Retrospective testing for mpox virus in routine STI screens from men who have sex with men in England, August-October 2022.

OBJECTIVES: A global outbreak of mpox (monkeypox) has been ongoing since 2022, with most cases in the UK detected in gay, bisexual and other men who have sex with men (GBMSM). Asymptomatic and pauci-symptomatic mpox infection has been reported outside of the UK. We aimed to investigate whether mpox could be detected in specimens from GBMSM in England who were attending sexual health services (SHSs) for asymptomatic sexually transmitted infection screening. METHODS: Anonymised, residual clinical specimens from GBMSM undertaking routine asymptomatic screening for gonorrhoea (Neisseria gonorrhoeae (NG)) and chlamydia (Chlamydia trachomatis (CT)) infection were tested for the presence of mpox virus. Specimens were collected between 1 August and 7 October 2022 from three SHSs in high-mpox incidence areas in England. Testing was performed using a dual-clade, mpox virus-specific real-time PCR. RESULTS: During the collection period, 2927 clinical specimens (951 pharyngeal swabs, 1022 urine specimens and 954 rectal swabs) were obtained from 1159 GBMSM. Mpox virus was detected in four specimens from two participants who attended the same SHS at different times (the first during the week 8-12 of August, the second during the week 19-23 of September). One participant was positive in the urine specimen only, while the other tested positive at all three sites. CONCLUSIONS: A very low prevalence (2 of 1159, 0.17%) of mpox infection was detected in GBMSM attending SHS in England for asymptomatic NG/CT screening, suggesting that undetected infection in this population was unlikely to be a main driver of transmission. Confirmed mpox cases in the UK declined from over 1100 per month in June and July to 764 cumulatively during the collection period. These data give reassurance that the observed reduction in cases during the collection period was not due to undetected infection or changes in presentation among SHS attendees. Currently, there is insufficient evidence to support routine testing of asymptomatic GBMSM for mpox infection in England.

No widespread dissemination of Chlamydia trachomatis diagnostic-escape variants and the impact of Neisseria gonorrhoeae positivity on the Aptima Combo 2 assay.

OBJECTIVES: A Finnish Chlamydia trachomatis (CT) new variant was detected in 2019 that escaped detection in the Hologic Aptima Combo 2 (AC2) assay due to a C1515T mutation in the CT 23S rRNA target region. Reflex testing of CT-negative/CT-equivocal specimens as well as those positive for Neisseria gonorrhoeae (NG) with the Hologic Aptima CT (ACT) assay was recommended to identify any CT variants. METHODS: From June to October 2019, specimens with discrepant AC2/ACT CT results were submitted to Public Health England and screened for detectable CT DNA using an inhouse real-time (RT)-PCR. When enough DNA was present, partial CT 23S rRNA gene sequencing was performed. Analysis of available relative light units and interpretative data was performed. RESULTS: A total of 317 discordant AC2/ACT specimens were collected from 315 patients. Three hundred were tested on the RT-PCR; 53.3% (n=160) were negative and 46.7% (n=140) were positive. Due to low DNA load in most specimens, sequencing was successful for only 36 specimens. The CT 23S rRNA wild-type sequence was present in 32 specimens, and two variants with C1514T or G1523A mutation were detected in four specimens from three patients. Of the discordant specimens with NG interpretation, 36.6% of NG-negative/CT-negative AC2 specimens had detectable CT DNA on the inhouse RT-PCR vs 53.3% of NG-positive/CT-negative specimens. CONCLUSIONS: No widespread dissemination of AC2 diagnostic-escape CT variants has occurred in England. We however identified the impact of NG positivity on the discordant AC2/ACT specimens; a proportion appeared due to NG positivity and the associated NG signal, rather than any diagnostic-escape variants or low DNA load. Several patients with gonorrhoea may therefore receive false-negative AC2 CT results. Single diagnostic targets and multiplex diagnostic assays have their limitations such as providing selection pressure for escape mutants and potentially reduced sensitivity, respectively. These limitations must be considered when establishing diagnostic pathways.

Detection of markers predictive of macrolide and fluoroquinolone resistance in Mycoplasma genitalium from patients attending sexual health services.

OBJECTIVES: This study sought to provide data on the prevalence of macrolide (23S rRNA) and fluoroquinolone (parC) resistance-associated mutations seen in Mycoplasma genitalium-positive specimens received in the UK national reference laboratory. METHODS: In total, 2580 clinical specimens from patients with suspected or confirmed M. genitalium infection were received at the national reference laboratory between September 2017 and November 2018. M. genitalium-positive clinical specimens were identified using a reverse transcription-PCR targeting two M. genitalium genes: MgPa and gap. Resistance-associated single nucleotide poylmorphisms were sought in all positive specimens by sequence analysis of the 23S rRNA and parC genes. RESULTS: Eighteen per cent (458 of 2580) of clinical specimens were positive for M. genitalium and 389 had sequence data for both macrolide and fluoroquinolone resistance markers. Of these, 71% (275 of 389) had macrolide resistance-associated mutations, 8% (31 of 389) had fluoroquinolone resistance-associated mutations (S83I/R and D87Y/N) and 7% (26 of 389) had mutations associated with resistance to both antimicrobials. Only 28% (108 of 389) had no mutations associated with resistance to either class of antibiotic. Five specimens had mutations of unknown clinical significance in the parC gene (eg, G81C and S83N). CONCLUSIONS: Mutations associated with resistance to macrolides were very frequent. By contrast, susceptibility to the second-line treatment, moxifloxacin (a fluoroquinolone), was estimated at 92% based on the absence of resistance-associated mutations. The few specimens with mutations of unknown clinical significance in the parC gene were excluded from the analysis and so the actual level of fluoroquinolone susceptibility may be slightly lower than that reported here. Surveillance of antimicrobial resistance in M. genitalium is imperative for this to remain a treatable infection.