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The suitability of artificially contaminated milk powder as a substrate for salmonella reference samples and its stability under different storage conditions were studied. The need for a reconstitution step in the standard isolation method for salmonellas from milk powders was also investigated. When milk powder was examined in this way with a reconstitution step, differences in laboratory methods and/or storage times had no significant effect on the results after storage at 4 degrees C. With powder stored at room temperature there was a systematic decrease in the number of samples positive as the storage time increased. It is concluded therefore that milk powder contaminated with salmonellas should be stored at 4 degrees C. Examination of such milk powder with a reconstitution step yielded better results than without it and this step is therefore necessary for improving the reproducibility of the method. No significant differences were encountered between the standard isolation method and that used in the authors' laboratories. The results of this study indicate that milk powder is suitable as basic material for reference samples and that a reconstitution step should be included in the standard salmonella isolation procedure.

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Zusammenfassung 259 Futterproben (235 Mischfutterproben und 24 Futterkomponenten) wurden 1978 und 1981/82 in abgestuften Gewichtsmengen von 1000—100—10—1 g bzw. 500—50—5—0,5 g unter Verwendung einer Voranreicherung in gepuffertem 0,1%igem Peptonwasser mit anschließend parallel durchgeführter Selektivanreicherung in Muller‐Kaufmann‐Tetrathionat‐Bouillon, MK (Bebrütung bei +43°C), und Selenit‐Cystin‐Bouillon, SeC (Bebrütung bei + 37°C), — je 1 Subkultur nach 18—24‐ und nach 42—48stündiger Bebrütung — auf Salmonellen untersucht. In 60 Proben (23,2%) konnten Salmonellen nachgewiesen werden. In den 235 Mischfutterproben allein erwiesen sich 55 (= 23,4%) als salmonella‐kontaminiert. In der überwiegenden Zahl der Fälle handelte es sich unter dem Gesichtspunkt der Salmonella‐Keimzahl um schwache Kontaminationen. Mehr als die Hälfte der salmonella‐positiven Proben wurde ausschließlich in den Probengewichtsklassen 1000 bzw. 500 g ermittelt. In 15 der 235 Mischfutterproben (= 6,4%) wurden Salmonellen parallel in 1000 und 100 g, in 500 und 50 g bzw. in 500, 50 und 5g nachgewiesen. 33mal erfolgte der Salmonella‐Nachweis gemeinsam aus beiden Selektivanreicherungen, 20mal allein in MK und 7mal allein in SeC. Die eigenen Untersuchungsbefunde werden unter Berücksichtigung der in der Bundesrepublik Deutschland bisher praktizierten bakteriologischen Futtermittelkontrollen (überwiegend Untersuchungen importierter Futtermittelkomponenten tierischer Herkunft) und unter dem Aspekt der epidemiologischen und gesundheitlichen Bedeutung des Vorkommens von Salmonellen in Futtermitteln diskutiert. Summary Salmonellae in Feedstuffs In 1978 and again in 1981/82 259 feedstuff samples (235 mixed feedstuff samples and 24 feedstuff components) were examined for Salmonellae in scaled quantities of 1,000, 100, 10 and 1 g, and 500, 50, 5 and 0.5 g as well. After pre‐enrichment in buffered peptone water (containing 0.1% peptone) selective enrichments were simultaneously carried out in Muller‐Kauffmann‐tetrathionate‐broth (MK, incubation at +43°C) and in selenite‐cystine‐broth (SeC, incubation at +37°C). Subcultures were made after incubation periods of 18–24 hours and 42–48 hours. Salmonellae could be detected in 60 samples (23.2%). 55 of the 235 mixed feedstuff samples (23.4%) were found to be contaminated by Salmonellae. Considering the microbial content, most of these samples showed a weak Salmonella contamination. More than half of the Salmonella‐positive cases were exclusively identified in the weight classes of 1,000 and 500 g. In 15 of the 235 mixed feedstuff samples (6.4%) Salmonellae were simultaneously detected in 1,000 and 100 g samples, in 500 and 50 g samples, and in 500, 50 and 5 g samples as well. Salmonellae were detected 33 times from both selective enrichment cultures, 20 times only in the MK‐broth and 7 times only in the SeC‐broth. The results of this research are discussed with regard to the bacteriological control of feedstuffs carried out up to now in the Federal Republic of Germany (mainly examination of imported feedstuff compo...