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ABSTRACT |
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INTRODUCTION |
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At least eight species of Acanthamoeba have been implicated in human infections: A. astronyxis, A. castellanii, A. culbertsoni, A. polyphaga, A. hatchetti, A. rhysodes, A. lugdunensis, A. palestinensis, A. griffini, and A. quina.1,2
Although Acanthamoeba keratitis may result from accidental eye trauma, most cases are associated with contact lens wearers, with soft contact lenses having the highest risk. More than 90% of cases of Acanthamoeba keratitis in Great Britain between 1992 and 1996 were attributed to contact lens wear.3 This is because the parasite thrives in contact lens cases, contaminated cleaning solution, and on the lens itself.
We present a case of Acanthamoeba keratitis in an adult from Kingston, Jamaica.
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CASE REPORT |
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On clinical examination, her best-corrected visual acuity was 6/12 and 6/18 in her right and left eye, respectively. The lids were edematous, and both conjunctivae were hyperemic and edematous. Her right cornea had a dendritiform ulcer with a surrounding stromal infiltrate and there was perineural infiltration superiorly. The left cornea had punctate epithelial involvement only. A few cells were seen in her right anterior chamber, and both pupils were iatrogenically dilated. The remainder of the examination was essentially normal.
Scrapings from her right cornea, the contact lens cases, and both lenses were sent to the microbiology laboratory for analysis. Multiple bacteria were isolated, and Acanthamoeba was visualized after trichrome staining of material from the corneal scraping. The polymerase chain reaction (PCR) was used to identify the species of Acanthamoeba that was isolated. Heavy mixed growth of Acinetobacter spp., Chryseo-bacterium spp., and Serratia marcescens was isolated. The latter two organisms were resistant to amoxicillin clavulanic acid and ampicillin, while all were sensitive to amikacin, ciprofloxacin, ceftazidine, cotrimoxazole, and gentamicin.
PCR was carried out using the method of Vodkin and others.4 Briefly, two different Acanthamoeba strains from the American Type Culture Collection (ATCC) were used as the positive control. Acanthamoeba isolates from the contact lens storage cases were cultivated on 2% non-nutrient agar plates at 25°C after filtration using a vacuum manifold system fitted with a filtration membrane of 0.45 µm (Millipore, Bedford, MA). DNA was extracted from the cultured amoebae and PCR performed using a genus-specific primer pair designed by Vodkin and others4 and species-specific primers designed by Ortega-Rivas and others.5,6 Amplifications were performed, essentially as previously described.5,6 PCR analysis revealed that the infecting species was Acanthamoeba polyphaga (Figure 1
).
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During the next 4 months, her right cornea showed slow regrowth of epithelium with severe scarring and vascularization. She has also developed cortical lens opacification and elevated intraocular pressures in that eye. Her left cornea and media have remained clear. The antimicrobial agents were eventually discontinued, and she was retained on antiglaucoma and lubricating drops only. She is awaiting penetrating keratoplasty and cataract surgery, which was expected to take place 6 to 12 months post eradication of the organism. In the meantime, she is being followed for recurrence of Acanthamoeba by clinical observation and laboratory workup.
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DISCUSSION |
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The patient was particularly at risk for amoebic keratitis because of her habit of not removing her lens while having a shower or swimming as recommended. It is unknown whether she used standard lens cleaning solution for the maintenance of her lenses. Amoebic keratitis caused by Acanthamoeba is associated with tap water use in contact lens care and swimming with the lens in place.8–10 Furthermore, infections are associated with the use of homemade saline solutions, poor contact lens hygiene, and corneal abrasions.11–13 Acanthamoeba has been reported from tap water, swimming pools, physiotherapy pools, lakes, ponds, and soils.2 It is therefore crucial that contact lens wearers (especially those with soft lenses) avoid contact with tap water and other sources of infection. The patient traveled throughout Jamaica and reported swimming in several pools and using water from the Kingston municipal water supplies and well water sources in the rural areas. However, she was not known to use untreated water for domestic and recreational purposes.
Acanthamoeba spp. are among the most common free-living protozoa and have been reported from soil, dust, air, natural and treated water, seawater, domestic tap water, hospitals and dialysis units, eyewash stations, and contact lens cases among other sites.2,14,15 Among these are eight species that are known to cause keratitis in the United States.
Infections are thought to begin with contamination of contact lens storage cases with Acanthamoeba from household water supplies. Subsequent contaminated contact lenses act as the vehicle to reach and adhere to the corneal epithelium.2,11,12 In the case under review, keratitis was initially thought to be of bacterial origin. However, the bacteria isolated are not associated with dendritiform lesions, and the infection did not respond after the use of antibiotics to which the organisms were sensitive. Furthermore, the course of the disease is in keeping with Acanthamoeba infection, especially the reemergence of disease in the eye after treatment. This signals a new wave of trophozoites in the absence of antiparasitic therapy.
This case serves as a illustration that Acanthamoeba is an emerging cause of severe disease and that at least one species associated with severe keratitis is endemic in the Caribbean.
Received September 2, 2004. Accepted for publication January 26, 2005.
Acknowledgments: The American Committee on Clinical Tropical Medicine and Travelers’ Health (ACCTMTH) assisted with publication expenses.
* Address correspondence to John F. Lindo, Department of Microbiology, University of the West Indies, Kingston, Jamaica. E-mail: john.lindo{at}uwimona.edu.jm 
Authors’ addresses: Zoe Wynter-Allison, Donovan Calder, Kraig Radlein, and John F. Lindo, University of the West Indies, Kingston, Jamaica. Jacob Lorenzo Morales and Antonio Ortega-Rivas, University of La Laguna, La Laguna, Tenerife, Canary Islands, Spain.
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This article has been cited by other articles:
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  C. M. Martin-Navarro, J. Lorenzo-Morales, M. G. Cabrera-Serra, F. Rancel, N. M. Coronado-Alvarez, J. E. Pinero, and B. Valladares The potential pathogenicity of chlorhexidine-sensitive Acanthamoeba strains isolated from contact lens cases from asymptomatic individuals in Tenerife, Canary Islands, Spain J. Med. Microbiol., November 1, 2008; 57(11): 1399 - 1404. [Abstract] [Full Text] [PDF]
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