Acanthamoeba isolates belonging to T1, T2, T3, T4 and T7 genotypes from environmental freshwater samples in the Nile Delta region, Egypt

Potentially pathogenic free-living amoebae at very high altitude: Detection by multiplex qPCR in the Northern Altiplano fascioliasis hyperendemic area in Bolivia

Free-living amoebae (FLA), which are frequently found in the environment, include opportunistic pathogenic genera/species such as Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Vermamoeba vermiformis. These pathogenic FLA are causative agents of amoebic encephalitis and keratitis in the case of Acanthamoeba genus and V. vermiformis. In addition, amoebic infections are often related to contamination of domestic and recreational water sources. This study aimed to identify potentially pathogenic FLA in the hyperendemic area of human fascioliasis in a very-high-altitude area (3800-4100 m a.s.l.) of Bolivia and examine whether an association between both pathogens could be established from the environmental point of view. A total of 55 samples (28 soil and 27 water samples) were collected from various locations in the Northern Altiplano of Bolivia. Samples were processed by multiplex qPCR to detect the four pathogenic FLA genera/species. All samples were positive for the presence of V. vermiformis, followed by Acanthamoeba spp. which was positive in 18 soil and 10 water samples. In contrast, B. mandrillaris was only detected in soil sources, whereas N. fowleri was not detected in any of the samples. The coexistence and diverse distribution of multiple FLA species in many locations at such a high altitude is worth mentioning and indicates a potential risk of coinfections. These findings suggest that FLA surveillance is a crucial factor to be considered when implementing preventive measures and improving public health in fascioliasis hyperendemic areas.

Assessment of pathogenic potential of Acanthamoeba isolates by in vitro and in vivo tests

Acanthamoeba are free-living protozoa present ubiquitously in numerous environmental reservoirs that exist as an actively feeding trophozoite or a dormant cyst stage. The pathogenic Acanthamoeba are known to cause Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). Despite their omnipresence, the number of infections is quite low. The reason behind this low frequency of Acanthamoeba infections could be the existence of many non-pathogenic strains or a successful host immune response to these infections. Studies in the past have proposed a few physiological parameters for the differentiation of pathogenic and non-pathogenic strains. Additionally, in vivo experiments are known to play an essential role in understanding the virulence of parasites, immunological aspects, and disease pathogenesis. The thermotolerance (30 °C, 37 °C, and 40 °C) and osmotolerance (0.5 M, 1 M, and 1.5 M) tests were performed on 43 Acanthamoeba isolates from patients with keratitis (n = 22), encephalitis (n = 5), and water samples (n = 16). In addition, the genotype of 10 Acanthamoeba isolates (keratitis (n = 2), encephalitis (n = 2), water (n = 6)) was determined and were then evaluated for pathogenicity on mouse model by inducing Acanthamoeba keratitis and amoebic encephalitis. The results of the thermotolerance and osmotolerance assays categorized 29/43 (67.4%) isolates as pathogenic, 8 as low pathogenic (18.6%), and the remaining 6 (13.9%) as non-pathogenic. The 10 Acanthamoeba isolates were categorized as T11 (5 isolates), T5 (2 isolates), T4 (2 isolates), and T10 (1 isolate) genotypes. Out of 10 Acanthamoeba isolates, 9 were successful in establishing AK, amoebic encephalitis, or both in the mice model, and a single isolate was found non-pathogenic. Two isolates from water samples were non-pathogenic in the physiological tests but successfully established Acanthamoeba infection in the mice model. The results of the physiological assays and in vivo experiments were analogous for 7 isolates while 1 isolate from the water was low pathogenic in the physiological assays but failed to produce pathogenicity during in vivo experiments. The physiological parameters are not very dependable to test the pathogenic potential of Acanthamoeba isolates, and thus results must always be validated by in vivo experiments. There is no infallible approach for determining the potential pathogenicity of environmental isolates of Acanthamoeba because several parameters regulate the pathogenic potential.

Identification and genotyping of Acanthamoeba spp. in the water resources of western Iran

Background

Acanthamoeba spp. is opportunistic amoeba that resides in water, soil, and air. Some pathogenic genotypes of the genus of Acanthamoeba can cause granulomatous amoebic encephalitis (GAE) in people with a defective immune system. The parasite can also cause Acanthamoeba keratitis (AK) among contact lens users. This study was conducted to isolate and identify the Acanthamoeba genotypes in water resources in Lorestan province, western Iran.

Methods

Collected 72 water samples from surface and groundwater (springs and aqueducts) in Lorestan province. Samples were filtered and cultured in non-nutrient 1.5% agar medium covered with Escherichia coli (E. coli) at 25 °C. DNA extraction was done and the PCR reaction was performed to detect the Acanthamoeba spp. The positive PCR products were sequenced to determine the genotypes of Acanthamoeba.

Results

Out of 72 examined water samples, 23.61% were positive for Acanthamoeba sp. by PCR. From PCR-positive samples, 8 (47.05%) samples were T4 genotypes and others were other Acanthamoeba genotypes (T1-T23). Therefore, approximately half of the genotypes belong to the pathogenic T4 genotype.

Conclusions

The water examined samples in western provinces of Iran have the potential risk factor for public health. Therefore, the efforts of healthcare providers are needed to identify, train, and prevention from human infections.

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.

Isolation and morphological and molecular characterization of waterborne free-living amoebae: Evidence of potentially pathogenic Acanthamoeba and Vahlkampfiidae in Assiut, Upper Egypt

