Three cohorts of Danish male military recruits (n=1069)
were studied for pharyngeal
meningococcal carriage during 3 months at different seasons: 39–47%
of entrants were
meningococcal carriers and the carriage rate remained constant over time
and season.
However, individual changes in the carrier state occurred frequently, and
after 3 months 34%
had changed carrier state on one or more occasions. Initially, a loss of
carriage predominated;
on the other hand almost 20% of non-carriers had acquisition of meningococci
within the first
month. The serological phenotypes of the 670 carrier strains were compared
with those of 261
invasive strains recovered concurrently from patients with meningococcal
disease country-wide.
Both carrier strains and invasive strains were phenotypically heterogeneous.
Almost 60% of
the invasive strains belonged to three phenotypes:
B[ratio ]15[ratio ]P1.7, 16, C[ratio ]2a[ratio ]P1.2, 5 and C[ratio ]2b[ratio ]P1.2,
5.
In contrast, these phenotypes only amounted to 3·2% of the carrier
strains, among which no
phenotype was found with a prevalence above 4·9%. However, 30% of
the carrier strains had
serological phenotypes identical to those of 80% of the invasive strains.
Our results indicated
that the transmission rate of potential pathogenic carrier strains did
not differ from that of
other carrier strains.