Isolation and Molecular Identification of Vermamoeba vermiformis Strains from Soil Sources in El Hierro Island, Canary Islands, Spain

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.

Isolation and identification of potentially pathogenic free-living amoeba in dialysis fluid samples of hydraulic systems in hemodialysis units

BACKGROUND

Free-living amoeba (FLA), including Acanthamoeba, Naegleria, Balamuthia and Vermamoeba, have been isolated from water, sand, soil, dust and air. Numerous studies considered that FLA are a significant cause of neurological and ocular complications in high-risk groups, including immunocompromised individuals. The present study aimed to identify morphological and molecular characteristics of FLA isolates in dialysis fluid samples of hydraulic systems in hemodialysis units in Iran.

METHODS

A total of 328 dialysis fluid samples were collected from 16 dialysis machines, including 164 samples before hemodialysis sessions (after cleaning) and 164 samples after hemodialysis sessions (before cleaning). Filtration and cultivation were performed on non-nutrient agar medium. Also, PCR and sequencing were applied by using the genus-specific primers along with a common primer set on positive samples.

RESULTS

Both morphology and molecular investigations showed that 22.5% (74/328) of dialysis fluid samples were positive for FLA. There was a positive relationship between the high frequency of FLA after hemodialysis sessions (before cleaning) compared with before hemodialysis sessions (after cleaning) (OR=2.86; 95% CI 1.5 to 5.45). Considering the PCR assay, 16.46% (54/328) samples were identified as Acanthamoeba spp. (belonging to T3 and T4 genotypes), 5.18% (17/328) as Vermamoeba vermiformis and 0.91% (3/328) as Vahlkampfiidae family (Naegleria australiensis, Naegleria pagei and Allovahlkampfia).

CONCLUSION

The present results support a need to improve filtration and purification methods for dialysis fluid of hydraulic systems in hemodialysis units. They also highlight the relevance of periodic screenings for FLA-related diseases in hemodialysis patients.

Free-Living Amoebae in Soil Samples from Santiago Island, Cape Verde

Free-Living Amoebae (FLA) are widely distributed protozoa, which contain some groups considered as pathogenic microorganisms. These members are able to produce several opportunistic diseases including epithelial disorders, such as keratitis and fatal encephalitis. Even though they have been reported in numerous sources, such as soils, dust and water, there is no legislation related to the presence of these protozoa in soil-related environments worldwide. Therefore, there are no established prevention or disinfection protocols to advise the population regarding FLA infections or eliminate these microorganisms from human-related environments to date. Acanthamoeba spp. are the most common FLA isolated in soil samples, which is also the most common genera found in clinical cases. Thus, the aim of the present study was to evaluate the presence of potentially pathogenic FLA in human-related soil samples of Santiago Island, Cabo Verde. A total of 26 soil samples were seeded in non-nutrient agar plates (2%), incubated at 26 °C, and monitored daily to evaluate the presence of FLA. DNA was extracted from those plates on which there was suspected FLA growth, and PCR amplification of the 18S rRNA gene was carried out. A total of 17 from the 26 analysed samples were positive for FLA, where Acanthamoeba is the most abundant isolated genus (14/17; 82.4%), with the T4 genotype being the most common (13/14; 92.9%), followed by the T5 genotype, A. lenticulata (1/14; 7.1%). Moreover, Vermamoeba vermiformis, Stenamoeba dejonckheerei and Vannella pentlandi were isolated in three other samples. To the best of our knowledge, this is the first report of FLA presence in Cape Verde and the first report of V. vermiformis in beach sand worldwide.

Parasitic amoebae found in water bodies of Ukraine

Two parasitic amoebian species are found in mollusks of the water bodies of Ukraine. Vahlkampfia sp. is found in hepatopankreas of Unio conus Spengler, 1793, and Acanthamoeba sp. is observed in mantle cavity of Viviparus viviparus Linnaeus, 1758. For these protist species, the mollusks are shown to be intermediate hosts where amoebae feed and reproduce. An experimental infection with Vahlkampfia sp. and Acanthamoeba sp. was not successful, no pathological changes in mollusks were observed. These amoebae are successfully cultured in fresh water and agar medium, hence we can safely consider them free-living.

Detection of viable Helicobacter pylori inside free-living amoebae in wastewater and drinking water samples from Eastern Spain

Helicobacter pylori is one of the most concerning emerging waterborne pathogens. It has been suggested that it could survive in water inside free-living amoebae (FLA), but nobody has studied this relationship in the environment yet. Thus, we aimed to detect viable H. pylori cells from inside FLA in water samples. Sixty-nine wastewater and 31 drinking water samples were collected. FLA were purified and identified by PCR and sequencing. For exclusively detecting H. pylori inside FLA, samples were exposed to sodium hypochlorite and assayed by specific PMA-qPCR, DVC-FISH and culture. FLA were detected in 38.7% of drinking water and 79.7% of wastewater samples, even after disinfection. In wastewater, Acanthamoeba spp. and members of the family Vahlkampfiidae were identified. In drinking water, Acanthamoeba spp. and Echinamoeba and/or Vermamoeba were present. In 39 (58.2%) FLA-positive samples, H. pylori was detected by PMA-qPCR. After DVC-FISH, 21 (31.3%) samples harboured viable H. pylori internalized cells. H. pylori was cultured from 10 wastewater samples. To our knowledge, this is the first report that demonstrates that H. pylori can survive inside FLA in drinking water and wastewater, strongly supporting the hypothesis that FLA could play an important role in the transmission of H. pylori to humans.