Isolation and molecular identification of Acanthamoeba spp. from hot springs in Mazandaran province, northern Iran

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.

Molecular evidence for a new lineage within the Acanthamoeba T4 genotype

Acanthamoeba is a widespread free-living amoeba capable of causing serious infections in humans and other animals, such as amoebic keratitis, disseminated infections, and fatal encephalitis. Strain identification is usually based on 18S rDNA sequencing, which allows the distinction of over twenty genotypes. Most sequences from environmental and clinical samples belong to the T4 genotype, which can be divided into seven subtypes, T4A to T4G, and by a nearly similar grouping of mitochondrial sequences into T4a to T4j subtypes. The co-clustering of nuclear and mitochondrial groups can be very useful for a better identification of lineages within the very rich T4 genotype. In this study, we provided molecular phylogenetic evidence for the delineation of a new nuclear subtype, hereafter labelled T4H, and its co-clustering with the mitochondrial T4j subtype. At least three cases of amoebic keratitis are due to strains belonging to this new group, present mainly in fresh water and detected in various countries (France, Iran, India and China).

Prevalence of free-living amoebae in swimming pools and recreational waters, a systematic review and meta-analysis

Free-living amoebae (FLA) are cosmopolitan microorganisms known to be pathogenic to humans who often have a history of contact with contaminated water. Swimming pools and recreational waters are among the environments where the greatest human exposure to FLA occurs. This study aimed to determine the prevalence of FLA in swimming pools and recreational waters, through a systematic review and meta-analysis that included studies published between 1977 and 2022. A total of 106 studies were included and an overall prevalence of FLA in swimming pools and recreational waters of 44.34% (95% CI = 38.57–50.18) was found. Considering the studies published up to 2010 (1977–2010), between 2010 and 2015, and those published after 2010 (> 2010–2022), the prevalence was 53.09% (95% CI = 43.33–62.73) and 37.07% (95% CI = 28.87–45.66) and 45.40% (95% CI = 35.48–55.51), respectively. The highest prevalence was found in the American continent (63.99%), in Mexico (98.35%), and in indoor hot swimming pools (52.27%). The prevalence varied with the variation of FLA detection methods, morphology (57.21%), PCR (25.78%), and simultaneously morphology and PCR (43.16%). The global prevalence by genera was Vahlkampfia spp. (54.20%), Acanthamoeba spp. (33.47%), Naegleria spp. (30.95%), Hartmannella spp./Vermamoeba spp. (20.73%), Stenamoeba spp. (12.05%), and Vannella spp. (10.75%). There is considerable risk of FLA infection in swimming pools and recreational waters. Recreational water safety needs to be routinely monitored and, in case of risk, locations need to be identified with warning signs and users need to be educated. Swimming pools and artificial recreational water should be properly disinfected. Photolysis of NaOCl or NaCl in water by UV-C radiation is a promising alternative to disinfect swimming pools and artificial recreational waters.

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.

Current report on the prevalence of free-living amoebae (FLA) in natural hot springs: a systematic review

The occurrence of potentially pathogenic free-living amoebae (FLA) in natural hot springs is considered a public health concern. FLAs are known to cause serious health outcomes to a wide spectrum of mammalian hosts. The present study aimed to provide the distribution of isolated cases of FLAs in hot springs through a systematic review process of available published articles online. Relevant studies are published between January 2010 and January 2020 involving the isolation of Naegleria spp., Acanthamoeba spp., Balamuthia spp., Sappinia spp., and Vermamoeba spp. in natural hot springs in the United States, South America, North America, Europe, Asia, and Africa. Articles were identified through a search of PubMed and Google Scholar databases. Out of 94 articles screened, a total of 20 articles are included in the study with consideration of established inclusion and exclusion criteria. The most common FLAs isolated in hot springs are Acanthamoeba spp. (134; 48.5%) and Naegleria spp. (127; 46.0%). Other FLAs isolated in hot springs include Balamuthia spp. (2; 0.7%) and Vermamoeba spp. (13; 4.7%). FLA in hot springs used for recreational and medical purposes is a potential source of infection. It is recommended that strict surveillance and maintenance of hot springs be implemented to prevent potential future infection.

