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Individual Risk Factors Associated With Nasopharyngeal Colonization With Streptococcus pneumoniae and Haemophilus influenzae: A Japanese Birth Cohort Study

Otsuka, Taketo MD, PhD*; Chang, Bin MD, PhD; Shirai, Takatoshi MD; Iwaya, Atsushi MD; Wada, Akihito MD, PhD; Yamanaka, Noboru MD, PhD§; Okazaki, Minoru MD, PhD*on Behalf of the SADO-study Working Group

The Pediatric Infectious Disease Journal: July 2013 - Volume 32 - Issue 7 - p 709–714
doi: 10.1097/INF.0b013e31828701ea
Original Studies

Background: The first step in a bacterial disease is the establishment of nasopharyngeal carriage.

Methods: We conducted a birth cohort study to identify factors associated with colonization in healthy children and evaluate the serotype distributions and resistances of Streptococcus pneumoniae/Haemophilus influenzae. Nasopharyngeal cultures were obtained from 349 subjects at 5 time points coinciding with health checkups (4, 7, 10, 18 and 36 months).

Results: A total of 551 S. pneumoniae (penicillin resistance rate: 46.3%) and 301 H. influenzae (ampicillin resistance rate: 44.5%) isolates were obtained from 1654 samples. In this study, 47.5% and 60.9% of S. pneumoniae isolates were included in the serotypes of 7- and 13-valent pneumococcal conjugate vaccines, respectively. Analyzing by Cox proportional hazards models, cohabiting older sibling(s) attending day-care (hazard ratios: 2.064–3.518, P < 0.001) and an early start of day-care attendance by the subjects themselves (2.259–2.439, P < 0.001) were associated with a higher risk of early colonization regardless of their susceptibility. Recent exposure to antimicrobials was also significantly associated with increased risk of colonization (odds ratios: 2.032–2.999, P < 0.001) but not with resistance rates. This data indicated that introduction of appropriate antimicrobial usage in areas of overuse of antimicrobials could contribute to lower colonization of S. pneumoniae/H. influenzae, resulting in a decrease in the absolute number of resistant isolates.

Conclusions: Strategies to control transmission at day-care centers or from older sibling(s) as well as appropriate use of antimicrobials are essential for reducing colonization and the absolute number of resistant isolates.

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From the *Department of Pediatrics, Sado General Hospital, Sado, Niigata; Department of Bacteriology I, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo; Department of Pediatrics, Ryotsu Hospital, Sado, Niigata; and §Department of Otolaryngology, Head and Neck Surgery, Wakayama Medical University, Wakayama-shi, Wakayama, Japan.

This work was supported by grants from the Japanese Society for Pediatric Infectious Diseases (grant number 2008-study-grant), St. Luke’s Life Science Institute (grant number 2009-3), The Mother and Child Health Foundation (grant number 20–3) and Takeda Science Foundation (grant number 2010-CM-6). The authors have no other funding or conflicts of interest to disclose.

Address for correspondence: Taketo Otsuka, MD, PhD, Department of Pediatrics, Sado General Hospital, 161, Chigusa, Sado, Niigata, 952–1209, Japan. E-mail:

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© 2013 by Lippincott Williams & Wilkins, Inc.