[Experimental-practical study of some methods for culturing and counting enterobacteria from raw materials and oral...

The technique of enterobacteria enumeration according to F.U., by rivivification in Lactose Broth for 5 h at 37 degrees C and subsequent incubation in Enterobacteriaceae Enrichment Broth, causes artful increases of the number of enterobacteria, often resulting higher than the total microbial charge. To eliminate the drawback we have assayed other two methods: a) incubation in Soybean Casein Digest Broth for 5 h at 37 degrees C, followed by enumeration onto Violet Red Bile Dextrose Agar plates; b) incubation into Soybean Casein Digest Agar plates for 5 h at 37 degrees C, followed by enumeration onto overlayed Violet Red Bile Dextrose Agar. The experimental investigations were performed on 8 artificially stressed (heating, freezing) strain of Enterobacteriaceae and carried out the superiority of the method onto Soybean Casein Digest Agar + Violet Red Bile Dextrose Agar plates. This method was tested on No. 302 samples of raw materials and pharmaceutical preparations, that shown an enterobacterial charge higher than 100 C.F.U. in 24 cases (8%). On the contrary, the enumeration of the enterobacteria according to the F.U. method (Lactose Broth + Enterobacteriaceae Enrichment Broth + Violet Red Bile Dextrose Agar) carried out an enterobacterial charge higher than 100 C.F.U. in 270 cases (89.4%). Indeed, the artful increase of the number of enterobacteria may make unacceptable pharmaceutical preparations suitable for the market. The employment of the method of enumeration of the enterobacteria onto Soybean Casein Digest Agar + Violet Red Bile Dextrose Agar plates is augured.