Detection of free-living amoebae using amoebal enrichment in a wastewater treatment plant of Gauteng Province, South Africa

Global prevalence of potentially pathogenic free-living amoebae in sewage and sewage-related environments-systematic review with meta-analysis

Free-living amoebae (FLA) include amphizoic microorganisms important in public health, widely isolated from air, water, and soil. However, its occurrence in sewage-related environments still needs to be systematically documented. This study summarizes the occurrence of FLA in sewage-related environments through a systematic review with meta-analysis. A total of 1983 scientific article were retrieved from different databases, of which 35 were selected and analyzed using a random effects forest plot model with a 95% confidence interval (IC). The pooled overall prevalence of FLA in sewage across 12 countries was 68.96% (95% IC = 58.5-79.42). Subgroup analysis indicates high prevalence in all environments analyzed, including sewage water from the sewage treatment plant (81.19%), treated sewage water (75.57%), sewage-contaminated water (67.70%), sediment contaminated by sewage (48.91%), and sewage water (47.84%). Prevalence values of Acanthamoeba spp., Hartmanella/Vermamoeba spp., and Naegleria spp. are 47.48%, 28.24%, and 16.69%, respectively. Analyzing the species level, the distribution is as follows: Acanthamoeba palestinensis (88%), A. castellanii (23.74%), A. astronyxis (19.18%), A. polyphaga (13.59%), A. culbertsoni (12.5%), A. stevensoni (8.33%), A. tubiashi (4.35%) and A. hatchetti (1.1%), Naegleria fowleri (28.4%), N. gruberi (25%), N. clarki (8.33%), N. australiensis (4.89%) and N. italica (4.29%), Hartmannella/Vermamoeba exundans (40%) and H.V. vermiform (32.61%). Overall, our findings indicate a high risk associated with sewage-related environments, as the prevalence of FLA, including pathogenic strains, is high, even in treated sewage water. The findings of this study may be valuable both for risk remediation actions against amoebic infections and for future research endeavors.

Monitoring potentially pathogenic protists in sewage sludge using Metataxonomics

Intestinal parasites continue to pose a significant threat to human health worldwide, particularly among children. Contaminated water and soil serve as major transmission vehicles for these parasites and intestinal protists are among the most prevalent parasites in both developed and developing nations. Traditionally, parasites have been studied using human or animal fecal samples, while studying them in environmental samples has been challenging due to technical limitations. However, advancements in Next-Generation Sequencing (NGS) and bioinformatic approaches now enable the detection of parasite DNA in environmental samples. In this study, we applied a metataxonomic and phylogenetic strategy to detect and classify DNA of protists present in sewage sludge from two major cities in Colombia: Medellin and Cali. We successfully detected several human pathogenic parasites including Giardia intestinalis, Entamoeba histolytica, and Blastocystis sp., among other protists, in all sludge samples examined. We also investigated the entry and exit of parasite DNA from the San Fernando wastewater treatment plant (WWTP). We observed a higher number of parasite DNA sequences in the plant's influent wastewater, but we also detected the discharge of DNA from pathogenic parasites in both effluent waters and biosolids.

First report of free-living amoebae in sewage treatment plants in Porto Alegre, southern Brazil

Free-living amoebae (FLA) are amphizoic protozoans with a cosmopolitan distribution. Some strains of species are associated with infections in humans. They feed on microorganisms by phagocytosis; however, some of these can become endocytobionts by resisting this process and taking shelter inside the amoeba. The whole world is experiencing increasing shortage of water, and sewage is being reused, so the study of this environment is important in public health context. The objective of this work was to identify FLA present in sewage treatment plants in Porto Alegre, Brazil. About 1 L samples were collected from eight stations (raw and treated sewage) in January, February, July, and August 2022. The samples were sown in monoxenic culture, and the isolated amoebae were subjected to morphological and molecular identification. Polymerase chain reaction results indicated the presence of the genus Acanthamoeba in 100% of the samples. Gene sequencing showed the presence of Acanthamoeba lenticulata and Acanthamoeba polyphaga - T5 and T4 genotypes - respectively, which are related to pathogenicity. The environment where the sewage is released can be used in recreational activities, exposing individuals to potential interactions with these amoebae and their potential endocytobionts, which may pose risks to public health.

Contact lenses contamination by Acanthamoeba spp. in Upper Egypt

Background

Acanthamoeba spp. are one of the free-living amoeba that spread worldwide causing keratitis. Owing to the increase in the use of lenses, whether for medical or cosmetic purposes, the incidence of disease increases every year. Contamination of the lenses with the Acanthamoeba trophozoites or cysts may lead to eye infection and cause sight-threatening keratitis in human. We isolated Acanthamoeba spp. from new lenses, used lenses, and contact lens disinfecting solutions and identified them based on morphological characteristics and molecular test.

Methods

New and used lenses and contact lens disinfecting solutions were cultured on monogenic media. Light and scanning electron microscope was used to identify Acanthamoeba spp. morphological features. Genotype identification was also evaluated using PCR sequencing of 18S rRNA gene specific primer pair JDP1 and JDP2.

