School of Optometry and Vision Science, The University of New South Wales, Sydney, Australia.
Centre for Vision Research, Westmead Institute for Medical Research, The University of Sydney, Sydney, Australia.
Clin Exp Optom. 2020 Nov;103(6):782-786. doi: 10.1111/cxo.13065. Epub 2020 Mar 29.
This study examined the prevalence of free-living Acanthamoeba in domestic tap water in the greater Sydney region, Australia, and determined any seasonal variation in prevalence.
Fifty-four participants were included in this study following approval from an institutional human research ethics committee. Each participant self-collected two samples (one in summer and another in winter) from the surface of the drain of the bathroom sink using an instructional kit. The samples were cultured by inoculating onto a non-nutrient agar plate seeded with Escherichia coli and incubation at 32°C for two weeks. The plates were microscopically examined for the presence of free-living amoeba. DNA was isolated from 20 samples and a polymerase chain reaction (PCR) assay was performed for amplification of the partial sequence of the 18S ribosomal RNA gene. The PCR amplified products were sequenced using Sanger sequencing and genotyping was performed based on the variation in nucleotide sequences.
A total of 97 samples were collected over the two collection periods, with 28.6 per cent of samples morphologically classified as Acanthamoeba. The summer period yielded 16 of 54 (29.6 per cent) samples classified as Acanthamoeba, while the winter period yielded 12 of 43 (27.9 per cent) samples classified as Acanthamoeba. There was no statistically significant difference (p = 0.85) between the prevalence of free-living Acanthamoeba in summer compared to winter. Phylogenetic analysis showed that 15 of 20 (75 per cent) isolates belonged to genotype T4, the most frequent genotype isolated in Acanthamoeba keratitis.
The prevalence of free-living Acanthamoeba characterised morphologically in domestic tap water of the greater Sydney region was higher than expected, especially considering the low incidence of Acanthamoeba keratitis in Australia. However, this study did not find variation between seasons. As the T4 genotype was most common, Sydney-based practitioners must always consider Acanthamoeba as a possible causative organism in cases of microbial keratitis, regardless of the season.
本研究检测了澳大利亚大悉尼地区家庭自来水中自由生活阿米巴的流行情况，并确定了流行率的任何季节性变化。
本研究经机构人类研究伦理委员会批准后，纳入了 54 名参与者。每位参与者使用指导工具从浴室水槽排水口的表面自行采集两个样本（一个在夏季，另一个在冬季）。将样本接种到非营养琼脂平板上，接种大肠杆菌并在 32°C 孵育两周。通过显微镜检查平板是否存在自由生活的阿米巴。从 20 个样本中分离出 DNA，并进行聚合酶链反应（PCR）检测，以扩增 18S 核糖体 RNA 基因的部分序列。使用 Sanger 测序对 PCR 扩增产物进行测序，并根据核苷酸序列的变异进行基因分型。
在两个采集期共采集了 97 个样本，其中 28.6%的样本形态学上被分类为棘阿米巴。夏季采集的样本中有 16 个（29.6%）被分类为棘阿米巴，而冬季采集的样本中有 12 个（27.9%）被分类为棘阿米巴。夏季与冬季自由生活棘阿米巴的流行率无统计学差异（p=0.85）。系统发育分析显示，20 个分离株中有 15 个（75%）属于 T4 基因型，这是棘阿米巴角膜炎中最常见的基因型。
大悉尼地区家庭自来水中自由生活棘阿米巴的流行率高于预期，尤其是考虑到澳大利亚棘阿米巴角膜炎的发病率较低。然而，本研究未发现季节之间的差异。由于 T4 基因型最为常见，悉尼地区的医生在遇到微生物角膜炎时，无论季节如何，都必须始终考虑棘阿米巴可能是致病原因。
