Aminoglycoside resistance in Pseudomonas aeruginosa due to outer membrane stabilization

Pseudomonas aeruginosa PAOl released a significant amount of a cytoplasmic enzyme, glucosc-6-phosphate dehydrogenase, in the presence of aminoglycoside and lysozyme. The extent of the enzyme release was inversely related to the MICs of the aminoglycoside. However, the aminoglycosidc-rcsistant strain F3721, treated in the same way; released a less enzyme. The F3721 LPS was extracted in the phenol phase instead of the water phase in which PAOl LPS was easily extracted. Electrophoretic analysis of the F3721 LPS showed the ladder bands at the high M,. position, suggesting that the LPS of the aminoglycosidc-rcsistant cells has a structural modification(s) which somehow protects the outer membrane from aminoglycoside-mediatcd damage.