Twenty-four patients with Acanthamoeba keratitis have been reported to CDC from 14 states in the last 9 months (Table 1). Although onset of illness for some patients dates to as early as 1982, most had onset of illness in 1985 or 1986. In two patients, the infected eye was enucleated; 12 patients underwent corneal transplantation.

Twenty (83%) of the patients wore contact lenses. Of these, two wore hard lenses (one hard, the other rigid gas-permeable); four wore extended-wear soft lenses; and 14 wore daily-wear soft lenses. Ten of these 20 patients cleaned their lenses with home-made saline solution prepared by mixing salt tablets with bottled, distilled, nonsterile water; four used commercially available lens-cleaning solutions followed by a tap water rinse; one used commercial bottled saline; and one cleaned lenses with tap water pumped from a private well. No lens-care information was available for four patients.

Twenty-two (90%) of the 24 patients were initially diagnosed as having corneal herpes simplex virus (HSV) infections; in the other two patients, corneal lesions were attributed to autoimmune disease. Acanthamoeba keratitis was diagnosed by examination of stained corneal scrapings or tissues (67%) and/or tissue indirect fluorescent antibody (IFA) test (52%) using species-specific antisera. Acanthamoebae were isolated from the corneal scrapings/biopsies of 17 (71%) of the patients. Three of the 17 patients' lens cases containing home-made saline solution were also cultured; all were positive for Acanthamoeba. Contact lens cases from other patients were not cultured. Patients' ages ranged from 17 years to 55 years; half were females. The right eye was affected in 13 (54%) patients and the left eye, in 11. A. castellanii was identified from nine (38%); A. polyphaga, from eight (33%); A. rhysodes, from four (17%); A. culbertsoni, from three (13%); and A. hatchetti, from one (4%). The species of Acanthamoeba was not determined for six (25%) patients. More than one species of Acanthamoeba was cultured from samples from four patients. Reported by C Newton, MD, Louisville, Kentucky; WT Driebe, Jr, MD, University of Florida, Gainesville, LR Groden, MD, G Genvert, MD, JH Brensen, PhD, University of South Florida, Tampa; AD Proia, MD, GK Clintworth, MD, M Cobo, MD, D Klein, PhD, Duke University Medical Center, Durham, P Morton, MD, Raleigh, North Carolina Dept of Human Resources; T Wolf, MD, University of Oklahoma, Oklahoma City; DB Jones, MD, RL Font, MD, M Osata, PhD, Baylor College of Medicine, Houston, MC Kincaid, University Health Science Center at San Antonio, MB Moore, MD, R Silvany, University of Texas Health Science Center at Dallas, Texas; RJ Epstein, MD, LA Wilson, MD, Emory University, Atlanta, Georgia; RA Miller, MD, P Gardner, MD, RC Tripathi, MD, DF Sahm, PhD, University of Chicago, Illinois; JS Wolfson, MD, S Foster, MD, MA Waldrom, Massachusetts General Hospital and Harvard University, Boston; CF Bahn, MD, Naval Hospital, Dept of the Navy, Bethesda, Maryland; G Rao, MD, FS Nolte, PhD, University of Rochester Medical Center, Rochester, New York; C Parlato, MD, JC Davis, PhD, Mountainside Hospital, Montclair, New Jersey, E Cohen, MD, Wills Eye Hospital and Thomas Jefferson University, Philadelphia, Pennsylvania; MJ Mannis, MD, CE Thirkill, PhD, University of California, Davis; Protozoal Disease Br, Div of Parasitic Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Members of the genus Acanthamoeba are the most common free-living amoebae in fresh water and soil. They have been isolated from brackish and sea water, airborne dust, and hot tubs. Acanthamoebae have also been recovered from the nose and throat of humans with impaired respiratory function and from apparently healthy persons, suggesting that these organisms are commonly inhaled (1). It is, therefore, not surprising that acanthamoebae may contaminate contact lenses or lens-cleaning/soaking fluids.

The first case of Acanthamoeba keratitis in the United States was reported in 1973 in a South Texas rancher with a history of trauma to his right eye (1). A. polyphaga was repeatedly cultured from his cornea, and both trophozoite and cyst forms of the organism were demonstrated in the corneal sections. Since then, 31 patients have been diagnosed in the United States (excluding those reported here). Nineteen of these 31 cases have been published (2-12); seven occurred before 1981; four occurred in 1981; one, in 1982; five, in 1983; and two, in 1984. The 24 Acanthamoeba keratitis cases described here represent a striking increase over those reported in previous years. A similar increase has been observed in the use of contact lenses during the past 5 years, from 14.5 million in 1980 to 23.1 million in 1985 (13).

