BackgroundBiofilm production by Haemophilus influenzae and Streptococcus pneumoniae has been implicated in the pathogenesis of otitis media, mainly in chronic and recurrent cases. We studied the “in vitro” biofilm production by these 2 species isolated alone or together from the nasopharynx of children with acute otitis media.MethodsThe studied strains were from 3 pneumococcal conjugate vaccine (PCV) periods: pre-PCV7, post-PCV7/pre-PCV13 and post-PCV13. A modified microtiter plate assay with crystal violet stain was used to study the biofilm production of 182 H. influenzae and 191 S. pneumoniae strains.ResultsOverall, 117/181 (64.6%) H. influenzae and 128/191 (66.8%) S. pneumoniae strains produced biofilm. The proportion of biofilm-producing H. influenzae strains was greater with than without the isolation of S. pneumoniae in the same sample (75.5% vs 52.3%, p = 0.001). Conversely, the proportion of biofilm-producing S. pneumoniae strains was not affected by the presence or not of H. influenzae (66.3% vs 67.4%). S. pneumoniae serotypes 6B, 15B/C, 19A, 35F and 35B were the better biofilm producers (80%). Serotypes 11A, 14, 15A, 19F and 19A were more associated with H. influenzae biofilm-producing strains. Overall, 89/94 (94.6%) of cases with combined isolation showed biofilm production by S. pneumoniae or H. influenzae.ConclusionThis study emphasizes the high proportion of biofilm production by H. influenzae and S. pneumoniae strains isolated from the nasopharynx of children with acute otitis media, which reinforces the results of studies suggesting the importance of biofilm in the pathogenesis of acute otitis media.Electronic supplementary materialThe online version of this article (10.1186/s12879-018-3657-9) contains supplementary material, which is available to authorized users.

The purpose of this investigation was to describe the evolution of serotypes and antibiotic susceptibility of Streptococcus pneumoniae strains isolated from both adults and children from the same population area with invasive pneumococcal disease (IPD) or acute otitis media (AOM), 5 years after the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13). From 2009 to 2015, 839 strains of S. pneumoniae strains were collected (481 from adults and 358 from children). Serotyping by latex antisera and molecular methods was performed. Antimicrobial susceptibility was tested. Compared to 2009, the total number of strains isolated in 2015 decreased in children (263 vs. 53, respectively) and in adults (220 vs. 131, respectively). Serotype coverage of PCV13 for IPD decreased significantly in adults from 67.7% (149/220) to 25.2% (33/131) and in children from 75.1% (61/81) to 18.5% (5/27). Especially, serotypes 1, 7F and 19A decreased significantly in children, while serotypes 7F and 19A decreased significantly in adults. PCV13 serotypes involved in AOM decreased significantly over the 5-year period, from 85.7% (156/182) to 38.5% (10/26), and were more susceptible to penicillin, amoxicillin and cefotaxime, p < 0.05. Serotypes 8, 9N and 10A seemed to emerge in adults, whereas any serotype prevalence was observed in children. Between 2009 and 2015, the introduction of PCV13 has resulted in a significant decrease of the number of S. pneumoniae strains isolated from IPD in children as in adults. It highlights a strong herd effect of vaccination in adults.