An examination was conducted to determine whether the isolation ratio of two serotypes of Salmonella inoculated simultaneously and then incubated varies with the enrichment broth and isolating medium used. Some serotypes were found to have a higher isolation ratio when a certain broth or medium was used. The isolation ratio varied with the serotype combinations. When S. Oranienburg and S. Chester were simultaneously inoculated and cultured in SC. S. Oranienburg was isolated in TSA at a higher ratio.
When S. Oranienburg and S. Chester were simultaneously inoculated in sterile physiological saline solution and isolated in SS agar, S. Oranienburg was detected at a ratio lower by one order.
When S. Infantis and S. Chester were simultaneously inoculated and cultured in TT or RV, the isolation ratio of S. Infantis lowered. When S. Enteritidis and S. Chester were simultaneously inoculated and cultured in RV, the isolation ratio of S. Enteritidis decreased.

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At low levels, enterohemorrhagic Escherichia coli should be selectively isolated by suppressing competing microflora in meat samples. In conventional methods, MacConkey II Agar with C-T Sorbitol (cefixime-tellurite, CT-SMAC) which utilizes the ability of E. coli O157 to ferment sorbitol, and media containing E.coli-specific chromogenic substrates, are used for detecting E. coli O157.
In this study, we compared two types of BD CHROMagar^TM O157 for the isolation of enterohemorrhagic E. coli O157 (improved BD CHROMagar^TM O157 and conventional BD CHROMagar^TM O157) with CT-SMAC by using the Miles-Misra method and evaluating the recovers from ground beef and human fecal samples. The results obtained are described below:
1. In the inoculation test with three media by the Miles-Misra method, improved BD CHROMagar^TM O157 inhibited the growth of all organisms except E. coli O157 better than the two other media and allowed easy differentiation from E. hermannii, which could not be distinguished on CT-SMAC.
2. In the E. coli O157 detection test for ground beef artificially inoculated with E. coliO157 at 1 cfu/g, the detection rate of improved BD CHROMagar ^TM O157 was 95%, CTSMAC 75% and conventional BD CHROMagar^TM O157 40%, respectively.
4. In the E. coli O157 detection test for E. coli O157 positive human fecal samples, the detection rate of improved BD CHROMagar^TM O157 was 54.5%, CT-SMAC 50% and conventional BD CHROMagar^TM O157 22.7%, respectively.

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The Oxoid Listeria Rapid Test was compared with a conventional culture method for detecting Listeria in food and environmental materials. According to this study, the test kit could detect twelve strains of six Listeria species. The result of the sensitivity test was a little different depending on the strain, however, if the incubation at 30° to form the flagella was done satisfactory, the sensitivity for L. monocytogenes was 10⁵cfu/ml. The agreement between the conventional method and the test kit was very good using 39 specimens from food and wiping swabs. Four of the 39 specimens which showed positive with the conventional method were negative with the test kit, but the concentration of the bacteria in these specimens was less than 10⁴ cfu/ml. The opposite result was not observed. L. monocytogenes was detected in 17 of the 39 specimens, and 15 specimens were positive with both methods.
Although the test kit was a little poorer than the conventional method in respect to the detection rate of L. monocytogenes, it was thought to be especially valuable as a screening test for Listeria species in food and environment materials.

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