Methods: We collected nasopharyngeal swabs from all students who lived in the dormitory when two cases were reported (n=809) and the teachers (n=131) who works at the school built in the same property as the dormitory. Secretions were plated directly onto Modified Thayer-Martin medium immediately after swabbing. After incubated for 18 hours, positive isolates were tested for serogroup and molecular epidemiological method named MLST. The test results were linked to demographic and clinical data of the participants collected by simple questionnaire that does not contain any personal information. Known risk factors for MM were evaluated using the chi-square test.
Results: The average age for the participants was 24.8 years old; 21.7 years old for students and 40.1 years old for teachers. Approximately 80% of the participants were male. Average number of students in the class was 130 (range 96-182). The carriage rate of N.meningitidis for whole group was 31.4%, for students 33.7% and 16.8% for teachers. No statistically significant high risk factors were found. Among randomly selected positive isolates (n=12), 11 (91.7%) was serogroup Y, ST-1655 and one untypable, ST-198.
Conclusion: Our results proved the higher carriage rate of N.meningitidis among dormitory residence in a low incidence of MM community. Isolated N. meningitidis from our study population (ST-1655 and ST-198) has been detected frequently in Japan previously indicates the high transmission of the strain among this population. In May 2015, conjugate meningococcal vaccine has been finally approved in Japan. Recommending vaccine to known MM high risk groups are necessary even in low MM incidence population.
T. Sunagawa, None
K. Oishi, None
M. Ohnishi, None