Disk-Diffusion Testing Is an Inappropriate Screening Tool for Cephalosporin-Resistant Gonorrhoea Strains in Clinical Practice in China

Abstract

Purpose

Injectable ceftriaxone and oral cefixime are the last agents effective against Neisseria gonorrhoeae. In vitro antimicrobial-susceptibility testing (AST) is done to identify the most efficacious antibiotic needed to combat the infection in that particular individual. The objective of this study was to evaluate whether Kirby–Bauer (KB) disk-diffusion tests can detect N. gonorrhoeae isolates that have decreased susceptibility to ceftriaxone and cefixime for appropriate clinical management.

Methods

A total of 1,633 consecutive clinical isolates of N. gonorrhoeae were collected from January 1, 2013 to December 31, 2017 from seven dermatology clinics located in five provinces in China. Consistency between KB disk-diffusion tests and the agar-dilution method, as well as sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility to ceftriaxone and cefixime, were determined using 1,306 clinical isolates that had been recovered to complete agar-dilution AST.

Results

The prevalence of isolates with decreased susceptibility to ceftriaxone and cefixime was 12.1% (198 of 1,633) and 12.7% (208 of 1,633), respectively, using KB disk-diffusion tests. The prevalence of isolates with decreased susceptibility was 9.9% (129 of 1,306) for ceftriaxone and 9.9% (129 of 1,305) for cefixime using agar-dilution AST. The categorical agreement of these two methods was 80.9% for both ceftriaxone and cefixime. Compared to agar-dilution AST, the sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility was 22.5% (29 of 129) for ceftriaxone and 29.5% (38 of 129) for cefixime, and its specificity 87.3% (1,028 of 1,177) for ceftriaxone and 86.7% (1,018 of 1,176) for cefixime.

Conclusion

Although KB tests are easy to carry out in clinical practice, their ability to detect cephalosporin-resistant gonorrhoea strains is limited. This method is not an appropriate selection for screening cephalosporin-resistant gonorrhoea strains in clinical practice in China.

Keywords:

• Neisseria gonorrhoeae
• Kirby–Bauer disk-diffusion tests
• agar-dilution method
• susceptibility
• screen

Acknowledgments

The China Gonorrhoeae Resistance Surveillance Program is a national program coordinated by the Chinese National Center for Sexually Transmitted Disease under the leadership of the Commission of Health in China. The authors thank the collaborating sexually transmitted–infection clinics where this study took place and the participants of this study for their cooperation. This work was supported by the Chinese Academy of Medical Sciences Initiative for Innovative Medicine (grant 2016-I2M-3–021)), the National Science and Technology Major Project (2018ZX10101001-004-003), and the Guangdong Provincial Medical Science and Technology Program (B2018124).

Disclosure

The authors report no conflicts of interest in this work.