[Assaying the Enterobacteriaceae contents of fishmeal as criterion for absence of Salmonellae (author's transl)].
1. During comparison of different test systems for examination on salmonellae the routine method revealed only 2 of 35 fishmeal consignments as positive. In second streaks after 48 hours on selective media 5 more consignments were discovered to contain samonellae. Using pre-enrichment culture gave evidence for 11 positive consignments altogether. 2. The pre-enrichment method led to about 20 times higher yields in isolating enterobacteriaceae than the usual enrichment method. 3. Neither salmonellae nor enterobacteriaceae statistically showed uniform distribution in fishmeal. In addition, with the aid of the variance test of homogenity, an extremely heterogeneous ratio of the both germ types to each other was proved. Consequently, assaying the enterobacteriaceae contents is not suitable to draw any reliable conclusions upon the salmonellae contents of fishmeal. 4. Assuming a constant contamination rate of 400.000 salmonella units in consignments of 100 tons and testing them by the required 47 random samples, it can be deduced from probability calculus that only about 1 per cent of a larger number of consignments will fail to be recognized as positive. This risk of acceptance increases progressively with diminishing rate of salmonella contamination. Thus about 80 per cent of consignments containing even as much as 20.000 salmonella units will be accepted as "false negatives". 5. Because of the usually low contamination rates of fishmeal it is an erroneous idea to increase the efficiency of assay by modifying the sample sizes in relation to the shipping weight. For this reason the orders for fishmeal examination in the Federal Republic of Germany should be revised. It is suggested to take at least the number of samples required hitherto for consignments of 100 tons. By this without doubt the risk of accepting "false negatives" can be reduced significantly, but it remains still impossible to recognite every contaminated fishmeal consignment and to stop its acceptance by bacteriological examination. 6. From practical examinations and theoretical considerations it is derivable that one has either to tolerate a low degree of salmonella contamination which hygienically may be without any importance or to treat every imported fishmeal by irradiation or heat pelleting.
D001431:Bacteriological Techniques; D004755:Enterobacteriaceae / Q000302:isolation & purification*; D005069:Evaluation Studies as Topic; D005394:Fish Flour; D005396:Fish Products; D005506:Food Contamination; D005516:Food Microbiology; D012475:Salmonella / Q000302:isolation & purification*
Feststellung des Enterobacteriaceen-Gehaltes von Fischmehl zur Beurteilung der Salmonellen-Freiheit