Reduced uptake and accumulation of norfioxacin

Accepted for publication 7 April 1994 Abstract Objective-To investigate the alteration of cell permeability toward fluoroquinolones in Neisseria gonorrhoeae, which is a major quinolone-resistance mechanism along with the alteration of DNA gyrase in gram-negative bacteria. The prevalence of fluoroquinolone-resistant N gonorrhoeae strains is rapidly increasing in Japan. Materials and methods-The uptake and accumulation of norfloxacin by gonococcal cells, including six clinical and five World Health Organization (WHO) reference strains, were measured. Of the six clinical strains, two were highly resistant to norfloxacin (MIC 8.0 and 4-0 4ugIml), two were moderately resistant (MIC 1.0 and 0 5 pglml), and two were sensitive (MIC 0-063 and 0.004.uglml). All five WHO reference strains were sensitive to norfloxacin (MIC <0-001 to 0.063 pglml). Results-Mean initial norfloxacin uptake in the four resistant strains (104 nglmg of dry cells) was significantly lower than that in the seven sensitive strains (158 nglmg of dry cells) (p < 0.05). The mean uptake after 20 minutes was also significantly lower in the four resistant strains (130 nglmg of dry cells) than in the seven sensitive strains (194 nglmg of dry cells) (p < 0-05). However, there was no significant difference in mean norfloxacin accumulation after 20 minutes between the four resistant strains (26 nglmg of dry cells) and the seven sensitive strains (36 nglmg of dry cells). The accumulation of norfloxacin after 20 minutes was almost zero in two of the four resistant strains, while the remaining two strains accumulated norfloxacin as well as the sensitive strains. Conclusions-These findings suggest that alteration ofbacterial cell permeability is