ACTINOBACILLUS-PLEUROPNEUMONIAE DOES NOT REQUIRE UREASE ACTIVITY TO PRODUCE ACUTE SWINE PLEUROPNEUMONIA

The role in virulence of Actinobacillus pleuropneumoniae urease activi ty was investigated. A urease-negative mutant was isolated following t ransposon mutagenesis with a mini-Tn10 derivative. Both the parent str ain and the urease-negative mutant exhibited identical LD(50) values i n a murine infection model. Pig challenge confirmed that the urease-ne gative mutant was fully virulent, since experimental inoculation with 5x10(7) colony forming units resulted in an acute disease indistinguis hable from that produced by the wild-type strain at the same dose. Our results demonstrate that urease activity is not required for the deve lopment of acute pleuropneumonia.