First time identification of Acanthamoeba genotypes in the cornea samples of wild birds; Is Acanthamoeba keratitis making the predatory birds a target?

Acanthamoeba spp.: Neglected Protists in Veterinary Medicine

PROPOSE

Acanthamoebaspp. are widespread free-living protists found in various natural and man-made habitats. At times, they can become parasitic, leading to conditions such as Acanthamoeba keratitis (AK), granulomatous amoebic encephalitis (GAE), and systemic infections in humans and animals. In veterinary medicine, infections caused by Acanthamoeba spp. are frequently underdiagnosed, necessitating a high degree of clinical vigilance and laboratory technical skill for accurate diagnosis and treatment.

METHODS

This review aimed to provide an overview of documented natural infections in animals with Acanthamoeba spp. to enhance veterinary professionals' awareness of these organisms' potential risks.

RESULTS

This review records natural infections of animals with Acanthamoeba and its interaction with pathogenic bacteria, highlighting the importance of Acanthamoeba spp. in veterinary medicine.

CONCLUSION

Acanthamebiasis should be considered in the differential diagnosis of systemic diseases, especially with neurologic involvement. Since this neglected infection can impact the lives and livelihoods of many animals, informing veterinarians and animal owners is necessary.

Vermamoeba vermiformis as the etiological agent in a patient with suspected non-Acanthamoeba keratitis

Vermamoeba vermiformis (V. vermiformis) is one of the most common free-living amoeba (FLA) and is frequently found in environments such as natural freshwater areas, surface waters, soil, and biofilms. V. vermiformis has been reported as a pathogen with pathogenic potential for humans and animals. The aim is to report a case of non-Acanthamoeba keratitis in which V. vermiformis was the etiological agent, identified by culture and molecular techniques. Our case was a 48-year-old male patient with a history of trauma to his eye 10 days ago. The patient complained of eye redness and purulent discharge. A slit-lamp examination of the eye revealed a central corneal ulcer with peripheral infiltration extending into the deep stroma. The corneal scraping sample taken from the patient was cultured on a non-nutritious agar plate (NNA). Amoebae were evaluated according to morphological evaluation criteria. It was investigated by PCR method and confirmed by DNA sequence analysis. Although no bacterial or fungal growth was detected in the routine microbiological evaluation of the corneal scraping sample that was cultured, amoeba growth was detected positively in the NNA culture. Meanwhile, Acanthamoeba was detected negative by real-time PCR. However, V. vermiformis was detected positive with the specific PCR assay. It was confirmed by DNA sequence analysis to be considered an etiological pathogenic agent. Thus, topical administration of chlorhexidine gluconate %0.02 (8 × 1) was initiated. Clinical regression was observed 72 h after chlorhexidine initiation, and complete resolution of keratitis with residual scarring was noticed in 5 weeks. In conclusion, corneal infections due to free-living amoebae can occur, especially in poor hygiene. Although Acanthamoeba is the most common keratitis due to amoeba, V. vermiformis is also assumed to associate keratitis in humans. Clinicians should also be aware of other amoebic agents, such as V. vermiformis, in keratitis patients.

Molecular identification of Acanthamoeba spp., Balamuthia mandrillaris and Naegleria fowleri in soil samples using quantitative real-time PCR assay in Turkey; Hidden danger in the soil!

Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri are pathogenic free-living amoeba (FLA) and are commonly found in the environment, particularly soil. This pathogenic FLA causes central nervous system-affecting granulomatous amebic encephalitis (GAE) or primary amebic meningoencephalitis (PAM) and can also cause keratitis and skin infections. In the present study, we aimed to determine the quantitative concentration of Acanthamoeba spp., B. mandrillaris, and N. fowleri in soil samples collected from places where human contact is high by using a qPCR assay in Izmir, Turkey. A total of 45.71% (n=16) of Acanthamoeba spp., 20% (n=7) of B. mandrillaris, and 17.4% (n=6) of N. fowleri were detected in five different soil sources by the qPCR assay. The quantitative concentration of Acanthamoeba spp., B. mandrillaris, and N. fowleri in various soil sources was calculated at 10 × 10⁵ - 6 × 10², 47 × 10⁴ to 39 × 10³, and 9 × 10³ - 8 × 10² plasmid copies/gr, respectively. While the highest quantitative concentration of Acanthamoeba spp. and B. mandrillaris was determined in garden soil samples, N. fowleri was detected in potting soil samples. Three different genotypes T2 (18.75%), T4 (56.25%), and T5 (25%) were identified from Acanthamoeba-positive soil samples. Acanthamoeba T4 genotype was the most frequently detected genotype from soil samples and is also the most common genotype to cause infection in humans and animals. To the best of our knowledge, the present study is the first study to identify genotype T5 in soil samples from Turkey. In conclusion, people and especially children should be aware of the hidden danger in the garden and potting soil samples that come into contact most frequently. Public health awareness should be raised about human infections that may be encountered due to contact with the soil. Public health specialists should raise awareness about this hidden danger in soil.

