Molecular detection of free-living amoebae from Namhangang (southern Han River) in Korea

Presence of Free-living Acanthamoeba in Loa and Salado Rivers, Atacama Desert, Northern Chile

Substantial knowledge has accumulated on the microbiome of the hyperarid Atacama Desert during the last two decades; however, information on Atacama free-living amoebae (FLA) is limited and increasing efforts are required. FLA are polyphyletic heterotrophic naked or testate protists that feed on organic matter, fungi, protozoa, and bacteria and may disseminate infections. Amoebae in Chile are represented by 416 taxa and 64 genera, and 29 taxa have been identified in arid shrub lands at the southern limit of the Atacama Desert, and Acanthamoeba are present in all the country's regions. To expand our knowledge and to contribute to the biogeographic distribution of Atacama FLA, we report the dominant presence of members of the genus Acanthamoeba in water and sediment sampled at the Loa and Salado rivers in the pre-Andean zone of the Antofagasta Region, northern Chile, at sites 2500 m above sea level. We expect these observations and preliminary evidence of FLA presence in other wetlands (Chiuchiu, Tebenquiche) in this region to be incentive for further exploration of Atacama amoebae.

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.

The Increasing Importance of Vermamoeba vermiformis

Vermamoeba vermiformis are one of the most prevalent free-living amoebae. These amoebae are ubiquitous and also thermotolerant. Of concern, V. vermiformis have been found in hospital water networks. Furthermore, associations between V. vermiformis and pathogenic bacteria have been reported, such as Legionella pneumophila. Moreover, V. vermiformis are well known to host viruses, bacteria, and other microorganisms and cases of keratitis due to V. vermiformis in conjunction with other amoebae have been reported. Despite the preceding, the medical importance of V. vermiformis is still an ongoing discussion and its genome has been only recently sequenced. Herein, we present a review of the current understanding of the biology and pathogenesis pertaining to V. vermiformis, as well as its' role as an etiological agent and trojan horse. An approach known as theranostics which combines both diagnosis and therapy could be utilized to eradicate and diagnose keratitis cases caused by such amoebae. Given the rise in global warming, it is imperative to investigate these rarely studied amoebae and to understand their importance in human health.

Understanding the true burden of "Naegleria fowleri" (Vahlkampfiidae) in patients from Northern states of India: Source tracking and significance

The present study is an attempt to investigate the presence of Naegleria fowleri in Indian population. A total of 307 patients were enrolled and water samples were collected from both residential and surrounding areas of patients found positive for N. fowleri. The different species of Naegleria from both clinical and water samples were identified taxonomically. Recommended microbiological conventional techniques were used to identify different Naegleria stages and other free-living amoebae from the samples. PCR assays, using both genus and species specific primers were also optimized. None of the samples were positive by conventional microbiological examinations. However, PCR assays detected only three samples positive for N. fowleri. A total of 10 water bodies (ponds), that were used by Naegleria positive patients were examined. The pH and temperature of the water samples collected from water bodies ranged between 5.6-7.2 and 25-32 °C respectively. Among all the 10 water samples tested, four samples were positive for genus Naegleria by PCR assay, of which only two samples, showed positive amplification for N. fowleri. The sequence analysis of N. fowleri strain belonged to genotype II.

Identification of Free-Living Amoebas in Tap Water of Buildings with Storage Tanks in Korea

Free-living amoebas (FLAs) can cause severe disease in humans and animals when they become infected. However, there are no accurate survey reports on the prevalence of FLAs in Korea. In this study, we collected 163 tap water samples from buildings, apartments, and restrooms of highway service areas in 7 Korean provinces with high population density. All these buildings and facilities have water storage tanks in common. The survey was separated into categories of buildings, apartments, and highway service areas. Five hundred milliliters of tap water from each building was collected and filtered with 0.2 µm pore filter paper. The filters were incubated in agar plates with heated E. coli at 25°C. After axenization, genomic DNA was collected from each FLA, and species classification was performed using partial 18S-rDNA PCR-sequencing analysis. We found that 12.9% of tap water from buildings with storage tanks in Korea was contaminated with FLAs. The highway service areas had the highest contamination rate at 33.3%. All of the FLAs, except one, were genetically similar to Vermamoeba vermiformis (Hartmannella vermiformis). The remaining FLA (KFA21) was very similar to Acanthamoeba lugdunensis (KA/E26). Although cases of human infection by V. vermiformis are very rare, we must pay attention to the fact that one-third of tap water supplies in highway service areas have been contaminated.