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Published on: December 8, 2017
Screening Swiss water bodies for potentially pathogenic free-living amoebae
Christian Gianinazzi1, Marc Schild, Fritz Wüthrich
1Institute of Parasitology, University of Bern, Länggasstrasse 122, CH-3012 Bern, Switzerland.
Abstract:
Free-ling amoebae (FLA) including Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia pedata, can cause opportunistic infections leading to severe brain pathologies. Human infections with pathogenic FLA have been increasingly documented in many countries. In Switzerland, thus far, the occurrence and distribution of potentially pathogenic FLA has not been investigated. Swiss water biotopes, including swimming pools, lakes, rivers and ponds, have now been screened for the presence of FLA, and assessment of their pathogenicity potential for a mammalian host has been undertaken. Thus, a total of 17 isolates were recovered by in vitro cultivation from these different aquatic sources. Characterization by sequence analysis of Acanthamoeba spp.-specific and 'FLA-specific PCR products amplified from 18s rDNA based on morphological traits, thermotolerance, and cytotoxicity towards murine fibroblasts yielded the following findings: Echinamoeba cf. exundans (3 isolates), Hartmannella spp. (3), Vannella spp. (4), Protacanthamoebica cf. bohemica (1), Acanthamoeba cf. castellanii (1) and Naegleria spp. (5). B. mandrillaris and N. fowleri did not range amongst these isolates. None of the isolates exhibited pronounced cytotoxicity and all failed to grow at 42 degrees C; therefore, they do not present any potential for CNS pathogenicity for humans.
Insights
Free-living amoebae (FLA) were surveyed in Swiss waters, with 17 isolates identified. None of the identified FLA exhibited pathogenic potential for humans, indicating a low risk in these water sources.
Area of Science:
- Environmental microbiology
- Parasitology
- Public health
Background:
- Free-living amoebae (FLA) are opportunistic pathogens capable of causing severe brain infections.
- Human infections with pathogenic FLA are increasingly reported globally.
- The prevalence and pathogenicity of FLA in Swiss water bodies remain uninvestigated.
Purpose of the Study:
- To investigate the occurrence and distribution of potentially pathogenic FLA in Swiss aquatic environments.
- To assess the pathogenicity potential of isolated FLA for mammalian hosts.
Main Methods:
- Screening of various Swiss water biotopes (swimming pools, lakes, rivers, ponds) for FLA.
- Isolation and in vitro cultivation of 17 FLA strains.
- Characterization using 18S rDNA sequence analysis, morphological traits, thermotolerance, and cytotoxicity assays against murine fibroblasts.
Main Results:
- Seventeen FLA isolates were identified, including Echinamoeba cf. exundans, Hartmannella spp., Vannella spp., Protacanthamoebica cf. bohemica, Acanthamoeba cf. castellanii, and Naegleria spp.
- Balamuthia mandrillaris and Naegleria fowleri were not among the isolated species.
- No isolates demonstrated significant cytotoxicity or grew at 42°C, indicating a lack of CNS pathogenicity potential.
Conclusions:
- The surveyed Swiss water bodies harbor diverse FLA, but the identified isolates do not pose a risk for human central nervous system infections.
- Further research may be needed to monitor FLA in recreational waters, especially concerning thermotolerant and cytotoxic strains.