Distribution and Current State of Molecular Genetic Characterization in Pathogenic Free-Living Amoebae

Free-living amoebae (FLA) are protozoa widely distributed in the environment, found in a great diversity of terrestrial biomes. Some genera of FLA are linked to human infections. The genus Acanthamoeba is currently classified into 23 genotypes (T1-T23), and of these some (T1, T2, T4, T5, T10, T12, and T18) are known to be capable of causing granulomatous amoebic encephalitis (GAE) mainly in immunocompromised patients while other genotypes (T2, T3, T4, T5, T6, T10, T11, T12, and T15) cause Acanthamoeba keratitis mainly in otherwise healthy patients. Meanwhile, Naegleria fowleri is the causative agent of an acute infection called primary amoebic meningoencephalitis (PAM), while Balamuthia mandrillaris, like some Acanthamoeba genotypes, causes GAE, differing from the latter in the description of numerous cases in patients immunocompetent. Finally, other FLA related to the pathologies mentioned above have been reported; Sappinia sp. is responsible for one case of amoebic encephalitis; Vermamoeba vermiformis has been found in cases of ocular damage, and its extraordinary capacity as endocytobiont for microorganisms of public health importance such as Legionella pneumophila, Bacillus anthracis, and Pseudomonas aeruginosa, among others. This review addressed issues related to epidemiology, updating their geographic distribution and cases reported in recent years for pathogenic FLA.

The Risk Factors and Clinical Features of Acanthamoeba Keratitis: First Time Detection of Acanthamoeba T5 Genotype from Keratitis Patients in Turkey

PURPOSE

The primary aim of this study is to investigate Acanthamoeba in clinical samples of keratitis cases (n = 60), in contact lens (CL) and lens care solutions of asymptomatic CL users (n = 41), and to identify the genotypes in positive samples. The secondary aim is to assess the risk factors and clinical features of Acanthamoeba keratitis (AK) patients.

METHODS

All samples from patients and asymptomatic CL users were examined by microscopy and inoculated in non-nutrient agar plates. PCR was performed using the DNA isolated from corneal scrapings, CL and lens care solution samples. Positive DNA samples were sequenced to determine the genotype of Acanthamoeba.

RESULTS

In none of the samples, Acanthamoeba was identified by microscopy, while Acanthamoeba was detected in a patient with keratitis by culture method. However, Acanthamoeba was detected in 11.66% (7/60) of the keratitis patients by PCR. The genotypes of these isolates detected by sequencing were T4 (4), and T5 (3). Acanthamoeba was detected in none of the samples of asymptomatic CL users by any of the three methods.

CONCLUSION

To best of our knowledge, this is the first study to detect T5 genotype in AK patients from Turkey. In addition, the CL use was found to be an important risk factor for AK.

Genotyping and Molecular Identification of Acanthamoeba Genotype T4 and Naegleria fowleri from Cerebrospinal Fluid Samples of Patients in Turkey: Is it the Pathogens of Unknown Causes of Death?

PURPOSE

This study was aimed to investigate the presence of pathogenic free-living amoebae (FLA) in suspected cases of meningoencephalitis with unknown causes of death in Turkey.

METHOD

A total of 92 patients, who were diagnosed as meningoencephalitis, were enrolled. All cerebrospinal fluid (CSF) samples were directly microscopically examined and cultured. Acanthamoeba, N. fowleri and B. mandrillaris were further investigated using molecular diagnostic tools including real-time PCR, sequencing, and phylogenetic analyses.

RESULTS

The examined CSF samples were not found positive for the presence of FLA by microscopic examination and culture method. However, two CSF samples were detected positive by real-time PCR assay. Of the positive CSF samples, one was identified as Acanthamoeba genotype T4 and the second positive sample was identified as N. fowleri belonging to genotype II. Furthermore, the pathogens diagnoses was verified through Sanger sequencing.

