Guidance

GRASP protocol

Updated 13 November 2025

Applies to England and Wales

Background

Gonorrhoea, caused by the bacterium Neisseria (N.) gonorrhoeae, is the second-most common sexually transmitted infection (STI) diagnosed in the UK. If untreated, gonorrhoea can lead to complications in women (for example, chronic pelvic pain, pelvic inflammatory disease, ectopic pregnancy) and men (for example, epididymitis, prostatitis, urethral strictures).

The emergence of resistance to antimicrobials used to treat gonorrhoea is a global public health concern. The ability of gonorrhoea to successively develop resistance to different antimicrobials has hampered control efforts and risks the disease becoming untreatable. Surveillance of antimicrobial resistance (AMR) is critical for informing national treatment guidelines to ensure appropriate patient management. Established in 2000, the Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) includes a suite of testing and surveillance systems to detect and monitor AMR in N. gonorrhoeae and potential treatment failures.

The cornerstone of GRASP is a national sentinel surveillance system. The GRASP sentinel surveillance system involves the collection of N. gonorrhoeae isolates from consecutive individuals attending a network of 26 sexual health services (SHSs) across England and Wales and their 19 associated laboratories, typically between August and September annually.

Since 2000, GRASP data has revealed important antimicrobial susceptibility trends and provided evidence to revise national treatment guidelines in 2005, 2011 and 2019.

Objectives

The objectives of GRASP are to:

• characterise annual antimicrobial susceptibility patterns in N. gonorrhoeae in England and Wales, and monitor trends over time
• identify associations between antimicrobial resistant gonococci and patient demographic, clinical and behavioural data
• inform the development of national gonorrhoea treatment guidelines
• apply molecular characterisation to further investigate any emerging resistance trends

Methods

GRASP is a collaboration between the:

• Blood Safety, Hepatitis, Sexually Transmitted Infections and HIV (BSHSH) division, part of the Clinical and Public Health (CPH) group at the UK Health Security Agency (UKHSA)
• Sexually Transmitted Infections Reference Laboratory (STIRL), part of the Science Group at UKHSA
• 26 SHSs throughout England and Wales and the 19 associated primary diagnostic laboratories

Analyses from the GRASP sentinel surveillance system are based on:

• antimicrobial susceptibility and whole genome sequencing (WGS) data from isolates collected from consecutive individuals with a gonorrhoea diagnosis at a sentinel SHS during the collection periods
• demographic, clinical and behavioural information from these individuals

In addition, STIRL receives putative ceftriaxone-resistant gonococcal isolates for confirmatory susceptibility testing from primary diagnostic laboratories. Data on suspected treatment failures is reported to UKHSA via the HIV and STI Data Exchange for registered users. Data from these sources also feed into the GRASP report.

All laboratory methods for identification and phenotypic determination of antimicrobial susceptibility of GRASP isolates are accredited to ISO 15189:2022 by the United Kingdom Accreditation Service. At the present time, the processes for whole genome sequencing and downstream analysis (including determination of ciprofloxacin susceptibility) are not accredited.

Activities and responsibilities

Sentinel sites overview

A GRASP sentinel SHS and corresponding laboratories are responsible for the collection and submission of:

• gonococcal isolates from consecutive individuals during the collection period (currently August to September) to the STIRL, UKHSA
• demographic, clinical and behavioural data on individuals diagnosed with gonorrhoea in their SHS to UKHSA

Gonorrhoea diagnoses made during the survey period from GRASP SHSs in England are extracted from the national STI surveillance data set, the GUMCAD STI Surveillance System, and linked to an electronic web-reporting form on the HIV and STI Data Exchange (access is restricted to registered users).

Participating SHSs access the form securely online to provide additional demographic, behavioural and antimicrobial prescribing data for GRASP. For participating SHSs in Wales, demographic, clinical and behavioural data for individuals captured in GRASP are reported via an electronic spreadsheet.

Sentinel site laboratory collection, handling and shipping of isolates

Isolates of N. gonorrhoeae are archived on cryobeads and are stored at -80°C. Frozen archives are collected via courier and are shipped on dry ice to UKHSA at designated times during the collection period, dictated by the number of isolates collected.

Prior to the start of the collection period, GRASP scientists estimate the number of isolates expected from collaborating laboratories on the basis of previous years’ submissions. Collection packs, comprising cryobeads, labels pre-printed with unique study numbers, the laboratory isolate collection protocol and list of participating SHSs is provided to the laboratories. A line listing form is distributed to all collaborating laboratories by email. Collection packs and courier shipments are provided and organised by UKHSA.

