Serum sensitivity of field isolates and laboratory strains of Brucella abortus.
OBJECTIVE
To evaluate the ability of bovine complement to kill a variety of field isolates and laboratory strains of Brucella abortus.


METHODS
The experimental approach was to determine the sensitivity of B abortus isolates to killing by bovine serum, and to document the role of complement in brucellacidal activity.


METHODS
Six laboratory isolates and 12 field isolates of B abortus were tested.


METHODS
The ability of B abortus to survive exposure to undiluted bovine serum for 2 hours at 37 C was assessed. The role of complement in killing was determined by examining the ability of heat (56 C for 60 minutes) and cobra venom factor to obliterate the activity in serum, and by detecting binding of the ninth component of bovine complement to serum-sensitive target cells.


RESULTS
Isolates of B abortus that were resistant to the bactericidal activity of normal bovine serum were revealed. These included field isolates and laboratory strains. Furthermore, the study confirmed earlier reports that bovine serum-mediated killing of B abortus is caused by the complement cascade.


CONCLUSIONS
Some isolates of B abortus, like other gram-negative bacteria, were resistant to complement-mediating killing. Resistance was associated with smooth colony morphology. Isolates lacking detectable O antigen were serum sensitive.
Eisenschenk
F C
FC
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611, USA.
Houle
J J
JJ
Hoffmann
E M
EM
D000818:Animals; D001770:Blood Bactericidal Activity; D002003:Brucella abortus / Q000145:classification / Q000276:immunology* / Q000502:physiology; D002007:Brucellosis, Bovine / Q000097:blood* / Q000276:immunology; D002417:Cattle; D003170:Complement Pathway, Alternative; D003165:Complement System Proteins / Q000276:immunology* / Q000502:physiology; D015151:Immunoblotting / Q000662:veterinary; D019081:O Antigens / Q000032:analysis
D019081:O Antigens; D003165:Complement System Proteins