CONCLUSION

This study was significant to report the presence of Acanthamoeba genotype T4 and N. fowleri genotype II in CSF samples by real-time PCR assay. The present study shows the significance of primary amoebic meningoencephalitis (PAM) and granulomatous amoebic encephalitis (GAE) as one of the differential diagnoses to be considered by clinicians during the evaluation of suspected meningoencephalitis or cases of unknown cause in Turkey. Using real-time PCR, this has made the rapid detection, in a short time-frame, of Acanthamoeba and N. fowleri in CSF samples from patients. The problems with qPCR is that it is not available in every laboratory, reagents are expensive, and it requires skilled and expert personnel to set up these assays.

Real-Time PCR Confirmation of a Fatal Case of Primary Amoebic Meningoencephalitis in Turkey Caused by Naegleria fowleri or Brain-Eating Amoeba

BACKGROUND

Naegleria fowleri, the causative agent of primary amoebic meningoencephalitis (PAM), is a free-living amoeba. It is a water-borne infection usually detected in children and young people with healthy immune system who swim, dive and perform activities in fresh and hot springs.

PURPOSE

In this study, it was aimed to raise awareness in the differential diagnosis of meningitis etiopathogenesis by showing that N. fowleri may also be the causative agent, albeit very rarely, in meningitis cases in Turkey.

METHODS

Our case was an 18-year-old male patient whose relatives stated that he has gone to the hot spring; his headache complaint started after 2 to 3 days after return from the hot spring. Cerebrospinal fluid (CSF) sample taken from the patient was investigated by direct microscopic examination, real-time PCR method and sequence analysis.

RESULTS

The CSF sample collected was taken into distilled water considering the possibility of transformation of trophozoites to intermediate form and incubated at 37 °C for 1 to 2 h, and pear-shaped non-permanent flagellated forms were observed in the direct microscopic examination, and molecular typing was performed to confirm the diagnosis. This study was a comprehensive case of N. fowleri whose etiological agent was isolated and confirmed by real-time PCR in Turkey.

CONCLUSION

Clinician awareness would be the key factor in correctly diagnosing PAM. It is also recommended to investigate all likely environmental water sources in Turkey for more detailed information on the distribution and molecular identification of Naegleria species, ultimately to evaluate the potential pathogenic threat to human health and to develop strategies to combat such threats.

Report of rare genotypes of Acanthamoeba from soil source of the Payeh Maga Highland forest, North-eastern Sarawak, Malaysia

Pathogenic Acanthamoeba species are the causative agents of Acanthamoeba keratitis and granulomatous amoebic encephalitis. Members of this amoeba genus are ubiquitous in the environments. In Malaysia, most environmental studies performed to date have targeted the detection and characterisation of Acanthamoeba sp. in different water sources, dust and soil samples collected near human habitats. However, no local study has yet to examine these amoebae in a forest, an isolated terrestrial environment, where human activity is relatively scarce. Further, there are also limited studies to investigate the same globally. The current study reported the isolation, morphological and genotypic characterisations of eleven Acanthamoeba sp. isolated from soils of the Payeh Maga Highland forest, Sarawak, Malaysia. Morphological analysis revealed that nine isolates belonged to Group II, whereas two isolates belonged to Group III as defined by the criteria of Pussard and Pons. The phylogenetic analysis based on complete 18S rRNA gene sequences showed that the isolates belonged to the rare T1 (six isolates), T6 (two isolates) and T13 (three isolates) genotypes. To the best of our knowledge, this is the first report about the detection of T6 Acanthamoeba sp. in this country. Overall, the current findings have enriched the knowledge pertaining to the occurrence, morphological and genotypic characteristics of Acanthamoeba sp. in an isolated terrestrial environment of Malaysia.

First time identification of subconjunctival Dirofilaria immitis in Turkey: giant episcleral granuloma mimicking scleritis

Dirofilariasis is a vector-borne disease that is present worldwide. This report describes a giant subconjunctival granuloma which mimics scleritis, caused by D. immitis. A 60-year-old man was referred with the complaints of irritation, redness, and swelling at the medial part of the right eye. He was living in Izmir province located in western Turkey. Slit-lamp examination showed a firm, immobile mass measuring 13.0 × 5.0 × 5.0 mm with yellowish creamy color. The mass was completely removed surgically under local anesthesia mainly for diagnosis. Histopathology revealed typical morphological features of a filarioid nematode in favor of Dirofilaria as characterized by the external smooth cuticular surface, cuticular layer, muscle layer, and intestinal tubule. Molecular study was performed using DNA isolated from paraffin-embedded tissue sections of the worm. PCR amplification and then DNA sequence analysis of cytochrome c oxidase subunit 1 (cox1) gene fragment confirmed that the worm was D. immitis. It is suggested that this may represent the first human case of D. immitis occurring in subconjunctival granuloma in Turkey. Although rare, D. immitis caused by ocular dirofilariasis in humans should be considered.

