Upper respiratory colonization by Streptococcus pneumoniae in healthy pre-school children in south-east Poland

Objective: Carriage of Streptococcus pneumoniae in upper respiratory tract of healthy children is a major factor in the horizontal transmission of pneumococcal strains, especially between children attending day-care centers and may be also the source of infection in other individuals. During 8-month prospective study including 3 seasons (autumn, winter, spring), we determined risk factors for S. pneumoniae colonization in general and colonization at 2 or 3 time points in healthy pre-school children, including penicillin non-susceptible likewise multidrug resistant strains.

Methods: Pneumococcal cultures were obtained from 311 children aged 3-5. Finally, a total of 342 isolates were identified. Resistance of pneumococcal isolates was determined and information about potential risk factors were obtained from questionnaires.

Results: A total of 72.4% children were colonized by pneumococci at least once, including 8.4% children colonized at 3 time points, 25.4% children - twice and 38.6% children - only once. Penicillin non-susceptible pneumococcal colonization was found in 36.3% children at least once while multidrug-resistant pneumococcal colonization in 34.1% children. Of the 10.9% and 10.6% children were colonized at 2 or 3 time points by penicillin non-sussceptible and multidrug-resistant isolates, respectively. Pneumococcal colonization (in general or by non-susceptible to penicillin isolates) was independently associated with day care attendance, having no siblings, frequent respiratory tract infections and higher number of antibiotic courses. Children attending day care center, with frequent respiratory tract infections, exposed to tobacco smoke were prone to colonization by multidrug-resistant isolates. Risk of colonization at 2 or 3 time points by pneumococcal isolates, including penicillin-nonsusceptible isolates, was associated with age and day care attendance while multidrug-resistant pneumococcal colonization was found to be significantly higher in children aged 3, with frequent respiratory tract infections and higher number of antibiotic courses.

Conclusion: These results indicate high rate of upper respiratory colonization by S. pneumoniae in healthy preschool children in Poland, including colonization by penicillin non-susceptible and multidrug-resistant pneumococci.