Susceptibility of Pseudomonas aeruginosa isolates to ceftazidime is unrelated to the expression of the outer membrane protein OprC

Previously, it has been postulated that the porin OprC facilitates the diffusion of ceftazidime through the outer membrane of Pseudomonas aeruginosa. To further investigate this claim, the outer membrane protein (OMP) profiles of 22 ceftazidime-susceptible clinical isolates were analyzed. No correlation was found between MIC values and the level of expression of OprC. Further, OprC was either undetectable or expressed in reduced amounts in 12 isolates. In contrast, OprF and OprE were present in all isolates studied. This study suggests that OprC is dispensable for the permeation of ceftazidime through the outer membrane of P. aeruginosa.