Evaluation of molecular characterization and phylogeny for quantification of Acanthamoeba and Naegleria fowleri in various water sources, Turkey

Free-living amoeba (FLA) is widely distributed in the natural environment. Since these amoebae are widely found in various waters, they pose an important public health problem. The aim of this study was to detect the presence of Acanthamoeba, B. mandrillaris, and N. fowleri in various water resources by qPCR in Izmir, Turkey. A total of (n = 27) 18.24% Acanthamoeba and (n = 4) 2.7% N. fowleri positives were detected in six different water sources using qPCR with ITS regions (ITS1) specific primers. The resulting concentrations varied in various water samples for Acanthamoeba in the range of 3.2x10⁵-1.4x10² plasmid copies/l and for N. fowleri in the range of 8x10³-11x10² plasmid copies/l. The highest concentration of Acanthamoeba and N. fowleri was found in seawater and damp samples respectively. All 27 Acanthamoeba isolates were identified in genotype level based on the 18S rRNA gene as T4 (51.85%), T5 (22.22%), T2 (14.81%) and T15 (11.11%). The four positive N. fowleri isolate was confirmed by sequencing the ITS1, ITS2 and 5.8S rRNA regions using specific primers. Four N. fowleri isolates were genotyped (three isolate as type 2 and one isolate as type 5) and detected for the first time from water sources in Turkey. Acanthamoeba and N. fowleri genotypes found in many natural environments are straightly related to human populations to have pathogenic potentials that may pose a risk to human health. Public health professionals should raise awareness on this issue, and public awareness education should be provided by the assistance of civil authorities. To the best of our knowledge, this is the first study on the quantitative detection and distribution of Acanthamoeba and N. fowleri genotypes in various water sources in Turkey.

The role of Acanthamoeba spp. in biofilm communities: a systematic review

Acanthamoeba spp. have always caused disease in immunosuppressed patients, but since 1986, they have become a worldwide public health issue by causing infection in healthy contact lens wearers. Amoebae of the Acanthamoeba genus are broadly distributed in nature, living either freely or as parasites, and are frequently associated with biofilms throughout the environment. These biofilms provide the parasite with protection against external aggression, thus favoring its increased pathogeny. This review aims to assess observational studies on the association between Acanthamoeba spp. and biofilms, opening potential lines of research on this severe ocular infection. A systematic literature search was conducted in May 2020 in the following databases: PubMed Central^®/Medline, LILACS, The Cochrane Library, and EMBASE^®. The studies were selected following the inclusion and exclusion criteria specifically defined for this review. Electronic research recovered 353 publications in the literature. However, none of the studies met the inclusion criterion of biofilm-producing Acanthamoeba spp., inferring that the parasite does not produce biofilms. Nonetheless, 78 studies were classified as potentially included regarding any association of Acanthamoeba spp. and biofilms. These studies were allocated across six different locations (hospital, aquatic, ophthalmic and dental environments, biofilms produced by bacteria, and other places). Acanthamoeba species use biofilms produced by other microorganisms for their benefit, in addition to them providing protection to and facilitating the dissemination of pathogens residing in them.

Variables Affecting the Recovery of Acanthamoeba Trophozoites

While the results of Acanthamoeba testing have been extensively published, laboratories conducting such testing are left to develop their own methods in the absence of a standardized methodology. The wide disparity of methods has resulted in equally inconsistent reported results for contact lens care (CLC) products. This study's objective was to determine the source of these discrepancies by evaluating basic Acanthamoeba biology and their impact on antimicrobial efficacy testing, including the ability of a recovery method to stimulate a single trophozoite to proliferate. Antimicrobial efficacy testing was conducted using well-published Acanthamoeba strains, storage conditions, and growth-based recovery methods. To identify variables that influence results, test solutions with low Acanthamoeba disinfection rates were utilized to prevent differences from being masked by high log reductions. In addition, single-cell proliferation assays were executed to understand the growth requirements to stimulate trophozoite propagation in two recovery methods. These studies indicated that both nutrient density (>106 CFU) and the length of plate incubation (at least 14 days) could significantly influence the accurate recovery of trophozoites. Together, this study emphasizes the need to understand how Acanthamoeba trophozoites biology can impact test methods to create divergent results.

