Culture media in film format for conducting microbial analysis and method of producing the media and loading it into cassettes

A cassette used to analyze a carrier liquid for the presence of a specific microorganism therein has a passageway extending through it and the passageway is provided with filter and viewing wells arranged such that each viewing well is preceded by a filter well. The carrier liquid is introduced into the passageway at one end thereof. Each filter well contains a filter material capable of effecting a one log reduction in the microorganisms within the liquid as the liquid passes through the filter. Each viewing cell contains plugs having a culture medium therein which is selective to a specific microorganism in the sense that only that microorganism will grow in the culture medium and change the light-transmitting characteristics of the viewing wells. To load the filter wells a pad of filter material is placed over the ends of the filter wells and the filters are simultaneously stamped from the pad and driven into the filter wells. To load the viewing wells, a flexible sheet of culture medium is placed over the ends of the viewing wells and the plugs are stamped therefrom and simultaneously driven into the viewing wells. The flexible sheet of culture medium is formed by adding a film-forming agent to liquid culture medium, pouring the solution so formed onto a surface, and then evaporating volatile components of the solution. After the volatile components evaporate, the flexible film remains.. The film-forming agent may be gelatin and glycerin, or it may be polyvinyl alcohol.