Identification of the proposed Neisseria meningitidis ST-5662 clonal complex with insight into genomic and antimicrobial resistance characteristics

Neisseria meningitidis is a major cause of meningitis and sepsis worldwide. Although ST-5662 has been reported to cause IMD, it remains unassigned to any known clonal complex. This study aimed to characterize ST-5662 lineage and evaluate its phylogenetic, epidemiological, antigenic genes, virulence genes, and antimicrobial resistance features. A total of 1370 N. meningitidis isolates collected between 1956 and 2025 were analyzed by cgMLST. A Bayesian phylogenetic analysis was performed on CC5662. Vaccine-associated antigens, virulence genes, and antimicrobial resistance genes were characterized. Antimicrobial susceptibility testing for 12 antibiotics was performed on 48 available CC5662 isolates, and genotype–phenotype associations were assessed. CC5662 was predominantly associated with serogroup B, with the first documented isolate in China in 1979 and has subsequently been detected in multiple countries across several continents. The fHbp peptide variant 2.18 predominated, with CC5662 having hmbR − / hpuAB + and hmbR + / hpuAB + haemoglobin receptor profiles. An antimicrobial resistance genes analysis indicated that the mutation rates of gyrA T91I (50.0%) and tet(B) (40.54%) in CC5662 were comparable to dominant Chinese lineages, but mtrA was deficient. Among the 48 available CC5662 isolates, all were susceptible to cefotaxime, ceftriaxone, azithromycin, minocycline, chloramphenicol, and rifampicin, whereas nearly all were resistant to sulfamethoxazole–trimethoprim. penA mutations and gyrA T91I were significantly associated with increased β-lactam and fluoroquinolone MICs, respectively. tet(B) -positive isolates showed higher minocycline MICs without resistance, whereas no significant association was observed between the absence of mtrA and azithromycin MICs. This study delineated a previously uncharacterized ST-5662-associated lineage and provided a comprehensive description of its phylogenetic, antigenic genes, virulence-associated, and antimicrobial resistance characteristics. These findings emphasized the significance of CC5662 in epidemiological surveillance and highlighted the value of continued genomic surveillance of CC5662.