High prevalence of Neisseria gonorrhoeae strains with reduced susceptibility to fluoroquinolones in Japan

Abstract

Objective - To study the antibiotic susceptibility of Neisseria gonorrhoeae strains isolated in Japan and, in particular, to examine the possibility of emerging fluoroquinolone resistance. Materials and methods - Sixty-nine strains of Neisseria gonorrhoeae isolated in 1992 were tested for susceptibility to 15 antibiotics including fluoroquinolones and were seroclassified. Twenty-seven strains isolated from 1981 to 1984 were also evaluated as controls. Results - The MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the isolates from 1992 were 2.0, 1.0, and 0.5 μg/ml, respectively. The MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the isolates from 1981-84 (controls) were 0.25, 0.125, and 0.063 μg/ml, respectively. These results indicate that the MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the strains from 1992 were 8-fold higher than those against the strains from 1981-84. However, there were no significant differences in susceptibility to β-lactams, tetracyclines, macrolides, and spectinomycin between the isolates from 1992 and those from 1981-84. The majority of the isolates belonged to the WII/WIII serogroup. There was no relationship between fluoroquinolone resistance and serogroup. Conclusions - Fluoroquinolones have been used frequently as first-line therapy and have provided excellent clinical efficacy for gonococcal infections for the last several years in Japan. However, our data indicate that a rapid decrease in the susceptibility of Neisseria gonorrhoeae to fluoroquinolones is occurring in our country.