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 specific primers for Acanthamoeba, Naegleria, and Vermamoeba/Hartmanella. Culture and PCR returned 50 and 65% positivity, respectively, for seawater samples where sequencing revealed Acanthamoeba T2, T5 and T6 genotypes and A. palestinensis and A. lenticulata, 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 Acanthamoeba T2, T4 and T11 genotypes and A. castellanii, A. palestinensis and A. stevensoni 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.

自由生活的变形虫（FLA）在各种环境条件下都蓬勃发展。本研究旨在确定里海的FLA分布以及伊朗桂兰的医院病房灰尘。2018年5月至6月收集了海水（20）和医院病房灰尘样品（100）。通过0.45μm孔径的膜对海水样品进行真空过滤。用无菌纱布收集灰尘，用无菌蒸馏水洗涤，然后收集洗液。类似地，将洗涤物过滤为海水样品。来自过滤材料的FLA在非营养琼脂中培养。通过PCR进行分子分析，并使用棘棘藻，Naegleria和Vermamoeba / Hartmanella的特异性引物进行测序。。培养和PCR返回50和65％阳性，分别为海水样品，其中测序揭示棘阿米巴T2，T5和T6基因型和A. palestinensis和A. lenticulata，以及N. dobsoni和N. clarki。此外，从医院病房灰尘样品中观察到了30％的阿米巴菌生长和16％PCR检测，测序结果显示了Acanthamoeba T2，T4和T11基因型以及A. castellanii，A。palestinensis和A. stevensoni以及N. clarki。对于海水和粉尘样品，棘阿米巴是主要的隔离株。从海水中检测出潜在致病的FLA可能对公众构成威胁，而灰尘中的FLA则对医院工作人员和患者（尤其是免疫功能低下的个人）均构成威胁。为了减轻和管理潜在的人类感染病例，必须进行公众教育，提高认识，改善卫生和个人卫生状况以及制定用于早期发现人类FLA的诊断策略。