Vingataramin Youri, Delumeau Aurélie, Quétel Isaure, Gros Olivier, Vedy Serge, Marcelino Isabel
Institut Pasteur de la Guadeloupe, Les Abymes, Guadeloupe, France.
Institut Pasteur de la Guadeloupe, Les Abymes, Guadeloupe, France.
Sci Total Environ. 2025 May 1;975:179204. doi: 10.1016/j.scitotenv.2025.179204. Epub 2025 Apr 5.
Free-living amoebae (FLA) are ubiquitous protists found in water, feeding mainly on bacteria. While most FLA are harmless, Acanthamoeba spp. and Naegleria fowleri can cause keratitis and/or meningitis. FLA can host amoeba-resistant bacteria (ARB), but their natural bacterial microbiota is largely unknown. This study aimed to identify the natural bacterial microbiota of Naegleria fowleri, Acanthamoeba castellanii, Acanthamoeba lenticulata, and Acanthamoeba sp. T17, isolated from untreated (rivers) and treated (tap) waters in Guadeloupe. The whole bacterial microbiota of the water source and the FLA grown with E. coli and under axenic culture conditions, during successive passages, were characterized using 16S rRNA gene metabarcoding. The culturable subset of ARB was identified by mass spectrometry (MALDI-TOF MS) followed by conventional 16S PCR, and bacterial antibiotic resistance was analyzed using the disk diffusion method. Transmission electron microscopy was used to locate ARB within the amoebae. The metabarcoding analyses identified Salmonella, Enterobacter and Klebsiella genera as the most abundant bacteria in untreated and treated waters. However, the most frequently detected amoeba-resistant bacteria (ARB) were from the Bosea, Escherichia-Shigella, Microbacterium, and Pseudomonas genera. Our findings revealed, for the first time, the natural occurrence of several bacteria within N. fowleri, including Pseudomonas spp. and Escherichia coli. Additionally, we detected Legionella in A. castellanii and Bordetella in A. lenticulata. The four pathogenic FLA showed both temporary and permanent associations with various bacterial genera, depending on the number of passages and culture conditions. Pseudomonas species isolated from distinct FLA exhibited resistance to different antibiotics. ARB were detected within the cytoplasm of trophozoites. The presence of pathogenic FLA and ARB in untreated and treated water in Guadeloupe's drinking systems pose health risks. Our results highlight the need for regular monitoring to ensure water safety and understanding amoebae-bacteria interactions for better management. The natural presence of ARB in pathogenic FLA also questions the host immune response during amoeba infection.
自由生活阿米巴（FLA）是普遍存在于水中的原生生物，主要以细菌为食。虽然大多数FLA无害，但棘阿米巴属和福氏耐格里阿米巴可引起角膜炎和/或脑膜炎。FLA可寄生抗阿米巴细菌（ARB），但其天然细菌微生物群在很大程度上尚不清楚。本研究旨在鉴定从瓜德罗普岛未处理（河流）和处理后（自来水）水源分离出的福氏耐格里阿米巴、卡氏棘阿米巴、豆形棘阿米巴和棘阿米巴T17的天然细菌微生物群。使用16S rRNA基因宏条形码技术对水源以及在连续传代过程中与大肠杆菌一起培养和在无菌培养条件下培养的FLA的整个细菌微生物群进行了表征。通过质谱（MALDI-TOF MS），随后进行常规16S PCR鉴定ARB的可培养子集，并使用纸片扩散法分析细菌抗生素耐药性。利用透射电子显微镜在阿米巴内定位ARB。宏条形码分析确定沙门氏菌属、肠杆菌属和克雷伯氏菌属是未处理和处理后水中最丰富的细菌。然而，最常检测到的抗阿米巴细菌（ARB）来自博斯氏菌属、埃希氏菌-志贺氏菌属、微杆菌属和假单胞菌属。我们的研究结果首次揭示了福氏耐格里阿米巴内几种细菌的自然存在，包括假单胞菌属和大肠杆菌。此外，我们在卡氏棘阿米巴中检测到嗜肺军团菌，在豆形棘阿米巴中检测到博德特氏菌。这四种致病性FLA根据传代次数和培养条件与各种细菌属表现出暂时和永久的关联。从不同FLA分离出的假单胞菌属对不同抗生素表现出耐药性。在滋养体细胞质内检测到ARB。瓜德罗普岛饮用水系统中未处理和处理后水中致病性FLA和ARB的存在构成健康风险。我们的结果强调需要定期监测以确保水安全，并了解阿米巴-细菌相互作用以便更好地管理。致病性FLA中ARB的自然存在也对阿米巴感染期间的宿主免疫反应提出了质疑。
