A comprehensive survey to document the presence of free-living amoebae of the genus Acanthamoeba was conducted in tap water and sea water sources related to human environments in Tenerife, Canary Islands, Spain. Acanthamoeba identification was based on the morphology of cyst and trophozoite forms and PCR amplification with a genus-specific primer pair. The pathogenic potential of Acanthamoeba isolates was characterized by temperature and osmotolerance assays and PCR reactions with two primer pairs related to Acanthamoeba pathogenesis. The results demonstrate the presence of potentially pathogenic strains in both sources. Thus, some of the amoebae in these aquatic habitats can act as opportunistic pathogens, could play a role in the diseases of aquatic organisms, and may present a risk to human health.

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In 2004, samples of tap water and of river and sea water associated with human activities were collected in Jamaica, West Indies, and checked for free-living Acanthamoeba. The morphologies of the cysts and trophozoites observed and the results of PCR-based amplifications with a genus-specific primer pair were used to identify the Acanthamoeba isolates. The potential of each isolate as a human pathogen was then evaluated using thermotolerance and osmotolerance assays and two PCR-based assays for Acanthamoeba pathogenesis. Acanthamoeba were identified in 36.1%, 26.4% and 49.6% of the tap-, river- and sea-water samples collected, respectively. Pathogenic potential was shown by 60.0% of the Acanthamoeba strains isolated from tap water, 68.4% of the strains from river water, and 40.4% of the seawater strains. Sequencing of ribosomal DNA revealed the T1, T2, T4, T5, T7, T9 and T11 genotypes. Isolates of the T4 genotype were collected from tap, rain and sea water and, as expected, exhibited the most pathogenic traits; most were osmotolerant, thermotolerant and expressing extracellular serine protease. This is the first study of the occurrence and distribution of Acanthamoeba in water in the West Indies, and the results confirm the presence of potentially pathogenic strains in Jamaica.

The resistance of Balamuthia mandrillaris to physical, chemical and radiological conditions was tested. Following treatments, viability was determined by culturing amoebae on human brain microvascular endothelial cells for up to 12 days. B. mandrillaris cysts were resistant to repeated freeze–thawing (five times), temperatures of up to 70 °C, 0.5 % SDS, 25 p.p.m. chlorine, 10 μg pentamidine isethionate ml−1 and 200 mJ UV irradiation cm−2.

Despite significant public health impact, there is no specific antiprotozoal therapy for prevention and treatment of Acanthamoeba castellanii infection. There is a need for new and efficient anti-Acanthamoeba drugs that are less toxic and can reduce treatment duration and frequency of administration. In this context a new, rapid and sensitive assay is required for high-throughput activity testing and screening of new therapeutic compounds. A colorimetric assay based on sulforhodamine B (SRB) staining has been developed for anti-Acanthamoeba drug susceptibility testing and adapted to a 96-well microtiter plate format. Under these conditions chlorhexidine was tested to validate the assay using two clinical strains of A. castellanii (Neff strain, T4 genotype [IC 4.68±0.6μM] and T3 genotype [IC 5.69±0.9μM]). These results were in good agreement with those obtained by the conventional Alamar Blue assay, OCR cytotoxicity assay and manual cell counting method. Our new assay offers an inexpensive and reliable method, which complements current assays by enhancing high-throughput anti-Acanthamoeba drug screening capabilities.

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We report the case of a 29-year-old Jamaican patient who presented with severe pain, redness, and swelling of both eyes. She was a regular soft contact lens wearer who did not maintain standard lens care. She was treated for a possible microbial/viral keratitis using topical ciprofloxacin drops, topical acyclovir ointment, and topical atropine drops. The response was inadequate, and scrapings from her cornea, contact lens cases, and both lenses revealed Acanthamoeba on microscopy, which was shown to be Acanthamoeba polyphaga using polymerase chain reaction. She was treated using chlorhexidine 0.02% hourly, ciprofloxacin every 4 hours, and atropine 1% every 12 hours, along with oral ketoconazole 200 mg twice daily with a dramatic response. However, she subsequently suffered slow corneal epithelial regrowth with severe scarring, vascularization, and cortical lens opacification and was referred for penetrating keratoplasty and cataract surgery. This is the first case of severe keratitis caused by Acanthamoeba to be reported from Jamaica and demonstrates that this emerging pathogen can be a cause of severe keratitis in the tropics.