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

Identification and quantification of Acanthamoeba spp. within seawater at four coastal lagoons on the east coast of Australia

Acanthamoeba is an opportunistic free-living heterotrophic protist that is the most predominant amoeba in diverse ecological habitats. Acanthamoeba causes amoebic keratitis (AK), a painful and potentially blinding corneal infection. Major risk factors for AK have been linked to non-optimal contact lens hygiene practices and Acanthamoeba contamination of domestic and recreational water. This study investigated the incidence and seasonal variation of Acanthamoeba spp. within coastal lagoons located on the eastern coast of Australia and then examined the association between Acanthamoeba and water abiotic factors and bacterial species within the water. Water samples were collected from four intermittently closed and open lagoons (ICOLLs) (Wamberal, Terrigal, Avoca and Cockrone) every month between August 2019 to July 2020 except March and April. qPCR was used to target the Acanthamoeba 18S rRNA gene, validated by Sanger sequencing. Water abiotic factors were measured in situ using a multiprobe metre and 16S rRNA sequencing (V3-V4) was performed to characterise bacterial community composition. Network analysis was used to gauge putative associations between Acanthamoeba incidence and bacterial amplicon sequence variants (ASVs). Among 206 water samples analysed, 79 (38.3%) were Acanthamoeba positive and Acanthamoeba level was significantly higher in summer compared with winter, spring, or autumn (p = 0.008). More than 50% (23/45) water samples of Terrigal were positive for Acanthamoeba which is a highly urbanised area with extensive recreational activities while about 32% (16/49) samples were positive from Cockrone that is the least impacted lagoon by urban development. All sequenced strains belonged to the pathogenic genotype T4 clade except two which were of genotype clades T2 and T5. Water turbidity, temperature, intl1 gene concentration, and dissolved O2 were significantly associated with Acanthamoeba incidence (p < 0.05). The ASVs level of cyanobacteria, Pseudomonas spp., Candidatus spp., and marine bacteria of the Actinobacteria phylum and Acanthamoeba 18S rRNA genes were positively correlated (Pearson's r ≥ 0.14). The presence of Acanthamoeba spp. in all lagoons, except Wamberal, was associated with significant differences in the composition of bacterial communities (beta diversity). The results of this study suggest that coastal lagoons, particularly those in urbanised regions with extensive water recreational activities, may pose an elevated risk to human health due to the relatively high incidence of pathogenic Acanthamoeba in the summer. These findings underscore the importance of educating the public about the rare yet devastating impact of AK on vision and quality of life, highlighting the need for collaborative efforts between public health officials and educators to promote awareness and preventive measures, especially focusing lagoons residents and travellers.

Molecular characterisation and potential pathogenicity analysis of Acanthamoeba isolated from recreational lakes in Peninsular Malaysia

The present study aims to identify the Acanthamoeba genotypes and their pathogenic potential in three recreational lakes in Malaysia. Thirty water samples were collected by purposive sampling between June and July 2022. Physical parameters of water quality were measured in situ while chemical and microbiological analyses were performed in the laboratory. The samples were vacuum filtered through nitrate filter, cultured onto non-nutrient agar and observed microscopically for amoebic growth. DNAs from positive samples were extracted and made to react with polymerase chain reaction using specific primers. Physiological tolerance tests were performed for all Acanthamoeba-positive samples. The presence of Acanthamoeba was found in 26 of 30 water samples by PCR. The highest rate in lake waters contaminated with amoeba was in Biru Lake (100%), followed by Titiwangsa Lake (80%) and Shah Alam Lake (80%). ORP, water temperature, pH and DO were found to be significantly correlated with the presence of Acanthamoeba. The most common genotype was T4. Temperature- and osmo-tolerance tests showed that 8 (30.8%) of the genotypes T4, T9 and T11 were highly pathogenic. The presence of genotype T4 in habitats related to human activities supports the relevance of this amoeba as a potential public health concern.

Epidemiology of free-living amoebae infections in Africa: a review

FLA-related conditions are a rare medical occurrence. Despite their rarity, they are considered a public health concern for two reasons: the absence of a regular treatment regimen in the case of central nervous system infections and the fast progression of the symptoms leading to fatal outcomes. A total of 358 articles were retrieved from different databases (91 from PubMed, 26 from NCBI, 138 from Academia, 102 from Science Direct, and one from IJMED). 7 (46.6%) clinical cases came from Egypt, 2 (13.3%) cases of FLA infection came from Nigeria, 3 (20%) cases came from the Gambia, and 1 (6.6%) case was reported from African countries like Algeria, Tunisia, South Africa, and Zambia. Medical conditions caused by free-living amoeba are considered significant public health concerns. These ubiquitous organisms can cause both fatal and debilitating health conditions. Immediate diagnosis of cases and proper hygienic practices are necessary to provide direct medical intervention. They may be the key to reducing the morbidity and mortality rates from FLA-acquired infections. Although several government-led initiatives have been implemented to mitigate a plethora of parasitic diseases, the case of FLA-related conditions in African countries has yet to be realized.

Ultraviolet – Chlorine combined treatment efficiency to eliminate Naegleria fowleri in artificial surf lagoons

Naegleria. fowleri, a protozoa belonging to the free-living amoeba group, is the causative agent of a central nervous system affecting disease that is fatal in more than the 95% of the reported cases. This parasite can be found in warm water bodies such as lakes, rivers or inadequately disinfected swimming pools. On the other hand, chlorination and UV light treatment are two of the most extensively used disinfection methods in recreational water facilities.

In this study the effect of chlorination and UV light on N. fowleri trophozoites was studied in a close water circuit with the aim to assess the efficacy of this disinfection methods in large pools. The obtained results showed that the chlorination was able to decrease the number of viable cells despite the elimination was not totally achieved. Nonetheless, the combination of the UV light with the chlorination allowed the complete removal of the N. fowleri trophozoites from the water in experimental testing conditions.