Free-living amoebae (FLA) are gaining attention due to the increasing number of related grave central nervous system (CNS) and sight-threatening eye infections and their role as Trojan horses for many bacteria and viruses. This study was conducted in Assiut City, Egypt to detect the presence of FLA in different water sources using morphological and molecular approaches and determine their potential pathogenicity. A total of 188 water samples (100 tap, 80 tank, and 8 swimming pool samples) were collected, cultivated on non-nutrient agar seeded with Escherichia coli, and inspected for FLA. Thermo- and osmo-tolerance assays were performed to determine their pathogenicity. Polymerase chain reaction and sequence analysis were performed to confirm the identification and analyze the genotype. Overall, 52 samples (27.7%) were positive for FLA. Of these, 20.7% were identified as Acanthamoeba, 1.6% as Vahlkampfiidae, and 5.3% as mixed Acanthamoeba and Vahlkampfiidae. Seven species of Acanthamoeba were recognized, of which A. triangularis, A. polyphaga, A. lenticulata, and A. culbertsoni are thermo- and osmo-tolerant, and A. astronyxis, A. comandoni, and A. echinulata are non-thermo- and non-osmo-tolerant. The phylogeny analysis revealed T4 and T7 genotypes. Among Vahlkampfiids, 61.5% were identified as thermo- and osmo-tolerant Vahlkampfia, and 30.8% were identified as non-pathogenic Naegleria. One isolate (7.7%) was identified as potentially pathogenic Allovahlkampfia, as confirmed by sequencing. This is the first report documenting the occurrence and phylogeny of waterborne FLA (Acanthamoeba/Vahlkampfiidae) in Assiut, Egypt. The presence of potentially pathogenic FLA highlights the possible health hazards and the need for preventive measures.

Isolation and identification of potentially pathogenic free-living amoeba in dental-unit water samples

Although the presence of free-living amoebae (FLAs) in various water sources has been reported, few studies have been surveyed on their abundance in medical-unit and dental-unit water samples. The current study aimed to identify morphological and molecular characteristics of FLA isolates in the water samples of the dental unit in Iran. A total of 232 water samples were collected from 17 dental units. Then, filtration and cultivation were conducted on a non-nutrient agar (NNA) medium. Also, polymerase chain reaction (PCR) assay and sequencing were performed by using the genus/species-specific primers plus a common primer set on positive samples. One hundred and sixty-six samples were positive for FLA by the microscopic method, whereas 114 samples were positive by the molecular method with a common primer set. Considering the PCR assay with genus/species-specific primers, 23.27% (54/232) samples were identified as Acanthamoeba spp. (belonging to T4 genotype), 36.63% (85/232) as Vermamoeba vermiformis, and 1.72% (4/232) as Vahlkampfiidae family (Naegleria lovaniensis). These results highlight a need to improve filtration systems in dental units and periodic screenings for FLA in dental-unit water.

Isolation and identification of potentially pathogenic free-living amoeba in dialysis fluid samples of hydraulic systems in hemodialysis units

BACKGROUND

Free-living amoeba (FLA), including Acanthamoeba, Naegleria, Balamuthia and Vermamoeba, have been isolated from water, sand, soil, dust and air. Numerous studies considered that FLA are a significant cause of neurological and ocular complications in high-risk groups, including immunocompromised individuals. The present study aimed to identify morphological and molecular characteristics of FLA isolates in dialysis fluid samples of hydraulic systems in hemodialysis units in Iran.

METHODS

A total of 328 dialysis fluid samples were collected from 16 dialysis machines, including 164 samples before hemodialysis sessions (after cleaning) and 164 samples after hemodialysis sessions (before cleaning). Filtration and cultivation were performed on non-nutrient agar medium. Also, PCR and sequencing were applied by using the genus-specific primers along with a common primer set on positive samples.

RESULTS

Both morphology and molecular investigations showed that 22.5% (74/328) of dialysis fluid samples were positive for FLA. There was a positive relationship between the high frequency of FLA after hemodialysis sessions (before cleaning) compared with before hemodialysis sessions (after cleaning) (OR=2.86; 95% CI 1.5 to 5.45). Considering the PCR assay, 16.46% (54/328) samples were identified as Acanthamoeba spp. (belonging to T3 and T4 genotypes), 5.18% (17/328) as Vermamoeba vermiformis and 0.91% (3/328) as Vahlkampfiidae family (Naegleria australiensis, Naegleria pagei and Allovahlkampfia).

CONCLUSION

The present results support a need to improve filtration and purification methods for dialysis fluid of hydraulic systems in hemodialysis units. They also highlight the relevance of periodic screenings for FLA-related diseases in hemodialysis patients.

Detection and Molecular Characterization of Potentially Pathogenic Free-Living Amoebae from Recreational and Public Soils in Mazandaran, Northern Iran

Background:

Free-living amoeba (FLA) belonging to Acanthamoeba spp., Naegleria, and Balamuthia mandrillaris are the soil-born protozoa. This study aimed to survey the occurrence of FLA, including Acanthamoeba spp., B. mandrillaris, Vermamoeba spp., and Naegleria spp., in soil samples collected from various districts of Mazandaran Province (Northern Iran) from July to December 2018.

Methods:

Overall, 118 soil samples from the recreational and public places were surveyed for the existence of Acanthamoeba spp., Vermamoeba, Naegleria, and B. mandrillaris using both morphological key and molecular tools with genus-specific primers of JDP1, NA, ITS1, and Bal, respectively. To verify the taxonomic status of isolated amoeba, the phylogenetic tree was made based on sequences of 18S rRNA by MEGA (5.05) software with the maximum likelihood model.

Results:

Overall, 61/118 samples (51.6%) were contaminated with FLA, and based on the sequencing data, 29 isolates were successfully sequenced. Among the samples, all isolated Acanthamoeba (52.4%) belonged to the T4 genotype with amplification of the DF3 region (18S rRNA gene). Internal transcribed spacer (ITS) sequencing revealed the presence of one strain of Naegleria americana. Twenty-eight V. vermiformis were also confirmed based on Nuclear SSU rDNA. Morphological survey and PCR assay did not show any positive samples for B. mandrillaris.

Conclusion:

The present study indicates the occurrence of FLA in soil sources of the recreational and public places in Mazandaran province that it can be a severe risk to human health. Thus, more studies are expected to survey the infection source in patients with FLA-related diseases.

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.

