Departamento de Parasitologia Animal, Universidade Federal Rural do Rio de Janeiro (UFRRJ), Rodovia BR 465, Km 07, s/n, Zona Rural, Seropédica, RJ, 23890-000, Brazil.
Departamento de Parasitologia Animal, Universidade Federal Rural do Rio de Janeiro (UFRRJ), Rodovia BR 465, Km 07, s/n, Zona Rural, Seropédica, RJ, 23890-000, Brazil.
Ticks Tick Borne Dis. 2019 Oct;10(6):101266. doi: 10.1016/j.ttbdis.2019.101266. Epub 2019 Aug 2.
The bacterium Rickettsia bellii has been detected in 25 species of ticks in the American continents, but its pathogenic potential is considered as undetermined. A possible role for this species in the phenomenon of transovarial exclusion of pathogenic members of the spotted fever group (SFG) of Rickettsia has been suggested and co-infections with pathogenic species have been reported infrequently in both North and South America. Traditional methods for the molecular detection of rickettsial agents in ticks focus largely on the identification of sequences found in SFG Rickettsia, an approach that may overlook the presence of co-infections with R. bellii. Two novel, species-specific polymerase chain reaction (PCR) assays, targeting the genes encoding the surface cell antigen (Sca), autotransporter proteins sca9 and sca14, were developed and validated for the detection of R. bellii using 150 Amblyomma ticks collected from wild birds in Brazil. Co-infection of R. bellii infected ticks was evaluated using a novel PCR assay targeting the ompA sequence characteristic of SFG Rickettsia. Preliminary species-level identification was achieved by restriction fragment length polymorphism (RFLP) analysis and subsequently confirmed by sequencing of amplicons. Nine out of seventy-three Amblyomma longirostre and one of two Amblyomma calcaratum ticks were shown to be co-infected with R. bellii and Rickettsia amblyommatis, while two out of sixty-seven Amblyomma sp. haplotype Nazaré ticks were recorded as co-infected with R. bellii and the Rickettsia parkeri-like bacterium, strain ApPR. Interestingly, our data represent the first records of R. bellii in association with A. calcaratum and Amblyomma sp. haplotype Nazaré. The novel PCR-RFLP systems reported herein, provide an alternative, rapid and cost-efficient (relative to strategies based on sequencing or real-time PCR), approach to evaluate rickettsial co-infection of ticks, a potentially significant phenomenon that has most likely been underestimated to date.
贝氏立克次体已在美洲大陆的 25 种蜱中被检测到，但它的致病潜力被认为是不确定的。有人提出，该物种可能在斑点热群（SFG）立克次体的卵传性排斥现象中发挥作用，并且在北美和南美都有报道称很少有与致病性物种的合并感染。传统的蜱中立克次体分子检测方法主要集中在鉴定 SFG 立克次体中发现的序列，这种方法可能会忽略与 R. bellii 的合并感染。本研究开发并验证了两种针对编码表面细胞抗原（Sca）、自转运蛋白 sca9 和 sca14 的基因的新型、种特异性聚合酶链反应（PCR）检测方法，用于检测巴西野生鸟类采集的 150 只硬蜱中的 R. bellii。使用针对 SFG 立克次体特征性的 ompA 序列的新型 PCR 检测方法评估了 R. bellii 感染蜱的合并感染情况。通过限制性片段长度多态性（RFLP）分析进行初步种水平鉴定，随后通过扩增子测序进行确认。在 73 只长角血蜱和 2 只尖角血蜱中，有 9 只和 1 只被检测到与 R. bellii 和 Rickettsia amblyommatis 合并感染，而在 67 只 Amblyomma sp. Nazaré 中，有 2 只被记录为与 R. bellii 和类似于 Rickettsia parkeri 的细菌，菌株 ApPR 合并感染。有趣的是，我们的数据代表了首次记录到 R. bellii 与尖角血蜱和 Amblyomma sp. Nazaré 相关。本文报道的新型 PCR-RFLP 系统提供了一种替代的、快速且经济高效的（相对于基于测序或实时 PCR 的策略）方法来评估蜱中的立克次体合并感染，这是一种潜在的重要现象，迄今为止很可能被低估了。
