Published in:
Open Access
01-12-2016 | Research article
Azithromycin-resistant Neisseria gonorrhoeae isolates in Guangzhou, China (2009–2013): coevolution with decreased susceptibilities to ceftriaxone and genetic characteristics
Authors:
Jing-Yao Liang, Wen-Ling Cao, Xiao-Dong Li, Chao Bi, Ri-Dong Yang, Yan-Hua Liang, Ping Li, Xing-Dong Ye, Xiao-Xiao Chen, Xi-Bao Zhang
Published in:
BMC Infectious Diseases
|
Issue 1/2016
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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 (CROD) 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 ≥ 1 mg/L), including 33 (6.8 %) with AZM low-level resistant (AZM-LLR, MIC = 1 mg/L) and 44 (9.1 %) with AZM middle-level resistant (AZM-MLR, MIC ≥ 2 mg/L). Significantly more CROD (MIC ≥ 0.125 mg/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/CROD isolates and combined AZM-MLR/CROD isolates (P > 0.05). No mutation A2059G or AZM high-level resistant (AZM-HLR, MIC ≥ 256 mg/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 CROD isolates are now present in Guangzhou, China, which deserve continuous surveillance and the mechanism of concurrent resistance needs further study.