Derivatisation of metronidazole enhances cytotoxic effect against Acanthamoeba genotype T4 isolates and leads to cytomorphological changes in trophozoites

Amoebae of the genus Acanthamoeba are worldwide distributed causative agents of serious human infections such as granulomatous amoebic encephalitis (GAE) and Acanthamoeba keratitis (AK). To date, treatment of these infections is non-uniform and frequently unsuccessful. Recently, the phosphonium salts were studied for their high levels of antimicrobial activity. This work was aimed to investigate the cytotoxic effect of metronidazole and two phosphonium salts (PS1, PS2) on two clinical Acanthamoeba isolates. The isolates showed distinctly higher susceptibility to both phosphonium salts than to metronidazole. The highest susceptibility was noted to PS1 after 48 h of incubation. Metronidazole derivate PS2 showed higher susceptibility than metronidazole. The values of EC₅₀ of PS2 were approximately twenty times lower than EC₅₀ of metronidazole for Acanthamoeba lugdunensis strain and sixteen times lower for Acanthamoeba quina strain after 48 h. Although the therapeutic effect of metronidazole in Acanthamoeba infections is usually insufficient, its derivatisation can result in a significantly higher amoebicidal effect. Cytomorphological changes of trophozoites after exposure to tested compounds included rounding up of the cells, damage of membrane integrity, presence of pathological protrusions, elongation of the cells or pseudocyst-like stages. Obtained results indicate possible therapeutic potential of studied phosphonium salts.

Distribution of amoebal endosymbiotic environmental chlamydia Neochlamydia S13 via amoebal cytokinesis

We previously isolated a symbiotic environmental amoeba, harboring an environmental chlamydia, Neochlamydia S13. Interestingly, this bacterium failed to survive outside of host cells and was immediately digested inside other amoebae, indicating bacterial distribution via cytokinesis. This may provide a model for understanding organelle development and chlamydial pathogenesis and evolution; therefore, we assessed our hypothesis of Neochlamydia S13 distribution via cytokinesis by comparative analysis with other environmental Chlamydiae (Protochlamydia R18 and Parachlamydia Bn₉ ). Dual staining with 4',6-diamidino-2-phenylindole and phalloidin revealed that the progeny of Neochlamydia S13 and Protochlamydia R18 existed in both daughter cells with a contractile ring on the verge of separation. However, in contrast to other environmental Chlamydiae, little Neochlamydia S13 16S ribosomal DNA was amplified from the culture supernatant. Interestingly, Neochlamydia S13 failed to infect aposymbiotic amoebae, indicating an intimate interaction with the host cells. Furthermore, its infectious rates in cultures expanded from a single amoeba were always maintained at 100%, indicating distribution via cytokinesis. We concluded that unlike other environmental Chlamydiae, Neochlamydia S13 has a unique ability to divide its progeny only via host amoebal cytokinesis. This may be a suitable model to elucidate the mechanism of cell organelle distribution and of chlamydial pathogenesis and evolution.

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.

Update on Acanthamoeba phylogeny

The evolutionary history of Acanthamoeba has been substantially resolved by the 18S rDNA phylogeny which made it possible to delimit the main lines associated with some classical species. Some of them have proven to be polyphyletic, but the inappropriate use of treating under the same names unrelated strains persists. In this study, phylogenies based on the complete genes of nuclear and mitochondrial rDNA were compared, in order to verify the congruence of the different lines. Various groups can thus be identified, some of which associated with the type strains of given species. Recognizing them only by their species names would significantly reduce the current confusion, in addition to logically following basic taxonomic rules. In this manner, the well-known polyphyletic taxa A. castellanii and A. polyphaga, are restricted to the two lines specified by their type strains, while other widely used strains like Neff and Linc-AP1 that are often confused with the previous ones, can be assigned to their own lines. New species are potentially present in other groups and additional efforts are needed to delimit them.

Thermotolerant Acanthamoeba spp. isolated from recreational water in Gorgan City, north of Iran

Acanthamoeba as free-living parasites are scattered ubiquitously, throughout the world. This study was aimed to evaluate the presence of Acanthamoeba spp. genotypes in the recreational water sources in Gorgan County, the capital of Golestan Province using both morphological and molecular approaches. Thirty water samples were collected from different recreational waters in Gorgan, the capital of Golestan Province, northern Iran during 2015-2016. Samples were filtered and followed by culture in non-nutrient agar. Acanthamoeba were identified both by morphological and molecular analysis. The pathogenical potential of positive cloned samples were also determined using tolerance test. Twenty-six percent of recreational water were identified as Acanthamoeba spp. based on the morphological analysis and from these positive samples, five samples were successfully sequenced after molecular studies. Phylogenetic analysis showed the clustering of four samples in T4 genotype group and only one sample as T15 genotype. Thermotolerance test revealed that all cloned samples were highly positive. Since the attractiveness of recreational places for people is increasing, the potential risk of this water should be monitored routinely in each region. More studies are needed to better evaluate the risk of this ubiquitous parasite for the human.

Cellulose fibrils formation and organisation of cytoskeleton during encystment are essential for Acanthamoeba cyst wall architecture

Acanthamoebae success as human pathogens is largely due to the highly resistant cysts which represent a crucial problem in treatment of Acanthamoeba infections. Hence, the study of cyst wall composition and encystment play an important role in finding new therapeutic strategies. For the first time, we detected high activity of cytoskeletal elements - microtubular networks and filamentous actin, in late phases of encystment. Cellulose fibrils - the main components of endocyst were demonstrated in inter-cystic space, and finally in the ectocyst, hereby proving the presence of cellulose in both layers of the cyst wall. We detected clustering of intramembranous particles (IMPs) and their density alterations in cytoplasmic membrane during encystment. We propose a hypothesis that in the phase of endocyst formation, the IMP clusters represent cellulose microfibril terminal complexes involved in cellulose synthesis that after cyst wall completion are reduced. Cyst wall impermeability, due largely to a complex polysaccharide (glycans, mainly cellulose) has been shown to be responsible for Acanthamoeba biocide resistance and cellulose biosynthesis pathway is suggested to be a potential target in treatment of Acanthamoeba infections. Disruption of this pathway would affect the synthesis of cyst wall and reduce considerably the resistance to chemotherapeutic agents.

