Genotypic, physiological, and biochemical characterization of potentially pathogenic Acanthamoeba isolated from the environment in Cairo, Egypt

Abstract

Acanthamoebae are the most common opportunistic amphizoic protozoa that cause life-threatening granulomatous amoebic encephalitis in immunocompromised individuals and sight-threatening amoebic keratitis (AK) in contact lens wearers. The present work aimed to determine the presence of Acanthamoeba isolates in different environmental sources: water, soil, and dust in Cairo, Egypt and to characterize the pathogenic potential of the isolated Acanthamoeba using physiological and biochemical assays as well as determination of the genotypes in an attempt to correlate pathogenicity with certain genotypes. The study included the collection of 22 corneal scrapings from patients complaining of symptoms and signs indicative of acanthamoeba keratitis (AK) and 75 environmental samples followed by cultivation on non-nutrient agar plates preseeded with E. coli. Positive samples for Acanthamoeba were subjected to osmo- and thermo-tolerance assays and zymography analysis. Potentially pathogenic isolates were subjected to PCR amplification using genus-specific primer pair. Isolates were classified at the genotype level based on the sequence analysis of Acanthamoeba 18S rRNA gene (diagnostic fragment 3). The total detection rate for Acanthamoeba in environmental samples was 33.3 %, 31.4 % in water, 40 % in soil, and 20 % in dust samples. Three and two Acanthamoeba isolates from water and soil sources, respectively, had the potential for pathogenicity as they exhibited full range of pathogenic traits. Other 12 isolates were designated as weak potential pathogens. Only ten of the environmental isolates were positive in PCR and were classified by genotype analysis into T4 genotype (70 %), T3 (10 %) and T5 (20 %). Potential pathogens belonged to genotypes T4 (from water) and T5 (from soil) while weak potential pathogens belonged to genotypes T3 (from water) and T4 (from water and soil). Additionally, T7 genotype was isolated from keratitis patients. There is a considerable variation in the response of Acanthamoeba members of the same genotype to pathogenicity indicator assays making correlation of pathogenicity with certain genotypes difficult. Presence of potentially pathogenic Acanthamoeba isolates in habitats related directly to human populations represent a risk for human health. Isolation of Acanthamoeba genotype T7 from AK cases, which is commonly considered as nonpathogenic, might draw the attention to other Acanthamoeba genotypes considered as non pathogenic and reevaluate their role in production of human infections. To our knowledge, this is the first study on the presence and distribution of Acanthamoeba genotypes in the environment, Cairo, Egypt.

Free-Living Amoebae in Soil Samples from Santiago Island, Cape Verde

“…genotype T5. Despite genotype T5 still being categorized as only potentially pathogenic [ 44 ], there have been reports demonstrating its potential pathogenicity through its weak binding capacity to corneal cells in vitro [ 45 ], a cornea infection in the USA [ 46 ], and a case of disseminated cutaneous infection [ 47 ].…”

Genotyping and interaction-reality of Acanthamoeba, enteric adenovirus and rotavirus in drinking water, Egypt.

“…Several studies conducted previously in Egypt, reported that 80%, 58.6%, 56.3%, 31.4%, 67.7% and 29.2% of water samples were positive for Acanthamoeba spp. in Beni-Suef governorate, Nile Delta governorates, Giza governorate, Cairo governorate and Faiyum governorate, respectively (Abd El Wahab et al, 2018;Al-Herrawy et al, 2017;Morsy et al, 2016;Tawfeek et al, 2016;Sakran et al, 2017;Gad and Al-Herrawy, 2016). Globally, Acanthamoeba spp.…”

Comparison Between Different Methods for Diagnosis of Acanthamoeba Infection and Isolation of Genotype T9 From a Contact Lens Cases

“…Al-Herrawy et al (2014) identified six Acanthamoeba species from 10 different swimming pools in Cairo; A. polyphaga, A. castellanii, A. rhysodes, A. mauritaniensis, A. royreba and A. triangularis. Tawfeek et al (2016) also detected three isolates; T4, T3, & T5 from environmental sources.…”

“…Molecular diagnosis improved AK diagnosis by amplifying Acanthamoeba DNA and detected scanty organisms in clinical cases (Laummaunwai et al, 2012). In the present study, genus-specific primers pair; JDP1 (forward) and JDP2 (reverse) were used for PCR amplification of Acanthamoeba-specific nuclear small subunit ribosomal RNA; 18S rRNA gene segment or the Acanthamoeba specific amplimer-S1 (ASA-S1), which were well accepted (Gatti et al, 2010;El-Sayed et al, 2014;Tawfeek et al, 2016).…”