Contaminants and microorganisms in Dutch organic food products: a comparison with conventional products.

Organic products were analysed for the presence of contaminants, microorganisms and antibiotic resistance and compared with those from conventional products. No differences were observed in the Fusarium toxins deoxynivalenol and zearalenone in organic and conventional wheat, during both a dry period and a very wet period which promoted the production of these toxins. Nitrate levels in head lettuce produced organically in the open field were much lower than those in conventional products. In iceberg lettuce and head lettuce from the greenhouse, no differences were detected. Organically produced carrots contained higher nitrate levels than conventional products. Both organic and conventional products contained no residues of non-polar pesticides above the legal limits, although some were detected in conventional lettuce. Organic products contained no elevated levels of heavy metals. Salmonella was detected in 30% of pig faeces samples obtained from 30 organic farms, similar to the incidence at conventional farms. At farms that switched to organic production more then 6 years ago no Salmonella was detected, with the exception of one stable with young pigs recently purchased from another farm. No Salmonella was detected in faeces at the nine farms with organic broilers, and at one out of ten farms with laying hens. This is comparable with conventional farms where the incidence for Salmonella lies around 10%. Campylobacter was detected in faeces at all organic broiler farms, being much higher than at conventional farms. One of the most remarkable results was the fact that faeces from organic pigs and broilers showed a much lower incidence of antibiotic resistant bacteria, except for Campylobacter in broilers. It is concluded that the organic products investigated scored as equally well as conventional products with regard to food safety and at the same time show some promising features with respect to antibiotic resistance.

[The New Dutch Kidney Test. I. Description of the method]. / De Nieuwe Nederlandse Niertest. I. Beschrijving van de methode.

The New Netherlands Kidney test is designed for the detection of antibacterial residues in slaughtered animals. It is a single-plate system in which the culture medium used is composed of Standard II nutrient agar, supplemented with 1 per cent of NaCl, 1 per cent of dextrose, 0.2 per cent of KH2PO4 and 0.28 per cent of Na2HPO4.12H2O. After autoclaving, this medium is cooled to 55 degrees C, which is followed by the addition of trimethoprim (0.12 microgram/ml of agar) and spores of Bacillus subtilis BGA (10(4) ml of agar). The pH should be adjusted to 7.00 +/- 0.05, the prepared medium then being poured out into plates specially designed for this purpose, in such a manner that the thickness of the layer of agar is 2.2 mm throughout. The following method is used in examining slaughtered animals for the presence of residues showing antibacterial activity. Four paper discs are placed in the renal pelvis for a minimum period of thirty minutes; two discs impregnated with fluid from the renal pelvis are frozen at -20 degrees C for possible re-inspection and the other two are laid diagonally on a test plate. 25 microliter of a trimethoprim solution (containing 2 micrograms of TMP per ml of a 10 per cent NaCl solution) are dropped on each of the two last-named discs. The test plates are incubated at 37 degrees C for a period ranging from thirteen to eighteen hours.(ABSTRACT TRUNCATED AT 250 WORDS)

[The New Dutch Kidney Test. II. Sensitivity of the test system]. / De Nieuwe Nederlandse Niertest. II. De gevoeligheid van het testsysteem.

When the in vitro sensitivity of the New Netherlands Kidney Test (NNKT) is compared with that of the test plates of the current Netherlands Kidney Test (NKT) and the EEC four-plate system (ECT), this shows that it occupies a middle position with regard to aminoglycosides, macrolides and tetracyclines. The test plate of the NNKT is more sensitive to sulphonamides. Experimental qualitative and quantitative studies in slaughtered pigs showed that the New Netherlands Kidney Test was equally sensitive or more so in detecting residues of sulphonamides, chloramphenicol, tetracyclines, aminoglycosides and penicillin derivatives than the ECT system for meat. In addition to the simplicity of the current Netherlands Kidney Test, the New Netherlands Kidney Test also shows the broad-spectrum sensitivity of the ECT system. When tolerance standard of nitrofurans or chloramphenicol respectively is 1 or 10 ppb, the New Netherlands Kidney Test will fail.

[The New Dutch Kidney Test. III. Practical evaluation]. / De Nieuwe Nederlandse Niertest. III. Praktijkevaluatie.

The New Netherlands Kidney Test (NNKT) is a method used to detect residues of antibacterial agents in slaughtered animals. This test will shortly be substituted for the current Netherlands Kidney Test (NKT). The new method was tested for its suitability in meat inspection in the field by four district laboratories, comparative studies with the current Netherlands Kidney test being done at the same time. These investigations showed that, when the new test (NNKT) was used, 5.3 per cent of the category of diseased animals and, using the current Netherlands Kidney Test, 2.2 per cent of these animals were positive. When control discs were used, it was shown that reproducibility of the new test (NNKT) within and between the participating laboratories was satisfactory. A method was developed to obtain similar results on re-examination with the NNKT as those obtained in the first inspection. By freezing the duplicate discs at the time of performance of the test and using these discs for re-inspection, reproducible results were obtained with the NNKT. The substance inhibiting the growth of bacteria was identified in a number of specimens diagnosed as positive when the NNKT was used. False-positive results were not recorded in the NNKT.

[The predictive value of urinalysis in the New Dutch Kidney Test]. / De voorspellende waarde van urine-onderzoek bij de Nieuwe Nederlandse Niertest.

A urine test is described, by which a reliable indication of the time of slaughter is obtained in normal as well as in diseased animals, in which the New Netherlands Kidney Test (NNKT) will be negative. The test plate and testing procedure of the NNKT are used in this urine test.

[Waiting periods in the New Netherlands Kidney Test]. / Wachttermijnen bij de Nieuwe Nederlandse Niertest.

The New Netherlands Kidney Test used in monitoring slaughtered animals for antimicrobial residues will be legalised in the near future. With regard to this new test, minimum pre-slaughter withdrawal periods required to obtain negative results of the test are roughly indicated. The problem of establishing reliable withdrawal periods is briefly discussed.