Animal isolates of Pasteurella were found to be resistant to beta-lact
ams, owing to production of the ROB-1 beta-lactamase, previously descr
ibed in a human Haemophilus influenzae isolate, ROB-1 is plasmid-encod
ed in nine strains out of ten. Analysis of the nucleic and amino acid
sequences indicates that the ROB-1 gene might have recently arisen in
Pasteurella species from gram positive bacteria. Then, it diffused amo
ng animal isolates of Pasteurellaceae, before spreading to strains pat
hogenic for humans.