L-prolineaminopeptidase activity as a tool for identification and differentiation of Serratia marcescens, Serratia liquefaciens and Hafnia alvei strains.

S. marcescens (316 strains), S. liquefaciens (10 strains) and Hafnia alvei (20 strains), in contrast to 18 other Enterobacteriaceae species, hydrolyzed L-proline-4-nitroanilide within 30 min at 37 degrees C. In this way, rapid identification of these species is possible. The substrate is applied in solution or in a paper disc. The substrate optimum of Hafnia alvei strains proved to be 16 times lower than that of the Serratia spp. Application of a tenth of the substrate concentration necessary for identification of Serratia spp. allows a rapid differentiation between the two species.