Antimicrobial susceptibility to β-lactam antibiotics and production of BRO β-lactamase in clinical isolates of Moraxella catarrhalis from a Japanese hospital

We investigated BRO-β-lactamase production of Moraxella catarrhalis isolates and its antimicrobial susceptibility to β-lactams. Of the 233 isolates, 232 were BRO producers and 224 were BRO-1 producers. Four isolates exhibited elevated ceftriaxone minimum inhibitory concentration (2 μg/mL) and different pulsed-field gel electrophoresis patterns and we expect this number to increase in the near future.