Genomic analysis and antimicrobial resistance of Neisseria gonorrhoeae isolates from Vietnam in 2011 and 2015-16

Abstract

Objectives: Antimicrobial resistance (AMR) in Neisseria gonorrhoeae, compromising gonorrhoea treatment, is a threat to reproductive health globally. South-East and East Asia have been major sources of emergence and subsequent international spread of AMR gonococcal strains during recent decades. We investigated gonococcal isolates from 2011 and 2015-16 in Vietnam using AMR testing, WGS and detection of AMR determinants.

Methods: Two hundred and twenty-nine gonococcal isolates cultured in 2015-16 (n = 121) and 2011 (n = 108) in Vietnam were examined. AMR testing was performed using Etest and WGS with Illumina MiSeq.

Results: Resistance among the 2015-16 isolates was as follows: ciprofloxacin, 100%; tetracycline, 79%; benzylpenicillin, 50%; cefixime, 15%; ceftriaxone, 1%; spectinomycin, 0%; and 5% were non-WT to azithromycin. Eighteen (15%) isolates were MDR. The MIC range for gentamicin was 2-8 mg/L. Among the 2015-16 isolates, 27% (n = 33) contained a mosaic penA allele, while no isolates had a mosaic penA allele in 2011. Phylogenomic analysis revealed introduction after 2011 of two mosaic penA-containing clones (penA-10.001 and penA-34.001), which were related to cefixime-resistant strains spreading in Japan and Europe, and a minor clade (eight isolates) relatively similar to the XDR strain WHO Q.

Conclusions: From 2011 to 2015-16, resistance in gonococci from Vietnam increased to all currently and previously used antimicrobials except ceftriaxone, spectinomycin and tetracycline. Two mosaic penA-containing clones were introduced after 2011, explaining the increased cefixime resistance. Significantly increased AMR surveillance, antimicrobial stewardship and use of WGS for molecular epidemiology and AMR prediction for gonococcal isolates in Vietnam and other Asian countries are crucial.

Figure 1.

Amino acid sequences of MtrD in WHO F (azithromycin susceptible) and WHO P (azithromycin non-WT) and a meningococcal MtrD sequence (included as reference). GCGS0834 and CDC 2 were included as the two previously described mosaic MtrD sequences most similar to the Vietnamese MtrD sequence, which had only four unique amino acid alterations (asterisks). Conserved regions are boxed. This figure appears in colour in the online version of JAC and in black and white in the print version of JAC.

Figure 2.

Phylogenomic tree with susceptibility to the most therapeutically relevant antimicrobials, AMR determinants, the most common MLST STs and N. gonorrhoeae multiantigen sequence typing (NG-MAST) STs for N. gonorrhoeae isolates from Vietnam in 2011 (n = 108) and 2015–16 (n = 121). The WHO Q reference strain and FC428 are included for comparison and are marked with white bars. This figure appears in colour in the online version of JAC and in black and white in the print version of JAC.

Figure 3.

Circular phylogenomic tree visualized using Microreact of all isolates from Vietnam (n = 229) compared with cefixime-resistant isolates (MIC >0.125 mg/L) from Japan (n = 69) and 11 European countries (n = 42). Coloured bars represent cefixime susceptibility and the presence of the mosaic penA allele. This figure appears in colour in the online version of JAC and in black and white in the print version of JAC.