Molecular characterization and phylogenetic analysis of Acanthamoeba isolates in tap water of Beni-Suef, Egypt

The genus Acanthamoeba is a free-living amoeba widely distributed in various aquatic environments. It is an etiologic cause of amoebic encephalitis and keratitis particularly for immunocompromised individuals. The purpose of the present study was to investigate Acanthamoeba species prevalence in household and hospital potable water in Beni-Suef governorate, Egypt, and to employ sequencing methods to identify positive Acanthamoeba species isolates and their potential health risks. Sixty tap water samples (30 household and 30 governmental and private hospital settings) collected from Beni-Suef governorate, Egypt were filtered, cultured on non-nutrient agar, identified by morphotyping keys after staining with Giemsa stain and then confirmed by PCR using Acanthamoeba specific primers. Twenty positive samples were successfully genetically characterized and phylogenetically analyzed to identify Acanthamoeba species. The total detection rate for Acanthamoeba was 48/60 (80%); Acanthamoeba contamination in water collected from domestic houses was higher than in hospitals; 27/30 (90%) versus 21/30 (70%) with statistical significant value (P value = 0.05). Sequencing of 20 positive isolates revealed Acanthamoeba T4 in 65% and T2 in 35%. To our knowledge, this is the first research that documents the occurrence and phylogeny of Acanthamoeba species in Beni-Suef, Egypt. The presence of a higher percentage of Acanthamoeba species in tap water, in particular T4, highlights the potential health hazards for immunocompromised individuals and emphasizes the urgent need for the implementation of effective filtration and disinfection measures.

Isolation and Genotyping of Acanthamoeba from Soil Samples in Markazi Province, Iran

AIM:

A previous study confirmed the contamination of water sources with this parasite in Arak, Markazi Province, Iran. The current study investigated soil sources and determined the predominant genotype of Acanthamoeba in this region of Iran.

MATERIAL AND METHODS:

Forty-eight soil samples, collected from different regions of Arak, Markazi province, Iran, were evaluated in this study. The samples were processed and identified by culturing on a specific medium, performing PCR assay, and sequencing the PCR products. Finally, using the NCBI database, the genotypes were determined.

RESULTS:

Of 48 soil samples, 33.3% and 31.25% were contaminated with Acanthamoeba according to the culture and molecular assays, respectively. The majority of these isolates belonged to the T4, T5 and T6 genotypes of Acanthamoeba.

CONCLUSION:

The genotypes of most isolates from soil samples in Arak similar to other regions of Iran belong to T4 genotype of this parasite. New sequence accession numbers include MG066681 and MG298785-MG298794.

Acanthamoeba keratitis in Mexico: Report of a clinical case and importance of sensitivity assays for a better outcome

Acanthamoeba keratitis (AK) is a sight-threatening corneal infection. The early symptoms include redness, pain, photophobia and intense tearing. Chronic infection usually progresses to stromal inflammation, ring ulcers, corneal opacification and hypopyon. Here we document an AK case in a high myopic 38-year-old woman from Mexico City, with a history of wearing contact lenses while swimming. Corneal scrapes cultures were positive only for amoebae, consequently a treatment including netilmicin 0.3% and oral itraconazole 100 mg/12 h was prescribed. The infection was resolved after 8 months, leaving a slight leucoma outside the visual axis, with a visual acuity of 20/150. In the laboratory, the amoebic isolate was axenized in PYG medium, with an optimal growth at 30 °C, and was identified morphologically as Acanthamoeba polyphaga according to the taxonomic criteria of Page (1988) and placed in the T4 group by genotyping. The virulence of this strain (40%) was determined by intranasal inoculation of 1 × 10⁶/20 μl trophozoites in BALB/c mice recovering from brain, proving their invasion ability and by the interaction with monolayers of epithelial cells of the established MDCK line of canine kidney origin (1:2 ratio of interaction), at 1, 3, 6, 8 and 24 h; trophozoites migrated to cell junctions inducing few lytic zones. In addition to the biological characterization, in vitro drug sensitivity tests were performed using chlorhexidine, itraconazole, netilmicin and voriconazole. Results revealed that voriconazole was the most effective compound. A. polyphaga remains as one of the most frequently isolated species producing AK. The treatment of AK case using netilmicin and oral itraconazole solved the disease, but the healing process was wide-ranging (8 months). The use of voriconazole and chlorhexidine may be an alternative treatment of future AK cases in Mexico.

Genotypic characterization and assessment of infectivity of human waterborne pathogens recovered from oysters and estuarine waters in Brazil

Waterborne, food-borne and sewage-borne pathogens are a major global concern, with the annual recurrence, most notably during the summer, of outbreaks of gastroenteritis of unconfirmed etiology associated with recreational activities in marine environments. The consumption of contaminated water-based foodstuffs is also related to outbreaks of human illness. The main goals of the present study were: i) to identify the genetic assemblages of Giardia duodenalis cysts in growing and depurated oysters destined for human consumption on the southern coast of São Paulo, Brazil; ii) to verify the main circulating G. duodenalis assemblages and their subtypes in different brackish waters used for the production of mollusks and for recreational purposes; iii) to track the contamination of growing and depurated oysters by the human adenovirus and identify the infectivity of adenoviral particles recovered from oysters before and after depuration; iv) to evaluate the occurrence and genotype of the free-living amoebae of the genus Acanthamoeba in brackish water and oysters from all the sites described above. Four sampling sites in the Cananeia estuary were selected to search for pathogenic and amphizoic protozoa (Giardia and Acanthamoeba respectively): site 1: oyster growth, site 2: catchment water (before UV depuration procedure), site 3: filter backwash (filtration stage of water treatment) and site 4: oyster depuration tank. Oysters at sites 1 and 4 were evaluated for the presence of adenovirus (HAdV). Analysis consisted of conventional microbiological as well as molecular methods. Giardia duodenalis were detected in all the water sites analyzed and the molecular analysis revealed that sub-assemblage AII was the most frequently distributed throughout the estuarine environment, although one sample was identified as belonging to the assemblage C. Acanthamoeba were also isolated from different locations of the estuarine area, and were detected at all the analyzed sites. The majority of isolates belonged to the T3 genotype, while the T4 genotype was identified once. The sequencing reaction of Giardia duodenalis revealed the contamination of three batches of depurated oysters by the sub-assemblage AII. With respect to viruses, seven batches of oysters (four growing and three depurated) were found to be harboring infectious HAdV particles when submitted to plaque assay. Overall, the results of the sequencing reactions combined with the plaque assay revealed that the isolates of Giardia duodenalis and the infectious HAdV particles identified in oyster tissues have the potential to infect humans and pose a threat if consumed raw or lightly cooked. This is the first report on the sub-assemblage AII identified in oysters which are submitted to a cleaning and disinfection procedure prior to human consumption in Brazil. Acanthamoeba specific genotypes were also identified for the first time in a recreational estuarine area in Brazil, contributing to knowledge of their molecular and environmental epidemiology, which is considered scarce even in marine and estuarine areas of the world.

