Acanthamoeba Isolates Research Articles

Inhibition Effect of Cell-Free Supernatants of Environmental Acanthamoeba Strains on the Viability of Metastatic Cell-Lines

It is known that some of the therapeutic agents against cancer cells are isolated from natural sources such as plants and animals. However, due to increasing drug resistance, studies on the discovery of new sources are needed. In this study, it was aimed to investigate the inhibition effects of four native Acanthamoeba strains on different cancer cell lines (MDA-MB-231, PC3, MAT-LyLu). 3T3 cells were used as normal cell line. All strains were recultured by using non-nutrient agar spread by heat-inactivated Escherichia coli ATCC 25922. A.castellanii ATCC 50373 was used as the standard strain. Molecular identification of the native Acanthamoeba isolates was done by polymerase chain reaction (PCR) and DNA sequence analysis using specific primer pairs (P-FLA-F, P-FLA-R, JDP-F, JDP-R). Axenic cultures of all strains were obtained in 25 cm2 tissue culture flasks and in peptone yeast extract glucose (PYG) medium. In order to investigate the effect of cell-free supernatants obtained from axenic cultures on cancer cell lines and 3T3 cell viability, MTT method was applied using different concentrations of cell-free supernatants (1%, 2%, 5%, 10%, 15%). It was determined that the viability of 3T3 cells was not affected by any Acanthamoeba cell-free supernatants (p≤ 0.05). All of the samples tested were found to have a significant inhibitory effect (p<0.05) on the viability of PC3 and MAT-LyLu cells (human and rat prostate cancer cell line). However, none of the samples had an inhibitory effect on the viability of MDA-MB-231 (breast cancer cell-line). Two native Acanthamoeba cell-free supernatants showed higher inhibitory potency (28% and 21.9%) at 2% concentration against PC3 cells compared to the reference strain (16%). Similarly, the same Acanthamoeba samples were also shown to have a better inhibition potential on the viability of MAT-LyLu cells than the reference strain. It was found that the inhibitory potential of Acanthamoeba cell-free supernatants may not be related to proteins and proteases. The results obtained from this study showed that Acanthamoeba species living in the aquatic environment isolated from our country have a potential inhibitory effect against the tested cancer cell lines. In addition to plants and animals, Acanthamoeba cell-free supernatants can also be a source for natural therapeutic substances that act against cancer cells. However, it is necessary to carry out new studies using more strains in order to detect strains with higher inhibitory effects.

Sub-Genotyping of Acanthamoeba T4 Complex: Experience from North India

The Acanthamoeba genus comprises the free-living amoebae that are ubiquitously present as opportunistic pathogens. They cause serious human diseases—for instance, Acanthamoeba keratitis (AK), granulomatous amoebic encephalitis (GAE), cutaneous acanthamoebiasis and disseminated infections. The traditional method for classifying Acanthamoeba was based on the morphological examination of cysts. However, this method was less consistent as the morphology of cysts changes with the culture conditions. After the advent of molecular techniques, genotyping is considered an essential tool in accurately identifying Acanthamoeba at the species level and is further helpful in classification up to the sub-genotype level. The most recommended and currently used methods for Acanthamoeba genotyping are 18S and 16S rDNA gene sequencing. Based on these two genes, Acanthamoeba is classified into 23 genotypes. Out of these, it is the T4 genotype that is most commonly associated with clinical disease and isolation from environmental samples. The T4 genotype contains more than ten species within it. Differences in geographical distribution, virulence, pathogenesis and drug susceptibility profile have been observed among different genotypes. However, whether such differences exist within sub-genotypes/species under T4 is yet unknown. In the present study, 11 Acanthamoeba isolates, which were already characterized as the T4 genotype by the hypervariable region of diagnostic fragment 3 (DF3) of the 18S rDNA, were sub-genotyped using the 16S rDNA mitochondrial sequence. Nine of these were isolated from patients with AK and two from water samples. Phylogenetic analysis of these isolates attributed them to four sub-genotypes (T4a (n = 6), T4b (n = 1), T4Neff (n = 2) and T4d (n = 2)). The study highlights the potential use of 16S in the sub-genotyping of Acanthamoeba T4. The 16S rDNA sequences of two isolates, one from an Acanthamoebic keratitis (AK) patient and one environmental, were found to group with A. mauritaniensis (T4d). This group was believed to be a non-pathogenic environmental Acanthamoeba and the identification of the AK isolate may be confirmed by whole-genome sequencing.

