Studies which describe the bacterial aetiology and antimicrobial susceptibility in AOM children in Latin America are scarce. Interestingly, when the MEF microbiology was analyzed among 1,108 children aged 2-92 months with OM between years 2002 and 2007, non-typable H. influenzae was the most common pathogen isolated from the MEF of children with a otitis media failing to appropriate antimicrobial therapy.

PCV-7 (3 + 1 regimen) was introduced into the Costa Rican national immunization program in January 2009 and in August/September of 2011, it was changed for PCV 13 (-2+1 regimen). Following PCV-7 universal introduction in Costa Rica, between March of 2010 and January of 2011, MEF samples from Costa Rican children with OM, having received 0-4 PCV 7 vaccine doses, were obtained via tympanocentesis (88%) or from spontaneous otorrhoea (12%). It was interesting to observed that among the initial 134 OM episodes, the most common bacterial pathogen identified was H. influenzae (55%) followed by S. pneumoniae (31%) and that among the S. pneumoniae episodes, 55% were already non-PCV-7 serotypes and that 25% of these isolates were multi-drug resistant.

The primary objectives of the study are to analyze the effect of early universal utilization of PCV-13 in Costa Rican children with the number of H. influenzae and PCV-13- S. pneumoniae positive MEF cultures by comparing the data collected prospectively and by the same group of investigators that have collected the original data since 1992, from children for the post-PCV-13 introduction with anonymised information collected retrospectively pre-PCV-7 data (1999-2004) during a transition period in which PCV-7 was used in only the private settings (2005-2008) and during universal use of PCV-7 (2009-September 2011).

Studies which describe the bacterial aetiology and antimicrobial susceptibility in AOM children in Latin America are scarce, however, since 1991, investigators in Costa Rica have follow the MEF microbiology of Costa Rican children with AOM including data before PCV 7, during a period of time when PCV-7 was used among high risk children and after universal introduction of a 3 + 1 PCV-7 regimen in Costa Rica. Published data from Costa Rican children with OM, collected between 1992 and 2007, describing the MEF microbiology indicated that overall S. pneumoniae was the most frequent pathogen followed by non-typable H. influenzae, M. catarrhalis and S. pyogenes. Interestingly, when the MEF microbiology was analyzed among 1,108 children aged 2-92 months with OM between years 2002 and 2007, non-typable H. influenzae was the mosto common pathogen isolated from the MEF of children with a otitis media failing to appropriate antimicrobial therapy.

PCV-7 (3 + 1 regimen) was introduced into the Costa Rican national immunization program in January 2009 and in August/September of 2011, it was changed for PCV 13 (-2+1 regimen). Following PCV-7 universal introduction in Costa Rica, between March of 2010 and January of 2011, MEF samples from Costa Rican children with OM, having received 0-4 PCV 7 vaccine doses, were obtained via tympanocentesis (88%) or from spontaneous otorrhoea (12%). It was interesting to observed that among the initial 134 OM episodes, the most common bacterial pathogen identified was H. influenzae (55%) followed by S. pneumoniae (31%) and that among the S. pneumoniae episodes, 55% were already non-PCV-7 serotypes and that 25% of these isolates were multi-drug resistant.

Based on the available information describing the worldwide modifications in the MEF microbiology of PCV-7 vaccinated children with OM (a proportional increase of cases caused by H. influenzae and non-PCV-7 S. pneumoniae serotypes), the primary objectives of the study are to analyze the effect of early universal utilization of PCV-13 in Costa Rican children with the number of H. influenzae and PCV-13- S. pneumoniae positive MEF cultures by comparing the data collected prospectively and by the same group of investigators that have collected the original data since 1992, from children for the post-PCV-13 introduction with anonymised information collected retrospectively pre-PCV-7 data (1999-2004) during a transition period in which PCV-7 was used in only the private settings (2005-2008) and during universal use of PCV-7 (2009-September 2011).

Inclusion Criteria:

• All subjects must satisfy all the following criteria at study entry:

  • Age: more than 3 months and less than 6 years at the time of informed consent. The subject becomes ineligible at the seven birthday.
  • Signs and symptoms include:One of the functional or general signs of otalgia (or its equivalent: irritability), conjunctivitis, fever; AND EITHER Paradise's criteria (bulging, diffused or localised inflamed tympanic membranes) or Spontaneous otorrhoea of less than 24 hours.

Exclusion Criteria:

• Hospitalised during the diagnosis of otitis media or during treatment.
• Having an otitis externa, or otitis media with effusion
• Presence of a transtympanic tubes.
• Children presenting with a new episode of otitis media but having received antibiotic systemic therapy in the past 3 days for a separate illness.
• Receiving antimicrobial prophylaxis for recurrent acute otitis media.
• Received antibiotics for otitis media in the last day (exception: children with otitis media treatment failures must received antibiotic treatment within 3 to 5 days prior to study inclusion for the current otitis media episode).

Children aged more than 3 months to less than 6 years, visiting with otitis media and from whom a middle ear fluid sample has been obtained.

A cohort of children with the first episode of otitis media occurring before or at the age of 24 months of age and at least one month after completion of two doses of pneumococcal 13 valent vaccine will be followed until the participant completes 36 months of life.