Rapid diagnostic testing may help tailor gonorrhea treatment

Rapid diagnostics that report an infection’s vulnerability to specific antibiotics may help health care providers extend the use of existing treatments for gonorrhea, a modeling study showed.

“Among the most urgent threats to our ability to treat infections is antibiotic-resistant gonorrhea,” Ashleigh R. Tuite, PhD, a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health, and colleagues wrote.

Tuite and colleagues noted that gonorrhea is most often diagnosed by using a nucleic acid amplification test, which provides no data on the infection’s susceptibility to antibiotics.

“Given the prevalence of susceptible isolates, one proposed strategy to control resistance is the use of rapid diagnostics that allow clinicians to both diagnose gonorrhea infections and tailor treatment to the antibiotic susceptibilities of individual infections,” the researchers wrote.

Tuite and colleagues developed a mathematical model that projected gonorrhea transmission and recorded the probabilities of emerging resistance to ciprofloxacin, azithromycin and ceftriaxone. The researchers evaluated the time to 1% and 5% prevalence of resistant strains, incorporating empiric treatment (azithromycin and ceftriaxone), as well as treatment guided by point-of-care (POC) testing of susceptibility to ciprofloxacin alone, followed by susceptibility to all three drugs.

The model projected that continued use of empiric treatments without POC testing resulted in more than 5% of gonorrhea isolates being resistant to both azithromycin and ceftriaxone within 15 years. However, using a POC test for either drug in 10% of cases delayed the increase in resistance by 5 years. A POC test for all three antibiotics delayed a 1% prevalence of triply-resistant strains by 6 years. However, the researchers wrote, a POC test for ciprofloxacin alone did not delay the emergence of resistance.

Tuite and colleagues wrote that “results were less sensitive to assumptions about fitness costs and test characteristics with increasing test uptake.”

The researchers acknowledged that the study was limited by the fact that the model did not include mixed infections in which multiple gonorrhea strains have different antibiotic susceptibilities.

“Despite these limitations, this mathematical model demonstrates both the promise and potential need for caution associated future POC tests for determining antibiotic susceptibility of gonococcal infections,” they wrote. “The use of such tests cannot be done in isolation; continued real-time surveillance will be critical for guiding decision-making and monitoring resistance emergence.” – by Andy Polhamus

 

Disclosures: The authors report no relevant financial disclosures.