Hsin-Chiung Lin MD Department of Ophthalmology Chang Gung Memorial Hospital, Chang Gung University School of Medicine 5, Fu-Hsing Street Kweishan, Taoyuan 333 Taiwan Tel: + 886 3 328 1200 (ext. 8666) Fax: + 886 3 328 7798 Email: email@example.com
Purpose: Acanthamoeba and fungal keratitis are rare ocular infections. We report cases of combined Fusarium and Acanthamoeba keratitis and the clinical course of medical treatment.
Methods: We reviewed the medical records of patients treated for culture-proven Acanthamoeba keratitis at a referral centre, during 2001−2006.
Results: Eleven consecutive patients were treated for culture-proven Acanthamoeba keratitis during the 5 years, two of whom had combined fungal infections. A 29-year-old man presented with ground-glass corneal oedema and epitheliopathy caused by contact lens use. The other patient, a 7-year-old girl, had eye trauma that led to a feathery corneal infiltrate. Both cases were treated with topical 0.02% polyhexamethylene biguanide (PHMB), 0.1% propamidine, 1% clotrimazole and 5% natamycin. Therapeutic keratoplasty was not required in either case.
Conclusions: Timely identification of the pathogen, with repeated culture and smear if necessary, as well as adequate dosage to prevent recurrence is highly recommended in order to preclude the need for therapeutic penetrating keratoplasty.
Acanthamoeba and fungal keratitis are relatively rare corneal infections that may respond poorly to medical therapy. Combined infection with these two pathogens is even rarer (Gussler et al. 1995; Tien & Sheu 1999; Froumis et al. 2001; Rumelt et al. 2001;Babu & Murthy 2007) . Contact lens wear is an established risk factor for Acanthamoeba keratitis. Verhelst et al. (2006) reported Acanthamoeba keratitis as second to Pseudomonas as a cause of contact lens-related corneal ulcers. The earliest signs of Acanthamoeba infection are at the epithelial level, with patchy oedema, microcysts and epithelial haze. These symptoms cause an irregular dendritiform ulceration, which is often misdiagnosed as keratitis caused by herpes simplex virus. Stromal findings, which occur later, include single or multiple stromal infiltrates and nummular keratitis. Ring infiltrates or satellite lesions usually suggest advanced disease. Effective medical treatment depends on early diagnosis (Bacon et al. 1993). Treatment regimens have varied from the biguanides polyhexamethylene biguanide (PHMB) and chlorhexidine, to the diamide propamidine, the aminoglycoside neomycin and the antifungal clotrimazole. The drugs have been used in different combinations, with varying degrees of success. Poor outcomes after therapeutic penetrating keratoplasty (TPK) for eradication of Acanthamoeba keratitis (Ficker et al. 1993) have made medical therapy even more significant.
Fungal keratitis often involves a history of trauma with vegetable matter or chronic ocular surface disease. Fusarium is common in warmer climates (Rosa et al. 1994) and the agricultural community, where it is generally found in organic matter such as plants and soil and represents normal flora for rice, beans and soybeans. The standard medical treatment for Fusarium fungal keratitis is frequent use of natamycin 5% drops, but any delay in diagnosis usually leads to TPK (Lin et al. 2005).
Diagnosis of mixed infection is often delayed and TPK is frequently required to re-establish integrity and eliminate the infectious process. The purpose of this study was to investigate the efficacy of medical treatment in combined infections.
Materials and Methods
The medical records for cases of Acanthamoeba keratitis treated at Chang Gung Memorial Hospital between January 2001 and December 2006 were retrospectively reviewed. Informed consent was obtained from patients according to the tenets of the Declaration of Helsinki. Corneal scrapings and contact lens case solutions, if available, were sent for culture and smears of bacteria, fungi and Acanthamoeba, on chocolate, 5% sheep blood, anaerobic blood agar, inhibitory mould agar (IMA), IMA supplemented with chloramphenicol and gentamicin (ICG) agar, and non-nutrient agar plates overlaid with Escherichia coli. External eye photographs were documented weekly and re-culture was performed in cases of progression or poor medical response after the cessation of empiric topical antibiotics for 24 hours. Information obtained from the medical records included age, sex, predisposing factors, prior diagnosis and treatment, complications and visual outcome.
