[Use of molecular methods in food microbiology with the example of probiotic use of lactobacilli]

The aim of molecular methods in food microbiology is the identification or strain specific differentiation of microorganisms. Identification methods include besides taxonomic purposes also the detection of virulence genes or resistance markers. Strain specific differentiation is used for epidemiological investigations or the quality control of technologically used bacteria. Probiotic strains of the Lactobacillus acidophilus-group were investigated with different molecular methods: for identification proteinfingerprinting and RAPD-PCR (Random Amplified Polymorphic DNA-PCR) were applied, for strain specific differentiation pulsed field gel electrophoresis (PFGE) and again RAPD-PCR were used. The molecular methods applied should be chosen depending on the objective (identification, differentiation) and with respect to the organism to be tested. In case of probiotic lactic acid bacteria like the L. acidophilus-group proteinfingerprinting has proved to be successful for identification and with some limitation also RAPD-PCR. For differentiation PFGE is suitable as well as RAPD-PCR. Those methods differ substantially in their work load and in personal requirements, and show different power of discrimination and reproducibility within and between laboratories. This should be considered while choosing the appropriate method.