Sentinel site clinic activities

GRASP demographic, clinical and behavioural data collections are based upon GUMCAD data submissions. All gonorrhoea diagnoses made and reported via GUMCAD are linked to an electronic web reporting form on UKHSA’s HIV and STI Data Exchange (access is restricted to registered users). The following fields are pulled directly from GUMCAD submissions and will already be completed in the reporting form:

• patient ID
• date of attendance
• attendance type
• concurrent STIs
• gender identity
• age at attendance
• sexual orientation
• ethnicity

GRASP clinic staff then enhance this data with additional demographic, clinical and behavioural data items obtained through review of patient medical records, including:

• diagnostic method used
• site(s) of infection and symptom presence
• previous gonorrhoea diagnoses
• HIV status and pre-exposure prophylaxis (PrEP) use
• antibiotic treatment for gonorrhoea and chlamydia
• test of cure
• sexual contacts (in the UK or abroad)
• STI prophylaxis

Testing of isolates for antimicrobial susceptibility

Regional primary diagnostic laboratories are responsible for dispatching the collected GRASP isolates to STIRL.

Receipt of isolates

Once isolates are received at UKHSA they are matched to the accompanying electronic line listing and any discrepancies identified are followed up with the submitting laboratory. Isolates are then entered into an electronic database. Isolates are stored at -80°C prior to testing.

Confirmatory testing

The identification of all isolates submitted to GRASP is confirmed by a N. gonorrhoeae-specific real-time polymerase chain reaction (PCR); further confirmatory testing (Gram stain, oxidase and MALDI-ToF) may also be carried out.

Due to the high-throughput nature of GRASP, lysates are made directly from cryobeads for testing on the real-time PCR. The assay specifically targets the N. gonorrhoeae porA gene which encodes the highly conserved, non-expressed porin-A protein. The assay also targets the sodC gene (which encodes a protein required for ion transport and metabolism) of Neisseria meningitidis, allowing for direct detection of mis-identified isolates. There is evidence that some N. gonorrhoeae isolates have recombined with N. meningitidis and carry the N. meningitidis porA sequence, therefore any isolates that are negative for both gene targets are identified further using MALDI-ToF analysis.

Isolates requiring MALDI-ToF analysis are first extracted using formic acid. Isolates with an identification score ≥2.3 are considered acceptable. Isolates whose MALDI-ToF score is repeatedly <2.3 are tested by API-NH (bioMérieux) to obtain a biochemical profile.

Beta-lactamase tests

Beta-lactamase activity is measured using Nitrocefin (Oxoid), a chromogenic cephalosporin substrate. Isolates exhibiting beta-lactamase activity rapidly catalyse the reagent inducing a colour change from yellow to red.

Antimicrobial susceptibility testing

Susceptibilities to 6 antimicrobials (penicillin, tetracycline, ceftriaxone, cefixime, azithromycin and ciprofloxacin) are ascertained for each isolate submitted to GRASP that can be case-matched within the GUMCAD STI Surveillance System and to enhanced data provided by SHSs. In previous years, susceptibility to spectinomycin and gentamicin was also ascertained. However, from 2024 onwards this is no longer done due to the rarity of resistant isolates and lack of clinical relevance.

Where more than one isolate is collected from an individual diagnosed with gonorrhoea, the following prioritisation hierarchy is applied for testing:

1. Pharyngeal.
2. Male rectal.
3. Male urethral.
4. Female cervical.
5. Any other site.

Since 2021, pharyngeal isolates have been prioritised ahead of all other sites due to concerns that resistance is most likely to emerge in this site.

Phenotypic antimicrobial susceptibility testing to determine the minimum inhibitory concentration (MIC) is carried out by agar dilution using BD Difco™ Dehydrated Culture Media: Gonococcal (GC) Medium Base supplemented with 1% Vitox (Oxoid).

Susceptibility testing plates are quality controlled using a panel of control isolates with well-characterised antimicrobial susceptibility profiles. Plates that pass quality control are used for the testing of GRASP isolates. Inoculated plates are incubated for 24 hours before reading using an automated plate reader, using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints for interpretation.

Breakpoint plates have been in use for penicillin since 2017. They were also used for tetracycline from 2018 to 2023, however testing has now reverted to the full MIC range.