The Status of Molecular Analyses of Isolates of Acanthamoeba Maintained by International Culture Collections.

Acanthamoeba is among the most ubiquitous protistan groups in nature. Knowledge of the biological diversity of Acanthamoeba comes in part from the use of strains maintained by the major microbial culture collections, ATCC and CCAP. Standard strains are vital to ensure the comparability of research. The diversity of standard strains of Acanthamoeba in the culture collections is reviewed, emphasizing the extent of genotypic studies based on DNA sequencing of the small subunit ribosomal RNA from the nucleus (18S rRNA gene; Rns) or the mitochondria (16S-like rRNA gene; rns). Over 170 different strains have been maintained at some time by culture centers. DNA sequence information is available for more than 70% of these strains. Determination of the genotypic classification of standard strains within the genus indicates that frequencies of types within culture collections only roughly mirror that from clinical or environmental studies, with significant differences in the frequency of some genotypes. Culture collections include the type of isolate from almost all named species of Acanthamoeba, allowing an evaluation of the validity of species designations. Multiple species are found to share the same Sequence Type, while multiple Sequence Types have been identified for different strains that share the same species name. Issues of sequence reliability and the possibility that a small number of standard strains have been mislabeled when studied are also examined, leading to potential problems for comparative analyses. It is important that all species have reliable genotype designations. The culture collections should be encouraged to assist in completing the molecular inventory of standard strains, while workers in the Acanthamoeba research community should endeavor to ensure that strains representative of genotypes that are missing from the culture collection are provided to the culture centers for preservation.

In Vitro Cytopathogenic Activities of Acanthamoeba T3 and T4 Genotypes on HeLa Cell Monolayer.

Amoebic keratitis and encephalitis are mainly caused by free-living amoebae of the genus Acanthamoeba, which consists of both pathogenic and nonpathogenic species. The global distribution, amphizoic properties and the severity of the disease caused by Acanthamoeba species have inspired the scientific community to put more effort into the isolation of Acanthamoeba, besides exploring the direct and indirect parameters that could signify a pathogenic potential. Therefore, this study was performed to characterize the pathogenic potential of Acanthamoeba isolated from contact lens paraphernalia and water sources in Malaysia. Various methodologies were utilized to analyze the thermotolerance and osmotolerance, the secretion level of proteases and the cytopathic effect of trophozoites on the cell monolayer. In addition, the in vitro cytopathogenicity of these isolates was assessed using the LDH-release assay. A total of 14 Acanthamoeba isolates were classified as thermo- and osmotolerant and had presence of serine proteases with a molecular weight of 45-230 kDa. Four T4 genotypes isolated from contact lens paraphernalia recorded the presence of serine-type proteases of 107 kDa and 133 kDa. In contrast, all T3 genotypes isolated from environmental samples showed the presence of a 56 kDa proteolytic enzyme. Remarkably, eight T4 and a single T3 genotype isolates demonstrated a high adhesion percentage of greater than 90%. Moreover, the use of the HeLa cell monolayer showed that four T4 isolates and one T3 isolate achieved a cytopathic effect in the range of 44.9-59.4%, indicating an intermediate-to-high cytotoxicity level. Apart from that, the LDH-release assay revealed that three T4 isolates (CL5, CL54 and CL149) and one T3 isolate (SKA5-SK35) measured an exceptional toxicity level of higher than 40% compared to other isolates. In short, the presence of Acanthamoeba T3 and T4 genotypes with significant pathogenic potential in this study reiterates the essential need to reassess the functionality of other genotypes that were previously classified as nonpathogenic isolates in past research.

Genotype diversity, phylogenetic analysis and seasonality of isolates of Acanthamoeba spp. in swimming pools in Kafrelsheikh, Egypt.