Isolation and molecular identification of free-living amoebae (Naegleria spp., Acanthamoeba spp. and Vermamoeba spp.) from mineral springs in Guilan Province, northern Iran

Free-living amoebae (FLA) include many genera which cause serious diseases such as sight-threatening keratitis, cutaneous ulcers and fatal encephalitis. This study was conducted due to the lack of research regarding genotypes Acanthamoeba, Naegleria and Vermamoeba in mineral springs of Guilan Province in northern Iran. Twenty-five water samples were collected from mineral springs in Guilan Province. After filtration through nitrocellulose membrane, samples were cultured on non-nutrient agar plates. The morphological key of Page was used to identify free-living amoebae (FLA) using an inverted microscope. Positive cultures were analyzed by polymerase chain reaction (PCR) and genotypes based on the NCBI database. Eleven (44%) samples were positive for Acanthamoeba, Naegleria and Vermamoeba. By sequencing the positive isolates, the strains were shown to belong to Acanthamoeba castellanii (three case isolates belonged to T4 genotype), three cases of Vermamoeba vermiformis, and two cases of N. australiensis, two cases of N. pagei and one case of N. gruberi. According to our research the occurrence of Acanthamoeba, Naegleria spp. and Vermamoeba spp. in mineral springs could be hazardous for high risk persons. Regular monitoring and posting warning signs of these waters by health planners could prevent free-living amoebae mediated diseases.

First Molecular Evidences of Acanthamoeba T3, T4 and T5 Genotypes in Hemodialysis Units in Iran

BACKGROUND

Acanthamoeba is a genus of the free-living amoeba that is widespread in the environment and is a causative agent of opportunistic infections in human. This study aimed to investigate the existence and genotyping of Acanthamoeba species in hemodialysis units in Iran.

METHODS

In the present study, forty water samples of hydraulic systems and twenty dust samples were collected from two hemodialysis units in Mazandaran Province, northern Iran. The samples were cultivated on non-nutrient agar and genotyping was performed by targeting the 18S rRNA gene.

RESULTS

Both morphology and molecular analyses showed that 17.5% (7/40) of water samples and 50% (10/20) of dust samples were positive for Acanthamoeba spp. The sequencing analysis of these isolates was found to be T3, T4 and T5 genotypes.

DISCUSSION

To the best of our knowledge, this is the first investigation to identify of Acanthamoeba species in hydraulic system of hemodialysis units in Iran. High contamination of hemodialysis units with virulent T4 genotype of Acanthamoeba may poses a risk for biofilm formation. Our results support urgent need to improve filtration methods in dialysis units and monitoring hemodialysis patients for Acanthamoeba infections.

Genotyping determination of Acanthamoeba strains: an original study and a systematic review in Iran

This study aimed to detect the presence of Acanthamoeba spp. in different water resources of Zahedan, southeast of Iran, and also systematically reviewed all publications regarding Acanthamoeba in Iran (2005-2018). Fifty water samples were collected from different water resources in Zahedan. The positive samples were identified morphologically and subjected to polymerase chain reaction (PCR) using fragments of 18S rRNA. In the systematic review, data collection using particular terms was carried out using the following electronic databases including Science Direct, ISI Web of Science, MEDLINE, EBSCO, Scopus, and Google Scholar. A total of 17 (34%) samples were positive for Acanthamoeba spp., and nucleotide sequencing indicated that 15 samples (88.23%) belonged to the T4 genotype and the rest belonged to the T5 genotype. A total of 39 studies reported genotyping of Acanthamoeba spp. from various geographical areas of Iran and revealed that T4 (35 studies), T5 (19 studies), T3 (11 studies), T11 (8 studies), and T2 (6 studies) genotypes were the most prevalent in Iran. The T4 genotype of Acanthamoeba is a prevalent free-living amoeba and widely distributed not only in Zahedan but also in other provinces of Iran. Phylogenetic analysis reveals that A. castellanii and A. griffini predominantly colocalize with the T4 genotype.