proteins pertussis toxin S1 and S3 subunits (ptxA and ptxC), pertactin (prn), and tracheal colonization factor (tcfA); and by fimbrial serotyping. The results reveal a relationship between geographic location and VNTR types, the frequency of the ptxC alleles, and serotypes. We have not observed a relationship between the strain characteristics we studied and vaccination programs. Our results provide a baseline which can be used to reveal changes in the B. pertussis population in Europe in the coming years.
Abbink, Frithjofna; Buisman, Anne M; Doornbos, Gerda; Woldman, Jan; Kimman, Tjeerd G; Conyn- van Spaendonck, Marina A E (2005-03-15)
BACKGROUND: Dutch people born between 1925 and 1945 were ineligible for vaccination with the inactivated poliovirus vaccine (IPV) introduced in 1957 and may have escaped natural infection because of reduced poliovirus circulation. We examined whether people with low or undetectable antibody levels are susceptible to infection and whether memory immunity provides protection against virus excretion. METHODS: A total of 429 elderly participants were challenged with monovalent oral poliovirus vaccine (type 1 or 3) and followed for 8 weeks. Immune responses and virus excretion were compared for 4 groups, defined on the basis of seronegativity for poliovirus type 1 or 3, natural immunity, and IPV-induced immunity. RESULTS: On the basis of the rapidity of the antibody response and the absence of immunoglobulin M, we saw clear evidence of memory immune responses in 33% of the participants without detectable antibodies against poliovirus type 1 and in 5% of the participants without detectable antibodies against poliovirus type 3. Fecal virus-excretion patterns were not significantly different for seronegative participants, regardless of whether they showed evidence of memory immunity. CONCLUSIONS: Rapid antibody responses after challenge with oral polio vaccine provide evidence for poliovirus-specific memory immunity in seronegative elderly people. However, in contrast to preexisting immunity, memory immunity does not protect against virus excretion. These results have important implications for the poliomyelitis-eradication initiative, in particular for future immunization policies after eradication has been achieved.
In a study of 291 mineral waters from 41 different countries, 9-20% exceeded the Dutch drinking water standards for chloride, calcium, magnesium, kalium, sodium, sulphate and fluorine. The mineral water quality cannot be qualified as bad since the standards for these compounds with the exception of fluorine, are not based on health effects but on undesirable taste effects and possible negative effects on the water supply system. For the mineral water data set the amount of dissolved compounds, hardness and chloride content appear to be the most distinctive criteria. A mineral water type classification based on these criteria will offer consumers a tool for assessing the mineral water on the basis of the chemical composition data on the bottle label. In terms of the criteria mentioned, average Dutch tap water strongly resembles the Belgian and Dutch mineral waters. This similarity does not extend to the price, since Dutch tap water is about 500 times cheaper.
Avendaño, M; Kunst, A E; Lenthe, F van; Bos, V; Costa, G; Valkonen, T; Cardano, M; Harding, S; Borgan, J-K; Glickman, M; et al. (2005-01-01)
This study assesses whether stroke mortality trends have been less favorable among lower than among higher socioeconomic groups. Longitudinal data on mortality by socioeconomic status were obtained for Finland, Norway, Denmark, Sweden, England/Wales, and Turin, Italy. Data covered the entire population or a representative sample. Stroke mortality rates were calculated for the period 1981-1995. Changes in stroke mortality rate ratios were analyzed using Poisson regression and compared with rate ratios in ischemic heat disease mortality. Trends in stroke mortality were generally as favorable among lower as among higher socioeconomic groups, such that socioeconomic disparities in stroke mortality persisted and remained of a similar magnitude in the 1990s as in the 1980s. In Norway, however, occupational disparities in stroke mortality significantly widened, and a nonsignificant increase was observed in some countries. In contrast, disparities in ischemic heart disease mortality widened throughout this period in most populations. Improvements in hypertension prevalence and treatment may have contributed to similar stroke mortality declines in all socioeconomic groups in most countries. Socioeconomic disparities in stroke mortality generally persisted and may have widened in some populations, which fact underlines the need to improve preventive and secondary care for stroke among the lower socioeconomic groups.
Jong, Nynke de; Klungel, Olaf H; Verhagen, Hans; Wolfs, Marion C J; Ocké, Marga C; Leufkens, Hubert G M (2007-05-19)
Current regulations focus on the mandatory safety evaluation of functional foods before they come to market, but Nynke de Jong and colleagues argue that the effects of such foods should also be evaluated after they have been launched
Meijer, Adam; Bosman, Arnold; Kamp, Esther E H M van de; Wilbrink, Berry; Du Ry van Beest Holle, Mirna; Koopmans, Marion P G (2006-03-01)
During the epizootic of highly pathogenic avian influenza A(H7N7) in 2003 in The Netherlands, RT-PCR and culture confirmed infection was detected in 89 persons who were ill. A modified hemagglutination inhibition (HI) test using horse erythrocytes and 2 hemagglutinating units of virus was applied to assess retrospectively the extent of human (subclinical) infection. Validation of the HI-test with sera from 34 RT-PCR and culture confirmed A(H7) infected persons and sera from 100 persons from a human influenza vaccine trial in autumn 2002 showed that this HI-test had a sensitivity of 85% and a specificity of 100% when using a cut-off titer of > or =10. Using this cut-off value, A(H7) specific antibodies were detected in 49% of 508 persons exposed to poultry and in 64% of 63 persons exposed to A(H7) infected persons. Correlation of seropositivity with the occurrence of eye symptoms in exposed persons who had not received antiviral prophylaxis and of reduced seropositivity with taking antiviral prophylaxis provided further evidence that the A(H7) HI antibody titers were real. In conclusion, by applying an HI-test using horse erythrocytes human antibodies against the avian A(H7N7) virus were detected with high sensitivity and specificity in an unexpectedly high proportion of exposed persons.
One hundred representative strains of Bacillus cereus were selected from a total collection of 372 B. cereus strains using two typing methods (RAPD and FT-IR) to investigate if emetic toxin-producing hazardous B. cereus strains possess characteristic growth and heat resistance profiles. The strains were classified into three groups: emetic toxin (cereulide)-producing strains (n=17), strains connected to diarrheal foodborne outbreaks (n=40) and food-environment strains (n=43), these latter not producing the emetic toxin. Our study revealed a shift in growth limits towards higher temperatures for the emetic strains, regardless of their origin. None of the emetic toxin-producing strains were able to grow below 10 degrees Celsius. In contrast, 11% (9 food-environment strains) out of the 83 non-emetic toxin-producing strains were able to grow at 4 degrees Celsius and 49% at 7 degrees Celsius (28 diarrheal and 13 food-environment strains). non-emetic toxin-producing strains. All emetic toxin-producing strains were able to grow at 48 degrees Celsius, but only 39% (16 diarrheal and 16 food-environment strains) of the non-emetic toxin-producing strains grew at this temperature. Spores from the emetic toxin-producing strains showed, on average, a higher heat resistance at 90 degrees Celsius and a lower germination, particularly at 7 degrees Celsius, than spores from the other strains. No difference between the three groups in their growth kinetics at 24 degrees Celsius, 37 degrees Celsius, and pH 5.0, 7.0, and 8.0 was observed. Our survey shows that emetic toxin-producing strains of B. cereus have distinct characteristics, which could have important implication for the risk assessment of the emetic type of B. cereus caused food poisoning. For instance, emetic strains still represent a special risk in heat-processed foods or preheated foods that are kept warm (in restaurants and cafeterias), but should not pose a risk in refrigerated foods.
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