We have previously reported that the presence of a 180-kilobase plasmid encoding production of aerobactin was correlated with the virulence of Klebsiella pneumoniae K1 and K2 isolates. This work demonstrates that a variant of a K2 strain which has lost this plasmid, pKP100, becomes avirulent. Labeling of this plasmid with the mobilizable, replication-defective element pME28, used here as a mobi...
