Free-living amoebae (FLA) thrive in diverse environmental conditions. The present study aimed to define the FLA distribution from the Caspian Sea as well as from hospital ward dust from Guilan, Iran. Seawater (20) and hospital ward dust samples (100) were collected from May to June 2018. Seawater samples were vacuum filtered through a 0.45 μm pore-size membrane. Dust was collected using sterile gauze, washed with sterile distilled water, with washings collected thereafter. Washings were similarly filtered as seawater samples. FLA from the filtered material was cultivated in non-nutrient agar. Molecular analysis was performed by PCR and sequencing using species-specific primers for Acanthamoeba, Naegleria, and Vermamoeba/Hartmanella. Culture and PCR returned 50 and 65% positivity, respectively, for seawater samples where sequencing revealed A. palestinensis T2 and T6, and A. lenticulata T5 genotypes as well as N. dobsoni and N. clarki. In addition, 30% amoebic growth and 16% PCR detection were observed from hospital ward dust samples where sequencing revealed A. castellanii T4, A. palestinensis T2, and A. stevensoni T11 genotypes as well as N. clarki. For both seawater and dust samples, Acanthamoeba was the dominant isolate. The detection of potentially pathogenic FLA from seawater may pose a threat to the public, while the presence of the same in dust spells threats to both hospital staff and patients, in particular, immunocompromised individuals. Public education, awareness, improved sanitation and hygiene, and the crafting of diagnostic strategies for the early detection of FLA in humans are necessary for the mitigation and management of potential human infection cases.


  • Free-living amoebae (FLA) detection in environmental and infrastructure-derived samples.

  • Pathogenic genotypes of FLA in the Caspian Sea.

  • FLA in hospital wards for immunocompromised patients.

  • Pathogenic genotypes of FLA in hospital ward dust.

  • Policies demand and hygiene to protect humans against FLA infections.

Graphical Abstract

Graphical Abstract
Graphical Abstract
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