Characterization of BRO enzymes and beta-lactamase transfer of Moraxella (Branhamella) catarrhalis isolated in Japan.

Of the 68 strains of beta-lactamase-producing Moraxella (Branhamella) catarrhalis isolated in Japan that were studied, 62 (91%) produced the BRO-1-type beta-lactamase and 6 (9%) produced the BRO-2 type. There were no strains containing the BRO-3-type beta-lactamase. We compared the susceptibility of BRO-1- and BRO-2-producing strains to various oral beta-lactam antibiotics. We found that the BRO-1-producing strains were less susceptible than the BRO-2-producing strains. Although the BRO-1 and BRO-2 types showed a similar hydrolysis pattern, the specific activity of BRO-1 was 3-fold that of BRO-2. We examined the transfer of the BRO-1 and BRO-2 genes to non-beta-lactamase-producing M. catarrhalis No. 4020 and found that of the 13 donor strains producing BRO-1, 11 (85%) were able to transfer the gene for BRO-1 production by conjugation. Of the 6 donor strains producing BRO-2, 2 (33%) were able to transfer the gene for BRO-2 production by conjugation. For 3 of the 13 (23%) BRO-1-producing strains and 1 of the 6 (17%) BRO-2-producing strains, about 13 Mdalton of plasmids were detected. These plasmid-containing strains were used as donors, and in beta-lactamase-producing transconjugants the same size of plasmids was detected. However, when the total DNA is extracted from strains with the ability to transfer by conjugation, the transformation of the beta-lactamase-producing gene can occur regardless of the presence or absence of plasmids. Furthermore, even if purified plasmids are transformed, beta-lactamase-producing transformants are not obtained.(ABSTRACT TRUNCATED AT 250 WORDS)