Genetic variability in Neisseria meningitidis strains isolated in a Japanese hospital

Objectives: Neisseria meningitidis is a significant pathogen causing invasive meningococcal disease, posing clinical and public health concerns worldwide. This study aimed to investigate the genetic characteristics of N. meningitidis clinical isolates at Okayama University Hospital in Japan.
Methods: Between 2018 and 2023, five clinical strains were isolated, of which three were subjected to the antimicrobial susceptibility testing and whole genetic analysis using MiSeq platform (Illumina, San Diego, CA, USA).
Results: One non-groupable isolate, belonging to sequence types (STs)-11026 (ST-32 complex), exhibited non-susceptibility to penicillin G, with a five-mutation pattern (F504L, A510V, I515V, H541N, and I566V) in the penA amino acid sequence and additional mutations (XXXIV and N513Y) characteristic of a mosaic penA gene. The other two isolates, ST-1655 (ST-23 complex) with serogroup Y and ST-2057 with serogroup B, were susceptible to penicillin G, neither of which contained the five-mutation pattern. Levofloxacin resistance was observed in two isolates carrying the T91I mutation in the gyrA protein.
Conclusion: Our findings suggest the presence of antimicrobial-resistant N. meningitidis in Japan, underscoring the necessity for continuous local surveillance. Additional research is crucial for clarifying the ongoing spread of resistance mechanisms and for establishing effective countermeasures to reduce the clinical burden of invasive meningococcal disease.