Bacterial etiology of acute otitis media in the era prior to universal pneumococcal vaccination in Taiwanese children

Background: Acute otitis media (AOM) is one of the most frequent bacterial infections in children. Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) are the two major bacterial pathogens. Pneumococcal conjugate vaccine was introduced into Taiwan in 2005 and only some children were vaccinated. This retrospective study assessed the bacterial etiology of AOM and its antimicrobial susceptibility in the era prior to universal pneumococcal vaccination in Taiwan. Methods: From December 2009 to November 2011, children presenting with AOM and having a middle ear effusion sample collected by tympanocentesis were enrolled. The study period was divided into two parts. Demographic data of patients and antibiotic susceptibility of the pathogens were collected and analyzed. Serotypes of S. pneumoniae were identified. Results: Among the 151 episodes, 46% of samples found bacterial pathogens. S. pneumoniae and NTHi were the leading causes of AOM, detected in 55.7% and 22.9% of bacterial AOM episodes, respectively. The prevalent serotypes of S. pneumoniae were 19 A and 19 F. Significantly more pneumococcal and serotype 19 A AOM were found in the later study period (18.4% vs. 33.3%, p = 0.0036; 10.5% vs. 24.0%, p = 0.028). Among the 39 S. pneumoniae isolates, 11 strains (28.2%) were penicillin-susceptible. Of the 16 NTHi, 10 (62.5%) were susceptible to amoxicillin/clavulanate and all were susceptible to cefotaxime. Conclusion: S. pneumoniae and NTHi were the leading causes of AOM in Taiwanese children in the study period. An increase in patient numbers and proportion of pneumococcal and serotype 19 A AOM occurred. Antimicrobial nonsusceptibility was common in the predominant pathogens.