Occurrence of Acanthamoeba genotypes in Central West Malaysian environments

Acanthamoeba species are ubiquitous free-living protozoa that can be found worldwide. Occasionally, it can become parasitic and the causative agent of acanthamoebic keratitis (AK) and Granulomatous Amoebic Encephalitis (GAE) in man. A total of 160 environmental samples and 225 naturally-infected animal corneal swabs were collected for Acanthamoeba cultivation. Acanthamoeba was found to be high in samples collected from environments (85%, 136/160) compared to infected animal corneas (24.89%, 56/225) by microscopic examination. Analysis of nucleotide sequence of 18S rRNA gene of all the 192 cultivable Acanthamoeba isolates revealed 4 genotypes (T3, T4. T5 and T15) with T4 as the most prevalent (69.27%, 133/192) followed by T5 (20.31%), T15 (9.90%) and T3 (0.52%). Genotype T4 was from the strain of A. castellanii U07401 (44.27%), A. castellanii U07409 (20.83%) and A. polyphagaAY026243 (4.17%), but interestingly, only A. castellanii U07401 was detected in naturally infected corneal samples. In environmental samples, T4 was commonly detected in all samples including dry soil, dust, wet debris, wet soil and water. Among the T4, A. castellanii (U07409) strains were detected high occurrence in dry (45%) followed by aquatic (32.50%) and moist (22.50%) samples but however A. castellanii (U07401) strains were dominant in dry samples of soil and dust (93.10%). Subsequently, genotype T5 of A. lenticulata (U94741) strains were dominant in samples collected from aquatic environments (58.97%). In summary, A. castellanii (U07401) strains were found dominant in both environmental and corneal swab samples. Therefore, these strains are possibly the most virulent and dry soil or dusts are the most possible source of Acanthamoeba infection in cats and dogs corneas.

Free-living amoebae in the water resources of Iran: a systematic review

Free-living amoebae (FLA) are a group of protozoa with the capabilities of growth in the environment and invasion to the human body which have been isolated from different water sources. Acanthamoeba, Naegleria, and Balamuthia are the most important FLA. These cause a variety of severe complications of eye and central nervous system. Despite the fact that various studies have demonstrated the prevalence of FLA in different parts of Iran, there is no comprehensive evaluation and conclusion regarding the pollution of various water sources in Iran. This review was carried out to achieve the prevalence pattern of FLA in water resources across Iran to design appropriate health strategies. For this purpose, 8 online databases in English and Persian and also graduate thesis and national parasitology congresses were studied. The key words such as "free living amoebae", "Acanthamoeba", "Naegleria", "Hartmannella", "Balamuthia", "Sappinia", "Vermamoebae", "Valkampfia", "water resources", "water" and "Iran" were used to search articles between 1990 to 2017. From a total of 236 articles found, 38 reliable articles were included in the study. From the total number of investigated studies, the estimated prevalence was obtained as 36% among 2430 samples. Although Acanthamoeba prevalence has been considered as a priority, most kinds of free-living amoebae were found in all kinds of water resources. Due to the lack of free-living amoebae prevalence in more than a quarter of the Iranian provinces, more studies are recommended to achieve a better perspective to make comprehensive decisions to improve the hygiene of water resources.

Isolation and molecular characterization of a Naegleria strain from a recreational water fountain in Tenerife, Canary Islands, Spain

Free-Living Amoebae (FLA) are widely distributed protozoa in the environment and have been isolated from many sources such as dust, soil and water. Among the pathogenic genera included in this group Acanthamoeba spp., Naegleria fowleri and Balamuthia mandrillaris have been reported to be causative agents of lethal encephalitis, disseminated infections and keratitis. Naegleria fowleri is a pathogenic FLA species which causes Primary Amoebic Meningoencephalitis (PAM). At present there are not many available data on the distribution of Naegleria species in Spain from environmental sources. Therefore, the aim of this study was to evaluate the presence of this genus in recreational water sources in the island of Tenerife, Canary Islands, Spain. In this study, ten samples collected from recreational water fountains were checked for the presence of Naegleria spp. using morphological and molecular identification tools. From the analysed samples, only one sample (seawater fountain) was positive for Naegleria spp. interestingly, not many reports of Naegleria spp. in seawater are available in the literature and thus awareness should be raised among the environmental and public health professionals.

Molecular and Morphometric Characterization of Acanthamoeba spp. from Different Water Sources of Northwest Iran as a Neglected Focus, Co-Bordered With the Country of Iraq

Background

Acanthamoeba spp. is a free-living opportunistic protozoan parasites, which can be found in tap, fresh and bottled mineral waters, contact lens solutions, soil etc.

Objectives

The present study is aimed to determine the Acanthamoeba spp. on the basis of their morpho-molecular aspects in different water sources of the West Azerbaijan province, Northwest of Iran.

Methods

In this cross-sectional study, 60 water samples were collected from rivers and tap waters during June to September 2015. The water samples were filtered through a cellulose nitrate filter and cultured on non-nutrient agar medium. The extracted DNAs were amplified and some ampliqons were sequenced using partial 18S rRNA for genotyping and phylogenetic analyses.

Results

Twenty-seven (45%) out of 60 water samples were positive to Acanthamoeba spp. using both culture and morphological examinations. In addition, 24 (40%) out of 27 positive samples in culture method were confirmed by PCR to be Acanthamoeba spp.

Conclusions

A relatively high prevalence of Acanthamoeba spp. in rivers reflects a risk alert for threatening human health in the region. However, well hygienic status of the tap waters considering Acanthamoeba spp. cannot be ignored in western co-border regions of Iran-Iraq. This study can also serve as a platform for further explorations of water sources in Iran and neighboring countries.

