title: Impact of the Seven-valent Pneumococcal Conjugate Vaccine on Acute Otitis Media in Japanese Children: Emergence of Serotype 15A Multidrug-resistant Streptococcus pneumoniae in Middle Ear Fluid Isolates.
abstract: BACKGROUND
  Streptococcus pneumoniae is one of the most common bacteria causing acute otitis media (AOM). In Japan, a 7-valent pneumococcal conjugate vaccine (PCV7) was introduced for voluntary vaccination of children in 2010, and it became a recommended vaccination in April 2013. We surveyed the serotypes and antimicrobial susceptibility profile of S. pneumoniae isolates obtained from the middle ear fluid of Japanese children with AOM.
  
  
  METHODS
  Between April and September 2013, a total of 176 S. pneumoniae isolates were obtained from the middle ear fluid of children aged 0-3 years with AOM. Isolates were collected from various regions of Japan. Minimum inhibitory concentrations were measured by the broth microdilution method. Serotyping was performed by observing the Quellung reaction.
  
  
  RESULTS
  Although 45.5% of the strains were susceptible to penicillin G, 42.6% were penicillin-intermediate strains and 11.9% were penicillin-resistant strains. Serotype 19A (27.3%), serotype 15A (14.2%) and serotype 3 (11.9%) showed a high frequency. Although PCV7 types only accounted for 4.5% of all strains, 44.9% were PCV13 types and 55.1% were non-PCV types. Serotype 15A strains were 100% nonsusceptible to penicillin G and all of these strains showed multidrug resistance. Serotype 15A was frequent in children up to 1 year old.
  
  
  CONCLUSIONS
  After this research was completed, PCV7 was switched to a PCV13 that also contained serotype 3 and serotype 19A. We need to consider the possibility that serotype 15A, which is not included in PCV13, may increase and cause intractable AOM in the future.
authors.affiliation: From the *Department of Otolaryngology-Head and Neck Surgery, and †Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan; ‡Department of Microbiology and Infectious Diseases, Nara Medical University, Kashihara, Nara, Japan; and §Department of Bacteriology, BML Inc., Kawagoe, Saitama, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Ozawa
authors.forename: Hisakazu
authors.initials: H
authors.lastname: Yano
authors.forename: Shiro
authors.initials: S
authors.lastname: Endo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hidaka
authors.forename: Risako
authors.initials: R
authors.lastname: Kakuta
authors.forename: Naohiro
authors.initials: N
authors.lastname: Okitsu
authors.forename: Hajime
authors.initials: H
authors.lastname: Kanamori
authors.forename: Miho
authors.initials: M
authors.lastname: Ogawa
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Ichimura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Shimojima
authors.forename: Shinya
authors.initials: S
authors.lastname: Inomata
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kaku
authors.forename: Yukio
authors.initials: Y
authors.lastname: Katori
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000008:administration & dosage*; D006801:Humans; D007223:Infant; D007564:Japan / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D010033:Otitis Media / Q000453:epidemiology* / Q000382:microbiology* / Q000517:prevention & control; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D015995:Prevalence; D065288:Serogroup; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D000069443:Heptavalent Pneumococcal Conjugate Vaccine