Carriage rates of Neisseria meningitidis serogroups: determination among freshmen conscripts before vaccination

Abstract

Background and objectives: Neisseria meningitidis is transmitted from person-to-person. Thus, close contact with a healthy carrier can facilitate the spread of the bacteria and lead to life-threatening meningococcal disease. The aim of this study was to identify oropharyngeal carriers of N. meningitidis in volunteers preparing for military service before vaccination.

Materials and methods: In a cross-sectional study, 226 volunteers entering military service were referred to the Shemiranat Health Center for meningococcal vaccination and assayed. Before vaccination, the participants underwent sampling of the throat using separate swabs. Thayer-Martin Agar medium and microbiological standard methods were used for culture and isolation of the organisms. The bacterial isolates were subjected to DNA extraction and polymerase chain reaction. The obtained data were descriptively analyzed.

Results: Out of the 226 (100%) young volunteers, only 18 (8%) yielded Gram-negative diplococci. The results showed the presence of N. meningitidis (carriage rate: 8%) in their oropharyngeal regions. The isolated serogroups were C, A, Y, W-135, and X with frequencies of 50, 22.2, 16.6, 5.5, and 5.5, respectively.

Discussion: This study showed that the carriage rate in young volunteers for military service is around 8% before vaccination. Although the rates for serogroups A and C were dominant, the existence of serogroups Y and W indicate the necessary revision of the A/C vaccine. More research is needed to determine serogroup diversity and decrease the risk of meningococcal disease in individual groups.

Keywords: Conscripts; Healthy carrier; Neisseria meningitidis; PCR.

Fig. 1.

Genogroups frequency is shown. The most common serogroups were C, A and Y, respectively

Fig. 2.

The results of PCR product electrophoresis of N. meningitides strain genotypes was shown. Line 1 is a 50-bp DNA ladder; line 2 is extracted DNA; line 3 indicates serogroup X; line 4 is serogroup Y; line 5 illustrates a 100-bp DNA ladder; line 6 represents serogroup A; line 7 is sero-group W-135 and line 8 represents serogroup C.