Results

A hundred samples were examined, 29 (29%) were infected with Acanthamoeba spp. That belonged to two strains of Acanthamoeba (Acanthamoeba 41 and Acanthamoeba 68). 18S rRNA of the Acanthamoeba 41 had 99.69% sequence identity to Acanthamoeba castellanii clone HDU-JUMS-2, whereas Acanthamoeba 68 had 99.74% similar pattern to that of Acanthamoeba sp. isolate T4 clone ac2t4 that are morphologically identified as Acanthamoeba polyphaga. The obtained data revealed that the isolated strains belong to T4 genotype that was evolutionarily similar to strains isolated in Iran.

Conclusions

Cosmetic lenses and disinfectant solutions are a major transmissible mode for infection. This genotype is common as the cause of Acanthamoeba keratitis. To avoid infection, care must be taken to clean the lenses and their preservative solutions and prevent contamination with the parasite.

Free-living amoebae and squatters in the wild: ecological and molecular features

Free-living amoebae are protists frequently found in water and soils. They feed on other microorganisms, mainly bacteria, and digest them through phagocytosis. It is accepted that these amoebae play an important role in the microbial ecology of these environments. There is a renewed interest for the free-living amoebae since the discovery of pathogenic bacteria that can resist phagocytosis and of giant viruses, underlying that amoebae might play a role in the evolution of other microorganisms, including several human pathogens. Recent advances, using molecular methods, allow to bring together new information about free-living amoebae. This review aims to provide a comprehensive overview of the newly gathered insights into (1) the free-living amoeba diversity, assessed with molecular tools, (2) the gene functions described to decipher the biology of the amoebae and (3) their interactions with other microorganisms in the environment.

From Many Hosts, One Accidental Pathogen: The Diverse Protozoan Hosts of Legionella

The 1976 outbreak of Legionnaires' disease led to the discovery of the intracellular bacterial pathogen Legionella pneumophila. Given their impact on human health, Legionella species and the mechanisms responsible for their replication within host cells are often studied in alveolar macrophages, the primary human cell type associated with disease. Despite the potential severity of individual cases of disease, Legionella are not spread from person-to-person. Thus, from the pathogen's perspective, interactions with human cells are accidents of time and space—evolutionary dead ends with no impact on Legionella's long-term survival or pathogenic trajectory. To understand Legionella as a pathogen is to understand its interaction with its natural hosts: the polyphyletic protozoa, a group of unicellular eukaryotes with a staggering amount of evolutionary diversity. While much remains to be understood about these enigmatic hosts, we summarize the current state of knowledge concerning Legionella's natural host range, the diversity of Legionella-protozoa interactions, the factors influencing these interactions, the importance of avoiding the generalization of protozoan-bacterial interactions based on a limited number of model hosts and the central role of protozoa to the biology, evolution, and persistence of Legionella in the environment.

Occurrence of Acanthamoeba Genotypes in Wastewater Samples in Tehran, Iran

BACKGROUND

Acanthamoeba spp. is potentially pathogenic free-living amoeba that can exist in various water sources. The presence of this amoeba in water sources could be a health hazard as Acanthamoeba could lead to severe diseases such as Acanthamoeba keratitis and encephalitis. This study aimed to determine the genotypes of isolated Acanthamoeba spp. in raw wastewater samples in Tehran, Iran.

METHODS

Overall, 90 raw wastewater samples were collected from water treatment facilities in west and south of Tehran, Iran during 2014-2016. Water samples were filtered and cultured on non-nutrient agar (NNA) medium enriched with Escherichia coli. Morphological and molecular analyses were done on positive strains. The pathogenic ability of the isolated strains was determined using physical assays.

RESULTS

Totally, 6 out of 90 (6.7%) samples were positive for Acanthamoeba, according to morphological characteristics of double-walled cysts. Genotyping and sequencing of the positive strains showed Acanthamoeba belonging to T4 (83%) and T11 (17%) genotypes. In vitro pathogenicity tests were revealed that five isolates were classified as non-pathogenic strains and one strain belonging to T4 genotype was classified as the highly pathogenic amoebae.

CONCLUSION

The current research reflected a low contamination of wastewater sources to Acanthamoeba. More studies regarding the contamination of wastewaters before and after treatment are required in different places of the country.

Prevalence of protozoa species in drinking and environmental water sources in Sudan

Protozoa are eukaryotic cells distributed worldwide in nature and are receiving increasing attention as reservoirs and potential vectors for the transmission of pathogenic bacteria. In the environment, on the other hand, many genera of the protozoa are human and animal pathogens. Only limited information is available on these organisms in developing countries and so far no information on their presence is available from Sudan. It is necessary to establish a molecular identification of species of the protozoa from drinking and environmental water. 600 water samples were collected from five states (Gadarif, Khartoum, Kordofan, Juba, and Wad Madani) in Sudan and analysed by polymerase chain reaction (PCR) and sequencing. 57 out of 600 water samples were PCR positive for protozoa. 38 out of the 57 positive samples were identified by sequencing to contain 66 protozoa species including 19 (28.8%) amoebae, 17 (25.7%) Apicomplexa, 25 (37.9%) ciliates, and 5 (7.6%) flagellates. This study utilized molecular methods identified species belonging to all phyla of protozoa and presented a fast and accurate molecular detection and identification of pathogenic as well as free-living protozoa in water uncovering hazards facing public health.