Outer membrane permeability of beta-lactamase inhibitors in Pseudomonas aeruginosa

Evaluation of four beta-lactamase inhibitors in terms of their outer membrane permeability in Pseudomonas aeruginosa revealed that sulbactam and tazobactam diffused most efficiently and equally well. That of BRL42715 appeared to be a factor of ten lower than that of the above two, but it showed the strongest beta-lactamase inhibitory activity. This is most likely due to its better beta-lactamase inactivating activity. BRL42715 at 1.56 micrograms ml-1 lowered the minimum inhibitory concentrations of ceftazidime and imipenem in a strain producing fully derepressed beta-lactamase and an undetectable level of the outer membrane protein OprD2.