In vivo CNS infection model of Acanthamoeba genotype T4: the early stages of infection lack presence of host inflammatory response and are a slow and contact-dependent process

This study was developed in order to describe the early morphological events observed during the invasion of two pathogenic strains of Acanthamoeba (genotype T4); A. castellanii and A. culbertsoni, at the olfactory meatus and cerebral, pulmonary, renal, hepatic and splenic tissues levels, an in vivo invasion study. Histological and immunohistochemical description of the events at 24, 48, 72, and 96 h postintranasal inoculations of BALB/c mice was performed. A. castellanii showed a higher invasion rate than A. culbertsoni, which was only able to reach lung and brain tissue in the in vivo model. The current study supports previous evidence of lack of inflammatory response during the early stages of infection. Acanthamoeba invasion of the CNS and other organs is a slow and contact-dependent process. The early morphological events during the invasion of amoebae include the penetration of trophozoites into different epithelia: olfactory, respiratory, alveolar space, and renal tubule, which resemble the process of amoebae invasion described in corneal tissue. The data suggest that after reaching the nasal epithelium, trophozoites continued invasion, separating and lifting the most superficial cells, then migrating and penetrating between the cell junctions without causing a cytolytic effect on adjacent cells. These results reaffirm the idea that contact-dependent mechanisms are relevant for amoebae of Acanthamoeba genus regardless of the invasion site.

High occurrence of Acanthamoeba genotype T4 in soil sources from Bolívar State, Venezuela

Pathogenic strains of Acanthamoeba are causative agents of keratitis and encephalitis that often may end fatal in humans and other animals. In the present study, twenty-seven soil samples were collected in the Bolivar State in Venezuela and checked for the presence of Acanthamoeba. Samples were cultivated onto 2% non-nutrient agar plates seeded with a layer of heat killed E. coli. Amplification by PCR and sequencing of the DF3 region of the 18S rDNA of Acanthamoeba was carried out in order to confirm morphological identification of the amoebae. Furthermore, Acanthamoeba spp. was isolated from 51.8% of soil samples. Sequencing of the DF3 region of the 18S rDNA resulted in the identification of genotype T4 in all samples. To the best of our knowledge, this is the first report of genotype T4 in soil sources from Venezuela. Further studies should be carried out in this State and in the country in order to determine the current occurrence of Acanthamoeba in Venezuelan environments.

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

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.

Prevalence of Naegleria fowleri in Environmental Samples from Northern Part of India

Naegleria fowleri the causative agent of Primary Amoebic Meningoencephalitis, is ubiquitously distributed worldwide in various warm aquatic environments and soil habitats. The present study reports on the presence of Naegleria spp. in various water bodies present in Rohtak and Jhajjar district, of state Haryana, India. A total of 107 water reservoirs were screened from summer till autumn (2012 and 2013). In order to isolate Naegleria spp. from the collected water samples, the water samples were filtered and the trapped debris after processing were transferred to non-nutrient agar plates already seeded with lawn culture of Escherichia coli. Out of total 107 water samples, 43 (40%) samples were positive by culture for free living amoeba after incubation for 14 days at 37°C. To identify the isolates, the ITS1, 5.8SrDNA and ITS2 regions were targeted for PCR assay. Out of total 43 positive samples, 37 isolates were positive for Naegleria spp. using genus specific primers and the most frequently isolated species was Naegleria australiensis. Out of 37 Naegleria spp. positive isolates, 1 isolate was positive for Naegleria fowleri. The sequence analysis revealed that the Naegleria fowleri strain belonged to Type 2.

Isolation and identification of pathogenic free-living amoeba from surface and tap water of Shiraz City using morphological and molecular methods

Free-living amoebae (FLA) are the most abundant and widely distributed protozoa in the environment. An investigation was conducted to determine the presence of free-living amoebae (FLA), Acanthamoeba and Vermamoeba in waterfronts of parks and squares and tap water of Shiraz City, Iran. FLA are considered pathogenic for human. These ubiquitous organisms have been isolated from different environments such as water, soil, and air. Eighty-two water samples were collected from different places of Shiraz City during the summer of 2013. All samples were processed in Dept. of Parasitology and Mycology, Shiraz University of Medical Sciences, Fars, Iran. Samples were screened for FLA and identified by morphological characters in the cultures, PCR amplification targeting specific genes for each genus and sequencing determined frequent species and genotypes base on NCBI database. Overall, 48 samples were positive for Acanthamoeba and Vermamoeba in non-nutrient agar culture based on morphological characteristics. The PCR examination was done successfully. Sequencing results were revealed T4 (62.96 %) genotypes as the most common genotype of Acanthamoeba in the Shiraz water sources. In addition, T5 (33.33 %) and T15 (3.71 %) were isolated from water supplies. Vermamoeba vermiformis was known the dominant species from this genus. The high frequency of Acanthamoeba spp. and Vermamoeba in different environmental water sources of Shiraz is an alert for the public health related to water sources. The result highlights a need for taking more attention to water supplies in order to prevent illnesses related to free-living amoebae.

Ophthalmology hospital wards contamination to pathogenic free living Amoebae in Iran

The present study was conducted to determine the occurrence of potentially pathogenic free-living amoeba in ophthalmology wards in reference hospitals in Iran. Since an increasing number of Acanthamoeba Keratitis cases after eye surgery and eye trauma have been recently observed in this country, it could be possible that the disinfection procedures undertaken in the clinical setting may not have a good hygiene and disinfection procedures, hence the aim of this study. Therefore, 42 dust and biofilm samples were collected from different areas of ophthalmology wards and checked for the presence of FLA using morphological criteria, PCR based analysis and DNA sequencing. Of the 42 samples from dust and biofilm sources, 18(42.86%) isolates were found to contain FLA and 12(92.3%) isolates belonged to Acanthamoeba T4 genotype. Isolation of the pathogenic genotype T4 from medical instruments, including slit lamp in corneal wards, may be a threat for patients undergoing eye surgery in these wards. Other FLA isolated in this study included Acanthamoeba genotype T5, Vahlkampfia sp, Naegleria australiensis, Vermamoeba vermiformis and Echinamoeba exudans. To our knowledge, this is the first report of the presence of potentially pathogenic FLA in ophthalmology wards in Iran. Improved disinfection methods and monitoring of hospitals ward are thus necessary in this area in order to minimize the risk of infection in patients.

