Diagnosis and management of Acanthamoeba keratitis

Abstract

Acanthamoeba keratitis continues to be a difficult infection to diagnose and manage. The frequency of these infections may be on the rise, most commonly associated with frequent replacement soft contact lenses. The best chance for a good outcome is based on early diagnosis, so it is important for ophthalmologists consider it in patients, especially in the contact lens wearer with suspected herpes simplex keratitis.

Acanthamoeba keratitis: improving the Scottish diagnostic service for the rapid molecular detection of Acanthamoeba species

“…However, conventional techniques to detect Acanthamoeba species may lack sensitivity, which is likely to result in the true prevalence being underestimated. The challenges of an early diagnosis are compounded by the ability of Acanthamoeba to mimic non-specific clinical symptoms of viral, bacterial and fungal ocular pathogens (Hammersmith, 2006). To add to the complexity of managing Acanthamoeba keratitis, the treatment regime is aggressive and sometimes lengthy, emphasizing the importance of a correct diagnosis to prevent unnecessary treatment being administered to those who are uninfected.…”

Reevaluation of an Acanthamoeba Molecular Diagnostic Algorithm following an Atypical Case of Amoebic Keratitis

“…Culture and direct examination are limited by poor sensitivity, the need for technical expertise, and long turnaround times, while molecular diagnostic methods offer the advantages of rapidity, sensitivity, and operator independence (5)(6)(7)(8). Several years ago, our laboratory selected the Riviere assay (11) as our molecular diagnostic approach, which appeared to offer the best possible limit of detection for acanthamoebae from clinical specimens (9,11) and was thus thought to be highly sensitive for the Acanthamoeba genus.…”

“…This infection usually occurs in the context of contact lens use, and outbreaks of AK have been linked to contact lens solutions that are inefficient in killing acanthamoebae adhering to the contact lenses during washing with amebacontaminated water, including the most recent outbreak in the United States, which affected 138 people (2) and led to the recall of several contact lens solutions and products by both the FDA and Health Canada (3,4). Delays in diagnosis have been associated frequently with poor visual outcomes and more severe clinical progression in AK (5,6). Traditional diagnostic procedures include direct microscopic examination of corneal scrapings or contact lens fluids stained with Giemsa stain, periodic acid-Schiff stain, hematoxylin and eosin, or acridine orange and culture of specimens on nonnutrient agar overlaid with Escherichia coli or Klebsiella pneumoniae; both methods are limited by poor sensitivity, operator dependence, and, in the case of culture, long turnaround times (5,6).…”

“…Delays in diagnosis have been associated frequently with poor visual outcomes and more severe clinical progression in AK (5,6). Traditional diagnostic procedures include direct microscopic examination of corneal scrapings or contact lens fluids stained with Giemsa stain, periodic acid-Schiff stain, hematoxylin and eosin, or acridine orange and culture of specimens on nonnutrient agar overlaid with Escherichia coli or Klebsiella pneumoniae; both methods are limited by poor sensitivity, operator dependence, and, in the case of culture, long turnaround times (5,6). As in all areas of clinical microbiology, molecular methods, including PCR, are quickly supplanting traditional techniques for the detection of acanthamoebae, due to superior sensitivity, standardized analytical procedures, and rapid turnaround (7)(8)(9)(10).…”

Development of an Immunochromatographic Assay Kit Using Fluorescent Silica Nanoparticles for Rapid Diagnosis of Acanthamoeba Keratitis

“…Culturing live Acanthamoeba isolates is timeconsuming, and a long incubation time is needed to confirm Acanthamoeba growth. This results in decreased sensitivity of the test and delays in starting treatment (14,18).…”