Bacterial Behaviour in Middle Ear Effusion Material: AnIn VitroStudy

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Abstract
Known numbers (CFU/ml) of middle ear pathogens (S. pneumoniae, H. influenzae, M. catarrhalis, S. aureus and β-haemolytic streptococci group A) and non-pathogens (α-haemolytic S. mitis) were inoculated into one end of a micropipet containing a 35 mm long pillar of culture-negative middle ear effusion. the micropipets with the effusion/bacterial suspension were incubated at 37°C and kept at various inclinations to the horizontal plane (15°, 30° and –75°). All S. aureus, M. catarrhalis, α- and β-haemolytic streptococci isolates examined survived in this medium for 18 h. the majority of α and β-haemolytic streptococci isolates penetrated the MEE, irrespective of the inclination of the micropipet, whereas the number of 5. pneumoniae (p < 0.01) and H. influenzae (p = NS) isolates penetrating the substrate increased when the micropipets were inclined at –75o to the horizontal. None of the S. aureus and M. catarrhalis isolates penetrated the MEE pillar during the incubation. the present in vitro study demonstrated that MEE possesses an antibacterial property and is able to selectively hinder bacterial penetration.