Differentiation of Lactococcus lactis and Lactococcus garvieae from humans by comparison of whole-cell protein patterns.

We tested 12 reference and 24 clinical strains of lactococci for physiologic characteristics using a conventional test system, the Gen-Probe Enterococcus 2 chemiluminescence assay (Gen-Probe Inc., San Diego, Calif.), the Rapid Strep identification system (Analytab Products, Plainview, N.Y.), and whole-cell protein analysis. The Gen-Probe Enterococcus 2 chemiluminescence assay for Enterococcus identification was negative with all strains. Neither the conventional test nor the Rapid Strep identification system could differentiate between the two Lactococcus spp. most commonly isolated from humans. A simple procedure, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was developed for comparing the whole-cell protein patterns of Lactococcus spp. L. lactis and L. garvieae were differentiated by unique protein patterns.