The WHO Enhanced Gonococcal Antimicrobial Surveillance Programme (EGASP) identifies high levels of ceftriaxone resistance across Vietnam, 2023

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a global public health concern that threatens the last antimicrobial recommended for first-line gonorrhoea treatment, ceftriaxone.¹ Most internationally-reported ceftriaxone-resistant isolates have contained the mosaic penA-60.001 allele, encoding a mosaic penicillin-binding protein 2 (PBP2) causing ceftriaxone resistance.^1,2 Most ceftriaxone-resistant gonococcal strains have been linked to Asia.^1,2 Enhanced quality-assured global AMR surveillance is imperative.¹

The WHO Enhanced Gonococcal Antimicrobial Surveillance Programme (EGASP), currently being expanded globally, uses standardised and quality-assured protocols and has recently implemented whole-genome sequencing (WGS). In mid-2023, the EGASP was implemented in Vietnam, and gonococcal isolates were cultured from 153 males (urethral samples) in Hanoi (June–December) and 101 in Ho Chi Minh City (HCMC, August–September). Species confirmation, AMR testing, and WGS were performed on 249 (98.0%) isolates (Appendix pp2-3).

The resistance to ceftriaxone, cefixime, and azithromycin was 26.9% (67/249), 30.9% (77/249), and 4.8% (12/249), respectively. The MIC distribution for ceftriaxone can be observed in Appendix, p5. Interestingly, only 11.9% (8/67) of the ceftriaxone-resistant isolates contained mosaic penA-60.001 (multi-locus sequence typing (MLST) ST13871 (n = 5), ST17523 (n = 2), ST18714 (n = 1)). Most (88.1%, 59/67) ceftriaxone-resistant isolates instead harboured non-penA-60.001 mosaic alleles, including mosaic penA-237.001 (n = 47; MLST ST1901 (n = 42), ST7365 (n = 2), ST1588 (n = 1), ST7822 (n = 1), ST8123 (n = 1)), penA-265.001 (n = 5; MLST ST1901 (n = 2), MLST ST18777 (n = 2), MLST ST7822 (n = 1)), penA-60.002 (n = 3; MLST ST1588 (n = 3)), penA-237.002 (n = 1; MLST ST13732), penA-270.001 (n = 1; MLST ST17672), penA-287.001 (n = 1; MLST ST1901), and the novel penA-291.001 (n = 1; MLST ST7363) (Fig. 1). All these penA alleles contain the ceftriaxone-resistance-associated PBP2 alterations A311V, V316 T/P, and T483S (Appendix p6). The ceftriaxone-resistant isolates were spread across the gonococcal species phylogeny. Most (n = 43) penA-237.001-containing isolates clustered with the first penA-237.001-containing strain identified (F92, in France but linked to Vietnam, 2022) within genomic lineage A.⁴ However, penA-237.001-containing isolates (n = 3) were also found close to WHO R (FC428), representing the internationally-spreading ceftriaxone-resistant clone,^2,3 within lineage A and additionally near WHO D (n = 1) within lineage B. Most (n = 7) penA-60.001-containing isolates clustered with WHO R (FC428),^2,3 but one penA-60.001-containing isolate was found in lineage B (Fig. 1). Ceftriaxone-resistant strains with mosaic penA-60.001 or penA-237.001 are now found in both the AMR-associated lineage A and more antimicrobial-susceptible lineage B; in several different genomic backgrounds, illustrating that both ceftriaxone-resistant strains and ceftriaxone resistance-mediating sequences are spreading. Azithromycin-resistant isolates contained resistance-associated semi-mosaic MtrD variant 13 (n = 10) or 39 (n = 1), or 23S rRNA C2611T (n = 1) (Appendix p6). Fortunately, all ceftriaxone-resistant isolates remained azithromycin susceptible.

Fig. 1.

Phylogenomic analysis based on core genome MLST of 2062 gene alleles of Neisseria gonorrhoeaegenomes from Vietnam in 2023 (n = 249) and publicly available genomes(n = 45,916) obtained from the European Nucleotide Archive (short-read archive). The locations of ceftriaxone-susceptible WHO D in the more antimicrobial-susceptible genomic lineage B and well-characterised ceftriaxone-resistant strains in AMR-associated genomic lineage A (WHO Q (penA-60.001), R (FC428; penA-60.001), X (H041; penA-37.001), Y (F89; penA-42.001), and F92 (penA-237.001))^3,4 are shown by arrows. On the left, number of ceftriaxone-resistant isolates and associated mosaic penA alleles in Hanoi and Ho Chi Minh City are shown on the map of Vietnam. NA, Not applicable.

