Assessment of genotypes, endosymbionts and clinical characteristics of Acanthamoeba recovered from ocular infection

Abstract

Introduction Acanthamoeba is an emerging pathogen, infamous for its resilience against antiprotozoal compounds, disinfectants and harsh environments. It is known to cause keratitis, a sight-threatening, painful and difficult to treat corneal infection which is often reported among contact lens wearers and patients with ocular trauma. Acanthamoeba comprises over 24 species and currently 23 genotypes (T1-T23) have been identified. Aims This retrospective study was designed to examine the Acanthamoeba species and genotypes recovered from patients with Acanthamoeba keratitis (AK), determine the presence of endosymbionts in ocular isolates of Acanthamoeba and review the clinical presentations. Methodology Thirteen culture-confirmed AK patients treated in a tertiary eye care facility in Hyderabad, India from February to October 2020 were included in this study. The clinical manifestations, medications and visual outcomes of all patients were obtained from medical records. The Acanthamoeba isolates were identified by sequencing the ribosomal nuclear subunit (rns) gene. Acanthamoeba isolates were assessed for the presence of bacterial or fungal endosymbionts using molecular assays, PCR and fluorescence in situ hybridization (FISH). Results The mean age of the patients was 33 years (SD ± 17.4; 95% CI 22.5 to 43.5 years). Six (46.2%) cases had AK associated risk factors; four patients had ocular trauma and two were contact lens wearers. A. culbertsoni (6/13, 46.2%) was the most common species, followed by A. polyphaga and A. triangularis. Most of the isolates (12/13) belonged to genotype T4 and one was a T12; three sub-clusters T4A, T4B, and T4F were identified within the T4 genotype. There was no significant association between Acanthamoeba types and clinical outcomes. Eight (61.5%) isolates harboured intracellular bacteria and one contained Malassezia restricta. The presence of intracellular microbes was associated with a higher proportion of stromal infiltrates (88.9%, 8/9), epithelial defect (55.6%, 5/9) and hypopyon (55.6%, 5/9) compared to 50% (2/4), 25% (1/4) and 25% (1/4) AK cases without intracellular microbes, respectively. Conclusions Genotype T4 was the predominant isolate in southern India. This is the second report of T12 genotype identified from AK patient in India, which is rarely reported worldwide. The majority of the Acanthamoeba clinical isolates in this study harboured intracellular microbes, which may impact clinical characteristics of AK.

A simple method for culturing Acanthamoeba from soft contact lens at a clinical laboratory of a hospital: Case report of Acanthamoeba keratitis

“…Acanthamoeba keratitis is still in association with the use of contact lenses in other countries 17 . As shown in tap water contamination with Legionella species, 12,13 Acanthamoeba species play a role as a carrier of bacteria 10 . The intracellular endosymbiosis of bacteria in Acanthamoeba species would be an underlying factor for the aggressive nature of infection in the cornea 18 …”

“…A previous study used the non-nutrient agar plate as well as the Sabouraud dextrose agar plate. 10 In summary, Acanthamoeba keratitis is an example where delayed diagnosis, topical corticosteroid use, topical treatment for herpes simplex virus keratitis prior to anti-amoebic therapy have been linked to inflammatory complications and adverse outcomes including devastating results which might lead to the extirpation of eye ball. 3,20 To avoid such adverse events, challenging culture of Acanthamoeba must be accomplished and timely diagnosis of Acanthamoeba keratitis is made.…”

“…Successful culture of Acanthamoeba is a key for making the timely diagnosis of Acanthamoeba keratitis. [8][9][10] In this study, we presented a patient with Acanthamoeba keratitis which was attributed to the use of a soft contact lens. The aim of this study is to review a culturing method for Acanthamoeba which can be done at a clinical laboratory with no special equipment in a hospital.…”

Antiamoebic Properties of Ceftriaxone and Zinc-Oxide–Cyclodextrin-Conjugated Ceftriaxone

“…Several antibiotics classes were observed to exhibit cytocidal activities against Acanthamoeba [ 9 ]. Yet, clinically it is still unclear whether antibiotics are effective as adjunct therapeutic measures against A. castellanii [ 47 , 48 ]. Accordingly, in light of the previously reported efficacy of CFT and AMPI in conjugation with ZnO and the cyclic oligosaccharide with hydrophilicity enhancing effects: CD against bacteria, we tested this nano-conjugation against A. castellanii [ 12 , 14 ].…”

Novel Anti-Acanthamoebic Activities of Irosustat and STX140 and Their Nanoformulations

“…[ 2 , 3 , 4 , 5 ]. With global warming and increased outdoor water-related activities as well as contact lens use for vision correction and cosmetics, it is expected that the number of infections due to pathogenic Acanthamoeba will continue to rise [ 5 , 6 ]. Acanthamoeba exists in two forms; an infective trophozoite form during which Acanthamoeba divides vegetatively via binary fission, and a cyst form, which is a dormant and inactive form [ 2 , 3 , 4 ].…”