Genetic characterization of clonal complex sequence type 2057 (cc2057) serogroup B Neisseria meningitidis strains unique to Japan and identification of a capsular-switched serogroup Y isolate cc2057

Epidemiology of invasive meningococcal disease, Japan, 2013 to 2023

BackgroundThe National Surveillance for Invasive Meningococcal Disease (IMD) initiative started in Japan in April 2013. Multiple international mass gathering events have since been held in Japan, and the COVID-19 pandemic has occurred.AimWe summarised 10 years of national surveillance data for IMD in Japan to describe epidemiological characteristics of IMD and evaluate the influence of mass gatherings and the COVID-19 pandemic on IMD.MethodsUpon diagnosis of IMD, patient information and specimens were collected and reported to local health centres. We analysed the epidemiology of IMD cases reported between 1 April 2013 and 31 March 2023.ResultsAmong 274 cases reported (median age: 55 years; 55% male), no outbreaks related to mass gathering events were identified. The annual reported incidence of IMD was 0.001-0.039 cases per 100,000 individuals between 2014 and 2022, with a notable decrease after 2020. The overall case fatality rate was 12% (33/274). The most frequent serogroups were Y and B (46 and 17%). Multilocus sequence typing revealed a predominance of clonal complex (cc) 23, followed by cc2057, while cc11 was detected in eight cases.ConclusionThe reported incidence of IMD in Japan is low compared with high-endemic countries and decreased further during the COVID-19 pandemic. This unique epidemiology of IMD in Japan lacks a clear explanation. However, distribution of meningococcal strains, such as predominance of serogroup Y, could be a contributing factor. Maintaining high-quality surveillance, including of serogroups and sequence types, is crucial to manage and prevent future IMD cases in Japan effectively.

Microevolution and Its Impact on Hypervirulence, Antimicrobial Resistance, and Vaccine Escape in Neisseria meningitidis

Neisseria meningitidis is commensal of the human pharynx and occasionally invades the host, causing the life-threatening illness invasive meningococcal disease. The meningococcus is a highly diverse and adaptable organism thanks to natural competence, a propensity for recombination, and a highly repetitive genome. These mechanisms together result in a high level of antigenic variation to invade diverse human hosts and evade their innate and adaptive immune responses. This review explores the ways in which this diversity contributes to the evolutionary history and population structure of the meningococcus, with a particular focus on microevolution. It examines studies on meningococcal microevolution in the context of within-host evolution and persistent carriage; microevolution in the context of meningococcal outbreaks and epidemics; and the potential of microevolution to contribute to antimicrobial resistance and vaccine escape. A persistent theme is the idea that the process of microevolution contributes to the development of new hyperinvasive meningococcal variants. As such, microevolution in this species has significant potential to drive future public health threats in the form of hypervirulent, antibiotic-resistant, vaccine-escape variants. The implications of this on current vaccination strategies are explored.

Emergence of ciprofloxacin- and penicillin-resistant Neisseria meningitidis isolates in Japan between 2003 and 2020 and its genetic features

Although we previously reported that some meningococcal isolates in Japan were resistant to penicillin (PCG) and ciprofloxacin (CIP), the antibiotic susceptibilities of Neisseria meningitidis isolates obtained in Japan remained unclear. In the present study, 290 N. meningitidis isolates in Japan between 2003 and 2020 were examined for the sensitivities to eight antibiotics (azithromycin, ceftriaxone, ciprofloxacin, chloramphenicol, meropenem, minocycline, penicillin, and rifampicin). All isolates were susceptible to chloramphenicol, ceftriaxone, meropenem, minocycline, and rifampicin while two were resistant to azithromycin. Penicillin- and ciprofloxacin-resistant and -intermediate isolates (PCGR, CIPR, PCGI and CIPI, respectively) were also identified. Based on our previous findings from whole genome sequence analysis, approximately 40% of PCGI were associated with ST-11026 and cc2057 meningococci, both of which were unique to Japan. Moreover, the majority of ST-11026 meningococci were CIPR or CIPI. Sensitivities to PCG and CIP were closely associated with genetic features, which indicated that, at least for Japanese meningococcal isolates, PCGR/I or CIPI/R would be less likely to be horizontally conferred from other neisserial genomes by transferring of the genes responsible (penA and gyrA genes, respectively), but rather that ancestral N. meningitidis strains conferring PCGR/I or CIPI/R phenotypes clonally disseminated in Japan.

Genomic characterization of Japanese meningococcal strains isolated over a 17-year period between 2003 and 2020 in Japan

While invasive meningococcal disease (IMD) is a major public concern worldwide, IMD is categorized as a rare infectious disease in Japan and, thus, its causative agents and epidemiology have not yet been characterized in detail. In the present study, we used molecular methods to epidemiologically characterize 291 meningococcal strains isolated in Japan over a 17-year period between 2003 and 2020 by whole genome sequencing (WGS). Serogroup Y meningococci (MenY) were the most abundant, followed by B (MenB) and then C and W among meningococci from IMD patients, while non-groupable as well as MenY and MenB were the most abundant among isolates from healthy carriers. Sequence type (ST) defined by multilocus sequence typing (MLST) showed that ST-1655 and ST-23 belonging to clonal complex (cc) 23 were dominant among Japanese IMD isolates, while ST-11026 (cc32) unique to Japan as well as ST-23 were dominant among Japanese non-IMD isolates. Phylogenetic analyses of ST by MLST revealed that Japanese isolates were classified with 12 ccs, including recently reported cc2057. Phylogenic analyses by WGS showed that isolates of ST-11026 and of ST-1655 were genetically close, whereas ST-23 isolates appeared to be diverse. Moreover, comparisons with other cc11 isolates isolated worldwide indicated that some Japanese cc11 isolates were genetically close to those isolated in Europe and China. An in silico analysis suggested that 14.3 and 44.2% of Japanese MenB were cross-reactive with 4CMenB and rLP2086 MenB vaccines, respectively. The results in the present study revealed that some epidemiological features were unique to Japan.