Neisseria gonorrhoeae cases resistant to azithromycin detected in San Diego led the Centers for Disease Control and Prevention to issue a “Dear Colleague” letter on May 12 reminding clinicians to limit use of azithromycin monotherapyto treat uncomplicated rectal and genitourinary infections caused by N.gonorrhoeae.*
Such azithromycin monotherapy typically is used in patients allergic to cephalosporins because recommended treatment for uncomplicated rectal and genitourinary N. gonorrhoeae infection is dual therapy including a 1-g dose of azithromycin and a cephalosporin (250 mg of ceftriaxone or 400 mg of cefixime, if ceftriaxone is not an option).*
The resistance concerns are related to five N. gonorrhoeae cases with reduced susceptibility to azithromycin identified in San Diego, the CDC reported in the May 13 Morbidity and Mortality Weekly Report.
"The five N. gonorrhoeae infections with high MICs to azithromycin identified in MSM [men who have sex with men] during a 3-month period in 2010 in San Diego County amount to an unusually large cluster," according to the report (MMWR 2011;60:579-81). The infections were identified in MSM with no known connections to each other – prompting concerns that the gonorrhea strains with reduced drug susceptibility might be more widespread in the community. The men presented with symptomatic urethritis.
The five cases were identified between August and October 2009 at San Diego County’s main municipal sexually transmitted diseases (STD) clinic. The five isolates had high azithromycin minimum inhibitory concentrations (MICs): three with 8 mcg/mL and two with 16 mcg/mL. The five were among 55 (9%) N. gonorrhoeae isolates obtained from men with symptomatic urethritis tested during the 3-month period.
During November 2009 to December 2010, of 229 new isolates obtained from MSM who were examined at the STD clinic, four (1.7%) new isolates at the same clinic were obtained and were found to have high MICs to azithromycin: three with 8 mcg/mL and one with 16 mcg/mL. Through December 2010, no treatment failures had been reported.
"Continued surveillance [using culture and susceptibility testing] for antimicrobial resistance in N. gonorrhoeae is essential for effective disease prevention and control," according to the CDC.
* CORRECTION, 5/17/2011: The original version of this article required clarification of the "Dear Colleague" letter. This version has been updated.