Acanthamoeba T3, T4 and T5 in swimming-pool waters from Southern Brazil

A history of over 40 years of potentially pathogenic free-living amoeba studies in Brazil - a systematic review

Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil’s Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

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.

Orthokeratology lens-related Acanthamoeba keratitis: case report and analytical review

Acanthamoeba keratitis (AK) is a rare but severe ocular infection with a significant risk of vision loss. Contact lens use is the main risk factor for AK. The orthokeratology (OK) lens, a specially designed contact lens, has been used worldwide as an effective method of myopia control. However, the OK lens is associated with an increased risk of Acanthamoeba infection. Many primary practitioners are concerned about this infection because of its relative rarity, the lack of promising therapeutic medications, and the need for referral. We herein report two cases of AK associated with OK lenses, present a systematic review of such cases, and discuss the possible reasons for the higher incidence rate of this infection in patients who wear OK lenses. We combined the clinical knowledge and skills of corneal specialists and lens experts with the sole objective of addressing these OK lens-related AK cases. We found that the most common risk factors were rinsing the lenses or lens cases with tap water. Prompt and accurate diagnosis along with adequate amoebicidal treatment are essential to ensure desirable outcomes for OK lens wearers who develop AK. Appropriate OK lens parameters and regular checkups are also important.

Isolation and identification of free-living amoebae isolated from well water in Istanbul

Free-living amoebae (FLA) are ubiquitous protozoa commonly found in water and soil environments. FLA belonging to various genera, including Acanthamoeba, Balamuthia, Naegleria, and Vermamoeba, can cause opportunistic and non-opportunistic infections in humans and animals such as keratitis or meningoencephalitis. In addition, some of them serve as hosts for a large number of pathogenic bacteria, yeasts, and viruses. The purpose of the present study was to assess the prevalence and molecular characterization of FLA in well water samples in İstanbul. Ten well water samples were collected from the taps and the presence of FLA was monitored both by the culture and polymerase chain reaction methods. FLA were isolated in 8 out of the 10 samples (80%) included in this study. Morphological analysis and partial sequencing of the 18S rDNA revealed the presence of Acanthamoeba genotypes T3 and T4, and Vermamoeba vermiformis in the investigated well water samples. This study reports for the first time the detection of Acanthamoeba genotype T3 in well water samples in İstanbul. The presence of potentially pathogenic amoebae in habitats related to human activities supports the relevance of FLA as a potential public health concern.

Molecular detection of Acanthamoeba spp. in Seven Crater Lakes of Laguna, Philippines

Acanthamoeba spp. are ubiquitous free-living amoeba with genotypes that cause severe pathology of the eyes, central nervous systems, and rare reports of cutaneous infections. The Seven Crater Lakes are freshwater water resources in Laguna, Philippines primarily used for aquaculture and tourism. A total of 16 surface water samples were collected from different sampling areas per Crater Lake and placed in sterile plastic containers. Samples were filtered using 1.2 μm pore size, glass microfiber filter. Filtered sediments were placed on non-nutrient agar lawned with Escherichia coli and incubated aerobically at 35 °C for 14 days. Six out of 16 water samples exhibited amoebic growth. Cystic stages revealed circular to stellate morphology under light microscopy which were initially classified as Acanthamoeba spp. DNA from positive isolates were made to react with polymerase chain reaction using Acanthamoeba specific primers JDP1 5′-GGCCCAGATCGTTTACCGTGAA-3′ and JDP2 5′-TCTCACAAGCTGCTAGGGAGTCA-3′confirmed the presence of several Acanthamoeba species. Phylogenetic analysis revealed the presence of seven isolates belonging to Acanthamoeba genotypes T4, T5, and T9. The presence of potentially pathogenic Acanthamoeba genotypes in the Seven Crater Lakes of Laguna signifies risk to human health which necessitates the development of programs, policies, and guidelines on the understanding, prevention, and management of potential human infections.

Detection of Acanthamoeba spp. in two major water reservoirs in the Philippines

Water reservoirs are important manmade structures providing water security to deliver clean and safe water for drinking and other purposes to the community. Eighty water samples were collected from Magat and Ipo water reservoirs using purposive sampling between November 2018 and January 2019. Water samples were collected in sterile containers for testing. The samples were cultured in non-nutrient agar and lawned with Escherichia coli and incubated at 33 °C. Twelve out of the 80 (15%) water samples were positive for amoebic growth. Light and scanning electron microscopy (SEM) revealed double-walled cystic stages and were initially identified as Acanthamoeba spp. based on morphological characteristic in reference to Page's established criteria. Their extracted DNAs were used in polymerase chain reaction using JDP1 and JDP2 primers and confirmed the presence of Acanthamoeba DNA in agarose gel electrophoresis. Aligned sequences from PCR products were deposited in GenBank under accession numbers MK886460, MK909919, MK905437, MK910997, MK911021 and MK886514. The presence of potentially pathogenic Acanthamoeba spp. in water reservoirs is considered a potential risk for public health, requiring appropriate processing of water in treatment plants.

