Development of myringosclerosis during acute otitis media caused by Streptococcus pneumoniae and non-typeable Haemophilus influenzae: a clinical otomicroscopical study using the rat model.

OBJECTIVE: The present study was performed in order to study development of myringosclerosis during acute otitis media caused by different bacteria in myringotomized and non-myringotomized ears. MATERIAL AND METHODS: A rat model of acute otitis media caused by Streptococcus pneumoniae type 3 and non-typeable Haemophilus influenzae was used. A sample consisted of 42 animals. Four days following middle ear inoculation, a myringotomy was performed in 10 animals from the Streptococcus pneumoniae group and 6 from the non-typeable Haemophilus influenzae group. Another group of 24 animals was inoculated only. On day 4, 7, 14 and 28 after inoculation the status of the drum was inspected under the otomicroscope for vascular reaction, effusion, perforation, myringosclerosis and scarring. RESULTS: On day 4 after inoculation all infected ears had typical signs of acute otitis media. Tympanic membranes healed with scar formation in most cases of myringotomized Streptococcus pneumoniae type 3 infection and deposition of sclerotic plaques was observed by day 14. Otomicroscopically visible myringosclerosis was not found after non-typeable Haemophilus influenzae induced acute otitis media neither in myringotomized nor in non-myringotomized animals. We conclude that Streptococcus pneumoniae type 3 provokes a severe clinical course of acute otitis media that healed with scarring and myringosclerosis formation in the tympanic membrane. Clinically visible myringosclerosis develops after middle ear infection caused by Streptococcus pneumoniae type 3, but not in cases caused by non-typeable Haemophilus influenzae.