Laboratory of Aquaculture, Institute of Oceanography and Fisheries, Split, Croatia.
Laboratory of Zoonotic Bacteria and Molecular Diagnosis of Bacterial Diseases, Department of Microbiology and Parasitology, Croatian Veterinary Institute, Zagreb, Croatia.
Parasit Vectors. 2019 Jul 30;12(1):381. doi: 10.1186/s13071-019-3636-z.
Inferring the microbiota diversity of helminths enables depiction of evolutionarily established ecological and pathological traits that characterize a particular parasite-host interaction. In turn, these traits could provide valuable information for the development of parasitosis control and mitigation strategy. The parasite Anisakis pegreffii (Nematoda: Anisakidae) realizes the final stage of its life-cycle within gastric chambers of aquatic mammals, causing mild-to-moderate granulomatous gastritis with eosinophilic infiltrate, to severe ulcerative gastritis with mixed inflammatory infiltrate, often associated with bacterial colonies. However, its interaction with the host microbiota remains unknown, and might reveal important aspects of parasite colonization and propagation within the final host.
MySeq Illumina sequencing was performed for the 16S rRNA gene from microbiota isolated from larvae, and uterus and gut of adult A. pegreffii parasitizing stranded striped dolphins (Stenella coeruleoalba). To assess the potential presence of Brucella ceti within isolated microbiota, Brucella-targeted real-time PCR was undertaken. In addition, TEM of the gastrointestinal tract of the infective third-stage (L3) and transitioning fourth-stage larvae (L4) was performed to characterize the morphological differences and the level of larval feeding activity.
In total, 230 distinct operational taxonomic units (OTUs) were identified across all samples (n = 20). The number of shared taxa was lower than the number of taxa found specifically in each parasite stage or organ. The dominant taxon was Mycoplasmataceae (genus Mycoplasma) in the gut and uterus of adult A. pegreffii, whereas Fusobacteriaceae (genus Cetobacterium) was the most abundant in 40% of larvae, alongside Mycoplasmataceae. No B. ceti DNA was detected in any of the microbiota isolates. TEM revealed differences in gut ultrastructure between L3 and L4, reflecting a feeble, most likely passive, level of feeding activity in L3.
Microbiota from L3 was more related to that of the gut rather than the uterus of adult A. pegreffii. Taxa of the larval microbiota showed qualitative and quantitative perturbations, likely reflecting the propagation through different environments during its life-cycle. This suggests an ontogenetic shift in the alpha and beta diversity of microbial communities from uterus-derived towards cetacean-derived microbiota. Although TEM did not reveal active L3 feeding, microbiota of the latter showed similarity to that of an actively feeding adult nematode.
推断寄生虫的微生物多样性可以描绘出寄生虫与其宿主之间特有的进化生态和病理特征。反过来，这些特征可以为寄生虫病控制和缓解策略的制定提供有价值的信息。寄生虫棘头虫属海狮蛔线虫（线虫：棘头虫科）在水生哺乳动物的胃囊中完成其生命周期的最后阶段，引起轻度至中度的肉芽肿性胃炎伴嗜酸性粒细胞浸润，严重的溃疡性胃炎伴混合炎症浸润，常伴有细菌菌落。然而，它与宿主微生物群的相互作用尚不清楚，这可能揭示寄生虫在终宿主内定植和繁殖的重要方面。
使用 Illumina MySeq 测序对来自搁浅条纹海豚寄生的棘头虫属幼虫、子宫和成虫的微生物群 16S rRNA 基因进行测序。为了评估分离的微生物群中是否存在鲸海分枝杆菌，进行了针对布鲁氏菌的实时 PCR。此外，对感染性第三阶段（L3）和过渡第四阶段幼虫（L4）的胃肠道进行 TEM 观察，以描述形态差异和幼虫摄食活动水平。
在所有样本中（n=20）共鉴定出 230 个独特的操作分类单元（OTU）。共享的分类单元数量低于在每个寄生虫阶段或器官中发现的分类单元数量。在成虫棘头虫属的肠道和子宫中，优势分类群是支原体科（支原体属），而在 40%的幼虫中，最丰富的是梭杆菌科（鲸丁酸菌属），同时还有支原体科。在任何微生物群分离物中均未检测到布鲁氏菌属 ceti 的 DNA。TEM 显示 L3 和 L4 之间的肠道超微结构存在差异，反映出 L3 中存在微弱的、可能是被动的摄食活动。
L3 的微生物群与成虫棘头虫属的肠道而非子宫更为相关。幼虫微生物群的分类群表现出定性和定量的扰动，可能反映了其生命周期中在不同环境中的传播。这表明微生物群落的 alpha 和 beta 多样性从子宫衍生向鲸衍生发生了个体发生转变。尽管 TEM 未显示出活跃的 L3 摄食，但后者的微生物群与活跃摄食的成年线虫相似。
