Detection of outer membrane porin protein, an imipenem influx channel, in Pseudomonas aeruginosa clinical isolates.

Decreased permeability to imipenem is the most frequent mechanism of imipenem resistance in Pseudomonas aeruginosa. We have determined the presence of OprD porin protein, an imipenem influx channel, in 70 carbapenem-resistant P. aeruginosa clinical isolates by Western blot analysis using rabbit anti-OprD polyclonal antibody. Ninety-eight percent (54 of 55 isolates) of imipenem-and meropenem-resistant P. aeruginosa clinical isolates were negative for OprD porin production. A small group of isolates resistant to imipenem but susceptible to meropenem (2 isolates) produced OprD protein but at a level 3-5 times lower than the wild type P. aeruginosa ATCC27853 strains. This study indicates that the loss of OprD porin protein was the main mechanism for imipenem resistance in P. aeruginosa clinical isolates. Determination of the status of OprD level in P. aeruginosa may help in the better selection of appropriate carbapenem antibiotics.