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Absence of an standardized water treatment protocol to eliminate N. fowleri.

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Treatment based only on chlorine was ineffective to eliminate N. fowleri.

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Combined chlorination and UV light treatment was effective to completely eliminate N.fowleri.

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Combination of chlorine - Uv would be a promising method for water disinfection.

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.

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.

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

Background:

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

Methods:

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

Results:

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

Conclusion:

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

Genotyping 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.

Occurrence and molecular characterisation of Acanthamoeba isolated from recreational hot springs in Malaysia: evidence of pathogenic potential

This study aimed to identify the Acanthamoeba genotypes and their pathogenic potential in five recreational hot springs in Peninsular Malaysia. Fifty water samples were collected between April and September 2018. Physical parameters of water quality were measured in situ while chemical and microbiological analyses were performed in the laboratory. All samples were filtered through the nitrocellulose membrane and tested for Acanthamoeba using both cultivation and polymerase chain reaction (PCR) by targeting the 18S ribosomal RNA gene. The pathogenic potential of all positive isolates was identified using thermo- and osmotolerance tests. Thirty-eight (76.0%) samples were positive for Acanthamoeba. Water temperature (P = 0.035), chemical oxygen demand (P = 0.026), sulphate (P = 0.002) and Escherichia coli (P < 0.001) were found to be significantly correlated with the presence of Acanthamoeba. Phylogenetic analysis revealed that 24 samples belonged to genotype T4, nine (T15), two (T3) and one from each genotype T5, T11 and T17. Thermo- and osmotolerance tests showed that 6 (15.79%) of the Acanthamoeba strains were highly pathogenic. The existence of Acanthamoeba in recreational hot springs should be considered as a health threat among the public especially for high-risk people. Periodic surveillance of hot spring waters and posting warning signs by health authorities is recommended to prevent disease related to pathogenic Acanthamoeba.

The most abundant cyst wall proteins of Acanthamoeba castellanii are lectins that bind cellulose and localize to distinct structures in developing and mature cyst walls

Background

Acanthamoeba castellanii, which causes keratitis and blindness in under-resourced countries, is an emerging pathogen worldwide, because of its association with contact lens use. The wall makes cysts resistant to sterilizing reagents in lens solutions and to antibiotics applied to the eye.

Methodology/Principal findings

Transmission electron microscopy and structured illumination microscopy (SIM) showed purified cyst walls of A. castellanii retained an outer ectocyst layer, an inner endocyst layer, and conical ostioles that connect them. Mass spectrometry showed candidate cyst wall proteins were dominated by three families of lectins (named here Jonah, Luke, and Leo), which bound well to cellulose and less well to chitin. An abundant Jonah lectin, which has one choice-of-anchor A (CAA) domain, was made early during encystation and localized to the ectocyst layer of cyst walls. An abundant Luke lectin, which has two carbohydrate-binding modules (CBM49), outlined small, flat ostioles in a single-layered primordial wall and localized to the endocyst layer and ostioles of mature walls. An abundant Leo lectin, which has two unique domains with eight Cys residues each (8-Cys), localized to the endocyst layer and ostioles. The Jonah lectin and glycopolymers, to which it binds, were accessible in the ectocyst layer. In contrast, Luke and Leo lectins and the glycopolymers, to which they bind, were mostly inaccessible in the endocyst layer and ostioles.

Conclusions/Significance

The most abundant A. castellanii cyst wall proteins are three sets of lectins, which have carbohydrate-binding modules that are conserved (CBM49s of Luke), newly characterized (CAA of Jonah), or unique to Acanthamoebae (8-Cys of Leo). Cyst wall formation is a tightly choreographed event, in which lectins and glycopolymers combine to form a mature wall with a protected endocyst layer. Because of its accessibility in the ectocyst layer, an abundant Jonah lectin is an excellent diagnostic target.

A half century ago, investigators identified cellulose in the Acanthamoeba cyst wall, which has two layers and conical ostioles that connect them. Here we showed cyst walls contain three large sets of cellulose-binding lectins, which localize to the ectocyst layer (a Jonah lectin) or to the endocyst layer and ostioles (Luke and Leo lectins). We used the lectins to establish a sequence for cyst wall assembly when trophozoites are starved and encyst. In the first stage, a Jonah lectin and glycopolymers were present in dozens of distinct vesicles. In the second stage, a primordial wall contained small, flat ostioles outlined by a Luke lectin. In the third stage, a Jonah lectin remained in the ectocyst layer, while Luke and Leo lectins moved to the endocyst layer and ostioles. A description of the major events during cyst wall development is a starting point for mechanistic studies of its assembly.

Naegleria species population found in pond water of parks in Mashhad city, Can the physicochemical factors affect it?

Naegleria species are the ubiquitous free-living amoebas that are found worldwide in soil and water. Among Naegleria spp., N. fowleri can cause primary amebic meningoencephalitis (PAM). Ninety water samples were collected from the pond of parks. Also, the water quality parameters were measured at the sampling site (such as temperature, pH, total dissolved solids (TDS), electrical conductivity (EC) and Turbidity).

After filtering, the samples were cultured on Bacto-agar enriched with Escherichia coli. A PCR assay was conducted on the culture-positive samples in the ITS1, 5.8SrDNA and ITS2 regions, and then the PCR products were sequenced.

The pond water of parks was contaminated with some Naegleria spp. (except N. fowleri) and a Vahlkampfia avara. There was no significant relationship between water quality parameters and the presence of Naegleria (p > 0.05).

Our protocol investigates to detect Naegleria spp. from ponds water of parks in Mashhad city and the relations between the water quality parameters and its presence.