Isolation and identification of Acanthamoeba genotypes and Naegleria spp. from the water samples of public swimming pools in Qazvin, Iran

Free-living amoeba (FLA), including Acanthamoeba and Naegleria are facultative parasites in humans. The amoeba have widespread distribution in various water sources. The aim of this study was isolation and molecular identification of Acanthamoeba and Naegleria isolated from swimming pools and also hot and cold tub waters in Qazvin province. The samples (166 water samples) were cultured to isolate and identify positive specimens. PCR (polymerase chain reaction) amplification, sequencing and phylogenetic analysis were conducted to confirm the isolated species and genotypes of amoeba. According to morphological characterizations, 18.6% of specimens were identified as FLA, which in 71% were Acanthamoeba by PCR method. Molecular analysis revealed that 36.3%, 18.1% and 4.5% of Acanthamoeba specimens were identified as T3, T4 and T11 Acanthamoeba genotypes, respectively. Protacanthamoeba bohemica (27.2%) and Acanthamoeba sp. (4.5%) were found among the specimens. The results of osmo-tolerance and thermo-tolerance assays demonstrated that 50% of T3 and 25% of T4 genotypes of Acanthamoeba were highly pathogenic parasites. The molecular approach showed the presence of Naegleria lovaniensis (9%) in hot tub water of swimming pools. This study demonstrated that the swimming pools and hot tub water in Qazvin province were contaminated with Acanthamoeba and Naegleria species.

Genotyping by Sequencing of Acanthamoeba and Naegleria Isolates from the Thermal Pool Distributed Throughout Turkey

PURPOSE

The main goal of this study was genotyping of free-living parasites and sub-grouping of pathogenic or non-pathogenic amebae obtained from Turkey's thermal springs. In so doing, distribution and abundance of possible pathogenic or causative strain for humans, which are caused by Acanthamoeba and Naegleria strains, would be elaborated. The number of extensive studies on the general occurrence and distribution of parasitic strains is very high worldwide, but there has been a paucity of information with regard to Turkey.

METHODS

From a total of 434 obtained thermal pool samples, free-living amebas were isolated from 148 water samples using the non-nutrient agar (NNA) culture method. Subsequently, the cultivated samples were used for DNA isolation; then 102 obtained DNA samples were subjected to PCR amplification using various primers for samples of genera Acanthamoeba and Naegleria. Ultimately, estimation of genotype or subtype was evaluated by sequencing.

RESULTS

About 29 samples that belong to Acanthamoeba and Naegleria were estimated from a total of 102 amplified PCR samples. These eukaryotic PCR products which have Acanthamoeba genus appearance, generated 26 subtypes and 3 Naegleria samples. Among the 26 Acanthamoeba genotypes, 22 aligned sequences were matched with various GenBank reference samples, while the 4 divergent genotypes were not elaborated and marked as ND. Most of the Acanthamoeba genera were determined as likely dominating groups and clustered as T form within totally eight groups. Eight, seven and three subtypes were found as T4A, T15 and T11 genotypes, respectively while the remainings were ultimately found in four groups. Results confirming the predominance of T4A, which is known the most causative form, the presence in the pools. Despite being uncommon, N. fowleri, lovaniensis and australiensis were also observed among the surveyed pools.

CONCLUSION

The present study is descriptive and is not unique. However, this is the most comprehensive study of the molecular distribution sampling of thermophilic Acanthamoeba and Naegleria that confirmed and demonstrated their ubiquitous presence throughout Turkey. By this estimation, in some spas, the most and likely causative form Acanthamoeba including T4 and Naegleria fowleri has also been confirmed.

Isolation and identification of Acanthamoeba from pond water of parks in a tropical and subtropical region in the Middle East, and its relation with physicochemical parameters

Background

Free-living amoeba (FLA) are wide-spread protozoa that are found in different environmental sources including water, soil, dust, hospital units and ventilation areas. These amoebas can act as opportunistic or non-opportunistic pathogens. Among FLAs, some genera such as Acanthamoeba are important because of their potential pathogenic ability in humans. The purpose of this study is to identify of Acanthamoeba isolated from pond water of parks in a tropical and subtropical region in the Middle East, and its relation with physicochemical parameters.From August to December 2015, 90 samples were collected from pond water of parks of 13 regions of Mashhad City. Physicochemical parameters were measured in situ. After filtering, the samples were cultured on Bacto-agar enriched with Escherichia coli. PCR analysis was conducted on the culture-positive samples, and then the PCR products were sequenced. Statistical analysis was performed by SPSS software and Fisher’s Exact and Mann-Whitney test.

