Clinical and demographic data from a study of Neisseria gonorrhoeae genome sequences demonstrated that gonorrhoeae transmission occurs across demographic groups and that antibiotic resistance was not the main drive of this spread. The data from this genomic epidemiology study were published in Clinical Infectious Diseases.
Investigators analyzed a convenience sample of genome sequences, antibiotic susceptibility, and patient data from 897 gonococcal isolates cultured at the New York City (NYC) Public Health Laboratory. The isolates were from patients of the NYC Department of Health and Mental Hygiene Sexual Health Clinic, primarily from 2012 to 2013.
A reconstructed gonococcal phylogeny of the NYC isolates reflected the global diversity, with 22 of the 23 prevalent global lineages present. Isolates clustered based on patient sexual behavior (P <.001) and race/ethnicity (P <.001). Compared with isolates from heterosexual patients, minimum inhibitory concentrations were higher across antibiotics in isolates from men who have sex with men (P <.001) and in isolates from Black heterosexual patients, compared with White heterosexual patients (P <.01). Within this dataset, all large transmission clusters, defined as ≥10 samples, of N gonorrhoeae were found to be susceptible to ciprofloxacin, ceftriaxone, and azithromycin and were made up of isolates from patients across demographic groups.
According to investigators, healthcare providers other than the one sampled here make most of the reported gonorrhea diagnoses in NYC, and their results show that not all patient populations are equally likely to be sampled for culture and susceptibility. Furthermore, “a large portion of NYC isolates (~35%) in our dataset were not clustered with any other isolate, suggesting that these transmission networks were not well sampled,” investigators noted.
It was also possible that transmission links were missed in mixed infection settings as only single colony isolates were sequenced. Finally, isolates from men who have sex with men were more likely to be clustered than were isolates from heterosexuals; and among heterosexuals, isolates from non-White patients were more likely to be clustered. Investigators believe this is likely related to sampling at sexual health clinics because of the populations that attend these clinics and the criteria for sending a specimen for culture, but the discrepancy may also be due to differences in sexual behavior.
The results indicated that during this study period, antibiotic resistance was not a major driver of transmission in NYC, because the major transmission clusters involved strains susceptible to currently recommended empiric therapy, along with cefixime and ciprofloxacin. Investigators note that since 2012-2013 resistance to azithromycin has reportedly increased, which may have contributed to more recent outbreaks. They added, “while resistance remains a major public health concern, strategies to reduce overall gonorrhea transmission are also needed as pre-existing transmission networks may present opportunities for rapid spread of resistant lineages.”
Investigators highlight that reductions in the overall case numbers allow public health resources to be directed at resistant cases and that, regardless of susceptibility, a greater understanding of the transmission dynamics would help the design of effective intervention strategies for controlling gonorrhea. They also stressed that continued investment in sexual health services and interventions are critical.
Mortimer TD, Pathela P, Crawley A, et al. The distribution and spread of susceptible and resistant Neisseria gonorrhoeae across demographic groups in a major metropolitan center [published online August 23, 2020]. Clin Infect Dis. doi:10.1093/cid/ciaa1229