Evaluation of Neisseria meningitidis Carriage with the Analysis of Serogroups, Genogroups and Clonal Complexes among Polish Soldiers

Neisseria meningitidis is an etiological factor of invasive meningococcal disease (IMD). This Gram-negative diplococcus is transmitted from person to person via droplets or through a direct physical contact with secretions of infected patients or asymptomatic carriers. The latter account for 5–10% of the general population. The aim of the study was to estimate the actual N. meningitidis carriage rate in the military environment with identification of serogroups, genogroups, sequence types and clonal complexes of the isolates detected among Polish soldiers. The study was conducted during winter seasons of 2015 and 2016 and involved 883 professional soldiers from the Armoured Brigade in Świętoszów, Poland. The material for testing were nasopharyngeal swabs obtained from study participants. The samples were tested using standard microbiological methods (culture, incubation, microscopy, biochemical and automated identification). N. meningitidis isolates were subjected to slide agglutination test (identification of serogroups), the bacterial DNA was extracted and allowed to determine genogroups, clonal complexes and sequence types. 76 soldiers were found to be carriers of N. meningitidis, they accounted for 8.6% of the study group. The meningococcal isolates mostly belonged to serogroup B. Sequence types ST-11439, ST-136, ST-1136 and the clonal complex 41/44CC were found to be predominant. Clonal complexes responsible for IMD were detected in 15.8% of carriers and 1.4% of the whole study participants. Carriage rates of N. meningitidis among Polish soldiers were found to be similar to those reported in the general population.