HealthDay News — Ciprofloxacin resistance has a positive association with increasing gonorrhea incidence, Harrell W. Chesson, PhD, a health economist with the CDC in Atlanta, and colleagues reported in Emerging Infectious Diseases.
They analyzed data on resistance pertaining to ciprofloxacin from the Gonococcal Isolate Surveillance Project and gonorrhea incidence rates from 17 cities from 1991 to 2006: Albuquerque, Atlanta, Baltimore, Birmingham, Cincinnati, Cleveland, Denver, Honolulu, Minneapolis, New Orleans, Philadelphia, Phoenix, Portland (Ore.), San Diego, San Francisco, Seattle and St. Louis.
The average gonorrhea rate across the 17 cities during the 16 study years was 270 cases per 100,000 persons.
The researchers then compared cities with relatively high ciprofloxacin resistance prevalence and those with relatively low prevalence and used regression analyses to examine the association between ciprofloxacin resistance and gonorrhea incidence.
In 2004, a median percentage of 3.3% of isolates were resistant to ciprofloxacin in the 17 cities. Cities with higher resistance included Denver, Honolulu, Minneapolis, Phoenix, Portland, San Diego, San Francisco, and Seattle. Cities with lower resistance were Albuquerque, Atlanta, Baltimore, Birmingham, Cincinnati, Cleveland, New Orleans, Philadelphia and St. Louis.
“In our simple comparison of higher resistance and lower resistance cities, we found divergent trends in gonorrhea incidence rates in the 2000s,” the researchers wrote.
From 2000 to 2006, gonorrhea incidence rates generally increased in cities with higher ciprofloxacin resistance and decreased in the lower resistance cities — with the timing of the divergent trends in gonorrhea incidence rates coinciding with divergent trends in ciprofloxacin resistance.
This association was consistent with mathematical model predictions in which resistance to treatment can increase gonorrhea incidence rates through increased duration of infection.
“[E]cologic studies, such as ours, of the population-level association between ciprofloxacin resistance and gonorrhea incidence cannot establish that this association is causal. Nonetheless, our study offers evidence consistent with that of a causal association between drug resistance and increased incidence,” the researchers concluded.