Isolation and molecular characterization of Acanthamoeba genotypes in recreational and domestic water sources from Jamaica, West Indies

Free living amoebae (FLA) are amphizoic protozoa that are ubiquitous in nature. Infection with FLA may result in neurological, ocular and skin infections. Exposure to Acanthamoeba occurs frequently through water contact and knowledge of the presence of the organisms in water sources is important in understanding transmission dynamics. The distribution of Acanthamoeba was studied in recreational and domestic water samples collected from across Jamaica. Morphological assessment and polymerase chain reaction revealed Acanthamoeba spp. isolates in 50.6% (42/83) and 17.3% (14/81) of recreational and domestic water, respectively. Sequencing of the DF3 region of the 18S rDNA resulted in the identification of genotypes T3, T4, T5, T10 and T11 corresponding to Acanthamoeba spp: A. griffini, A. triangularis, A. lenticulata, A. culbertsoni and A. hatchetti. Moreover, T4 was the most frequently isolated genotype in both recreational and domestic water. Thermotolerance and osmotolerance assays indicated that most isolates were potentially pathogenic. This is the first report of T3 and T10 genotypes in the Caribbean and the first report of these Acanthamoeba spp. in Jamaican waters. The study shows that there is potential risk of infection to contact wearers who practise poor lens care. Further, Acanthamoeba should be considered as a cause of neurological infections in Jamaica.

Molecular Characterization of Pathogenic Acanthamoeba Isolated from Drinking and Recreational water in East Azerbaijan, Northwest Iran

Acanthamoeba- related infections, such as amoebic keratitis and granulomatous amoebic encephalitis, can develop in high-risk population through contaminated water sources. Thus, surveying water resources, particularly those available for human use, is of the utmost importance. In the present study, 67 water samples were collected from water resources in East Azerbaijan, a province in northwestern Iran. Samples were cultured on enriched non-nutrient agar plates, and sequencing-based approaches were used for genotyping. The pathogenic potential of the isolates was determined using thermo- and osmo-tolerance tests. Acanthamoeba were detected in 17 (25.4%) of the 67 collected samples. Sequencing analysis revealed that the isolates belonged to the T3 (23.52%), mixed T3/T4 (5.88%), T4 (58.82%), T5 (5.88%), and T13 (5.88%) genotypes. Through thermo- and osmo-tolerance tests, 88.23% of isolates were resistant to 37 °C, 40 °C temperature, and 0.5 M and 1 M osmolarity; thus, these isolates had the potential for pathogenicity. These findings point toa serious public health concern in the studied region. This study is the first to report Acanthamoeba isolated from drinking and recreational water sources in East Azerbaijan and Acanthamoeba T13 isolated from tap water in Iran.

Molecular characterization of Acanthamoeba strains isolated from domestic dogs in Tenerife, Canary Islands, Spain

The present study describes two cases of Acanthamoeba infections (keratitis and ascites/peritonitis) in small breed domestic dogs in Tenerife, Canary Islands, Spain. In both cases, amoebic trophozoites were observed under the inverted microscope and isolated from the infected tissues and/or fluids, without detecting the presence of other viral, fungal or bacterial pathogens. Amoebae were isolated using 2 % non-nutrient agar plates and axenified for further biochemical and molecular analyses. Osmotolerance and thermotolerance assays revealed that both isolates were able to grow up to 37 °C and 1 M of mannitol and were thus considered as potentially pathogenic. Moreover, the strains were classified as highly cytotoxic as they cause more than 75 % of toxicity when incubated with two eukaryotic cell lines. In order to classify the strains at the molecular level, the diagnostic fragment 3 (DF3) region of the 18S rDNA of Acanthamoeba was amplified and sequenced, revealing that both isolates belonged to genotype T4. In both cases, owners of the animals did not allow any further studies or follow-up and therefore the current status of these animals is unknown. Furthermore, the isolation of these pathogenic amoebae should raise awareness with the veterinary community locally and worldwide.

Morphological Features and In Vitro Cytopathic Effect of Acanthamoeba griffini Trophozoites Isolated from a Clinical Case

Light and transmission electron microscopy observations are reported on the structure and in vitro cytopathic effect of Acanthamoeba griffini trophozoites isolated from a clinical case. Live trophozoites were moderately active with a remarkable pleomorphism which changed from ovoid to quite elongated shapes. When moving, amoebae formed cytoplasmic projections such as wide lamellae and acanthopodia of diverse size and thickness which contain a significant amount of actin. Ultrastructurally, the cytoplasm showed the main organelles found in other free-living amoebae. Coincubation of trophozoites with MDCK cell monolayers resulted in a local damage to target cells after 24 h of interaction, suggesting that the cytopathic effect is contact-dependent. By transmission electron microscopy, amoebae appeared to engulf small portions of the MDCK cells; however, the cells that were not in contact with trophozoites had an unaltered morphology. When epithelial monolayers were incubated with conditioned medium for 24 h, small areas of cell injury were also observed. The phylogenetical analysis as well as the sequencing of the acquired amplified product for the DF3 region of the amoebae isolate confirmed that it belongs to genotype T3, which includes other pathogenic amoebae; besides the activity of two drugs currently used against Acanthamoeba was tested on A. griffini.

Presence of potentially pathogenic free-living amoebae strains from well water samples in Guinea-Bissau

Free-living amoebae (FLA) include opportunistic pathogens such as Naegleria fowleri, Balamuthia mandrillaris, and the genera Sappinia and Acanthamoeba. In this study, a survey was conducted in order to evaluate the presence of potentially pathogenic amoebic strains in water samples collected from wells located in the western part of Guinea-Bissau. The samples were left to precipitate for 48 hours and then the sediments were seeded on non-nutrient agar plates containing Escherichia coli spread and cultures were checked daily for the presence of FLA. Identification of FLA strains was based on the morphological and polymerase chain reaction (PCR) using the 18S rDNA or 16S mitochondrial rDNA genes in the case of Naegleria and Balamuthia genera, respectively. In the case of positive samples of Acanthamoeba, strains were further classified at the genotype level by sequencing the diagnostic fragment 3 (DF3) region located in the 18S rDNA gene as previously described. Sappinia sp. was not isolated during the study and thus, no molecular analysis was performed for this genus. The obtained results revealed the presence of Acanthamoeba (genotypes T3 and T4), Naegleria fowleri, and Balamuthia mandrillaris. To the best of our knowledge, this is the first report demonstrating the presence of FLA in water bodies from Guinea-Bissau and the first report on the isolation of Balamuthia mandrillaris from environmental sources in Africa.

