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

Global prevalence of free-living amoebae in solid matrices - A systematic review with meta-analysis

The ubiquitous free-living amoebae (FLA) are microorganisms of significant medical, sanitary, and ecological importance. However, their characterization within solid matrices such as soil, dust, sediment, mud, sludge, and compost remain to be systematized. In this study, we conducted a systematic review with meta-analysis to explore the global distribution of FLA in solid matrices. From the analysis of 104 out of 4,414 scientific articles retrieved from different databases, it was found that the general global prevalence of FLA in solid matrices was of 55.13% (95% confidence interval (CI) 49.32-60.94). Specifically, FLA prevalence was high in soil (72.40%, 95% CI 69.08-75.73), sediment (57.91%, 95% CI 50.01-65.81), mud (52.90%, 95% CI 24.01-81.78), dust (48.60%, 95% CI 43.00-54.19), and sewage sludge (40.19%, 95% CI 30.68-49.70). In aerosols it was comparatively lower (17.21%, 95% CI 12.76-21.66). Acanthamoeba spp. (52.23%) and Hartmanella/Vermamoeba spp. (36.06%) were found to be more prevalent, whereas Naegleria spp. (34.98%) and Balamuthia spp. (27.32%) were less prevalent. The distribution of the highest global prevalence values for species of Acanthamoeba spp., considering different publication periods of the studies, is as follows: A. hatchetti (51.46%), A. rhysodes (47.49%), A. polyphaga (36.37%), A. culbertsoni (34.31%), A. castellanii (34.21%), and A. lenticulata (32.82%). For other FLA species, the distribution is: Hartmannella/Vermamoeba vermiformis (91.57%), Naegleria fowleri (42.32%), Naegleria gruberi (32.39%), and Balamuthia mandrillaris (25%). The most prevalent Acanthamoeba genotypes were T4 (33.38%) and T3 (23.94%). Overall, the global prevalence of FLA in solid matrices is as high as or greater than that reported in water by previous systematic reviews. Thus, actions aimed at reducing exposure to FLA or exploring their ecological dynamics should consider not only water but also the various solid matrices. The finding outlined here can provide valuable insights for such actions, e.g., informing on the level of exposure to FLA, or on the microbial biodiversity of specific environmental compartments.

Detection of Acanthamoeba spp. in groundwater sources in a rural area in the Philippines

Research on free-living amoebae (FLA) and its public health implication as an etiologic agent of parasitic infection in humans has recently gained traction in the Philippines. This study aimed to identify potential FLAs in collected groundwater samples from Masinloc, Zambales, Philippines. Fifty-four (54) water samples were collected in 250-mL sterile polyethylene containers by purposive sampling from selected groundwater sources in six (6) barangays of Masinloc. The samples were vacuum filtered through a 1.2-μm pore glass microfiber filter, cultured onto non-nutrient agar (NNA) lawned with Escherichia coli, and observed microscopically for amoebic growth for 14 days using light microscopy. Amoebic growth was observed in 11.1% (6/54) of water samples. DNAs from positive samples were extracted and were made to react with polymerase chain reaction using Acanthamoeba-specific JDP1 (5'-GGCCCAGATCGTTTACCGTGAA-3') and JDP2 (5'-TCTCACAAGCTGCTAGGGAGTCA-3') primers, and universal primer Euk A (5'-AACCTGGTTGATCCTGCCAGT-3') and Euk B (5'-TGATCCTTCTGCAGGTTCACCTAC-3'). The presence of Acanthamoeba genotypes T4, T7, and T11 was confirmed using molecular and phylogenetic analysis. Our results confirmed that groundwater sources from two of six sampling sites (33.3%) in Masinloc, Zambales, were contaminated with potentially pathogenic FLAs. Proper identification of risk factors that may cause contamination consequently leads to the implementation of programs that will prevent future infections.

