Persistence of genetically related Neisseria gonorrhoeae strains causing Disseminated Gonococcal Infection (DGI) cases in southwestern Michigan during 2019 to 2023.

Background: Disseminated gonococcal infection (DGI) is a rare complication of Neisseria gonorrhoeae (Ng) infection, historically affecting 0.5-3% of individuals. In 2019, a DGI genomic cluster associated with the ST-7822 strain was identified in southwest Michigan. This study retrospectively assessed the persistence of this strain.

Methods: Ninety Ng isolates from disseminated sites of infection from Michigan (2019-2023) were sequenced; antimicrobial susceptibility testing (AST) was performed. Phylogenetic analysis was performed to assess genetic relatedness. Data from 370 ST-7822 urogenital and extragenital gonococcal infection (UGI) isolates were included in the phylogenetic analysis. The porB1A allele, a marker associated with DGI, and antimicrobial resistance markers were also analyzed.

Results: Phylogenetic analysis identified seven DGI clades, with clade 7 (n = 26) containing the 2019 cluster (n = 11). Clade 7 isolates (mean SNP difference: 32) formed two sub-clusters from a single ancestor between 2019-2023 and clustered with local UGI isolates. All clade 7 DGI isolates and 82.7% of ST-7822 UGI isolates carried the porB1A allele. Among DGI isolates with AST data (n = 21), all were susceptible to ceftriaxone; no mosaic penA alleles were identified.

Conclusions: The persistence of clade 7 associated with the 2019 Michigan DGI cluster suggests ongoing regional transmission of the ST-7822 strain type that has a high proportion with porB1A allele, which has been associated with invasive infection. The genetic similarity between DGI and UGI isolates suggests that DGI strains are not genetically distinct but derived from circulating strains causing mucosal infections. Continued genomic surveillance is essential to understand virulence factors contributing to disseminated infections.