An unusual case of Acanthamoeba Polyphaga and Pseudomonas Aeruginosa keratitis
© Hong et al.; licensee BioMed Central Ltd. 2014
Received: 4 December 2013
Accepted: 18 May 2014
Published: 3 June 2014
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A 56-year-old woman with a history of disposable soft contact lens wear was referred to our university eye center for a corneal ulcer. Based on the microbial culture, the initial diagnosis was bacterial keratitis, which was unresponsive to topical fortified antibiotics. The patient was then examined using in vivo confocal microscopy, which revealed Acanthamoeba infection. This case emphasizes the need to suspect Acanthamoeba infection in soft contact lens wearers who present with progressive ulcerative keratitis or progressively worsening corneal ulcers that are not responsive to the usual antimicrobial therapy. It is also important to consider the possibility of a coinfection with bacterial and Acanthamoeba species.
KeywordsContact lens Acanthamoeba species Pseudomonas aeruginosa
Acanthamoeba keratitis (AK) is a destructive disease characterized by significant visual morbidity, and prompt diagnosis is important for a good visual outcome. Like AK, Pseudomonas aeruginosa keratitis usually progresses rapidly and presents with suppurative stromal infiltrate and marked mucopurulent exudate. It should be noted that there is a possibility, in theory, that AK can develop in eyes with advanced bacterial keratitis. Coinfections with other microorganisms have been reported in patients with culture-proven AK [1, 2]. However, the exact clinical characteristics of such mixed infections remain unknown. Few publications have addressed this issue. Herein, we report an unusual case of coinfection with Acanthamoeba polyphaga and Pseudomonas aeruginosa as causes of corneal keratitis in a contact lens wearer in Shanghai.
Upon confirmation of the presence of the Acanthamoeba species via the IVCM examination, an additional treatment regimen of topical 0.2% metronidazole and 0.02% polyhexamethylene biguanide drops given hourly was begun. Over the next two weeks, the stromal infiltrate showed slight improvement, and after 3-months treatment, the Acanthamoeba cysts could not be detected by IVCM examination. Five months after that, the patient underwent combined phacoemulsification and viscogoniosynechialysis due to the presence of peripheral synechiae and a cataract. The topical treatment was continued for a prolonged period, tapering off over 12 months. At present, the patient’s best-corrected vision is 1/20. The left eye shows no signs of inflammation (Figure 1C) or Acanthamoeba infection (Figure 1F) using IVCM but there are a few superficial blood vessels in the peripheral cornea. There is also a large, central corneal scar obscuring the visual axis. The intraocular appearance is normal, and ultrasonography indicates a normal posterior segment. The patient is currently awaiting a corneal transplantation.
This case emphasizes the need to suspect Acanthamoeba infection in soft contact lens wearers who present with progressive ulcerative keratitis and in progressively worsening corneal ulcers that are unresponsive to the usual antimicrobial therapy. It is also important to consider the possibility of a bacterial coinfection with the Acanthamoeba species. The exact reason why this combined inflammation occurred in our patient is still unknown. However, inquiries should be made regarding the patient’s contact lens cleaning history and the potential contamination of the contact lenses. Previous reports have revealed the presence of Pseudomonas aeruginosa and Acanthamoeba in the microbiological cultures obtained from contact lenses [1, 5, 6]. In addition, previous studies have shown that almost 50% of Acanthamoeba-positive eyes had cultures that were positive for bacteria as well [2, 7]. A bacterial infection capable of supporting amoebic growth might play an important role in the pathogenesis of AK . In light of these observations, it is advisable to use real-time polymerase chain reaction or IVCM in the early detection and treatment of AK. This case emphasizes the importance of suspecting Acanthamoeba infection in at-risk patients.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.
The authors were supported by grants from the Key Clinic Medicine Research Program, the Ministry of Health, China (2010–2012); the National Science and Technology Research Program, the Ministry of Science and Technology, China (2012BAI08B01); the National Natural Science Foundation of China (81170817, 81200658); and the Scientific Research Program, Science and Technology Commission of Shanghai Municipality, Shanghai (13430720400, 134119a8800, 13430710500). The sponsor or funding organization had no role in the design or conduct of this research.
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