Outer surface changes of Pseudomonas aeruginosa in relation to resistance to gentamicin and carbenicillin.

The outer surface structure of clinical isolates of Pseudomonas aeruginosa resistant to carbenicillin or gentamicin or both was studied by thin-section electronmicroscopy and compared with that of sensitive isolates. The latter had a fairly smooth outer layer. Strains resistant to both antibiotics were characterised by extrusions that appeared to constitute extensions of the outer membrane.

Outer membrane proteins in a carbenicillin-resistant strain of Pseudomonas aeruginosa.

The outer membrane of a clinical isolate of Pseudomonas aeruginosa sensitive to carbenicillin, and its derivative adapted to grow in the presence of carbenicillin were analysed by polyacrylamide gel electrophoresis. The lack of beta-lactamase activity showed that the resistance of the adapted strain was not due to hydrolysis of carbenicillin. The appearance of several outer membrane proteins almost exclusively in the resistant strain supports the view of altered cell envelope properties in this strain.