CAPNOCYTOPHAGA KERATITIS - A CLINICOPATHOLOGICAL STUDY OF 3 PATIENTS,INCLUDING ELECTRON-MICROSCOPIC OBSERVATIONS

Background: Histopathologic studies of this unusual keratitis caused b y Capnocytophaga species have not been reported previously. Methods: T he authors report the light microscopic and ultrastructural findings o f three patients with a distinctive necrotizing keratitis caused by an anaerobic gramnegative bacillus. In three patients, ages 19, 81, and 91 years, a necrotizing stromal keratitis developed; two of these pati ents had a previous penetrating keratoplasty for pseudophakic bullous keratopathy. The first patient did not have ocular surgery previously and was treated initially for presumed Acanthamoeba keratitis. Results : By light microscopy, all three keratectomy specimens were strikingly similar and showed a necrotizing and/or suppurative stromal keratitis displaying myriad slender, fusiform, gram-negative bacilli located an terior to Descemet's membrane and extending into the deep corneal stro ma, assuming a ''picket fence'' appearance. Cultures of the cornea in case 1 grew Capnocytophaga ochracea. For the remaining two patients, a diagnosis presumptively was made based on characteristic histopatholo gic features. Results of electron microscopic examination showed numer ous bacilli that were mostly extracellular; occasional organisms were phagocytosed by macrophages. Conclusion: The histopathologic features of Capnocytophaga keratitis are unique; therefore, a presumptive diagn osis can be made based on the morphology and location of the bacilli i n the keratectomy specimens. To the authors' knowledge, this is the fi rst study describing the typical histopathologic and electron microsco pic findings of Capnocytophaga keratitis.