Azithromycin-resistant Neisseria gonorrhoeae isolates in Guangzhou, China (2009-2013): Coevolution with decreased susceptibilities to ceftriaxone and genetic characteristics

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Abstract

Background: The recent emergence of azithromycin-resistant (AZM-R) N. gonorrhoeae isolates that have coevolved decreased susceptibility to extended-spectrum cephalosporins has caused great concern. Here we investigated the prevalence of decreased susceptibility to ceftriaxone (CRO D ) in AZM-R isolates and genetically characterized AZM-R isolates in Guangzhou, China from 2009 to 2013. Methods: The minimum inhibitory concentration (MIC) of AZM and ceftriaxone was determined using an agar-dilution method. All AZM-R isolates were screened for mutations in 23S rRNA, mtrR and penA genes and genotyped using N. gonorrhoeae multi-antigen sequence typing (NG-MAST). Results: Of the 485 identified N. gonorrhoeae isolates, 445 (91.8%) were isolated from male urethritis subjects, and 77 (15.9%) were AZM-R (MIC≥1mg/L), including 33 (6.8%) with AZM low-level resistant (AZM-LLR, MIC=1mg/L) and 44 (9.1%) with AZM middle-level resistant (AZM-MLR, MIC≥2mg/L). Significantly more CRO D (MIC≥0.125mg/L) showed in AZM-MLR isolates (43.2%, 19/44) as compared with that in AZM-LLR isolates (18.2%, 6/33) (p<0.05). For the 23S rRNA, mtrR, penA or combined 23S rRNA/MtrR/penA mutations, no significant difference was found between AZM-LLR isolates and AZM-MLR isolates (P>0.05); similar results were detected between combined AZM-LLR/CRO D isolates and combined AZM-MLR/CRO D isolates (P>0.05). No mutation A2059G or AZM high-level resistant (AZM-HLR, MIC≥256mg/L) isolate was detected. Among 77 AZM-R isolates, 67 sequence types (STs) were identified by NG-MAST, of which 30 were novel. Most STs were represented by a single isolate. Conclusions: The AZM-R together CRO D isolates are now present in Guangzhou, China, which deserve continuous surveillance and the mechanism of concurrent resistance needs further study.

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Liang, J. Y., Cao, W. L., Li, X. D., Bi, C., Yang, R. D., Liang, Y. H., … Zhang, X. B. (2016). Azithromycin-resistant Neisseria gonorrhoeae isolates in Guangzhou, China (2009-2013): Coevolution with decreased susceptibilities to ceftriaxone and genetic characteristics. BMC Infectious Diseases, 16(1). https://doi.org/10.1186/s12879-016-1469-3

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