With antimicrobial-resistant gonorrhoea now an urgent health threat, requiring improved antibiotic stewardship, one option frequently proposed is laboratory-guided recycling of older antibiotics (Lewis (STI); Ison & Unemo (STI); A new kind of treatment for gonorrhoea? (STI/blogs)).  Lewis (STI) alludes to the potential use of floroquinolone therapy – specifically in respect to the oropharyngx, which is the site at which treatment failure is most likely to occur.  Epidemiological typing to detect markers associated with antibiotic resistance makes this kind of intervention a real possibility (Graham & Jennison (STI).

Lao-tzu & Klausner (L&K) have recently reported a trial that claims to demonstrate the feasibility of just the kind of therapy envisaged by Lewis.  The researchers at University of California Los Angeles (UCLA) Health Clinical Microbiology Laboratory developed and implemented a molecular assay for the prediction of gonorrhoea (Ng) ciprofloxacin susceptibility.  Over the period from November 2015 to July 2016 all Ng positive specimens were subjected to the assay, and treatment recommendations issued on that basis.  In the final two months (June-July 2016) electronic reminder notifications were introduced – and it was only at that point that the intervention had any substantial impact on the treatment of patients.

Of the 176 infections detected, 121 (69%) were successfully genotyped.  Of the latter, 72 (60%) showed wild-type gyrA (the gene associated with antimicrobial resistance, 49 (40%) were mutant.  In the final successful two-month phase of assay implementation, this enabled 9 out of 11 (82%) of Ng infections to be treated with ciprofloxacin. The authors claim this shows the potential for laboratory-guided treatment of floroquinolones to limit recourse to ceftriaxone – and thereby slow the emergence of antibiotic resistant Ng.  Clearly, the trial needs to be run again, but this time using electronic reminder notifications from the start.

When it comes to the more specific issue of antimicrobial resistance to Ng at the oropharyngeal site, the results of the study are less promising. The proportion of gyrA mutant Ng infections did not vary significantly by site (pharyngeal 33%; rectal 45.7%; vaginal/cervical 57%; urine 39%); but of the 62 pharyngeal infections, most (40) could not be genotyped.  So laboratory-guided ciprofloxacin treatment would be of limited usefulness in key populations – such as MSM.