Results

Among the samples that were examined, 19 samples (21.1%) were positive for Acanthamoeba. The sequencing revealed that Acanthamoeba isolates belonged to T4 genotype of Acanthamoeba. There was no significant relationship between physicochemical parameters and the presence of Acanthamoeba.

Conclusion

The prevalence of Acanthamoeba in pond water of parks was relatively high, but there was no significant relationship between physicochemical parameters and the presence of Acanthamoeba.

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 Infected Free-Living Amoebae in Cooling Towers of Southern Brazil

This study determined the occurrence of potentially pathogenic free-living amoebae (FLA) and bacteria associated with amoebae in air-conditioning cooling towers in southern Brazil. Water samples were collected from 36 cooling systems from air-conditioning in the state of Rio Grande do Sul, Brazil. The organisms were identified using polymerase chain reaction (PCR) and sequencing automated. The results showed that these aquatic environments, with variable temperature, are potential "hot spots" for emerging human pathogens like free-living amoebae and bacteria associated. In total, 92% of the cooling-tower samples analyzed were positive for FLA, and Acanthamoeba was the dominant genus by culture and PCR. Amoebal isolates revealed intracellular bacteria in 39.3% of them and all were confirmed as members of the genus Pseudomonas. The results obtained show the important role of cooling towers as a source of amoebae-associated pathogens.

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

Acanthamoeba is a free-living amoeba which can be isolated from environment and among others well known as an opportunist protozoan parasite causing infections in humans and animals. Eyes are extremely important for the wild birds and losing sight ability due to Acanthamoeba can be dangerous. The studies on Acanthamoeba infection in wild birds is very few in world and Turkey therefore we aimed to screen deceased wild birds found in İzmir and Manisa provinces located in western Turkey using PCR and non-nutrition agar (NNA) plate method. Cornea samples were obtained from 18 deceased wild birds. During the external examination, signs of keratitis were observed in two Eurasian sparrowhawks (Accipiter nisus). All of the corneal samples were analyzed by two PCR methods and NNA plate. According to results, the Acanthamoeba positivity in corneal samples was 16.6% and 5.5% by PCR and plate method, respectively. According to sequencing data, two of isolates belonged to genotype T5 and one was genotype T4. In conclusion, Acanthamoeba infection was detected in wild bird cornea samples with/without keratitis for the first time in the world. The result of this study also show that Acanthamoeba can be a cause of keratitis in wild birds of Turkey and thus these predator birds can be a target of other wild animals due to loss of sight ability. In terms of public health, these results show the importance of wild birds as a source of Acanthamoeba infection in nature.

Adhesion forces and mechanics in mannose-mediated acanthamoeba interactions

The human pathogenic amoeba Acanthamoeba castellanii (A. castellanii) causes severe diseases, including acanthamoeba keratitis and encephalitis. Pathogenicity arises from the killing of target-cells by an extracellular killing mechanism, where the crucial first step is the formation of a close contact between A. castellanii and the target-cell. This process is mediated by the glycocalix of the target-cell and mannose has been identified as key mediator. The aim of the present study was to carry out a detailed biophysical investigation of mannose-mediated adhesion of A. castellanii using force spectroscopy on single trophozoites. In detail, we studied the interaction of a mannose-coated cantilever with an A. castellanii trophozoite, as mannose is the decisive part of the cellular glycocalix in mediating pathogenicity. We observed a clear increase of the force to initiate cantilever detachment from the trophozoite with increasing contact time. This increase is also associated with an increase in the work of detachment. Furthermore, we also analyzed single rupture events during the detachment process and found that single rupture processes are associated with membrane tether formation, suggesting that the cytoskeleton is not involved in mannose binding events during the first few seconds of contact. Our study provides an experimental and conceptual basis for measuring interactions between pathogens and target-cells at different levels of complexity and as a function of interaction time, thus leading to new insights into the biophysical mechanisms of parasite pathogenicity.