Prognostic factors mainly affected the necessity for TPK in the acute infectious status. There were 11 cases of culture-proven Acanthamoeba keratitis, 191 cases of fungal corneal infection, and two of Acanthamoeba keratitis combined with fungal infection that were treated with medication alone. Seven Acanthamoeba keratitis patients underwent surgery other than diagnostic biopsy. These included four TPK procedures, two amniotic membrane transplantations, and one evisceration (Table 1).
In June 2003, a 29-year-old man, who had previously worn soft contact lenses, presented with pain, redness and decreased visual acuity (VA) in the right eye. He reported no home-made saline or tap water usage, nor did he wear the lenses overnight. He had been treated in another clinic with topical norfloxacin, topical steroids and acyclovir ointment for 3 weeks. The patient was then transferred to our hospital, where slit-lamp examination revealed diffuse coarse punctate keratitis, keratic precipitates, ground-glass oedema and infiltration of the stromal inflammatory cells. His best corrected visual acuity (BCVA) was 0.2. Corneal scraping and analysis of the solution in his contact lens case revealed the presence of Acanthamoeba.
Polyhexamethylene biguanide (0.02% PHMB; Leiter’s Pharmacy, San Jose, CA, USA) solution was instilled every hour around the clock. A localized infiltrate with endothelial plaque occurred in the inferior temporal cornea 10 days later (Fig. 1) and VA dropped to 0.01. Repeat smears and cultures were performed on the new lesion, which revealed hyphae in the smear, whereas the culture grew Fusarium species. Topical 5% natamycin and 0.02% PHMB solution were instilled every hour and 0.1% propamidine and 1% clotrimazole (Leiter’s Pharmacy) solution was added 13 days later.
The applications of PHMB, propamidine and clotrimazole were gradually tapered over the following month according to the improved corneal condition, and finally discontinued 4 months later. Natamycin was discontinued after 1.5 months. The subject’s BCVA at 6 months was 1.0.
In December 2003, a 7-year-old girl presented with pain and redness in her right eye after a foreign body struck it at a school reconstruction site. She went to a local clinic, where ciprofloxacin and neomycin solution every 3 hours was prescribed. The corneal ulcer progressed in the following week and she was referred to our hospital.
Visual acuity in her right eye was 0.1 and slit-lamp examination revealed central stromal infiltrates with feathery margins (Fig. 2A). Samples for smears and cultures were taken and topical cefazolin (25 mg/ml) and amikacin (25 mg/ml) were administered every hour around the clock. After 5 days of treatment, the feathery infiltrates were still progressing and natamycin solution was started hourly. Re-cultures of the lesion, including Acanthamoeba, were performed. However, hypopyon, endothelial plaque and a strong anterior chamber reaction appeared 3 days later.
Initially the culture grew Fusarium solani. The re-culture revealed Acanthamoeba cysts from corneal scraping with haematoxylin and eosin staining. Hourly treatment with PHMB, propamidine and clotrimazole was started. The hypopyon disappeared within 2 weeks, the stromal infiltrates abated and corneal neovascularization formed gradually. The patient was discharged after 1 month. Her medication was adjusted to PHMB hourly, and clotrimazole and natamycin, alternately, administered every 2 hours.
However, 1 month after discharge, the stromal infiltrates deteriorated and the hypopyon reappeared. The patient reported that she often missed her eyedrop instillations at home. She was re-admitted and received intracameral amphotericin B injection (Kuriakose et al. 2002;Yilmaz et al. 2007) in addition to topical anti-amoebic and antifungal medications. The hypopyon and corneal infiltrates decreased gradually over the following month and neovascularization developed (Fig. 2B).
