title: Relationship with original pathogen in recurrence of acute otitis media after completion of amoxicillin/clavulanate: bacterial relapse or new pathogen.
abstract: OBJECTIVE
  We sought to determine whether recurrent acute otitis media (rAOM) occurring within 30 days of amoxicillin/clavulanate treatment was caused by bacterial relapse or new pathogens.
  
  
  METHODS
  Pneumococcal conjugate vaccinated children, age 6-36 months, enrolled in a prospective, longitudinal study experiencing rAOM<1 month after completing amoxicillin/clavulanate therapy were studied. AOM episodes occurred between June 2006 and November 2012. Multilocus sequence typing was used to genotype isolates.
  
  
  RESULTS
  Sixty-six children were in the study cohort; 63 otopathogens were recovered from middle ear fluid after tympanocentesis. Nontypeable Haemophilus influenzae (NTHi) accounted for 47% of initial AOMs versus 15% by Streptococcus pneumoniae (Spn), P<0.0001. NTHi accounted for 42% of rAOM versus 24% by Spn (P value=0.04). NTHi was the main otopathogen that caused true bacteriologic relapses (77%). β-lactamase-producing NTHi and penicillin nonsusceptible Spn were not more common in rAOM than initial AOM infections. Among 21 paired (initial and rAOM events) NTHi isolates genotyped, 13 (61.9%) were the same organism; 1 of 9 (11.1%) of paired Spn isolates was the same (P value=0.017). rAOM occurring within a week of stopping amoxicillin/clavulanate was a different pathogen in 21% of cases, 8-14 days later in 33%, 15-21 days in 41% and 22-30 days in 57% (P=0.04).
  
  
  CONCLUSIONS
  In amoxicillin/clavulanate-treated children, NTHi was the main otopathogen that caused true bacteriologic relapses. New pathogens causing rAOM versus persistence of the initial pathogen significantly increased week to week. Neither relapses nor new infections were caused more frequently by β-lactamase producing NTHi or penicillin nonsusceptible Spn.
authors.affiliation: From the *Rochester General Hospital Research Institute; and †Legacy Pediatrics, Rochester, NY.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Kaur
authors.forename: Janet R
authors.initials: JR
authors.lastname: Casey
authors.forename: Michael E
authors.initials: ME
authors.lastname: Pichichero
mesh_terms: D000208:Acute Disease; D019980:Amoxicillin-Potassium Clavulanate Combination / Q000008:administration & dosage*; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006192:Haemophilus Infections / Q000188:drug therapy / Q000382:microbiology; D006193:Haemophilus influenzae / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D010033:Otitis Media / Q000188:drug therapy* / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000188:drug therapy / Q000382:microbiology; D012008:Recurrence; D013296:Streptococcus pneumoniae / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D019980:Amoxicillin-Potassium Clavulanate Combination