Estimation of outer membrane permeability of carbapenem antibiotics to Pseudomonas aeruginosa

The outer membrane permeability of carbapenems (imipenem [IPM], panipenem [PAPM], meropenem [MEPM], and biapenem [BIPM]) and ceftazidime (CAZ) to Pseudomonas aeruginosa was determined by the Zimmermann and Rosselet method. The permeability coefficients of beta-lactams tested at 50 M concentration of substrates ranged from (0.40 +/- 0.10) x 10-6 cm/s for CAZ to (2.33 +/- 0.33) x 10-6 cm/s for IPM, indicating that the outer membrane permeability of carbapenems to P. aeruginosa was high in comparison with that of CAZ. In particular, IPM and BIPM showed a higher rate of penetration than MEPM and PAPM.