By Anna Tsioulias
Antimicrobial resistance of Neisseria gonorrhoeae is a significant threat against efforts to treat and control gonorrhea. According to the CDC, rates of the disease have increased more than 11% in five years, with cases increase from 583,405 in 2018 to 648,056 in 2022.
The CDC has classified drug-resistant gonorrhea as an urgent threat because it has rapidly developed resistance to all but one class of antibiotics with roughly 50% of all infections are resistant to at least one antibiotic. Although culture is an inexpensive, specific and sensitive method for diagnosing infection, it has many challenges due to the fastidious nature of N. gonorrhoeae, but is the only method to test antimicrobial susceptibility (MMWR Recomm Rep 2014;63[RR02]:1-19).
Kamran Azad, PhD, D(ABMM), the scientific director at Quest Diagnostics Infectious Disease, and his colleagues used phenotypic antibiotic diagnostic testing to assess drug susceptibility of various isolates and looked at resistance patterns over time.
Treatments efforts have been affected by N. gonorrhoeae, Dr. Azad wrote in an email to IDSE. “To address this threat, our study evaluated the overall antibiotic susceptibility profile of NG [N. gonorrhoeae] to commonly tested antibiotics over a period of 6 years, between 2018 and 2024.”
The results of this study, presented recently at ASM Microbe 2024 in Atlanta, suggest cephalosporin antibiotics, including cefixime and ceftriaxone, remain an effective first-line treatment option for gonorrhea. Dr. Azad also emphasized that continuously monitoring of susceptibility data is essential to understanding resistance patterns, especially in patients with persistent infection.
Over the course of six years, more than 500 isolates primarily from anogenital, blood, joint fluid, and urine were evaluated with gradient diffusion methodology (Etest). Antibiotics tested included cefixime, ceftriaxone, ciprofloxacin and ofloxacin. “Other antibiotics are not part of our routine susceptibility panel testing for N. gonorrhoeae,” Dr. Azad said. Sixty-nine percent of the isolates, were from male patients with a median age of 34 years (range 26-47 yrs) and 28.6% were from women, median age 30 years (range 22-38 yrs).
For cefixime and ceftriaxone, 0.18% of the isolates were non-susceptible and 0.37% had an elevated minimum inhibitory concentration, according to the poster. Ciprofloxacin and ofloxacin resistance rates were 48.6% and 50.2%, respectively. These results mirror reports from the CDC’s 2021 Gonococcal Isolate Surveillance Project noting an increased resistance to ciprofloxacin.
This demonstrates that alternative testing strategies using rapid molecular resistance markers may be required to implement resistance guided therapy to ensure preservation of front-line treatment options, according to Dr. Azad and his colleagues.
“Rapid diagnostic testing for NG antibiotic resistance is not widely available,” Dr. Azad said. “For this [gradient diffusion methodology] test, the maximum laboratory turnaround time was 3 to 5 days.”
