Siripanth Chutatip
Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand.
J Med Assoc Thai. 2005 May;88(5):701-7.
A large variety of species of free-living amoebae (FLA) caused an indefinite form of these protozoa. Non-fixed form, as indicated by amoeboid movement and possed the bacteria to survive in nature. Two species of pathogenic FLA: Naegleria fowleri and Acanthamoeba spp. were identified as the causative agents of Primary Amoebic Meningoencephalitis (PAM) and Granulomatous Amoebic Encephalitis (GAE) respectively. They were suggested to amphizoic protozoa, capable of living as parasites or as free-living and they were also considered to be distributed worldwide. These amoebae were detected in lakes, rivers and ponds. The first case of meningoencephalitis was observed in 1961 by Fowler Many cases were reported later on and the pathogenicity was tested by nasal inoculation of mice. In fact, quite a number of FLA were isolated but only a few species were pathogenic to humans. The three typical features which allow recognition of Naegleria spp. flagellate stage, round cyst and promitotic trophozoite. This promitosis distinguishes the Naegleria genus from Acanthamoeba spp. The disease caused by PAM usually occurs with acute onset, whereas chronic for GAE. The GAE cases mentioned are mostly in debilitated patients, chronic alcoholics or patients under treatment with immunosuppressive methods. About 6 cases of PAM were reported in Thailand during 1982-1997. Four cases of GAE were reported in 1994 and two isolated cases ofAcanthamoebafrom keratitis patients were reported in 2000. Finally one case of PAM and one case of GAE were reported in 2001. The surveys of FLA were set up to study the distribution of these pathogenic amoebae and determine the prevalence of amoebae in aquatic habitats of human environments. About 40% were identified as Acanthamoeba spp., 30% were Naegleria spp., 20% were Hartmanella and 10% were Vahlkampfia. Only 10% of Naegleria spp. belonged to Naegleria fowleri.
多种多样的自由生活阿米巴（FLA）构成了这些原生动物的不确定形式。非固定形式，如变形虫运动所示，使这些细菌能够在自然环境中生存。两种致病性FLA：福氏耐格里阿米巴和棘阿米巴属，分别被确认为原发性阿米巴脑膜脑炎（PAM）和肉芽肿性阿米巴脑炎（GAE）的病原体。它们被认为是兼性原生动物，能够以寄生虫或自由生活的方式生存，并且也被认为分布于世界各地。这些阿米巴在湖泊、河流和池塘中被检测到。1961年福勒观察到首例脑膜脑炎病例。后来报道了许多病例，并通过对小鼠进行鼻腔接种来测试其致病性。事实上，分离出了相当数量的FLA，但只有少数种类对人类致病。识别耐格里属的三个典型特征是鞭毛阶段、圆形包囊和前有丝分裂滋养体。这种前有丝分裂将耐格里属与棘阿米巴属区分开来。PAM引起的疾病通常急性发作，而GAE为慢性。所提到的GAE病例大多发生在身体虚弱的患者、慢性酒精中毒者或接受免疫抑制治疗的患者中。1982年至1997年期间泰国报告了约6例PAM。1994年报告了4例GAE，2000年报告了2例来自角膜炎患者的棘阿米巴分离病例。最后在2001年报告了1例PAM和1例GAE。开展了FLA调查以研究这些致病性阿米巴的分布，并确定人类环境水生栖息地中阿米巴的流行情况。约40%被鉴定为棘阿米巴属，30%为耐格里属，20%为哈特曼阿米巴，10%为瓦氏阿米巴。耐格里属中只有10%属于福氏耐格里阿米巴。
