Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP)

Methods

The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) was established in June 2000, as a collaboration between the Communicable Disease Surveillance Centre (CDSC), the Genitourinary Infections Reference Laboratory (GUIRL), Bristol and Imperial College and was funded by the Department of Health.

Currently, and since 2005, the susceptibility testing has been carried out at the Sexually Transmitted Diseases Reference Laboratory (STBRL), Colindale. The GRASP annual collection is undertaken by the Health Protection Agency, Centre for Infections (formerly CDSC).

The annual GRASP collection combines laboratory and clinical data on gonococcal isolates diagnosed in sentinel laboratories. GRASP covers two distinct geographical regions: London, which includes seven laboratories and 9 GUM clinics and outside of London where 17 GUM clinics and laboratories were purposely selected to provide good geographic coverage (with representation of all NHS regions) and to maximise the number of isolates collected. Each region is represented by at least two large clinics, with the exception of the North East.

All consecutive gonococcal isolates (one from each patient episode) identified in participating laboratories during the months of July, August and September are sent to the GRASP reference laboratory within STBRL for susceptibility testing. At each local laboratory, primary isolates of N. gonorrhoeae are sub-cultured to obtain a pure growth and frozen in glycerol broth for transportation. Following retrieval and confirmation of identity of N. gonorrhoeae at STBRL, the MICs are determined for the following antimicrobial agents (the range of concentrations tested is shown in parentheses): penicillin (0.03-4.0mg/L), ciprofloxacin (0.002-64mg/L), spectinomycin (2-64mg/L), tetracycline (1-32mg/L), ceftriaxone (0.002 to 0.125mg/L), azithromycin (0.03 - 256mg/L) and cefixime (0.002-0.25mg/L).

GUM clinics provide demographic, behavioural and clinical data for each GUM patient included in the GRASP collection. Routinely collected clinical data are utilized, these include: gender, age, ethnic background, sexual orientation, postal area, previous gonococcal infection, symptom presence, concurrent STIs, number of partners in the UK and abroad, test of cure and therapy received. This patient data (from GUM clinics) is then linked to the susceptibility data (from the reference laboratory) of their isolates.
Since 2005, the percentage of isolates that are resistant to a particular antibiotic has been estimated using a weighted analysis. This is because a simple percentage would under weight isolates from sites that have a lower retrieval rate. The weight for a particular clinic in a particular year is inversely proportional to its retrieval rate and each estimate of the percentage resistant to a particular antibiotic in a particular year is a weighted average of the percentages from the participating sites in that year.

Last reviewed: 8 March 2010