Molecular detection and genotyping of Acanthamoeba spp. among stray dogs using conjunctival swab sampling

Acanthamoeba is one of the most common free-living amoebas (FLA) that present in environment. In humans, Acanthamoeba can cause an infection of the eye termed Acanthamoeba keratitis, which mostly occurs in contact lens wearers. In the present study, we aimed to screen the presence of Acanthamoeba DNA in stray dogs using previously collected conjunctival swab samples in a hyper-endemic area for canine leishmaniasis. Totally, 184 dogs were included in the study and 27 of them (14.6%) were found positive for Acanthamoeba according to the 18s rRNA gene sequencing. Two different genotypes (T4 and T5) were identified and T5 was firstly reported in Turkey in the present study. Statistical analysis was performed and no correlation was found between Leishmania and Acanthamoeba positivity (P<0.05). To best of our knowledge, this is the first study conducted to screen Acanthamoeba among stray dogs. Further studies are necessary to reveal the infection status and genotypes among dogs and its possible correlation with leishmaniasis.

Comparative proteomic analysis of extracellular secreted proteins expressed by two pathogenic Acanthamoeba castellanii clinical isolates and a non-pathogenic ATCC strain

Acanthamoeba keratitis (AK) is a serious ocular disease caused by pathogenic Acanthamoeba gaining entry through wounds in the corneal injury; generally, patients at risk for contracting AK wear contact lenses, usually over a long period of time. Moreover, pathogenic Acanthamoeba causes serious consequences: it makes the cornea turbid and difficult to operate on, including procedures such as enucleation of the eyeball. At present, diagnosis of this disease is not straightforward, and treatment is very demanding. We have established the comparative transcriptome and extracellular secreted proteomic database according to the non-pathogenic strain ATCC 30010 and the pathogenic strains NCKU_B and NCKU_D. We identified 44 secreted proteins successfully, 10 consensus secreted proteins and 34 strain-specific secreted proteins. These proteins may provide targets for therapy and immuno-diagnosis of Acanthamoeba infections. This study shows a suitable approach to identify secreted proteins in Acanthamoeba and provides new perspectives for the study of molecules potentially involved in the AK.

Isolation and identification of Acanthamoeba spp. from thermal swimming pools and spas in Southern Brazil

Free-living amoebae (FLA) are widely distributed in soil and water. A few number of them are implicated in human disease: Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia diploidea. Species of Acanthamoeba can cause keratitis and brain infections. In this study, 72 water samples were taken from both hot tubs and thermal swimming pools in the city of Porto Alegre, RS, Brazil, to determine the presence of Acanthamoeba in the water as well as perform the phenotypic and genotypic characterization of the isolates. The identification of the isolates was based on the cysts morphology and PCR amplification using genus-specific oligonucleotides. When the isolates were submitted to PCR reaction only 8 were confirmed as belonging to the genus Acanthamoeba. The sequences analysis when compared to the sequences in the GenBank, showed genotype distribution in group T3 (12,5%), T5 (12,5%), T4 (25%) and T15 (50%). The results of this study confirmed the presence of potentially pathogenic isolates of free living amoebae in hot swimming pool and spas which can present risks to human health.

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.

Characterization of isolates of Acanthamoeba from the nasal mucosa and cutaneous lesions of dogs

Acanthamoeba spp. are free-living amoebae that are ubiquitously distributed in the environment and can cause encephalomyelitis in animals and humans. The factors that contribute to Acanthamoeba infections include parasite biology, genetic diversity, environmental spread, and host susceptibility. The aim of the present study was to characterize isolates of Acanthamoeba from the nasal mucosa and cutaneous lesions of dogs in order to access the occurence and pathogenicity of these organisms in this animal group. We studied 13 isolates of Acanthamoeba confirmed by polymerase chain reaction. They were sequenced, the genotype was determined, and their potential of pathogenicity was evaluated.

Cooccurrence of free-living amoebae and nontuberculous Mycobacteria in hospital water networks, and preferential growth of Mycobacterium avium in Acanthamoeba lenticulata

The incidence of lung and other diseases due to nontuberculous mycobacteria (NTM) is increasing. NTM sources include potable water, especially in households where NTM populate pipes, taps, and showerheads. NTM share habitats with free-living amoebae (FLA) and can grow in FLA as parasites or as endosymbionts. FLA containing NTM may form cysts that protect mycobacteria from disinfectants and antibiotics. We first assessed the presence of FLA and NTM in water and biofilm samples collected from a hospital, confirming the high prevalence of NTM and FLA in potable water systems, particularly in biofilms. Acanthamoeba spp. (genotype T4) were mainly recovered (8/17), followed by Hartmannella vermiformis (7/17) as well as one isolate closely related to the genus Flamella and one isolate only distantly related to previously described species. Concerning mycobacteria, Mycobacterium gordonae was the most frequently found isolate (9/17), followed by Mycobacterium peregrinum (4/17), Mycobacterium chelonae (2/17), Mycobacterium mucogenicum (1/17), and Mycobacterium avium (1/17). The propensity of Mycobacterium avium hospital isolate H87 and M. avium collection strain 104 to survive and replicate within various FLA was also evaluated, demonstrating survival of both strains in all amoebal species tested but high replication rates only in Acanthamoeba lenticulata. As A. lenticulata was frequently recovered from environmental samples, including drinking water samples, these results could have important consequences for the ecology of M. avium in drinking water networks and the epidemiology of disease due to this species.