Species of Acanthamoeba Volkonsky, 1931 are the commonest among free-living amoebae that are widespread in different water resources but with lacking phylogenetic data. This study aims at detecting molecular prevalence and genetic diversity of Acanthamoeba isolates in Kafrelsheikh Governorate, Egypt. Forty-eight water samples were collected from 12 swimming pools; four samples during each season over one year. Samples were filtered, cultivated on non-nutrient agar plates and examined microscopically. Polymerase chain reaction (PCR) and sequence analysis of positive samples targeting diagnostic fragment 3 (DF3) of the small subunit rRNA gene were done. Cultivation succeeded to detect 14 (29%) positive samples while PCR missed three positive samples. The obtained sequences were phylogenetically analysed. The phylogenetic tree was constructed for them with sequences of reference species from the NCBI database. The identified species were Acanthamoeba castellanii Douglas, 1930 (T4), A. astronyxis (Ray et Hayes, 1954) (T9) and A. hatchetti Sawyer, Visvesvara et Harke, 1977 (T11). The prevalence of species of Acanthamoeba was higher during summer and fall. Therefore, the control of the presence of Acanthmoeba spp. in swimming pools needs immediate, effective and practical measures to prevent and control infection with species of Acanthamoeba.

Acanthamoeba keratitis – Clinical signs and potential specific conservative treatment

AbstractAcanthamoeba keratitis is a “chameleon”. It presents classically with greyish epithelial changes, perineuritis, superficial multifocal stromal infiltrates and ring infiltrate. In the presence of clinical signs, polymerase chain reaction, in vitro culture or histopathological examination have to be used to confirm the diagnosis. In vivo confocal microscopy is applied as an early non‐invasive ad‐hoc diagnostic method. Our finding emphasizes that pre‐testing the in vitro susceptibility of the AK isolate with the non‐nutrient E. coli agar plate assay against the anti‐amoebic drug intended for treatment will give valuable information on whether the drug is likely to be active on the Acanthamoeba isolate in vivo.

Acanthamoeba keratitis – Specific conservative treatment or surgery?

AbstractClinical signs of acanthamoeba keratitis are in early stages grey‐dirty epithelium, pseudodendritiformic epitheliopathy, perineuritis, multifocal stromal infiltrates, ring infiltrate and in later stages scleritis, iris atrophy, anterior synechiae, secondary glaucoma, mature cataract, and chorioretinitis. Our finding emphasizes that pre‐testing the in vitro susceptibility of the AK isolate with the non‐nutrient E. coli agar plate assay against the anti‐amoebic drug intended for treatment will give valuable information on whether the drug is likely to be active on the Acanthamoeba isolate in vivo. In therapy resistant cases, surgical treatment options such as corneal cryotherapy, amniotic membrane transplantation, riboflavin‐UVA cross‐linking, and penetrating keratoplasty are applied.

Occurrence and molecular characterization of Acanthamoeba, Naegleria fowleri and Blastocystis in water samples from various sources in Egypt

PCR-testing coupled to isolate sequencing was conducted to detect prevalence and various genotypes/subtypes of 3 neglected waterborne protists (Acanthamoeba, Naegleria fowleri and Blastocystis) in water samples from various sources in Dakahlia governorate, Egypt. Out of 62 protozoan-suspected samples by microscopy, Acanthamoeba was molecularly confirmed in 24 (38.7%) samples from various sources including tap water. Twenty Acanthamoeba isolates were successfully-sequenced; 18 were designated as the genotype T3 and 2 as T4. Naegleria spp. were detected in 6 (9.6%) samples from the Nile, of them 2 (3.2%) were identified as N. fowleri. Blastocystis spp. were found in 4 (6.4%) samples from waste water and ground water. Blastocystis subtype 2 was found in a sample from waste water, which may reflect human infection with this subtype and constitutes a public health hazard because waste water is occasionally discharged in the Nile with minimal treatments. Findings of the present study were analyzed in combination with those of earlier surveys from the other Egyptian governorates to evaluate the whole situation of the 3 protists in water from Egypt. Results of this analysis showed that Acanthamoeba had a high mean prevalence (43.03%) throughout Egypt, with insignificant variations among various water sources. Various Acanthamoeba genotypes were detected, and the highly pathogenic T4 was the most significantly identified type. A common T4 haplotype circulated in water from Egypt and 3 other countries (Tanzania, Rwanda, Uganda) located on the Nile basin, and included isolates from keratitis-infected patients, which confirms the potential role of water in the epidemiology of Acanthamoeba keratitis infecting humans in these countries. The estimated mean prevalence for Naegleria spp. was 23.79%, being the highest in the Nile water. In the present study, occurrence of 3 potentially pathogenic protists has been confirmed in water from Egypt, which should alert the authorities to revise the procedures for controlling these pathogens in water.

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

IntroductionAcanthamoeba 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.AimsThis 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.MethodologyThirteen 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).ResultsThe 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.ConclusionsGenotype 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.

