To investigate nasopharyngeal
carriage and antibiotic susceptibility of bacteria among day-care center
attendees, nasopharyngeal swabs were collected from 259 children attending 16
day-care centers in Amsterdam and from 276 well-baby clinic controls in the same
city during the first trimester of 1999. Day-care center children showed a
higher frequency of respiratory tract infections and an increased use of
antibiotics. Furthermore, these children had a two to four-fold increased risk
of colonization with Streptococcus pneumoniae, Moraxella catarrhalis and
Haemophilus influenzae.
We also investigated the
molecular epidemiology of 319 Streptococcus pneumoniae strains collected from
this study. All pneumococcal isolates were penicillin-susceptible. The most
predominant serotypes in both the day-care center and the control group were
the serotypes 19F (19% and 17%, resp.), 6B (14% and 16%, resp.), 6A (12% and
8%, resp.), 23F (10% and 6%. resp.), and 9V (8% and 8%, resp.). The theoretical
vaccine coverage of the 7-valent conjugate vaccine is 60% for the day-care
center and 56% for the control group. Genetic analysis of the pneumococcal
isolates revealed 75% clustering among pneumococci isolated from day-care
center attendees versus 51% in the control group. The average pneumococcal
cluster size in the day-care center group was 4.3 isolates (range 2 to 13
isolates per cluster), while the average cluster size for the control group was
3.0 (range 2 to 7 isolates per cluster). Similar to observations in other
countries, these results clearly suggest that pneumococci in Dutch day-care
centers have a higher tendency to spread compared to the general population.
The increased frequency of pneumococcal colonization implies a higher risk for
pneumococcal (invasive) infections among day-care center attendees. These data
suggest that this group of children may benefit from the implementation of a
conjugate-vaccine program.