Veld PH in 't ,
Strijp-Lockefeer NGWM van ,
Hoekstra JA
30 p
in Dutch
1992
Toon Nederlands
English Abstract A feasibility study was undertaken for the
certification of a reference material containing low numbers of Salmonella.
A batch of 8800 capcules was prepared and eleven laboratories each
enumerated 50 capsules from this batch, according to a standardized
procedure. The results from four laboratories were excluded from the
analysis of data after the first step of the statistical analysis based on
their results found for homogeneity and mean contamination level. The
remaining seven laboratories found contamination levels that did not differ
significantly from each other. The mean contamination level found by these
seven laboratories was 5.65 cfu/capsule. The homogeneity, based on all
counts by these seven laboratories, was not fully conform to a Poisson
distribution. A ratio of variance to mean of 1.18 was found, which is
considered acceptable. The proportion of negative capsules found in the
study was 0.58% and the upper limit of the corresponding confidence
interval (one sided, (alpha = 0.05) was 1.8%. Concluded was that the batch
prepared is of sufficient to be used for a certification
study.