Molecular Characteristics of Neisseria Meningitidis Carriage Strains Isolated from Korean Adolescents

Background:

Neisseria meningitidis is a diverse commensal bacterium that occasionally causes severe invasive diseases. The relationship between carriage and invasive disease is not fully understood. The analysis of isolates based by multilocus sequence typing (MLST) is improving the understanding of the dynamics of meningococcal transmission. The meningococcal sequence type was investigated in the meningococcal carriage strains isolated from adolescents in Korea.

Methods:

From April 2015 to May 2015, the oropharyngeal samples were collected from the first grade students of high schools (aged 15 to 16 years old) in Korea. Neisseria meningitidis were identified using Vitek MS system (bioMérieux, France) and all isolates were characterized by molecular serogrouping and MLST.

Results:

Of the 1,460 oropharyngeal swabs, 56 isolates (carriage rate, 3.4%) were identified as Neisseria meningitidis. Serogroup B was the most common serogroup, followed by serogroup C, then by serogroup Y (Table 1). By MLST analysis, 26 different sequence types (ST) were identified in this study. The most frequent ST was ST-3091 (9 strains), ST-11278 (7), and ST-44 (5). They belonged to clonal complex (CC)-269, CC-32, and CC-41/44, known as hyper-virulent clones. The distribution of serogroups and ST is illustrated in the eBURST diagram (Figure 1).

Conclusion:

Like other Western countries, meningococcal serogroup B seems to have emerged in Korea, and hypervirulent clones such as CC-269 were identified. Further monitoring of N. meningitidis and assessing the potential strain coverage of meningococcal vaccines, in particular meningococcal B vaccine, is necessary.

Table 1. Serogroup distribution and sequence types of isolates

 Figure 1. eBURST analysis of meningococcal carriage isolates. The circle sizes correlate with the number of strains of each sequence type. Serogroups of sequence types are shown in brackets.

CC: clonal complex; NG: nongroupable