Review of the 19 published cases indicates that nearly all infections were preceded by some degree of ocular trauma and/or exposure to contaminated water. Only recently has it been suggested that wearing contact lenses or using contaminated lens-cleaning/soaking solution may predipose the wearer to developing Acanthamoeba keratitis (10). Although information on contact lens use was not specified in all the published reports, at least 13 of the 19 patients were known users, and in the present report, 20 (83%) of 24 patients wore contact lenses.

Acanthamoebae are resistant to killing by freezing, dessication, a variety of antimicrobial agents, and levels of chlorine that are routinely used to disinfect municipal drinking water, swimming pools, and hot tubs (14). Recent studies indicate that thermal disinfection systems for contact lenses are superior to cold chemical disinfection in preventing the growth of Acanthamoeba (15). Although 10 of the 20 patients who wore contact lenses used home-made saline cleaning solutions, it is not known how many of them heat-sterilized the solutions before use.

Since the clinical characteristics of Acanthamoeba keratitis, especially the irregular epithelial lesions, the stromal infiltrative keratitis, and edema seen in most patients may resemble HSV keratitis, many patients are initially diagnosed and treated for this infection. Until recently, the correct diagnosis was made only after detailed histologic examination of corneal tissue removed at the time of transplantation. The following clinical features are suggestive of Acanthamoeba keratitis: (1) severe ocular pain; (2) a characteristic 360-degree or partial paracentral stromal ring infiltrate; (3) recurrent corneal epithelial breakdown; and (4) a corneal lesion refractory to the usual medications. The diagnosis can be confirmed by vigorously scraping the cornea with a swab or platinum-tipped spatula, staining the material obtained with Giemsa or trichrome stain, and examining it at 400X with a standard light microscope. In addition, some of the corneal scrapings should be cultured on non-nutrient agar seeded with Escherichia coli (1).

Medical management of Acanthamoeba keratitis is complicated by the resistance of these organisms to most of the commonly used antibacterial, antifungal, antiprotozoal, and antiviral agents. Although some patients have recently been treated successfully using ketoconazole, miconazole, and propamidine isethionate (Brolene*), penetrating keratoplasty usually has been necessary to recover useful vision (5,7-11). Further studies are needed to better estimate the true risk of infection, to improve diagnostic and treatment methods, and to evaluate the ability of different lens cleaning/soaking solutions to prevent growth of Acanthamoeba.

References

1. Visvesvara GS. Free-living pathogenic amoebae. In: Lennette EH, Balows A, Hausler, WJ Jr, Truant JP, eds. Manual of Clinical Microbiology, 3rd edition. 1980:704-8.

2. Jones DB, Visvesvara GS, Robinson NM. Acanthamoeba polyphaga keratitis and Acanthamoeba uveitis associated with fatal meningoencephalitis. Trans Ophthalmol Soc UK 1975;95:221-32.

3. Key SN, III, Green WR, Willaert E, Stevens AR, Key SN, Jr. Keratitis due to Acanthamoeba castellanii: a clinicopathologic case report. Arch Ophthalmol 1980;98:475-9.

4. Ma P, Willaert E, Juechter KB, Stevens AR. A case of keratitis due to Acanthameoba in New York, New York, and features of 10 cases. J Infect Dis 1981;143:662-7.

5. Hirst LW, Green WR, Merz W, et al. Management of Acanthamoeba keratitis. A case report and review of the literature. Ophthalmology 1984;91:1105-11.

6. Blackman HJ, Rao NA, Lemp MA, Visvesvara GS. Acanthamoeba keratitis successfully treated with penetrating keratoplasty: suggested immunogenic mechanisms of action. Cornea 1984:3:125-30.

7. Samples JR, Binder PS, Luibel FJ, Font RL, Visvesvara GS, Peter CR. Acanthamoeba keratitis possibly acquired from a hot tub. Arch Ophthalmol 1984;102:707-10.

8. Scully RE, Mark EJ, McNealy BN, et al. Case 10-1985. N Engl J Med 1985;312:634-41.

9. Cohen EJ, Buchanan HW, Laughrea P, et al. Diagnosis and management of Acanthamoeba keratitis. Am J Ophthalmol 1985;100:389-95.

10. Moore MB, McCulley JP, Luckenbach M, et al. Acanthamoeba keratitis associated with soft contact lenses. Am J Ophthalmol 1985;100:396-403.

11. Theodore FH, Jakobiec FA, Juechter KB, et al. The diagnostic

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