Rapid identification of dairy Propionibacterium species by restriction analysis of the insertion within the 23S rRNA gene

An amplified sequence of approximately 350 bases from the 23S rRNA gene of each bacteria was used to identify 37 strains of dairy propionibacteria. After generation of the fragment by PCR (polymerase chain reaction), it was cut with the restriction endonuclease MspI. The resulting electrophoretic pattern showed a distinct profile for each of the Propionibacterium species. Purification of DNA was not necessary and the analyses could also be performed with crude bacterial extract. A collection of anaerobic bacteria commonly found in milk and milk products was also submitted to the analysis. None yielded the same pattern as propionibacteria. The analysis of the propionibacteria was compared to that performed by electrophoresis of the soluble cell-free protein extracts and that of classical microbiological tests. Our method gave identical results and was less time consuming (results could be obtained within a single day and were also easier to read) than both the classical tests and protein electrophoresis. (C) Inra/Elsevier, Paris.