A Solid Brilliant Green Lactose Bile Medium, for Direct Plating, with Results in Seventeen Hours

Abstract

Interest has increased in recent years in the use of brilliant green lactose bile, as a supplement to or a possible substitute for the standard lactose broth medium of water analysis. This trend has been stimulated by certain negative aspects of the latter medium. Jordan (1) has stressed (a) the too frequent non-specificity of lactose broth for the primary colon group in some waters, (b) its over-sensitiveness in others-also suggested by us (2), and (c) the loss of time for control purposes during successive steps of confirmation.To meet these objections, Jordan has suggested planting the two media in parallel. When both are found positive, he regards the finding as specific for the presence of the coli-aerogenes group. If the lactose broth only is positive, however, he recommends another transfer to brilliant green bile, which, if then positive, would again be regarded as specific for the group, whereas if negative, further confirmatory evidence would have to be obtained. The purpose of this dual testing procedure was to gain in specificity and to shorten the time required by the completed standard methods. Of course, it did not yield quantitative findings which could be expressed in any reliable way.Our previous studies with ferro cyanide citrate agar (3) suggested the possible feasibility of converting the well known liquid brilliant green lactose bile medium to a solid form, suitable for direct plating purposes. The outcome of our effort in this direction is the pour plate medium here reported, which is necessarily altered in composition, but contains all the ingredients of the original liquid medium, in concentrations to produce optimum growth of coli-aerogenes organisms. In addition, ferric chloride, erioglaucine, basic fuchsin, and anhydrous sodium sulphite have been added in order to bring

The Relative Productivity of Certain Culture Media

“…The extent to which, raw water planting may alter the picture ,obtained with pure cultures in brilliant green lactose bile broth and brilliant green lactose bile agar is shown in figure 7. These were compiled from the data of an earlier report' (4). They represent results from only 17 samples, and hence, can only be regarded as suggestive, Nevertheless, by showing the distribution and exact location of the trial medium ratios in each distribution, for comparison with the experimental distribution of the standard medium, they bring out marked differences.…”