Pyrrolidonyl Peptidase in Bacteria: A New Colrimetric Test for Differentiation of Enterobacteriaceae

Summary: A simple and rapid colorimetric test has been developed for the detection of pyrrolidonpl peptidase (PLP) activity in bacteria. Of 2354 strains belonging to various groups of enteric bacteria tested, 451 were PLP-positive. These included Citrobacter, 223 out of 226 strains, Klebsiella (178/188), Enterobacter (49/52), and one strain of Serratia. Pyrrolidonyl peptidase was not detected in 1146 Shigella strains, 354 Salmonella strains, 333 Escherichia strains, 21 Arizona strains, nor in 33 strains of Proteus, Providencia and Hafnia. In addition, 56 cultures of various Gram-negative and Gram-positive bacteria were tested for PLP. Enzyme activity was found in strains belonging to the genera Bacillus, Streptococcus, Staphylococcus, Micrococcus, Sarcina, Neisseria and Pseudomonas. The possibility of employing the PLP test for differentiation within the family Enterobacteriaceae is discussed.