Genotyping and physiological characteristics of Acanthamoeba isolated from beaches in Phuket Province, Thailand

Abstract. Boonman N, Wanna C, Chutrtong J, Chotpantarat S, Boonsilp S. 2022. Genotyping and physiological characteristics of Acanthamoeba isolated from beaches in Phuket Province, Thailand. Biodiversitas 23: 4377-4384. Acanthamoeba is widely distributed in water, soil, dust and air. Beaches are popular tourist destinations for water-related activities while they can also be reservoirs for Acanthamoeba to humans. This study aimed to determine the genotyping of Acanthamoeba in the beach environment and characterized their pathogenicity potential. A total of 63 samples were collected from six beaches in Phuket Province, Thailand. Twenty-one samples of each source including wet sand, dry sand and seawater, were collected and cultivated on 2% non-nutrient agar coated with heat-killed Escherichia coli. Acanthamoeba was found in 100% (n=21) wet sand, 52.4% (n=11) dry sand and 14.3% (n=3) seawater. Sequence analysis of the GTSA.B1 region in 18S rRNA revealed that 83.9% of sequenced isolates belonged to the T5 genotype and 16.1% belonged to the T4 genotype. The T5 genotype was predominant, differing from other reports of Acanthamoeba prevalence in natural sources. In vitro thermal and salt-tolerance showed that all isolates had growth rates similar to clinical Acanthamoeba isolates. This research was undertaken to increase awareness of human eye and brain infections caused by Acanthamoeba on beaches. Further studies on these Acanthamoeba isolates are still required such as co-culture assay between the trophozoites and human cell lines to confirm their pathogenicity as well as their susceptibility to the chemotherapeutic agents.

Antiamoebic Susceptibility in Acanthamoeba Keratitis: Comparison of Isolates From South India and Northern California.

Outcomes of Acanthamoeba keratitis are often worse in India than in the United States. The goal of this study was to determine whether antiamoebic susceptibility patterns were different when comparing Acanthamoeba isolates from India with those of the United States. Acanthamoeba isolates were obtained from corneal scrapings of 43 patients with infectious keratitis seen at the Francis I. Proctor Foundation (N = 23) and Aravind Eye Hospital (N = 20) from 2008 through 2012 and plated on growth media. A previously described minimum cysticidal concentration (MCC) assay was performed by a single laboratory technician to assess susceptibility to 5 antiamoebic agents for all isolates. Testing was conducted in triplicate, with the median MCC chosen for analyses. The MCC (μg/mL) of polyhexamethylene biguanide was 6.25 [IQR 5.47-12.5] for Aravind isolates and 6.25 [IQR 6.25-9.375] for Proctor isolates ( P = 0.75), corresponding values were 6.25 [IQR 3.125-6.25] and 3.125 [IQR 3.125-9.375] for chlorhexidine ( P = 0.81), 2500 [IQR 2500-5000] and 5000 [IQR 1250-20,000] for voriconazole ( P = 0.25), 15.6 [IQR 15.6-39.0625] and 15.6 [IQR 15.6-31.25] for hexamidine ( P = 0.92), and 15.6 [IQR 7.81-15.6] and 15.6 [IQR 7.81-31.25] for propamidine ( P = 0.42). This study found no statistically significant differences in antiamoebic susceptibility of Indian versus US samples from Acanthamoeba keratitis clinical isolates. These findings suggest that differences in antiamoebic susceptibility are likely not responsible for differential outcomes in Acanthamoeba keratitis between the 2 locations.

Molecular detection and genotype identification of Acanthamoeba species from bronchoalveolar lavage of patients with pulmonary symptoms suspected of cancer.

