Bovine pneumonic pasteurellosis: chemiluminescent response of bovine peripheral blood leukocytes to living and killed Pasteurella haemolytica, Pasteurella multocida, and Escherichia coli

Abstract

A luminol-dependent chemiluminescence (LDCL) assay was used to evaluate the response of bovine polymorphonuclear leukocytes; (neutrophils [PMN]) to living and heat-killed Escherichia coli, Pasteurella multocida (type A, serotype 3), and P haemolytica (biotype A, serotype 1), and to heat-killed P haemolytica and sterile culture supernatant from living P haemolytica. Control cultures containing PMN that had not been phagocytically stimulated with bacteria had a modest increase in LDCL during the initial 10 minutes of incubation, followed by a gradual decline throughout the 120-minute incubation period. Bovine PMN emitted LDCL more efficiently when the cells were exposed to living E coli or P multocida than when they were exposed to the same bacteria killed by heat. The mean LDCL values for reaction mixtures containing living E coli or P multocida peaked at 30 minutes of incubation and remained above values for mixtures containing the same heat-killed bacteria. Kinetics of the LDCL response of bovine PMN to heat-killed P haemolytica were similar (although reduced in amplitude) to that observed with killed E coli or P multocida. The LDCL response of bovine PMN to living P haemolytica was not like that for E coli or P multocida, and was characterized by the development of a peak response at 10 minutes followed by a precipitous decrease in responsiveness and a subsequent complete cessation of LDCL. Addition of sterile culture supernatant from living P haemolytica to test samples containing heat-killed P haemolytica induced a response similar to that obtained with the living microorganism.(ABSTRACT TRUNCATED AT 250 WORDS)