Ciprofloxacin Resistance and Gonorrhea Incidence Rates in 17 Cities, United States, 1991–2006

Harrell W. Chesson

, Robert D. Kirkcaldy, Thomas L. Gift, Kwame Owusu-Edusei, and Hillard S. Weinstock

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Abstract

Antimicrobial drug resistance can hinder gonorrhea prevention and control efforts. In this study, we analyzed historical ciprofloxacin resistance data and gonorrhea incidence data to examine the possible effect of antimicrobial drug resistance on gonorrhea incidence at the population level. We analyzed data from the Gonococcal Isolate Surveillance Project and city-level gonorrhea incidence rates from surveillance data for 17 cities during 1991–2006. We found a strong positive association between ciprofloxacin resistance and gonorrhea incidence rates at the city level during this period. Their association was consistent with predictions of mathematical models in which resistance to treatment can increase gonorrhea incidence rates through factors such as increased duration of infection. These findings highlight the possibility of future increases in gonorrhea incidence caused by emerging cephalosporin resistance.

Each year, the estimated 820,000 incident cases of gonorrhea in the United States result in lifetime direct medical costs of $162 million (1,2). Although substantial, the incidence of gonorrhea in the United States has decreased since the 1970s in part because of sexually transmitted disease (STD) prevention programs (3–5). However, treatment and control efforts can be hindered by antimicrobial drug resistance (6–8).

Neisseria gonorrhoeae has been remarkably adept at acquiring and maintaining resistance to antimicrobial drugs used for treatment, such as penicillin, tetracyclines, and fluoroquinolones (e.g., ciprofloxacin). After first spreading in Hawaii and California during the late 1990s and early 2000s, ciprofloxacin-resistant gonococcal strains became increasingly prevalent in the United States during the 2000s. By 2007, the Centers for Disease Control and Prevention (CDC) no longer recommended ciprofloxacin or other fluoroquinolones for treatment of gonorrhea, which make the cephalosporins cefixime or ceftriaxone the only remaining recommended treatment option (9).

During the past several years, gonococcal susceptibility to the cephalosporins has been decreasing (6–8). In response to increasing cefixime MICs in the United States, CDC recently updated its treatment recommendations for gonococcal infections (10). CDC now recommends dual therapy with ceftriaxone (an injectable cephalosporin) and a second antimicrobial drug as the only remaining recommended first-line treatment option for gonorrhea (10). However, the possible emergence and spread of cephalosporin resistance could eventually threaten the effectiveness of this regimen and pose a major public health challenge (6–8).

Although the course of emerging cephalosporin resistance and the possible effect on gonorrhea incidence are difficult to predict, it is possible to analyze historical trends in gonorrhea incidence during periods of increasing resistance to previously recommended antimicrobial drugs. In this study, we analyzed historical ciprofloxacin resistance data and gonorrhea incidence data to examine the possible effect of antimicrobial drug resistance on gonorrhea incidence at the population level. Assessing the historical population-level association between ciprofloxacin resistance and gonorrhea incidence can provide information about cephalosporin resistance in the future.