Abstract
To evaluate the chromogenic substrate medium method for detecting coliform bacteria, we isolated 441 coliform bacterial colonies from 1, 165 food samples and inoculated them into various test media (lactose broth, colillert, fluorocult laurylsulfate X-GAL broth and X-GAL agar). With inoculation of 100-101 cfu, the results obtained from these four media coincided in 81.2% and the chromogenic substrate medium method was slightly superior to the traditional lactose fermentation method in sensitivity. Increasing the number of cells (>102 cfu) used for inoculation slightly changed the results, indicating that detecting coliform bacteria with these media requires 100-101 cfu for the initial inoculation. Next, we ried to identify the colonies associated with differences in results. As a result, 73 coloniesconsisting of 7 genera (15 species) were identified. Especially Enterobacter and Serratia showed a greater number. In conclusion, detection of coliform bacteria using chromogenic substrate media is equal to or higher than that by the traditional method (lactose broth) at least under the present experimental conditions. The chromogenic substrate medium method is useful because of the rapidity of detection, but particular attention should be given to detecting bacteria that belong to the genera Enterobacter and Serratia.
