Reproduction of bovine keratoconjunctivitis with a purified haemolytic and cytotoxic fraction of Moraxella bovis.
Evidence that the beta-haemolysin produced in vitro by Moraxella bovis is an important virulence determinant in vivo was strengthened by studies using a haemolytic preparation of greater purity than previously available. A concentrated haemolytic fraction containing outer-membrane bound vesicles was separated from the cell-free filtrate of a bacterial culture using a process comprising tangential flow ultrafiltration, ion-exchange and gel-filtration high-performance liquid chromatography and centrifugal-driven filtration. The cytotoxicity of haemolytic fractions for calf-corneal epithelial cells in vitro was investigated at progressive stages of this attempted haemolysin purification procedure and the results demonstrated a positive correlation for the levels of haemolytic and cytotoxic activity throughout. Further support for the role of the haemolysin was obtained in vivo following the intra-corneal injection of calves with a crude or a purified haemolytic fraction. The ocular damage caused by both preparations, together with the healing processes and microscopic pathology of the experimentally induced damage closely resembled published descriptions of naturally occurring infectious bovine keratoconjunctivitis. No effect was obtained in vitro or in vivo from equivalent fractions prepared from a non-haemolytic strain of M. bovis.
Department of Animal Health, University of Sydney, Camden, NSW, Australia.
M K
MK
Beard
L J
LJ
Moore
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D002458:Cell Fractionation; D002478:Cells, Cultured; D003315:Cornea; D003603:Cytotoxins / Q000302:isolation & purification; D004591:Electrophoresis, Polyacrylamide Gel; D006461:Hemolysis; D007639:Keratoconjunctivitis, Infectious / Q000382:microbiology*; D008297:Male; D016955:Moraxella bovis / Q000472:pathogenicity* / Q000648:ultrastructure; D016870:Neisseriaceae Infections / Q000382:microbiology / Q000662:veterinary*
D003603:Cytotoxins