Characterization of Listeria monocytogenes isolates by esterase electrophoresis

Abstract

Multiple bands of α-naphthyl-propionyl esterase (αNPE) activity observed following starch gel electrophoresis of cell extracts allowed 219 Listeria monocytogenes isolates from milk, nondairy foods, and clinical and veterinary sources to be assigned to 17 different αNPE types. Multilocus enzyme electrophoresis (MEE) analysis was used to obtain electrophoretic mobility data for αNPEs and nine other metabolic enzymes; on the basis of these data, the 219 strains were assigned to 59 electrophoretic types. Each of the methods separated the strains into two main groups, and there was extensive agreement on assignment of the strains to the groups. Although the method is less discriminatory than MEE, the usefulness of αNPE electrophoresis alone as a rapid, simple typing method for L. monocytogenes for certain purposes is indicated by agreement among αNPE, MEE, and restriction fragment length polymorphism types as molecular markers for persistent and transient L. monocytogenes strains found in sequential raw-milk and nondairy food samples obtained from different processors.