抄録
Comparative studies were carried out on the pre-enrichment media for the isolation of salmonellae from fish meal samples.
In Experiment I, the following three media: buffered saline solution (BS), buffered peptone water (BPT) and Enterobacteriaceae enrichment mannitol broth (EEM) were compared with their selectivities for qualitative pre-enrichment media.
In Experiment II, seven pre-enrichment media, including the directly employed selenite broth for the quantitative estimation of salmonellae were evaluated for their effectiveness, using S. typhimurium suspension and the fish meal sample inoculated with the same organism.
Results obtained can be summarized as follows: In Exp. I, 39 commercial fish meal samples were examined to compare selectivities of 3 pre-enrichment media, and BS exhibited the highest positive rates being 24.9%, followed by BPT (23.0%), while the positive rates of EEM were as low as 11.1%. In Exp. II, it was found that 0.1% meat extract containing BS (BSM), 0.1% peptone water (0.1% PW) and nutrieut broth gave high recoveries, followed by a half concentration of BPT. However, BPT, EEM and the directly employed selenite broth gave rather poor recoveries as compared with the former four media. As a selective culture medium of salmonellae, Hajina's tetrathionate broth was found to give higher recoveries than the selenite broth.
Based on the aforementioned results, the author wishes to propose the following procedures for the isolation and estimation of salmonellae from fish meal samples; BS will be employed as a pre-enrichment culture medium at 37°C, and for the qualitative test, Hajina's tetrathionate broth will be used as a selective enrichment medium at 43°C, in addition, for the quantitative estimation, BSM is recommended as the pre-enrichment medium.
