At 14 days after treatment for pharyngeal and rectal gonorrhea, DNA of the disease was detected in 8% of men who have sex with men, according to researchers from Australia.
This persistence appears to be associated with increased minimum inhibitory concentrations (MICs) of ceftriaxone and azithromycin, the researchers wrote in Clinical Infectious Diseases.
The researchers evaluated 190 MSM who were diagnosed with pharyngeal or rectal gonorrhea at the Melbourne Sexual Health Centre from April 2012 to March 2013. Eligible participants who had culture-confirmed Neisseria gonorrhoeae of the pharynx or rectum later received an intramuscular injection of ceftriaxone 500 mg and oral azithromycin 1 g. Participants were asked to abstain from sex until a test of cure was obtained at 7 days after treatment.
Study participants returned for follow-up visits at 7 and 14 days after treatment. Those who received treatment for pharyngeal gonorrhea had a single pharyngeal swab taken from both tonsils and the posterior oropharynx at both of these appointments. Men who had undergone treatment for rectal gonorrhea had an anal swab taken.
The researchers used real-time PCR methods to detect N. gonorrhoeae DNA.
The researchers found that in the cases of pharyngeal gonorrhea, N. gonorrhoeae DNA positivity was detected in 13% of men at 7 days (95% CI, 6.4%-19.6%) and in 8% of men at 14 days (95% CI, 2.7%-13.3%). Among the rectal gonorrhea patients, N. gonorrhoeae DNA positivity was detected in 6% of men at 7 days (95% CI, 1.4%-10.7%) and in 8% of men at 14 days (95% CI, 2.7%-13.3%).
Ceftriaxone MIC of at least 0.06 mg/L and azithromycin MIC of no less than 0.5 mg/L was present in 10 of the 200 baseline pharyngeal and rectal isolates, and three of these had persistent DNA at day 14. The 190 isolates with lesser ceftriaxone and azithromycin MICs were less likely to have persistent DNA, with only 13 (7%) having DNA detected at day 14 (OR=5.8; 95% CI, 1.3-25.4). In one participant — a man originally infected with NG-MAST type 2400 — type 4244 infection was detected at day 14, suggesting gonorrhea reinfection.
“It is uncertain whether the DNA detected 14 days following treatment represented viable organism, that is, continued infection with ongoing transmission potential or successfully treated infection with residual nonviable organism,” the researchers wrote. “It is possible the greater persistence of DNA seen with infections involving higher MICs reflected a slower kill of N. gonorrhoeae.”
Disclosure: The researchers report no relevant financial disclosures.