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Azithromycin-resistant gonorrhea emerges in US
The incidence of azithromycin-resistant Neisseria gonorrhoeae appears to have increased from 0.6% to 2.5% between 2013-2014, according to recently published surveillance data.
Although these isolates did not exhibit resistance to cefixime or ceftriaxone, azithromycin nonsusceptibility would threaten the combination antibiotic therapy currently recommended by the CDC for gonorrhea infection, researchers wrote.
“The confluence of emerging drug resistance and very limited alternative options for treatment creates a perfect storm for future gonorrhea treatment failure in the U.S.,” Jonathan Mermin, MD, director of the CDC’s National Center for HIV/AIDS, Viral Hepatitis, STD, and Tuberculosis Prevention, said in a press release. “History shows us that bacteria will find a way to outlast the antibiotics we’re using to treat it. We are running just one step ahead in order to preserve the remaining treatment option for as long as possible.”
Jonathan Mermin
Robert D. Kirkcaldy, MD, MPH, medical epidemiologist in the CDC’s Division of STD Prevention, and colleagues examined N. gonorrhoeae sampling data collected through the CDC’s Gonococcal Isolate Surveillance Project from 2000 to 2014. They reported recent and longitudinal trends in antimicrobial resistance, as determined by previously established minimum inhibitory concentrations (MICs), and stratified collected isolates by relevant epidemiologic characteristics, such as the sexual behaviors of sampled donors.
There were 86,517 isolates submitted to the surveillance system, 5,093 of which were collected from 27 sites in 2014. The researchers said 37.1% of those from 2014 were from men who have sex with men or men who have sex with men and women. Among the 94.3% of cases in 2014 treated with intramuscular ceftriaxone, 96.4% were co-treated with azithromycin, 2.2% with doxycycline and 0.1% with another antibiotic.
Robert Kirkcaldy
Although infrequent throughout most of the study period, the prevalence of azithromycin-resistant isolates increased from 0.6% in 2013 to 2.5% in 2014, the researchers wrote. This increase occurred regardless of individuals’ sexual preferences, and it appeared nationwide but was greatest in the Midwest.
The researchers also reported a 25.3% rate of tetracycline resistance, a 19.2% rate of ciprofloxacin resistance and a 16.2% rate of penicillin resistance in 2014. Cefixime resistance increased from 0.4% to 0.8% from 2013 to 2014, but is lower than the 1.4% rate observed in 2010 and 2011. Ceftriaxone resistance was highest in 2011 (0.4%), and decreased to 0.1% in 2013 and 2014. No isolates that were resistant to azithromycin exhibited reduced susceptibility to cefixime or ceftriaxone, and isolates from MSM were more often tetracycline-, ciprofloxacin- or penicillin-resistant than those from men who have sex with women.
“It is unclear whether these increases mark the beginning of trends, but emergence of cephalosporin and azithromycin resistance would complicate gonorrhea treatment substantially,” Kirkcaldy and colleagues wrote. “Continued surveillance, appropriate treatment, development of new antibiotics and prevention of transmission remain the best strategies to reduce gonorrhea incidence and morbidity.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Timothy F. Jones
The substantial increase in azithromycin resistant-gonorrhea is cause for concern from both clinical and public health perspectives.
While it is too early to know whether this trend will continue, and the absolute rate of resistance remains low enough that there are no changes in recommended treatment, it is a warning shot across the bow. As nonculture diagnostics become more common for a growing number of pathogens, sentinel surveillance systems that maintain the capacity to do phenotypic testing of isolates (programs such as GISP) are increasingly important.
Disclosure: Jones reports no relevant financial disclosures.