Acanthamoeba spp. are the most common free-living amoeba worldwide, inducing life-threatening diseases such as Granulomatous Amoebic Encephalitis, pulmonary infection, and amoebic keratitis. This study aimed to identify the FLA and Acanthamoeba genotypes in patients with pulmonary symptoms suspected of cancer in Kashan's hospitals, Kashan, Iran. This cross-sectional study was conducted on 97 bronchoalveolar lavage samples of patients with respiratory symptoms suspected of lung cancer, who were admitted to the Shahid Beheshti Hospital of Kashan from 2019 to 2020. The samples were cultured onto 1.5% non-nutrient agar enriched with killed Escherichia coli and examined for the presence of FLA. Following amoeba isolation and DNA extraction, Acanthamoeba spp. were determined by Polymerase Chain Reaction using JDP1 and JDP2 primers, which amplified a 490bp fragment from the 18 S rDNA gene. Eighteen Acanthamoeba isolates were sequenced, and the genotypes were identified. The prevalence of FLA and Acanthamoeba and the relationship between symptoms and demographic variables were analyzed with SPSS Software version 16. The prevalence rates of FLA and Acanthamoeba in the BAL samples was 86.6% and 73.2%, respectively. All Acanthamoeba isolates belonged to the T4 genotype. The most symptoms among Acanthamoeba-positive patients were dyspnea and cough; however, their difference was not statistically significant. The findings indicated the high prevalence of FLA and Acanthamoeba in BAL in the population suspected of cancer in Kashan. Since the T4 genotype is a pathogenic genotype of Acanthamoeba, training health and improving sanitation levels would help to prevent infection.

Efficacy of Off-Label Anti-Amoebic Agents to Suppress Trophozoite Formation of Acanthamoeba spp. on Non-Nutrient Agar Escherichia Coli Plates.

Acanthamoeba keratitis (AK) is a dangerous infectious disease, which is associated with a high risk of blindness for the infected patient, and for which no standard therapy exists thus far. Patients suffering from AK are thus treated, out of necessity, with an off-label therapy, using drugs designed and indicated for other diseases/purposes. Here, we tested the capability of the off-label anti-amoebic drugs chlorhexidine (CH; 0.1%), dibromopropamidine diisethionate (DD; 0.1%), hexamidine diisethionate (HD; 0.1%), miltefosine (MF; 0.0065%), natamycin (NM; 5%), polyhexamethylene biguanide (PHMB; 0.02%), povidone iodine (PVPI; 1%), and propamidine isethionate (PD; 0.1%) to suppress trophozoite formation of Acantamoeba castellanii and Acanthamoeba hatchetti cysts on non-nutrient agar Escherichia coli plates. Of the eight off-label anti-amoebic drugs tested, only PVPI allowed for a complete suppression of trophozoite formation by drug-challenged cysts for all four Acanthamoeba isolates in all five biological replicates. Drugs such as NM, PD, and PHMB repeatedly suppressed trophozoite formation with some, but not all, tested Acanthamoeba isolates, while other drugs such as CH, DD, and MF failed to exert a relevant effect on the excystation capacities of the tested Acanthamoeba isolates in most, if not all, of our repetitions. Our findings suggest that pre-testing of the AK isolate with the non-nutrient agar E. coli plate assay against the anti-amoebic drug intended for treatment should be performed to confirm that the selected drug is cysticidal for the Acanthamoeba isolate.

Molecular identification and phylogenetic analysis of free-living amoeba in the water resources of Arak, Iran.

The aim of the present study was to detect free-living amoeba (FLA) in the water resources of Arak, Iran using molecular tools. A total of 154 samples were collected from different water supplies. Molecular analyses, sequencing, and phylogenetic study were conducted to confirm the species and genotypes of FLA. Fisher exact test was used to determine the significance. Of 154 water samples, 19 (12.3%) samples were tested positive for FLA. Three genotypes of Acanthamoeba including T4, subtype D, and T5 were identified among the isolates. The pathogenicity assay showed that the isolate of Acanthamoeba in drinking water was highly pathogenic. Three species of Naegleria, including N. australiensis, N. pagei, and N. gruberi were found among the samples. Six isolates of Vermamoeba were identified as V. vermiformis. Meanwhile, three other species including Vannella sp., Vahlkampfia avara, and Stenamoeba polymorpha were also recovered from the water samples. Statistical analysis showed a significant difference between the various water resources contaminated with FLA. This is the first study to reveal the presence of S. polymorpha in water sources in Iran. According to the findings of the present study, health officials should be beware of potential public health impacts of FLA in water resources.

Surveillance of Amoebic Keratitis-Causing Acanthamoebae for Potential Bacterial Endosymbionts in Ontario, Canada.

