Review of "Acanthamoeba: Biology and Pathogenesis" by Naveed Ahmed Khan

Isolation, characterization, and pathogenicity assay of Acanthamoeba and its endosymbionts in respiratory disorders and COVID-19 hospitalized patients, northern Iran

Acanthamoeba spp., are common free-living amoebae found in nature that can serve as reservoirs for certain microorganisms. The SARS-CoV-2 virus is a newly emerged respiratory infection, and the investigation of parasitic infections remains an area of limited research. Given that Acanthamoeba can act as a host for various endosymbiotic microbial pathogens and its pathogenicity assay is not fully understood, this study aimed to identify Acanthamoeba and its bacterial and fungal endosymbionts in patients with chronic respiratory disorders and hospitalized COVID-19 patients in northern Iran. Additionally, a pathogenicity assay was conducted on Acanthamoeba isolates. Urine, nasopharyngeal swab, and respiratory specimens were collected from two groups, and each sample was cultured on 1.5% non-nutrient agar medium. The cultures were then incubated at room temperature and monitored daily for a period of two weeks. Eight Acanthamoeba isolates were identified, and PCR was performed to confirm the presence of amoebae and identify their endosymbionts. Four isolates were found to have bacterial endosymbionts, including Stenotrophomonas maltophilia and Achromobacter sp., while two isolates harbored fungal endosymbionts, including an uncultured fungus and Gloeotinia sp. In the pathogenicity assay, five isolates exhibited a higher degree of pathogenicity compared to the other three. This study provides significant insights into the comorbidity of acanthamoebiasis and COVID-19 on a global scale, and presents the first evidence of Gloeotinia sp. as a fungal endosymbiont. Nevertheless, further research is required to fully comprehend the symbiotic patterns and establish effective treatment protocols.

Differentiation of acanthamoeba keratitis from other non-acanthamoeba keratitis: Risk factors and clinical features

INTRODUCTION

Infectious Keratitis is one of the most common ocular emergencies seen by ophthalmologists. Our aim is to identify the risk factors and clinical features of Acanthamoeba Keratitis (AK).

METHODS

This retrospective chart review study was conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia, and included all the microbial keratitis cases, male and female patients of all ages. The main outcome is the differentiation between various microbial keratitis types.

RESULTS

We included 134 consecutive eyes of 126 persons. We had 24 cases of acanthamoeba keratitis, 22 bacterial keratitis, 24 fungal keratitis, 32 herpetic keratitis, and 32 bacterial co-infection. Contact lens wear was found in 33 eyes (24.6%). Among acanthamoeba keratitis patients, 73% were ≤ 39 years of age, and 73% were females (P <0.001). Also, in AK cases, epithelial defect was found in all cases (100%), endothelial plaques were found in 18 eyes (69.2%), 12 cases had radial keratoneuritis (46.2%), and ring infiltrate was found in 53.8% of AK cases.

CONCLUSIONS

We determined the factors that increase the risk of acanthamoeba infection and the clinical characteristics that help distinguish it from other types of microbial keratitis. Our findings suggest that younger females and patients who wear contact lenses are more likely to develop acanthamoeba keratitis. The occurrence of epitheliopathy, ring infiltrate, radial keratoneuritis, and endothelial plaques indicate the possibility of acanthamoeba infection. Promoting education on wearing contact lenses is essential to reduce the risk of acanthamoeba infection, as it is the most significant risk factor for this infection.

Amoebicidal effect of Allium cepa against Allovahlkampfia spelaea: A keratitis model

Allovahlkampfia spelaea (A. spelaea) is a free-living amoeba, proved to cause Acanthamoeba-like keratitis with quite difficult treatment. This study aimed to evaluate the amoebicidal effect of Allium cepa (A. cepa) on A. spelaea trophozoites and cysts both in vitro and in vivo using Chinchilla rabbits as an experimental model of this type of keratitis. Chemical constituents of the aqueous extract of A. cepa were identified using Liquid Chromatography-mass Spectrometry (LC-MS). In vitro, A. cepa showed a significant inhibitory effect on trophozoites and cysts compared to the reference drug, chlorhexidine (CHX) as well as the non-treated control (P < 0.05) with statistically different effectiveness in terms of treatment durations and concentrations. No cytotoxic effect of A. cepa on corneal cell line was found even at high concentrations (32 mg/ml) using agar diffusion method. The in vivo results confirmed the efficacy of A. cepa where the extract enhanced keratitis healing with complete resolution of corneal ulcers in 80% of the infected animals by day 14 (post infection)pi compared to 70% recovery with CHX after 20 treatment days. The therapeutic effect was also approved at histological, immune-histochemical, and parasitological levels. Our findings support the potential use of A. cepa as an effective agent against A. spelaea keratitis.