Isolation and Molecular Identification of Acanthamoeba and Naegleria from Agricultural Water Canal in Qazvin, Iran

Background:

Free-living amoeba (FLA) are widely distributed in different environmental sources. The most genera of the amoeba are Acanthamoeba, Naegleria and Vermamoeba. The most common consequences of the infections in immune-deficient and immuno-competent persons are amoebic encephalitis and keratitis. The aim of this study was to investigate the presence of Acanthamoeba spp. and Naegleria spp., isolated from the main agricultural water canal in Qazvin.

Methods:

Totally, 120 water specimens were collected and later the specimens were cultured and cloned to identify positive samples. PCR amplification and sequencing were carried out to identify the isolated species as well as the genotypes of amoeba.

Results:

According to morphological surveys, 41.7% (50/120) of water specimens were positive for FLA. Molecular analysis revealed that 68.6% and 31.4% of Acanthamoeba specimens were identified as T3 and T4 genotypes, respectively. Also, two species of Naegleria named as N. lovaniensis (57.1%) and Naegleria sp. (42.8%) were identified. The results of pathogenicity assays demonstrated that 38.5% of T3 and 61.5% of T4 genotypes of Acanthamoeba were highly pathogenic parasites.

Conclusion:

The water flowing in the agricultural canal of the area is contaminated with potential pathogenic FLA, therefore, it is recommended that more attention to be paid towards proper treatment of water sources to prevent possible risk of the disease.

Genotyping of Acantamoeba spp. from rhisophere in Hungary

The protista Acanthamoeba is a free-living amoeba existing in various environments. A number of species among protista are recognized as human pathogens, potentially causing Acanthamoeba keratitis (AK), granulomatous amoebic encephalitis (GAE), and chronic granulomatous lesions. In this study, 10 rhizosphere samples were collected from maize and alfalfa plants in experimental station at Institute of Genetics, Microbiology and Biotechnology, Szent István University. We detected Acanthamoeba based on the quantitative real-time PCR assay and sequence analysis of the 18S rRNA gene. All studied molecular biological methods are suitable for the detection of Acanthamoeba infection in humans. The quantitative real-time PCR-based methods are more sensitive, simple, and easy to perform; moreover, these are opening avenue to detect the effect of number of parasites on human disease. Acanthamoeba species were detected in five (5/10; 50%) samples. All Acanthamoeba strains belonged to T4 genotype, the main AK-related genotype worldwide. Our result confirmed Acanthamoeba strains in rhizosphere that should be considered as a potential health risk associated with human activities in the environment.

Comparison of an in house and a commercial real-time polymerase chain reaction targeting Toxoplasma gondii RE gene using various samples collected from patients in Turkey

Background

Toxoplasma gondii is an opportunistic protozoan parasite that can infect all warm-blooded animals including humans and cause serious clinical manifestations. Toxoplasmosis can be diagnosed using histological, serological, and molecular methods. In this study, we aimed to detect T. gondii RE gene in various human samples by in house and commercial real time polymerase chain reactions.

Methods

A total of 38 suspected cases of toxoplasmosis [peripheral blood (n:12), amnion fluid (n:11), tissue (n:9), cerebrospinal fluid (n:5), and intraocular fluid (n:1)] were included to the study. An in house and a commercial RT-PCR were applied to investigate the T. gondii RE gene in these samples.

Results

The compatibility rate of the two tests was 94.7% (37/38). When the commercial RT-PCR kit was taken as reference, the sensitivity and specificity of in house RT-PCR test was 87.5 and 100%. When the in house RT-PCR test was taken as reference, the commercial RT-PCR kit has 100% sensitivity and 96.8% specificity. Incompatibility was detected in only in a buffy coat sample with high protein content.

Conclusions

Both the commercial and in house RT-PCR tests can be used to investigate T. gondii RE gene in various clinical specimens with their high sensitivity and specificity. In house RT-PCR assay can be favorable due to cost savings compared to using the commercial test.

Ocular Surface Disease in Birds

Avian ocular disease may be primary or a manifestation of systemic disease. Various infectious and noninfectious diseases have been reported to cause ocular pathology. Thorough physical examination and diagnostic testing are necessary to determine a treatment plan.