Acanthamoeba spp. are the causative pathogens of several infections, including amoebic keratitis (AK), a vision-threatening infection. Acanthamoebae from corneal specimens of patients with AK harbor bacterial endosymbionts, which may increase virulence. We sought to understand the spectrum of bacterial endosymbionts present in clinical isolates of Acanthamoeba spp. identified in our reference parasitology laboratory. Isolates of Acanthamoeba spp. obtained from our biobank of anonymized corneal scrapings were screened for potential endosymbionts by PCR using primer pairs detecting bacteria belonging to orders Chlamydiales, Rickettsiales, or Legionellales and pan16S primers. Three primer pairs specific to the 18s rRNA gene of Acanthamoeba spp. were used for the amplification of Acanthamoeba DNA used for sequencing. Sanger sequencing of all PCR products was performed, followed by BLAST analysis for species identification. We screened 26 clinical isolates of Acanthamoeba spp. for potential endosymbionts. Five isolates (19%) were found to contain bacterial DNA belonging to Legionellales. Three (11%) contained members of the Rickettsiales and Pseudomonas genticulata was detected in a Rickettsia-positive sample. One strain (4%) contained Neochlamydia hartmannellae, a member of the Chlamydiales order. Bacterial endosymbionts are prevalent in clinical strains of Acanthamoeba causing AK isolated from corneal scrapings. The demonstration of these organisms in clinical Acanthamoeba isolates supports a potential exploration of anti-endosymbiont therapeutics as an adjuvant therapy in the treatment of AK.

Occurrence and genetic evaluation of potentially pathogenic Acanthamoeba genotypes in nasal mucosa of immunocompromised patients: a case-control study in Iran.

The occurrence of granulomatous amoebic encephalitis (GAE) was investigated due to the exposure of a large number of immunocompromised patients to opportunistic Acanthamoeba infections, which in most cases are fatal. In this case-control study, 160 samples from the nasal mucosa of immunocompromised patients were collected between February 2019 to February 2020 in Isfahan, central Iran, using sterile cotton swabs; 150 ethnically matched controls were included. The pathogenic potential of the identified isolates was evaluated using temperature and osmotolerance assays. The identification of Acanthamoeba infection was confirmed by both morphological and phylomolecular tools. Of 310 collected samples, 32 strains, including 25 (15.6%) and 7 (4.6%) isolates, were positive for the Acanthamoeba genus in the patient and control groups, respectively. The topology of the phylogenetic tree indicated that all the Acanthamoeba strains belonged to the T4 genotype. Only five of the isolates genotyped as T4 were positive for potential pathogenic assays. The heterogeneity analysis of 18S ribosomal RNA sequences of Acanthamoeba in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) and hepatitis B and C patients revealed significant genetic diversity (haplotype diversity [Hd] 0.511) compared with that of healthy individuals (Hd 0.210). The circulation of pathogenic isolates of Acanthamoeba, particularly in HIV/AIDS patients, along with their genetic traits, indicates that clinicians should be more aware of fatal cases of GAE, especially in suspected encephalitis, in Iran and worldwide.

Transcriptional changes of proteins of the thioredoxin and glutathione systems in Acanthamoeba spp. under oxidative stress - an RNA approach.

The thioredoxin (Trx) and the glutathione (GSH) systems represent important antioxidant systems in cells and in particular thioredoxin reductase (TrxR) has been shown to constitute a promising drug target in parasites. For the facultative protozoal pathogen Acanthamoeba, it was demonstrated that a bacterial TrxR as well as a TrxR, characteristic of higher eukaryotes, mammals and humans is expressed on the protein level. However, only bacterial TrxR is strongly induced by oxidative stress in Acanthamoeba castellanii. In this study, the impact of oxidative stress on key enzymes involved in the thioredoxin and the glutathione system of A. castellanii under different culture conditions and of clinical Acanthamoeba isolates was evaluated on the RNA level employing RT-qPCR. Additionally, the effect of auranofin, a thioredoxin reductase inhibitor, already established as a potential drug in other parasites, on target enzymes in A. castellanii was investigated. Oxidative stress induced by hydrogen peroxide led to significant stimulation of bacterial TrxR and thioredoxin, while diamide had a strong impact on all investigated enzymes. Different strains displayed distinct transcriptional responses, rather correlating to sensitivity against the respective stressor than to respective pathogenic potential. Culture conditions appear to have a major effect on transcriptional changes in A. castellanii. Treatment with auranofin led to transcriptional activation of the GSH system, indicating its role as a potential backup for the Trx system. Altogether, our data provide more profound insights into the complex redox system of Acanthamoeba, preparing the ground for further investigations on this topic.

