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Yan Han,1,2 Yue-Ping Yin,1,2 Wen-Qi Xu,1,2 Xiao-Yu Zhu,1,2 Shao-Chun Chen,1,2 Xiu-Qin Dai,1,2 Li-Gang Yang,3,4 Bang-Yong Zhu,5 Na Zhong,6 Wen-Ling Cao,7 Xiao-Hui Zhang,3,4 Zhi-Zhou Wu,8 Liu-Feng Yuan,9 Zhong-Jie Zheng,10 Jun Liu,11 Xiang-Sheng Chen1,2 1Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing, Jiangsu, People’s Republic of China; 2National Center for STD Control, Chinese Center for Disease Control and Prevention, Nanjing, Jiangsu, People’s Republic of China; 3Dermatology Hospital, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China; 4Guangdong Provincial Dermatology Hospital, Guangzhou, Guangdong, People’s Republic of China; 5Institute of Dermatology, Nanning, Guangxi Autonomous Region, People’s Republic of China; 6Hainan Provincial Center for STD/Skin Disease Control and Prevention, Haikou, Hainan, People’s Republic of China; 7Guangzhou Institute of Dermatology, Guangzhou, Guangdong, People’s Republic of China; 8Jiangmen Dermatology Hospital, Jiangmen, Guangdong, People’s Republic of China; 9Beijing Ditan Hospital Capital Medical University, Beijing, People’s Republic of China; 10Tianjin Center for Disease Control and Prevention, Tianjin, People’s Republic of China; 11Harvard Medical School, Boston, MA, USACorrespondence: Yue-Ping YinInstitute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, 12 Jiangwangmiao Street, Nanjing 210042, People’s Republic of ChinaTel/ Fax +86 258 547 8024Email yinyp@ncstdlc.orgPurpose: 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

Shao-Chun Chen,1,2,* Jing-Wei Liu,1,2,* Xing-Zhong Wu,3 Wen-Ling Cao,4 Feng Wang,5 Jin-Mei Huang,3 Yan Han,1,2 Xiao-Yu Zhu,1,2 Bang-Yong Zhu,6 Quan Gan,6 Xiao-Zheng Tang,7 Xing Shen,8 Xiao-Lin Qin,3 Yu-Qi Yu,3 He-Ping Zheng,3 Yue-Ping Yin1,2 1Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing, People’s Republic of China; 2National Center for STD Control, Chinese Center for Disease Control and Prevention, Nanjing, People’s Republic of China; 3Clinical Laboratory, Guangdong Provincial Dermatology Hospital, Guangzhou, Guangdong, People’s Republic of China; 4Clinical Laboratory, Guangzhou Dermatology Hospital, Guangzhou, Guangdong, People’s Republic of China; 5Shenzhen Center for Chronic Diseases Control, Shenzhen, Guangdong, People’s Republic of China; 6Clinical Laboratory, Guangxi Provincial Dermatology Hospital, Nanning, Guangxi, People’s Republic of China; 7Clinical Laboratory, Hainan Provincial Dermatology Hospital, Haikou, Hainan, People’s Republic of China; 8Zhuhai Center for Chronic Diseases Control, Zhuhai, Guangdong, People’s Republic of China*These authors contributed equally to this workCorrespondence: Yue-Ping YinNational Center for STD Control,Chinese Center for Disease Control and Prevention, 12 Jiangwangmiao Street, Nanjing 210042, People’s Republic of ChinaTel +86-25-85478024Email yinyp@ncstdlc.orgHe-Ping ZhengGuangdong Provincial Dermatology Hospital, 2 Lujing Road, Guangzhou 510091, People’s Republic of ChinaEmail zhhpf@hotmail.comIntroduction: Antimicrobial resistance (AMR) of Neisseria gonorrhoeae (N. gonorrhoeae) becomes a grave public health problem in the world. A strengthened Antimicrobial Resistance Surveillance Program is needed to track the trend of AMR development. However, the lack of a proper antimicrobial susceptibility test (AST) method is a barrier to expand the AMR surveillance in China. Traditional agar dilution (AD) method is laborious and E-test strips have no approval license for clinical use. Herein, a Chinese group modified the microdilution (MD) method for clinical ASTs. The objective of this study is to compare the MD method with the AD method for N. gonorrhoeae AST.Materials and Methods: A total of 166 clinical isolates were tested for antimicrobial susceptibility of ceftriaxone, spectinomycin, azithromycin, ciprofloxacin, tetracycline, and penicillin using MD and AD method simultaneously. Results of MD method were read manually or automatically. Rates of essential agreement (EA), category agreement (CA), minor error, and very major error were compared.Results: The total EAs (compared with results read manually) of penicillin, tetracycline, ciprofloxacin, spectinomycin, ceftriaxone, and azithromycin were 90.4%, 97.0%, 85.5%, 100.0%, 94%, and 72.3%; and CAs were 82.5%, 94.0%, 100%, 100%, 95.2%, and 94%, respectively.Conclusion: We conclude that the MD method might be an alternative for clinical AST of N. gonorrhoeae in China. In particular, MD method has the potency of accurate differentiation of isolates resistant to ceftriaxone or azithromycin, which were empirically recommended for gonococcal treatment, but its quality remained suboptimal, and further improvement is needed for clinical use.Keywords: Neisseria gonorrhoeae, antimicrobial susceptibility test