Incidences of nasopharyngeal colonization of respiratory bacterial pathogens in Japanese children attending day‐care centers

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Abstract
Background : In Japan, many younger children attending day‐care centers tend to frequently experience acute respiratory infections and prolonged otitis media. Objectives : To evaluate the carriage rate of respiratory bacterial pathogens in children attending day‐care centers in our district. Methods : Nasopharyngeal cultures of 156 healthy children between the ages of 1 month and 5 years were conducted at two day‐care centers in Japan, in April 1999. The carriage rates of four major pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus) and the antibiotic susceptibilities of the isolates were examined. Results : Streptococcus pneumoniae, H. influenzae, M. catarrhalis and S. aureus were detected in 94 (60.3%), 83 (53.2%), 54 (34.6%) and 28 (17.9%) children, respectively. A total of 141 (90.4%) children carried at least one pathogen among these four pathogens and 87 (55.8%) children carried more than one pathogen. Fifty‐seven of the 94 (60.6%) S. pneumoniae isolates were penicillin‐intermediately or highly resistant strains of S. pneumoniae (PISP/PRSP). Beta‐lactamase producing H. influenzae was not detected. Twelve of the 28 (42.9%) S. aureus isolates were methicillin‐resistant. The incidence of colonization by PISP/PRSP in children younger than 3 years (43/69, 62.3%) was significantly higher than that in children aged 3−5 years (14/87, 16.1%) (P < 0.0001). Conclusions : We conclude that the rates of colonization by respiratory bacterial pathogens, especially by antibiotic‐resistant strains, were high in children attending day‐care centers in our district, suggesting their horizontal spread among children in day‐care centers. Considering that the majority of children attending day‐ care centers carried one or more of the bacterial pathogens, the judicious use of antimicrobials will be required to prevent the increase of antibiotic‐resistant rates among the colonizing pathogens.