Acanthamoeba genotypes T3 and T4 as causative agents of amoebic keratitis in Mexico

Abstract

Free-living amoebae (FLA) are widely distributed worldwide. Some genera included in this group act as opportunistic pathogens causing fatal encephalitis and Acanthamoeba keratitis (AK), a sight-threatening infection of the cornea associated with the use of soft contact lenses that could even end in blindness if an early diagnosis and treatment are not achieved. Furthermore, the numbers of AK cases keep rising worldwide mainly due to an increase of contact lens wearers and lack of hygiene in the maintenance of lenses and their cases. In Mexico, no cases of AK have been described so far although the isolation of other pathogenic FLA such as Naegleria fowleri and Balamuthia mandrillaris from both clinical and environmental sources has been reported. The present study reports two cases of Acanthamoeba keratitis diagnosed in two patients admitted to the Hospital "Luis Sánchez Bulnes" for Blindness Prevention in Mexico City, Mexico. Corneal scrapes and contact lenses were checked for the presence of Acanthamoeba strains in both patients. Strains were axenized after initial isolation to classify at the genotype level. After sequencing the diagnostic fragment 3 (DF3) region located on the 18S ribosomal DNA (rDNA) gene of Acanthamoeba, genotype T3 and genotype T4 were identified in clinical case 1 and 2, respectively. To our knowledge, these are the first reported cases of AK in Mexico in the literature and the first description of Acanthamoeba genotypes T3 and T4 as causative agents of amoebic infection.

Isolation of Acanthamoeba T5 from Water: Characterization of Its Pathogenic Potential, Including the Production of Extracellular Vesicles

“…Some cases of pulmonary and cutaneous manifestations have also been reported [2,3]. Genotype T4 is Pathogens 2020, 9, 144 2 of 16 responsible for 90% of these clinical cases, while the rest of them are produced mostly by genotypes T2, T3, T6, T11, T13 and T15 [4][5][6][7][8].…”

Virulent T4 Acanthamoeba causing keratitis in a patient after swimming while wearing contact lenses in Southern Brazil

“…During the 1980s, a dramatic upsurge in the incidence of this condition was observed among contact lens wearers, subsequently acknowledged as being associated with the use of contact lenses (Hirst et al 1984;Moore et al 1985;Mutoh et al 2010). Typically, only one eye is affected, although some cases of bilateral AK have been reported in the literature (Wilhelmus et al 2008;Lorenzo-Morales et al 2013;Omaña-Molina et al 2016).…”

“…Accordingly, awareness should be raised when suspected herpetic keratitis does not respond to antiviral therapy (Page and Mathers 2013;Lorenzo-Morales et al 2015;Omaña-Molina et al 2016). Most AK cases are initially misdiagnosed as herpetic keratitis or, less frequently, as bacterial or fungal keratitis because AK signs and symptoms may be nonspecific (Hsieh and Dornic, 1989).…”

“…Twenty different Acanthamoeba genotypes have been established based on sequence variation, namely T1-T12 (Stothard et al 1998), T13 (Horn et al 1999), T14 (Gast 2001), T15 (Hewett et al 2003), T16 (Corsaro 2010), T17 (Nuprasert et al 2010), T18 (Qvarnstrom et al 2013), T19 (Magnet et al 2014), and T20 (Corsaro et al 2015). T4 is the most abundant of these genotypes in the environment and includes many pathogenic strains, which have been associated with neurological and eye diseases (Lorenzo-Morales et al 2015;Omaña-Molina et al 2016).…”

Clinical course of Acanthamoeba keratitis by genotypes T4 and T8 in Hungary

“…or in case of corneal trauma. AK is mainly caused by isolates with T4 genotype [8][9][10]; however, T2, T3, T5, T6, T8, T9, T11, T13, and T15 genotype species have also been identified in patients with AK, as shown in Table I [11][12][13][14][15][16][17][18].…”