Prevalence of Acanthamoeba spp. (Sarcomastigophora: Acanthamoebidae) in wild populations of Aedes aegypti (Diptera: Culicidae)

Studies of interrelationship between microorganisms and mosquitoes are of great importance, since it can provide support for better understand related to biology, development and their control. In this way, it is known that mosquito larvae and free-living amoebae (FLA) normally occupy similar aquatic microhabitats. However, few studies have been conducted about such coexistence. For that reason, the objective of the present study was to verify the prevalence of Acanthamoeba spp. in wild populations of Aedes aegypti, as well as to characterize the genotypic lineage, and their possible pathogenicity through thermo- and osmotolerance. Amoebae were investigated in 60 pools, each containing ten larvae of A. aegypti, collected in Porto Alegre (Rio Grande do Sul, Brazil). The Acanthamoeba isolates were morphologically characterized and submitted to the polymerase chain reaction technique to confirm identification of the genus. In addition, genotype analyses as well as tests for presumptive pathogenicity in some samples were performed. Of the 60 pools examined, 54 (90 %) were positive for FLA. Of these isolates, 47 (87 %) belonged to the genus Acanthamoeba. The genotypic groups T4, T3 and T5 were identified, numbering 14 (53.8 %), ten (38.5 %) and two (7.7 %) isolates, respectively. The physiological tests performed with 14 strains showed that 12 (85.7 %) were non-pathogenic, while two (14.3 %) were considered as having low pathogenic potential. These results provide a basis for a better understanding of the interaction between these protozoan and mosquitoes in their natural habitat. This study is the first to report the isolation of Acanthamoeba spp. from wild mosquitoes.

Occurrence and characterization of Acanthamoeba similar to genotypes T4, T5, and T2/T6 isolated from environmental sources in Brasília, Federal District, Brazil

Species of Acanthamoeba can cause keratitis and brain infections. The characterization of environmental isolates is necessary to analyze the risk of human infection. We aimed at identifying and genotyping Acanthamoeba isolates from soil, swimming pools, and water features in Brasília, Federal District, Brazil, as well as determining their physiological characteristics and pathogenic potential. Among the 18 isolates studied, eight were similar to genotype T5, five to T4, and one to T2/T6, classified by the sequence analysis of 18S rDNA. Genotypes of four isolates were not determined. Ten isolates (55%) grew at 37 °C and seven (39%) grew in media with 1.5M mannitol, which are the physiological parameters associated with pathogenic Acanthamoeba; also, four isolates from swimming pools presented high pathogenic potential. Our results indicate a widespread distribution of potentially pathogenic Acanthamoeba T4, T5, and T2/T6 in different environmental sources in Brasília, revealing the potential risk of human infection and the need of preventive measures.

Prevalence of acanthamoeba from tap water in rio grande do Sul, Brazil

A total of 136 samples of tap water were collected from state and municipal schools between March and November 2009. The samples were filtered through cellulose nitrate membranes that were seeded at non-nutrient agar 1.5% containing an overlayer of Escherichia coli suspension. Thirty-one (22.79%) tap water samples investigated were found positive for free-living amoebae (FLA). From these, 13 presented as FLA that seems to belong to the genus Acanthamoeba. All samples of FLA were cloned and identified as belonging to the genus Acanthamoeba by the morphology of cysts and trophozoites and by PCR using genus-specific primers that amplify the ASA.S1 region of 18S rDNA gene. Physiological tests of thermotolerance and osmotolerance were used to evaluate the pathogenicity of the isolates. The sequencing analysis by comparing the sequences submitted to GenBank, showed genotype distribution into groups T2, T2/T6, T6, and T4. In tests of thermotolerance and osmotolerance, 50% of the isolates had a low pathogenic potential. The results indicated the presence of Acanthamoeba in tap water in Rio Grande do Sul, Brazil, revealing its importance and the need for more epidemiological studies to determine their distribution in the environment and its pathogenic potential.