Repurposing an old drug: aztreonam as a new treatment strategy for gonorrhoea

Developing a model to predict individualised treatment for gonorrhoea: a modelling study

OBJECTIVE

To develop a tool predicting individualised treatment for gonorrhoea, enabling treatment with previously recommended antibiotics, to reduce use of last-line treatment ceftriaxone.

DESIGN

A modelling study.

SETTING

England and Wales.

PARTICIPANTS

Individuals accessing sentinel health services.

INTERVENTION

Developing an Excel model which uses participants' demographic, behavioural and clinical characteristics to predict susceptibility to legacy antibiotics. Model parameters were calculated using data for 2015-2017 from the Gonococcal Resistance to Antimicrobials Surveillance Programme.

MAIN OUTCOME MEASURES

Estimated number of doses of ceftriaxone saved, and number of people delayed effective treatment, by model use in clinical practice. Model outputs are the predicted risk of resistance to ciprofloxacin, azithromycin, penicillin and cefixime, in groups of individuals with different combinations of characteristics (gender, sexual orientation, number of recent sexual partners, age, ethnicity), and a treatment recommendation.

RESULTS

Between 2015 and 2017, 8013 isolates were collected: 64% from men who have sex with men, 18% from heterosexual men and 18% from women. Across participant subgroups, stratified by all predictors, resistance prevalence was high for ciprofloxacin (range: 11%-51%) and penicillin (range: 6%-33%). Resistance prevalence for azithromycin and cefixime ranged from 0% to 13% and for ceftriaxone it was 0%. Simulating model use, 88% of individuals could be given cefixime and 10% azithromycin, saving 97% of ceftriaxone doses, with 1% of individuals delayed effective treatment.

CONCLUSIONS

Using demographic and behavioural characteristics, we could not reliably identify a participant subset in which ciprofloxacin or penicillin would be effective. Cefixime resistance was almost universally low; however, substituting ceftriaxone for near-uniform treatment with cefixime risks re-emergence of resistance to cefixime and ceftriaxone. Several subgroups had low azithromycin resistance, but widespread azithromycin monotherapy risks resistance at population level. However, this dataset had limitations; further exploration of individual characteristics to predict resistance to a wider range of legacy antibiotics may still be appropriate.

Aztreonam for Neisseria gonorrhoeae: a systematic review and meta-analysis

BACKGROUND

Ceftriaxone is the only consistently active antimicrobial agent recommended for the treatment of Neisseria gonorrhoeae. Although some new antimicrobials are in development, the necessity to expand treatment options in the near term may require using older drugs that have not been widely used to treat gonorrhoea.

METHODS

We conducted a literature review of clinical trials and case series, published from 1983 to 2017, reporting treatment efficacy results following administration of 1 g aztreonam intramuscularly or IV for uncomplicated gonococcal infections. We summed trial data, stratified by anatomical site of infection, and calculated summary efficacy estimates and 95% CI for each site of infection.

RESULTS

The 10 identified clinical trials enrolled 678, 38 and 16 individuals with urogenital, rectal and pharyngeal gonorrhoea, respectively. Aztreonam had an efficacy of 98.6% (95% CI: 97.5%-99.4%) for urogenital, 94.7% (95% CI: 82.3%-99.4%) for rectal and 81.3% (95% CI: 54.4%-96.0%) for pharyngeal gonococcal infections.

CONCLUSIONS

Although most clinical trials included in this meta-analysis were conducted >30 years ago, aztreonam appears to have excellent efficacy for urogenital gonorrhoea; its efficacy at extragenital sites remains uncertain.