The very high ceftriaxone-resistance level (26.9%) was mainly caused by widespread dissemination of penA-237.001-containing (in both Hanoi and HCMC) and penA-60.001-containing (particularly in HCMC) ceftriaxone-resistant strains. Importantly, 88.1% of the ceftriaxone-resistant isolates contained other penA alleles than penA-60.001, which several currently-used PCR assays predicting ceftriaxone resistance are targeting.5, 6, 7 Notably, another most recent study also found a high level of ceftriaxone resistance in Hanoi, however, mostly attributed to the penA-60.001 allele.⁵ This was most likely because only a penA-60.001 real-time PCR was used, which should not detect other penA alleles, however, some of the penA alleles we identified in the present study using WGS are highly similar to the penA-60.001 allele and may result in low, false positivity in penA-60.001 real-time PCRs.^6,7 This emphasizes the importance of using WGS in gonococcal AMR surveillance internationally. In the Vietnamese gonorrhoea treatment guidelines, first-line treatment is ceftriaxone 250 mg or cefixime 400 mg or spectinomycin 2 g, combined with azithromycin 1 g for treatment of chlamydial coinfection. Based on our present results, ceftriaxone 1 g with a mandatory test-of-cure should be recommended for all gonorrhoea cases, ideally combined with azithromycin 2 g (at least for treatment failures and pharyngeal infections), which will be in accordance with the soon to be published WHO STI treatment guidelines. Importantly, based on case reports² and pharmacodynamics studies,⁸ ceftriaxone 1 g can treat most infections caused by ceftriaxone-resistant strains with MICs of 0.25–0.5 mg/L (94.0% (63/67) in Vietnam in 2023). Furthermore, cefixime and spectinomycin should not be used if ceftriaxone is available.

Gonococcal resistance to ceftriaxone, the last remaining option for empiric first-line gonorrhoea treatment, is a major public health concern and strains across the gonococcal species phylogeny have shown their capacity to develop ceftriaxone resistance (Fig. 1). Enhanced quality-assured gonococcal AMR surveillance, including WGS, is essential globally, and is a main focus for WHO EGASP. Furthermore, improved prevention and early diagnosis and treatment (including test-of-cure) are imperative. Ultimately, novel antimicrobials for gonorrhoea treatment, e.g. zoliflodacin (https://gardp.org/positive-results-announced-in-largest-pivotal-phase-3-trial-of-a-first-in-class-oral-antibiotic-to-treat-uncomplicated-gonorrhoea/) and gepotidacin (https://www.gsk.com/en-gb/media/press-releases/eagle-1-phase-iii-data-show-potential-for-gepotidacin-as-a-new-oral-treatment-option-for-uncomplicated-gc/), and ideally a gonococcal vaccine are crucial.

EGASP-Vietnam WGS study group

Le Huu Doanh, Pham Thi Lan, Pham Quynh Hoa, Pham Dieu Hoa, Pham Thi Minh Phuong, Trinh Minh Trang, Thai Thi Dieu Van, Pham Trieu Nam, Nguyen Thi Ha Vinh, Quach Thi Ha Giang, Vu Thanh Tung, Nguyen Doan Tuan (National Hospital of Dermatology and Venereology, Hanoi); Hao Trong Nguyen (Pham Ngoc Thach University of Medicine and Ho Chi Minh City Hospital of Dermatology and Venereology, Vietnam); Thuy Thi Phan Nguyen, Thao Thi Phuong Vu, Phuong Thi Thanh Nguyen, Bao Hac Duong, Em Van Loi Doan, Dung Thi Thuy Nguyen, Khanh Tuan Le, Tan Minh Bui, Nguyen Nhat Pham, Trang Thi Kieu Nguyen, Trang Thi Thanh Phan, Anh Duy Quynh Dang (Ho Chi Minh City Hospital of Dermatology and Venereology, Vietnam); Nguyen Thi Thuy Van (WHO Country Office, Hanoi, Vietnam); Nguyen Trong Khoa (Ministry of Health, Hanoi, Vietnam); Kristen Kreisel, Robert McDonald (Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA); Monica M Lahra (WHO Collaborating Centre for Sexually Transmitted Infections and Antimicrobial Resistance, New South Wales Health Pathology, Microbiology, Randwick, NSW, Australia); Ismael Maatouk, Teodora Wi (Global HIV, Hepatitis and STI Programmes, WHO, Geneva Switzerland); Daniel Golparian, Susanne Jacobsson, Daniel Schröder, Magnus Unemo (WHO Collaborating Centre for Gonorrhoea and Other STIs, Örebro University, Örebro, Sweden).

Contributors

PTL, HTN, NTTV, IM and MU designed and initiated the study. DG, IM and MU coordinated the study. The EGASP-Vietnam WGS study group were involved in recruiting patients; obtaining clinical, epidemiologic and laboratory data; and EGASP-Vietnam coordination. DG performed the WGS. DG and MU analysed and interpreted the WGS results in combination with the metadata. PTL and MU wrote a first draft of the paper. PTL, HTN, DG, NTTV, IM, MU, and the EGASP-Vietnam WGS study group members read, commented on, and approved the final manuscript. PTL, DG, and MU had full access to all the data in the study and had final responsibility for the decision to submit for publication.

Data sharing statement

All sequence data were deposited at the National Center for Biotechnology Information (NCBI) under BioProject PRJEB75240. Most data collected and analysed in this study are included in the paper. However, remaining datasets can be made available from the corresponding author after publication on reasonable request and approval by WHO.

Editor note

The Lancet Group takes a neutral position with respect to territorial claims in published maps and institutional affiliations.

Declaration of interests

We declare no competing interest.