Genotyping of Acanthamoeba Isolated from Hospital Environments and Thermal Water of Recreational Baths in Markazi Province, Iran

Background

Due to the opportunism character of Acanthamoeba, the presence of this parasite in the thermal water of recreational baths and hospital environments can be a risk to the health of staff, patients and others. The aim of this study was to investigate the distribution of potentially pathogenic Acanthamoeba genotypes isolated from the hospital environment and the thermal water of recreational baths in Markazi Province, central Iran.

Methods

Overall, 180 samples including thermal water from recreational baths in Mahallat City and dust, soil and water from different hospitals of Arak, Farahan and Komijan cities, central Iran were collected. The presence of Acanthamoeba was investigated using microscopic examination and molecular methods. The PCR and sequencing was performed based on a specific 18S fragment of ribosomal DNA.

Results

Based on the microscopic survey, totally 134 positive samples were detected including 35% in thermal water samples and 44.7% in hospital samples. In molecular analysis, 53.5% of the samples were identified as Acanthamoeba and 46.7% as Protacanthamoeba bohemica. The genotypes were detected as T4 (33.3%), T2 (10%), T11 (6.7%), and T5 (3.3%).

Conclusion

The T4 was the most common genotype found in hospitals sampling sites while the T2 genotype and P. bohemica were detected in thermal water sampling sites.

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 Phylogenetic Analysis of Free-Living Amoebae (Acanthamoeba, Naegleria, and Vermamoeba) in the Farmland Soils and Recreational Places in Iran

PURPOSE

Free-living amoeba (FLA) including Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria are among the soil-born parasites. There are reports of FLA-related keratitis with a history of contact with soil and dust sources, particularly among the farmers. Due to lack of the previous studies on the farmland soils and a limited number of researches conducted on recreational soils in Iran, the present study was conducted.

METHODS

A total of 93 soil samples including farming lands and recreational places were tested for the presence of Acanthamoeba spp. Balamuthia mandrillaris, Naegleria, and Vermamoeba using morphological key and sequencing-based tools. Pathogenicity of Acanthamoeba positive strains was also evaluated. To verify genetic associations and taxonomic status of isolated amoeba, a phylogenetic tree was built by MEGA 5.05 software inferred by the 18S rRNA gene based on maximum likelihood algorithm.

RESULTS

Overall, 28 samples (30%) were contaminated with potentially pathogenic FLA, and according to the sequencing data, 17 strains were successfully sequenced. The isolated Acanthamoeba belonged to T2, T4, T5, mixed T4 and T5 contaminations, and T11. ITS sequencing revealed the occurrence of one strain of Naegleria canariensis. Four strains of Vermamoeba vermiformis were also confirmed. Morphological survey and PCR assay failed to show any positive results for Balamuthia mandrillaris. Pathogenic potential of the Acanthamoeba strains showed that T2, T4, and T11 genotypes were highly pathogenic, whereas T5 genotypes demonstrated lower pathogenic potential.

CONCLUSION

The results indicate that soil could be a serious hazard to human health, and therefore, further studies are expected to investigate the source of infection in patients developing FLA-related diseases. The present study is the first to investigate FLA in the farmland soils in Iran and the first to report the presence of N. canariensis in the country.

Acanthamoeba and its pathogenic role in granulomatous amebic encephalitis

Acanthamoeba is a free-living amoeba that is widely distributed in the environment. It is an opportunist protist, which is known to cause rare yet fatal infection of the central nervous system (CNS), granulomatous amebic encephalitis (GAE) in humans. GAE cases are increasingly been reported among immunocompromised patients, with few cases in immunocompetent hosts. Diagnosis of GAE primarily includes neuroimaging, microscopy, cerebrospinal fluid (CSF) culture, histopathology, serology and molecular techniques. Early diagnosis is vital for proper management of infected patients. Combination therapeutic approach has been tried in various GAE cases reported worldwide. We tried to present a comprehensive review, which summarizes on the epidemiology of GAE caused by Acanthamoeba along with the associated clinical symptoms, risk factors, diagnosis and treatment of GAE among infected patients.

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.