title: Association between nasopharyngeal load of Streptococcus pneumoniae, viral coinfection, and radiologically confirmed pneumonia in Vietnamese children.
abstract: BACKGROUND
  The interplay between nasopharyngeal bacterial carriage, viral coinfection, and lower respiratory tract infections (LRTIs) is poorly understood. We explored this association in Vietnamese children aged less than 5 years.
  
  
  METHODS
  A hospital-based case-control study of pediatric LRTIs was conducted in Nha Trang, Vietnam. A total of 550 hospitalized children (274 radiologically confirmed pneumonia [RCP] and 276 other LRTIs) were enrolled and 350 healthy controls were randomly selected from the community. Polymerase chain reaction-based methods were used to measure bacterial loads of Streptococcus pneumoniae (SP), Haemophilus influenzae, and Moraxella catarrhalis and to detect 13 respiratory viruses and bacterial serotypes in nasopharyngeal samples of study participants.
  
  
  RESULTS
  The median nasopharyngeal bacterial load of SP was substantially higher in children with RCP compared with healthy controls or children with other LRTIs (P < 0.001). SP load was 15-fold higher in pneumonia children with viral coinfection compared with those children without viral coinfection (1.4 x 10⁷/mL vs. 9.1 x 10⁵/mL; P 0.0001). SP load was over 200-fold higher in serotypeable SP compared with nontypeable SP (2.5 x 10⁶/mL vs. 1 x 10⁴/mL; P < 0.0001). These associations were independent of potential confounders in multiple regression models. No clear association was found between nasopharyngeal load of Haemophilus influenzae or Moraxella catarrhalis and viral coinfection in either RCP or other LRTIs groups.
  
  
  CONCLUSIONS
  An increased load of SP in the nasopharynx was associated with RCP, viral coinfection, and presence of pneumococcal capsule.
authors.affiliation: Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Huong Thi Thu
authors.initials: HT
authors.lastname: Vu
authors.forename: Lay Myint
authors.initials: LM
authors.lastname: Yoshida
authors.forename: Motoi
authors.initials: M
authors.lastname: Suzuki
authors.forename: Hien Anh Thi
authors.initials: HA
authors.lastname: Nguyen
authors.forename: Cat Dinh Lien
authors.initials: CD
authors.lastname: Nguyen
authors.forename: Ai Thi Thuy
authors.initials: AT
authors.lastname: Nguyen
authors.forename: Kengo
authors.initials: K
authors.lastname: Oishi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Kiwao
authors.initials: K
authors.lastname: Watanabe
authors.forename: Thiem Dinh
authors.initials: TD
authors.lastname: Vu
mesh_terms: D058491:Bacterial Load; D016022:Case-Control Studies; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology* / Q000821:virology; D011018:Pneumonia, Pneumococcal / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000382:microbiology* / Q000821:virology; D011024:Pneumonia, Viral / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000382:microbiology* / Q000821:virology; D012328:RNA Viruses / Q000302:isolation & purification; D013902:Radiography, Thoracic; D012044:Regression Analysis; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*; D014744:Vietnam / Q000453:epidemiology; D019562:Viral Load