EXPERIMENTAL OTITIS-MEDIA INDUCED BY COAGULASE-NEGATIVE STAPHYLOCOCCUS AND ITS L-FORMS

In a previous study, we found 15% L-forms of bacteria (predominately c oagulase negative staphylococci (CNS)) in ears which gave negative cul tures by conventional methods. In this study, we used an animal model to test whether CNS and its L-forms can be pathogenic and whether L-fo rms have a crucial role in the tendency to secretory otitis media (SOM ). We inoculated the tympanic bullas of guinea pigs, in 2 groups, with CNS and its L-forms (revertant forms). We observed that both CNS and its L-forms had the capability of causing infection. However. it was m ilder for the L-forms than CNS. We clearly noticed that on day 30 60% of the ears inoculated with L-forms had effusion and/or retraction of the tympanic membrane. These ears were histopathologically characteriz ed by hypertrophied pseudostratified epithelium or stratified squamous epithelial metaplasia. The ears inoculated with the original form of CNS had only 16.66% effusion. On day 60 we observed similar findings. Thus, it might be proposed that L-forms could be responsible for chron ic irritation to middle ear mucosa leading to SOM.