Evaluation of Kirby-Bauer disc diffusion test for antibiotic susceptibility of Neisseria gonorrhoeae

Abstract

Objective To evaluate the accuracy of disc diffusion method for detecting the susceptibility of Neisseria gonorrhoeae to seven surveillance drugs. Methods The agar dilution method and the disc diffusion method were compared in assessing the susceptibility of 60 N. gonorrhoeae strains to ceftriaxone, cefixime, spectinomycin, azithromycin, ciprofloxacin, tetracycline and penicillin. Comparison of results between the two methods included the categorical agreements, minor errors, major errors, and very major errors of drug susceptibility test. Results The categorical agreements of ceftriaxone, cefixime, spectinomycin, azithromycin, ciprofloxacin, tetracycline and penicillin were 95.0%, 76.7%, 100%, 80.0%, 93.3%, 63.3% and 90.0%, respectively. Among the tested antibiotics, minor errors were found for ceftriaxone, cefixime, ciprofloxacin, tetracycline, and penicillin, with rates of 5.0%, 23.3%, 6.7%, 30.0% and 10.0%, respectively. For azithromycin and tetracycline, the very major error rates were 20.0% and 6.7%, respectively. Conclusion With the exception of cefixime, azithromycin and tetracycline, the disc diffusion method is more accurate in assessing drug susceptibility of N. gonorrhoeae.

Keywords

• neisseria gonorrhoeae
• agar dilution
• disc diffusion method
• antimicrobial susceptibility test