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. 2018 Apr 26;62(5):e02499-17.
doi: 10.1128/AAC.02499-17. Print 2018 May.

Increasing Resistance to Azithromycin in Neisseria gonorrhoeae in Eastern Chinese Cities: Resistance Mechanisms and Genetic Diversity among Isolates from Nanjing

Chuan Wan  1 , Yang Li  1 , Wen-Jing Le  1 , Yu-Rong Liu  1 , Sai Li  1 , Bao-Xi Wang  1 , Peter A Rice  2 , Xiao-Hong Su  3
Affiliations

Increasing Resistance to Azithromycin in Neisseria gonorrhoeae in Eastern Chinese Cities: Resistance Mechanisms and Genetic Diversity among Isolates from Nanjing

Chuan Wan et al. Antimicrob Agents Chemother. .

Abstract

Azithromycin resistance (AZM-R) of Neisseria gonorrhoeae is emerging as a clinical and public health challenge. We determined molecular characteristics of recent AZM-R Nanjing gonococcal isolates and tracked the emergence of AZM-R isolates in eastern Chinese cities in recent years. A total of 384 N. gonorrhoeae isolates from Nanjing collected from 2013 to 2014 were tested for susceptibility to AZM and six additional antibiotics; all AZM-R strains were characterized genetically for resistance determinants by sequencing and were genotyped using N. gonorrhoeae multiantigen sequence typing (NG-MAST). Among the 384 isolates, 124 (32.3%) were AZM-R. High-level resistance (MIC, ≥256 mg/liter) was present in 10.4% (40/384) of isolates, all of which possessed the A2143G mutation in all four 23S rRNA alleles. Low- to mid-level resistance (MIC, 1 to 64 mg/liter) was present in 21.9% (84/384) of isolates, 59.5% of which possessed the C2599T mutation in all four 23S rRNA alleles. The 124 AZM-R isolates were distributed in 71 different NG-MAST sequence types (STs). ST1866 was the most prevalent type in high-level AZM-R (HL-AZM-R) isolates (45% [18/40]). This study, together with previous reports, revealed that the prevalence of AZM-R in N. gonorrhoeae isolates in certain eastern Chinese cities has risen >4-fold (7% to 32%) from 2008 to 2014. The principal mechanisms of AZM resistance in recent Nanjing isolates were A2143G mutations (high-level resistance) and C2599T mutations (low- to mid-level resistance) in the 23S rRNA alleles. Characterization of NG-MAST STs and phylogenetic analysis indicated the genetic diversity of N. gonorrhoeae in Nanjing; however, ST1866 was the dominant genotype associated with HL-AZM-R isolates.

Keywords: Neisseria gonorrhoeae; antimicrobial resistance; azithromycin; eastern Chinese cities; molecular epidemiology.

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Figures

FIG 1
FIG 1
Distributions of MICs for AZM-R N. gonorrhoeae isolates in Nanjing from 2013 to 2014 (n = 384).
FIG 2
FIG 2
Phylogenetic tree constructed using MEGA7 with the concatenated sequences of porB and tbpB alleles for NG-MAST STs of 124 AZM-R N. gonorrhoeae isolates from Nanjing, China, 2013 to 2014. ST1866 is indicated by a red asterisk; non-ST1866, HL-AZM-R STs are indicated by green asterisks.
FIG 3
FIG 3
Geographic distribution and chronological emergence of reported AZM-R N. gonorrhoeae isolates in four Chinese cities. On the map, eastern China is shown in blue; southeastern China, in light green.
See this image and copyright information in PMC

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