title: Individual risk factors associated with nasopharyngeal colonization with Streptococcus pneumoniae and Haemophilus influenzae: a Japanese birth cohort study.
abstract: 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.
authors: Department of Pediatrics, Sado General Hospital, Sado, Niigata, Japan. ootsukataketo@hotmail.com
authors: Taketo
authors: T
authors: Otsuka
authors: Bin
authors: B
authors: Chang
authors: Takatoshi
authors: T
authors: Shirai
authors: Atsushi
authors: A
authors: Iwaya
authors: Akihito
authors: A
authors: Wada
authors: Noboru
authors: N
authors: Yamanaka
authors: Minoru
authors: M
authors: Okazaki
mesh_terms: D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D015331:Cohort Studies; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000382:microbiology; D006193:Haemophilus influenzae / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification*; D006801:Humans; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D015995:Prevalence; D012307:Risk Factors; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification*