Bovine pneumonic pasteurellosis: chemiluminescent response of bovine peripheral blood leukocytes to living and killed Pasteurella haemolytica, Pasteurella multocida, and Escherichia coli
Chang, Y.F.; Renshaw, H.W.; Augustine, J.L.
American Journal of Veterinary Research 46(11): 2266-2271
1985
ISSN/ISBN: 0002-9645 PMID: 3907434 Document Number: 263115
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 bacteria 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. Collectively, the results indicated that metabolically active P. haemolytica synthesized a heat-labile factor that was released into the culture supernatant and that was retained in a form associated with the cell. This factor, which may be the same as the P. haemolytica cytotoxin described by others, had the ability to biologically incapacitate the oxygen-dependent activation of the hexose monophosphate shunt in PMN and thereby rendered inoperative an important antimicrobial system of the cell. The LDCL assay may be useful for further evaluations of this factor and for clarification of the factor's importance as a potential virulence factor of P. haemolytica.