title: Characterization of the plasmid-mediated beta-lactamase in Branhamella catarrhalis, with special reference to substrate affinity.
abstract: The plasmid-mediated Branhamella catarrhalis beta-lactamase BRO-1, also found in Moraxella nonliquefaciens, was characterized as regards substrate profile, isoelectric point and relative substrate affinity index (RSAI) to various substrates and compared in these aspects with the TEM-1 enzyme of Haemophilus influenzae. As measured by a biological assay and with high performance liquid chromatography (HPLC), BRO-1 was found to hydrolyse carbenicillin, mecillinam, methicillin and cefaclor with a higher rate than TEM-1. The only substrates having a relative rate of hydrolysis higher for TEM-1 than for BRO-1 were ampicillin and cephaloridine. The rates of hydrolysis registered with these two methods were comparable for all but 2 of 13 tested substrates. Isoelectric focusing yielded a main band at pH 5.6 and several satellite bands consistent with those reported by other authors for Branhamella enzymes having a substrate profile similar to that of BRO-1. A tenfold or higher difference in RSAI between BRO-1 and TEM-1 was recorded for five of the 15 compounds tested. BRO-1 seems to be the most common beta-lactamase in Bran. catarrhalis, irrespective of geographic origin. Its substrate profile, isoelectric pattern and RSAI differ from those of other known plasmid-mediated beta-lactamases described, thus justifying a specific designation.
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003227:Conjugation, Genetic; D006193:Haemophilus influenzae / Q000187:drug effects / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007525:Isoelectric Focusing; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D009346:Neisseriaceae / Q000201:enzymology* / Q000235:genetics; D010957:Plasmids; D013379:Substrate Specificity; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases