Ventilation of middle ear cavity by insertion of tympanostomy tubes and changes of virulence in Streptococcus pneumoniae

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Recently it has been a serious problem in Japan that acute otitis media (AOM) of children, especially in younger age, is getting intractable in spite of treatment with antibiotics. High prevalence of drug-resistant microbes in younger age and immature immunity to AOM pathogens are thought to be major causes for this intractability of AOM. It is widely accepted that myringotomy is the efficient treatment modality of AOM especially for severe and/or intractable cases. We know empirically that myringotomy can provide pain and fever relief more promptly than antibiotics. But there is no evidence in long term this surgical treatment is superior in improvement of otitis proneness than conservative treatment using antibiotics. Today, we can choose as surgical device for myringotomy not only a conventional knife also a CO_2 laser. By conventional myringotomy, the incision on the drum will close within 4-5 days and may result insufficient ventilation effect on the middle ear cavity. On the othe … More r hand, laser assisted myringotomy can keep the ventilation long enough 2-3 weeks and can be safety performed on very young children.In this study, we compared clinical efficacies on cases with intractable AOM among laser-assisted myringotomy, conventional myringotomy and medication with antibiotics. In both LAM and COM groups, Drum Scores 2 weeks after treatments were significant decreased rather than those at the time of treatment, while the patients treated with conservative medication did not show such significant reduction of Drum Scores at 2 weeks after. Separating patients by severity of Drum Scores, both LAM and COM were effective against severe cases rather than moderate cases of otitis media. Bacteriological study evaluated the serotypes distribution of Streptococcus pneumoniae (S. pneumoniae) and antimicrobial resistances. The prevalence of serotypes were 19F (19.8%), 23F (15.8%), 14 (11.9%), 6B (11.9%), 6A (8.9%), and 3 (8.9%). Penicillin susceptible S. pneumoniae (PSSP), penicillin intermediately resistant S. pneumoniae (PISP), and penicillin resistant S. pneumoniae (PRSP) were 34.7%, 40.6%, and 24.8%, respectively. By use of the chinchillas, S. penumonaie showed different outcomes of experimental acute otitis media depending on serotypes. Serotype 6A and 19F were carried long time in middle ear cavities. Serotype 6A was not lethal but all of chinchilla infected with serotype 19F died. In contrast to the former two serotypes, serotype 14 did not infect to chinchillas and cleared very fast from the tympanic bulla.The current study revealed that S. pneumoniae showed different virulence depending their capsular types. In fact, S. pneumoniae changes the virulence according to the environmental condition, such as in hypoxic environment the pathogen enthicked capsule and become virulence. So we considered that surgical drainage show relative early and in short-term improvement of tympanic membrane in intractable AOM. Less