Effect of outer-membrane permeabilizers on the activity of antibiotics and plant extracts against Pseudomonas aeruginosa.

Several known outer membrane permeabilizers increased susceptibility of a highly resistant pathogenic strain Pseudomonas aeruginosa to different antibiotics and plant extracts. Of all the chemicals tested, EDTA, sodium citrate and sodium hexametaphosphate (HMP) were found to be potent permeabilizers as shown by enhanced lysis of the bacteria in the presence of lysozyme. In the presence of EDTA and sodium citrate susceptibility of the strain to gentamicin and rifampicin increased markedly. The strain was resistant to vancomycin but became susceptible when grown in the presence of increasing amounts of EDTA and sodium citrate. Similar results were obtained for erythromycin when treated with sodium citrate. EDTA was found to be most potent permeabilizer in enhancing the activity of the plant extracts. Though HMP was an effective permeabilizer it had a weak or no effect on the activity of the antibiotics and plant extracts.