Balamuthia mandrillaris is an opportunistic free-living amoeba that has been reported to cause skin lesions and the fatal Balamuthia amoebic encephalitis (BAE) in humans and other animals. Currently, around 200 human BAE cases have been reported worldwide, although this number is considered to be underestimated. The highest number of BAE cases has been reported in the American continent, mainly in the southwest of the USA. Peru seems to be another hotspot for BAE with around 55 human cases having been identified, usually involving cutaneous infection, especially lesions in the central face area. The isolation of Balamuthia from environmental sources has been reported on only three prior occasions, twice from Californian soils and once from dust in Iran and so it seems that this amoeba is relatively rarely encountered in samples from the environment. We investigated that possibility of finding the amoebae in soil samples from different regions where clinical cases have been reported in Peru. Twenty-one samples were cultured in non-nutrient agar plates and were checked for the presence of B. mandrillaris-like trophozoites and/or cysts. Those samples that were positive for these amoebae by microscopic criteria were then confirmed by PCR amplification and DNA sequencing of the mitochondrial 16S rDNA gene of B. mandrillaris. We have detected the presence of B. mandrillaris in four samples collected in the regions of Piura (3) and Lima (1) where infection cases have been previously reported. We hypothesize that B. mandrillaris is present in Peru in soil and dust which therefore constitutes a source of the infection for the BAE cases previously reported in this country. Further studies should be carried out in the area to confirm the generality of this finding.

译文

Balamuthia mandrillaris是一种机会主义的自由生活的变形虫,据报道会在人类和其他动物中引起皮肤病变和致命的Balamuthia阿米巴脑炎 (BAE)。目前,全世界已经报道了大约200例人类BAE病例,尽管这一数字被认为被低估了。在美洲大陆,主要是在美国西南部,报告的BAE病例数量最多。秘鲁似乎是BAE的另一个热点,已发现约55例人类病例,通常涉及皮肤感染,尤其是中央面部区域的病变。以前只有三次报道过从环境中分离出Balamuthia,两次是从加利福尼亚的土壤中分离出来的,一次是从伊朗的灰尘中分离出来的,因此似乎在环境样品中很少遇到这种变形虫。我们调查了在秘鲁报道了临床病例的不同地区的土壤样品中发现变形虫的可能性。在非营养琼脂平板中培养了21个样品,并检查了曼氏杆菌样滋养体和/或囊肿的存在。然后通过PCR扩增和对曼氏杆菌线粒体16S rDNA基因进行DNA测序,确认了通过显微镜标准对这些变形虫呈阳性的样品。我们已经在Piura (3) 和Lima (1) 地区收集的四个样本中检测到曼氏杆菌的存在,这些地区以前曾报道过感染病例。我们假设秘鲁的土壤和灰尘中存在曼氏杆菌,因此构成了该国先前报道的BAE病例的感染源。应在该地区进行进一步研究,以确认这一发现的普遍性。

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