[beta-Lactamases of Branhamella catarrhalis and their phenotypic implications]

Of the 50 strains of beta-lactamase-producing Branhamella catarrhalis isolated at Saint Joseph's Hospital (Paris) that were studied, 94% produced BRO-1 type beta-lactamase and 6% produced the BRO-2 type. We examined the transfer of BRO-1 and BRO-2 genes and found that, among 7 donor strains producing BRO-1, all were able to transfer the gene for BRO-1 production by conjugation. Of the 4 donor strains producing BRO-2, 2 were able to transfer the gene for BRO-2 production by conjugation. Three BRO-1 beta-lactamase-producing transformants were obtained from total DNA extracted from 3 strains producing BRO-1. Plasmid bands were demonstrated in strains of B. catarrhalis, but no change in plasmid profiles was seen in beta-lactamase-positive recombinants, supporting previous studies that suggested the beta-lactamases are chromosomal. In vitro activity of oral beta-lactams was tested for 67 strains of B. catarrhalis (56 beta-lactamase-producing strains). Cefixime, cefpodoxime and the combination ampicillin-clavulanic acid were very active against the beta-lactamase-producing strains. BRO-1 beta-lactamase appears to affect the activity of cefaclor, cefuroxime and loracarbef. BRO-2 beta-lactamases have no effect on the activity of these cephalosporins. Cefixime and cefpodoxime seemed the least affected by beta-lactamase production.