Genotyping of potentially pathogenic Acanthamoeba strains isolated from nasal swabs of healthy individuals in Peru

Free Living Amoebae (FLA) of Acanthamoeba genus are widely distributed in the environment and can be found in the air, soil and water; and have also been isolated from air-conditioning units. In humans, they are causative agents of a sight-threating infection of the cornea, Acanthamoeba keratitis (AK) and a fatal infection of the central nervous system known as Granulomatous Amoebic Encephalitis (GAE). In this study, a survey was conducted in order to determine the presence and pathogenic potential of free-living amoebae of Acanthamoeba genus in nasal swabs from individuals in two regions of Peru. Identification of isolates was based on cyst morphology and PCR-sequencing of the Diagnostic Fragment 3 to identify strains at the genotype level. The pathogenic potential of the isolates was also assayed using temperature and osmotolerance assays and extracellular proteases zymograms. The obtained results revealed that all isolated strains exhibited pathogenic potential. After sequencing the highly variable DF3 (Diagnostic Fragment 3) region in the 18S rRNA gene as previously described, genotype T4 was found to be the most common one in the samples included in this study but also genotype T15 was identified. To the best of our knowledge, this is the first study on the characterization of Acanthamoeba strains at the genotype level and the first report of genotype T4 and T15 in Peru.

Influence of Acanthamoeba genotype on clinical course and outcomes for patients with Acanthamoeba keratitis in Spain

Genotype T4 is by far the most frequent genotype of Acanthamoeba keratitis (AK) and therefore has been considered the most virulent. This study included 14 cases of AK of genotype T4 and three cases of non-T4 genotype. We found that cases of non-T4 genotype had a worse response to medical therapy, greater need for surgical intervention, greater risk of extracorneal involvement, and remarkably poorer final visual outcome than those of T4 genotype, suggesting an association between Acanthamoeba virulence and genotype that requires additional case investigation.

Diversity and seasonal impact of Acanthamoeba species in a subtropical rivershed

This study evaluated the presence of Acanthamoeba species in the Puzih River watershed, which features typical subtropical monsoon climate and is located just above the Tropic of Cancer in Taiwan. The relationship between the seasonal and geographical distributions of Acanthamoeba species in this rivershed was also investigated. Acanthamoeba species were detected in water samples using the amoebal enrichment culture method and confirmed by PCR. A total of 136 water samples were included in this study, 16 (11.7%) of which contained Acanthamoeba species. Samples with the highest percentage of Acanthamoeba (32.4%) were obtained during the summer season, mainly from upstream areas. The identified species in the four seasons included Acanthamoeba palestinensis (T2), Acanthamoeba sp. IS2/T4 (T4), Acanthamoeba lenticulata (T5), Acanthamoeba hatchetti (T11), Acanthamoeba healyi (T12), and Acanthamoeba jacobsi (T15). The most frequently identified Acanthamoeba genotype was T4 (68.7%). Acanthamoeba genotype T4 is responsible for Acanthamoeba keratitis and should be considered for associated human health risk potential in the rivershed.

Co-isolation of Vahlkampfia and acanthamoeba in acanthamoeba-like keratitis in a Spanish population

PURPOSE

To report the co-isolation incidence of Acanthamoeba and Vahlkampfia in amoebic keratitis from a tertiary care institution in Madrid, Spain.

METHODS

In this retrospective case series, 7 eyes of 7 consecutive patients with culture-proven or polymerase chain reaction-positive Acanthamoeba keratitis were seen at a tertiary care institution from January 2010 to April 2011, and their charts were reviewed.

RESULTS

Two of 7 patients showed mixed Acanthamoeba and Vahlkampfia keratitis. Good clinical response to the treatment was strongly correlated with early diagnosis, whereas delayed diagnosis resulted in poor response to the treatment in single or mixed infection.

CONCLUSIONS

Co-isolation of Vahlkampfia and Acanthamoeba in Acanthamoeba-like keratitis has recently been detected in our population. This finding should raise awareness of the existence of other amoeba different from Acanthamoeba causing keratitis. There are not enough cases yet to determine the impact of mixed amoebic keratitis in the prognosis of this disease.

Isolation and molecular characterization of potentially pathogenic Acanthamoeba genotypes from diverse water resources including household drinking water from Khyber Pakhtunkhwa, Pakistan

Acanthamoeba, an opportunistic protozoan pathogen, is ubiquitous in nature, and therefore plays a predatory role and helps control microbial communities in the ecosystem. These Acanthamoeba species are recognized as opportunistic human pathogens that may cause blinding keratitis and rare but fatal granulomatous encephalitis. To date, there is not a single report demonstrating Acanthamoeba isolation and identification from environmental sources in Pakistan, and that is the aim of this study. Acanthamoeba were identified by morphological characteristics of their cysts on non-nutrient agar plates seeded with Escherichia coli. Additionally, the polymerase chain reaction (PCR) was performed with genus-specific primers followed by direct sequencing of the PCR product for molecular identification. Furthermore, our PCR and sequencing results confirmed seven different pathogenic and nonpathogenic genotypes, including T2-T10, T4, T5, T7, T15, T16, and T17. To the best of our knowledge, we have identified and isolated Acanthamoeba sp., for the first time, from water resources of Khyber Pakhtunkhwa, Pakistan. There is an urgent need to address (1) the pathogenic potential of the identified genotypes and (2) explore other environmental sources from the country to examine the water quality and the current status of Acanthamoeba species in Pakistan, which may be a potential threat for public health across the country.

Acanthamoeba keratitis: an emerging disease gathering importance worldwide?

Acanthamoeba keratitis (AK) is increasingly being recognized as a severe sight-threatening ocular infection worldwide. Although contact lens wear is the leading risk factor for AK, Acanthamoeba parasites are also an important cause of keratitis in non-contact lens wearers. Diagnosis of AK is challenging, and the available treatments are lengthy and not fully effective against all strains. The pathogenesis of Acanthamoeba is still under study, and the identification of the key factors involved in this process should be useful for the development of fully effective therapies. This review focuses on recent developments on AK pathogenesis and diagnosis as well as novel strategies for the evaluation of anti-amoebic agents that could be applied in the near future against these pathogens.