Genotyping and phylogenetic analysis of free-living amoeba (Acanthamoeba and Naegleria) in treated and untreated water in the northeastern provinces of Iran

Abstract Free-living amoebae (FLA) are widely distributed protozoa in natural or man-made aquatic environments without the need for a host organism for survival. Several strains of FLA are known to be pathogenic. As of date, there is inadequate data on the geographical distribution of FLA in northeastern and northern Iran. This study aimed to investigate the prevalence and genotype distribution of Acanthamoeba and Naegleria in drinking water and surface water samples in northern and northeastern Iran. A total of 60 water samples were collected and filtered from various sources for the presence of amoebae. DNA extraction was performed, and PCR confirmed the presence of FLA. PCR products were sequenced to identify the species/genotype. Phylogenetic relationships and taxonomic status constructed using MEGA X software. The findings on growth media showed 35% (21/60) and 26% (16/60) were positive for Acanthamoeba and Naegleria, respectively, while PCR analysis also obtained similar results. All isolates of Acanthamoeba were identified as T4 genotype. Poor water quality, as well as insufficient preservation and treatment, might indicate that chlorine disinfection is ineffective in removing contamination of amoebas in treated water samples. Therefore, regular water quality monitoring is essential to control amoeba's growth, reducing the risk of human infections with FLA.

Molecular identification of Acanthamoeba genotypes isolated from oral cavity of heart transplant patients in Iran

Heart transplant is one of the accepted treatments for some patients with advanced heart failure. Of note, transplant surgeries may cause different infections and complications for patients during the post-transplant period. A wide variety of opportunistic organisms caused these infections including bacteria, fungi, viruses, and protozoa particularly Free-living amoebae (FLA). This study aims to study the presence of pathogenic FLA from the oral cavity of post-heart transplant recipients. Throat swabs were collected from 80 patients who underwent post-heart transplant surgery. All swabs were immediately cultured in non-nutrient agar (2%). PCR and sequencing of 18S rRNA gene (DF3 region) of Acanthamoeba isolates were performed using genus-specific primers. Genetic associations among sequenced genotypes inferred by the 18S rRNA gene obtained by MEGA X and a phylogenetic tree were constructed using the maximum likelihood algorithm and Kimura 2-parameter model. Out of 80 samples collected from post-heart transplant patients, six (7.5%) samples showed positive outgrowth of Acanthamoeba based on the page key and sequencing of the DF3 region. Sequence similarity of ASA1 by basic local alignment search tool(n) showed that five isolates (ANHT1, ANHT2, ANHT3, ANHT4, and ANHT5) belonged to Acanthamoeba T5 genotype corresponding to A. lenticulata and one strain (ANHT6) belonged to the T4 genotype. To the best of our knowledge for the first time, a comprehensive study of Acanthamoeba genotypes isolated from throat samples of heart transplant recipients is described. Heart transplantation patients can be colonized by FLA and are therefore at risk of developing an invasive infection. Physicians' awareness of central nervous system infections related to FLAs and preventive and control measures of patients with compromised immune status due to heart transplant surgery are of utmost importance.

Molecular Identification of Pathogenic Free-Living Amoeba from Household Biofilm Samples in Iran: A Risk Factor for Acanthamoeba Keratitis.

Free-living amoeba (FLA) are ubiquitously distributed in the environment. However, they are also the causative agents of opportunistic infections in humans and other animals. A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. Moreover, FLA have been detected in various biofilms around the world. Therefore, the present study aimed to check for presence of FLA in samples from household biofilms in Iran and to characterize them at the molecular level. A total of 69 biofilm samples collected from showerheads, kitchen areas, and bathroom sinks were analyzed. Positive samples for FLA were characterized at the morphological and molecular levels. Furthermore, the results of morphology analysis indicated that 26.08% (18/69) of biofilm samples were positive for Acanthamoeba spp., Vermamoeba genus, and Vahlkampfiids. According to sequence analysis, five strains of Acanthamoeba isolates related to the T4 genotype and two strains belonged to the T2 genotype. In addition, the pathogenic potential of Acanthamoeba-positive isolates was conducted using the tolerance ability test. The results of BLASTn of Vermamoeba sequences were similar to what was expected for Vermamoeba vermiformis. The above-mentioned reasons revealed that the relative high contamination of household biofilm samples with FLA may pose a risk for people using soft contact lenses and for patients with traumatic cataract. Our finding proposes that filtration should be performed in shower heads and indicates the need to monitor people at increased risk of Acanthamoeba keratitis.