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Keratitis
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Contact lens wear is a well-known risk factor for Pseudomonas aeruginosa and Acanthamoeba keratitis and is increasingly becoming an important risk factor for mycotic keratitis. Water exposure is also a risk factor for Acanthamoeba keratitis. Trauma is the main predisposing factor for keratitis due to filamentous fungi such as Aspergillus and Fusarium and is most often seen in young males doing outdoor work or working in agriculture. Other risk factors are previous ocular surgery, ocular surface disease and previous use of corticosteroids. Humidity, rainfall and wind may also increase risk of infection. Systemic or local defect is a risk factor for Candida keratitis. Local defects (i.e. insufficient tear secretion or defective eyelid closure) or systemic conditions (i.e. diabetes mellitus, immunosuppression) predispose to infection with Candida spp.
Corneal Ulcers and Contact Lens Keratitis
Published in Amy-lee Shirodkar, Gwyn Samuel Williams, Bushra Thajudeen, Practical Emergency Ophthalmology Handbook, 2019
Acanthamoeba keratitis: Symptoms disproportionate to the clinical signs is characteristic of acanthamoeba keratitis due to irritation of the corneal nerves and hence usually missed in the early assessment. There will be history of contact lens wear with poor hygiene or contact with water. Clinical signs can be very subtle with irregular corneal surface and punctate staining. Acanthamoeba can also present as a dendritic staining pattern, and hence one should always rule out acanthamoeba keratitis when a contact lens wearer presents with a dendritic ulcer. Gradual enlargement and coalescence of the infiltrates lead to a ring infiltrate and stromal infiltrate can lead to corneal melt. Perineural infiltrates are pathognomonic and are visible as white lines corresponding to inflammation of the corneal nerves (see Figure 5.5). Acanthamoeba related ulcers can be differentiated from HSV because they are raised, rather than ulcerated, and do not necessarily stain with fluorescein.
Acanthamoeba castellanii
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
AK commonly occurs in contact lens wearers. A traumatic injury to the corneal epithelium occurs before the cornea is invaded by Acanthamoeba spp. Affected individuals often complain of redness of the eyes, ocular pain, blurred vision, photophobia, irritation in the eye, and excessive lacrimation (Table 49.2) (9,23). As these symptoms resemble other common eye infections, an early diagnosis is often missed, which is essential for early treatment of Acanthamoeba keratitis. These symptoms progress to appearance of ring-like pus formation on the sclerocorneal junction. Untreated AK leads to uveitis, and corneal damage and blindness (Figure 49.2a) (5,9). Skin infections in immunocompetent individuals are self-limiting, while in immunocompromised patients they appear as broad ulcers with added bacterial infections (Figure 49.2b and c).
Acanthamoeba Keratitis: an update on amebicidal and cysticidal drug screening methodologies and potential treatment with azole drugs
Published in Expert Review of Anti-infective Therapy, 2021
Brian Shing, Mina Balen, James H. McKerrow, Anjan Debnath
Acanthamoeba spp. are often associated with Acanthamoeba keratitis, a severe corneal infection. This infection typically occurs in contact-lens wearers, but it can also occur in patients with recent corneal trauma. Most keratitis infections are caused by the T4 genotype. Clinical testing has been performed on strains of this genotype, taken from the affected patients [7]. While effective therapies, such as topical combinations of chlorhexidine gluconate and polyhexamethylene biguanide (PHMB), exist to treat Acanthamoeba keratitis, the parasite can encyst in the ocular tissue to resist current standard-of-care therapies and lead to recurrent keratitis. As such, discovering and identifying therapeutics that are effective against both stages of the parasite would be critical to reducing Acanthamoeba keratitis recurrence and improving existing therapies. This review will discuss current treatments and advances in screening and identifying novel therapeutics for Acanthamoeba keratitis treatment.
Curcuma longa ethanol extract and Curcumin inhibit the growth of Acanthamoeba triangularis trophozoites and cysts isolated from water reservoirs at Walailak University, Thailand
Published in Pathogens and Global Health, 2020
Watcharapong Mitsuwan, Chooseel Bunsuwansakul, Theodore Ebenezer Leonard, Sawanya Laohaprapanon, Kruawan Hounkong, Kingkan Bunluepuech, Chalermpon Kaewjai, Tooba Mahboob, Chandramathi Sumudi Raju, Mahaveer Dhobi, Maria de Lourdes Pereira, Muhammad Nawaz, Christophe Wiart, Abolghasem Siyadatpanah, Roghayeh Norouzi, Veeranoot Nissapatorn
Free-living amebae belonging to the genus Acanthamoeba are protozoa ubiquitously in nature such as water and soil. The protozoa are causative agents of several diseases including granulomatous amebic encephalitis [1–3] and amebic keratitis [4]. The occurrence of Acanthamoeba keratitis in contact lens users can cause severe vision loss and complete blindness [5]. In addition, the infection caused by the organism is severe in immunocompromised patients. The parasite has two stages of growth including trophozoite and cyst. Trophozoite is a vegetative amoeba form moving by amoeboid locomotion. Cyst form is dormant stage that survives in harsh environment conditions such as lack of nutrients. Acanthamoeba cysts are classified into three groups including astronyxids, polyphagids, and culbertsonids [6]. The cysts contain two strong layers of cyst wall including ectocyst and endocyst walls. Acanthamoeba cysts have been reported to resist to antimicrobial substances [7,8]. Therefore, the treatment of Acanthamoeba infections is difficult due to its double-walled cyst layers.
Diagnostics and management approaches for Acanthamoeba keratitis
Published in Expert Opinion on Orphan Drugs, 2020
Nóra Szentmáry, Lei Shi, Loay Daas, Berthold Seitz
In the last few years additional techniques have been described with potential in the diagnosis of Acanthamoeba keratitis. In 2014, phospholipid classes of A. castellanii protozoa that could serve as specific biomarkers have been described [13]. Maschio et al. reported on successful diagnostics using proteomic analysis of soluble and surface-enriched proteins from Acanthamoeba castellanii trophozoites. Their analysis allowed the identification of proteins with potential for immunodiagnostic assays [14]. In 2016, Del Chierico et al. revealed the capability of the MALDI-TOF MS Biotyper to identify and genotype the Acanthamoeba strains [15]. Nevertheless, these diagnostic methods are still only available in a few single centers around the world.