Anaerobic Capnocytophaga corneal ulcer

Capnocytophaga keratitis. A clinicopathologic study of three patients, including electron microscopic observations

BACKGROUND

Histopathologic studies of this unusual keratitis caused by Capnocytophaga species have not been reported previously.

METHODS

The authors report the light microscopic and ultrastructural findings of three patients with a distinctive necrotizing keratitis caused by an anaerobic gram-negative bacillus. In three patients, ages 19, 81, and 91 years, a necrotizing stromal keratitis developed; two of these patients 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 anterior to Descemet's membrane and extending into the deep corneal stroma, 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 histopathologic features. Results of electron microscopic examination showed numerous bacilli that were mostly extracellular; occasional organisms were phagocytosed by macrophages.

CONCLUSION

The histopathologic features of Capnocytophaga keratitis are unique; therefore, a presumptive diagnosis can be made based on the morphology and location of the bacilli in the keratectomy specimens. To the authors' knowledge, this is the first study describing the typical histopathologic and electron microscopic findings of Capnocytophaga keratitis.

Capnocytophaga endophthalmitis

PURPOSE

This article presents three patients with endophthalmitis associated with infection with Capnocytophaga species.

METHODS

The medical records of three patients with culture-positive Capnocytophaga endophthalmitis were reviewed. A panel of isolates of Capnocytophaga were then tested for sensitivity to third-generation cephalosporins.

RESULTS

Endophthalmitis with Capnocytophaga species developed in three patients. Infection in the setting of sepsis developed in one patient. Two other patients, one with a penetrating injury and another with keratitis in association with a corneal graft, developed mixed infection with Capnocytophaga being the predominant infecting organism by culture. Two patients recovered vision with clearance of the infection. The third patient underwent enucleation. Capnocytophaga was found to be sensitive to several of the third-generation cephalosporins. To the best of the authors' knowledge, these are the first reported cases of endophthalmitis with Capnocytophaga species.

CONCLUSION

Capnocytophaga species, previously shown to cause necrotizing keratitis, is a potential cause of endophthalmitis, either as a single organism or as part of a mixed infection.

Spontaneous ulcerative keratitis in immunocompromised patients

We studied the occurrence of ulcerative keratitis in five eyes of four patients who were examined at the University of Maryland Hospital ophthalmology clinic over a 12-month period. All were young women who were intravenous drug abusers, with no known predisposing factors for ulcerative keratitis. Two patients had acquired immunodeficiency syndrome (AIDS), one was human immunodeficiency virus (HIV)-positive, and the fourth refused HIV testing. One had a corneoscleral limbus to corneoscleral limbus keratitis; three had inferiorly located corneal ulcers (bilateral in one patient with AIDS). Corneal cultures disclosed Capnocytophaga species in the corneoscleral limbus to corneoscleral limbus keratitis. The remaining ulcers were polymicrobial; cultures of three grew Candida albicans, cultures of two grew alpha-hemolytic streptococci, cultures of two grew Staphylococcus aureus, and culture of one grew Pseudomonas aeruginosa. Treatment with topical fortified antibiotics and antifungal agents resulted in complete healing in all four inferiorly located ulcers. The corneal ulcer became perforated and the eye was eviscerated. Histopathologic analysis of the eviscerated specimen disclosed acute keratitis with necrosis and no microorganisms.

Microbial keratitis--the false negative

The investigation of presumed microbial keratitis includes microscopy and culture of corneal specimens obtained by scraping the infiltrated cornea. Routine microscopy fails to identify the infecting organism in about 15% of cases. We discuss the problems presented by 20 such eyes which required further investigation. We present a diagnostic algorithm aimed at reducing the delay in identifying the pathogen and increasing the rate of positive culture. This is important since unusual pathogens may require treatment with drugs other than the 'first line' broad spectrum combination of an aminoglycoside and a cephalosporin. The algorithm allows sequential restaining and reculturing of specimens for more thorough investigation. In addition to the use of special stains and culture conditions, it presents indications for further corneal scrapes and biopsies. Uncontrolled infection resulted in five perforations and penetrating keratoplasty was indicated in 11 cases. The visual outcome for these patients was poor with fewer than 30% achieving 6/12 acuity. The delay in diagnosis increases morbidity and this should be significantly reduced by adopting the algorithm we propose.