Since 2024, susceptibility of N. gonorrhoeae to ciprofloxacin is predicted based on genotypic detection of resistance markers using WGS and phenotypic testing is no longer performed.

Alert value MICs

Alert MICs are MICs representing resistance to a level of antibiotic that is higher than is typically encountered in the UK, and beyond the MIC range tested by the agar dilution method. The alert values are:

• >0.5 mg/L of cefixime
• >0.25 mg/L of ceftriaxone
• >4 mg/L of azithromycin

Isolates with these MICs are tested by ETEST (bioMérieux) on GCVIT medium to confirm the MIC. Isolates testing susceptible to penicillin, but with a positive nitrocefin result are investigated further. N. gonorrhoeae isolates exhibiting resistance to cefixime (>0.125 mg/L) are unlikely to be susceptible to ciprofloxacin; any isolates exhibiting this profile are investigated further.

Archive isolates

Isolates are submitted to GRASP on cryobeads. Therefore, further archiving is not necessary for most isolates. Where contamination was identified on sub-culture or where isolates were more fastidious, purified isolates are re-archived on cryobeads.

Isolate preservation

All isolates of N. gonorrhoeae are stored at –80°C to preserve viability.

Whole genome sequencing

DNA extraction is carried out using the QIAGEN DSP DNA Mini or Midi kit and the Blood protocol on the QIAsymphony. DNA yield is determined using the Quant-IT kit on the Glomax system. A minimum yield of 6 ng/μL is required for WGS. DNA is sent to UKHSA’s Colindale Sequencing Laboratory where Illumina DNA Prep libraries are generated and sequenced on the NextSeq 1000 platform. Deplexed and trimmed reads are run through an in-house bioinformatics pipeline to:

• confirm N. gonorrhoeae and screen for contaminants (Kraken2)
• generate a de novo assembly (SPAdes) and assembly statistics (QUAST)
• determine multilocus sequence type (MLST), Neisseria gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR), and Neisseria gonorrhoeae multiantigen sequence type (NG-MAST) sequence types (in-house software)
• detect known AMR determinants (in-house software and AMRFinderPlus)

As of 2024, susceptibility to ciprofloxacin is predicted based on the presence of resistance-associated point mutations in gyrA, parC, and the norM promoter.

Ethics

GRASP is a routine public health surveillance activity, and no specific consent is required from individuals captured within it.

UKHSA has permission to handle data obtained by GRASP under Section 251 of the UK National Health Service Act of 2006 (previously Section 60 of the Health and Social Care Act of 2001), which was renewed annually by the ethics and confidentiality committee of the National Information Governance Board until 2013. Since then, the power of approval of public health surveillance activity has been granted directly to UKHSA.

Data reporting

There are several outputs related to the reporting of findings from GRASP. These include:

• the annual GRASP report, produced within the year following the collection period
• the annual GRASP collaborators’ meeting, which features presentations and discussions of the latest data on antimicrobial resistance in N. gonorrhoeae
• clinic and laboratory-specific reports, comprising data on local gonorrhoea diagnoses and resistance trends for all GRASP participating sites
  • a shortened report will be provided where less than 20 diagnoses were included from a participating clinic in the GRASP year and this data will also be masked when reporting longitudinal trends in subsequent years; this is due to difficulties interpreting the data where numbers are small

These outputs are disseminated via:

• internet: the annual GRASP report, summarising the latest trends and epidemiology on gonococcal antimicrobial resistance
• peer-reviewed articles: anticipated articles will be produced for dissemination in peer-reviewed medical journals
• oral and poster presentation: anticipated presentations of GRASP findings to end-users (including sexual health, public health and microbiology specialties) at appropriate fora (for example conferences, meetings, special interest groups)

Use of GRASP isolates and data

The GRASP data set draws data from GUMCAD. Therefore, UKHSA staff seeking access to GRASP data must complete a GUMCAD data request form detailing the purpose of the request and the data that is required. Typically, a new form is required for each new analysis planned. Once completed, the form should be sent to grasp.enquiries@ukhsa.gov.uk for review. The request will be discussed with the GRASP team and the GRASP Steering Group where appropriate.

If the requestor is not a member of UKHSA staff, then:

• an honorary contract must be set up for an employee of another organisation who is coming to complete work or a project with UKHSA
• a visiting worker’s agreement must be set up if the requestor does not have a principal employer (for example, an MSc student)