The medications were gradually tapered under regular follow-ups and were subsequently discontinued after 4 months. Two years later, the subject’s BCVA was 0.01 as a result of central stromal scarring and neovascularization.
Of the six cases of combined Acanthamoeba and fungal keratitis reported in the medical literature, five (Gussler et al. 1995; Tien & Sheu 1999; Froumis et al. 2001) (Table 2) were diagnosed with Acanthamoeba keratitis before fungi were identified in the corneal buttons after TPK. In the sixth patient (Rumelt et al. 2001), Acanthamoeba and fungal co-infection were noted during a second corneal scraping 15 days after the eye trauma had occurred. However, medications were unable to halt the infection and TPK was indicated for cornea perforation. Successful medical treatment of Acanthamoeba keratitis as a result of early diagnosis has been reported (D’Aversa et al. 1995; Azuara-Blanco et al. 1997). Poor response to medical treatment often leads to TPK (Illingworth et al. l996; Wang et al. 1997). Confocal microscopy provides in vivo views of the cornea and delineates both the trophozoite and cyst. The double-walled cysts are particularly prominent and radial keratoneuritis can be appreciated, providing an adjunctive modality for early diagnosis (Babu & Murthy 2007). To the best of our knowledge, this study describes the first reported culture-proven cases of medical treatment for combined Acanthamoeba and fungal keratitis.
Table 2. Reported spectrum of corneal co-infection with Acanthamoeba and fungus.
The unfavourable results reported of combined fungal and Acanthamoeba infection may be attributed to several factors. Firstly, both pathogens are resistant to initial empirical antimicrobial agents. Secondly, in mixed infections, Acanthamoeba may progress faster because the fungi may serve as nutrients for the Acanthamoeba. Studies on contact lens cases contaminated with Acanthamoeba have demonstrated that the presence of bacteria and fungi may be an important factor in the survival and growth of Acanthamoeba. (Donzis et al. 1989; Trevor et al. 1995).
Acanthamoeba are ubiquitous protozoa that exist in two forms. Under unfavourable conditions, trophozoites transform into cysts that are resistant to extremes of temperature, pH and desiccation (Aksozek et al. 2002). Cysts are difficult to kill, which is one reason why this infection is so hard to eradicate. Only one class of medications is known to have cystocidal activity, the biguanides. Polyhexamethylene biguanide has been shown to kill both the trophozoite and cyst without toxic effects to the healing epithelium (Larkin et al. 1992). Some reports have recommended the combined use of propamidine and polymyxin B/neomycin/gramicidin (Neosporin), or the use of propamidine combined with one of the biguanides or clotrimazole as primary therapy.
Some anti-amoebic drugs may have antifungal activity, such as PHMB, which has been shown to inhibit Fusarium keratitis (Fiscella et al. 1997). Clotrimazole, a synthetic imidazole derivative, is an antifungal agent that has been shown to have an excellent effect on Acanthamoeba keratitis (Driebe et al. 1988), but in Fusarium keratitis, a combination with a polyene derivative is suggested (Mselle 2001).
Fungal keratitis is characteristically slow-growing and early cessation of antifungal medication usually leads to recrudescence, and a delay in diagnosis often leads to blindness (Dursun et al. 2003). The risk of activation of dormant cysts in Acanthamoeba infections can lead to patient relapse following apparently effective treatment. With anti-amoebic and antifungal medications, clinical signs appear to worsen during the first few days of therapy and improvement may not be evident until 1–2 weeks have elapsed. In general, therapy should be continued for at least 3–4 months to eradicate viable cysts or fungi in the deep stroma (O’Day & Head 2000). Both Acanthamoeba and fungal keratitis are rare, but they represent infections of the cornea that can potentially cause blindness. Early diagnosis and adequate dosing is essential to prevent recourse to TPK.