Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks of the Ixodes ricinus complex and causes febrile illness in humans and animals. We used multilocus sequence typing (MLST) and ankA gene-based typing to study the molecular epidemiology of the A. phagocytophilum strains circulating in a German cattle herd over one pasture season. The aim was to investigate whether co-infection with two distinct variants, reinfection with the same and/or superinfection by a different strain occurred during one pasture season. Eight genetic loci were sequenced in 47 PCR-positive samples from 15 animals. Five different sequence types (ST) and four ankA alleles were detected in the cattle herd. Three different ST caused clinically overt tick-borne fever in primary infected animals. The concordance between ST and ankA allele was 100%. Therefore, the housekeeping genes used for MLST and the highly variable ankA gene were concatenated to increase resolution. Co-infection could be proven because samples of chronologically close collection dates were included. Co-infecting A. phagocytophilum strains differed by 14 to 18 single nucleotide polymorphisms (SNPs). Most superinfecting variants varied by 14 SNPs from the previous strain and appeared in median after a free interval of 31 days. Thus, it is unlikely that superinfecting strains arose by in-animal evolution. Immunity against re- or superinfection was assumed because the cattle developed clinical signs only during primary infection. The tick-pathogen-vertebrate host interaction is probably much more complex than previously thought taking into account the frequently occurring events of co-infection, reinfection and superinfection. This complex situation could not be easily simulated in an experimental infection and underlines the value of field studies.

中文翻译：

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基于ankA基因和多位点序列分型的牛群中嗜吞噬细胞无形体菌株的共感染、再感染和重复感染


嗜吞噬细胞无形体是一种革兰氏阴性专性细胞内细菌，在中性粒细胞中复制。它通过蓖麻硬蜱传播，引起人类和动物发热性疾病。我们使用多位点序列分型 (MLST) 和基于 ankA 基因的分型来研究在一个牧草季节在德国牛群中传播的嗜吞噬细胞放线菌菌株的分子流行病学。目的是调查在一个牧草季节是否发生两种不同变种的共同感染、相同菌株的再感染和/或不同菌株的重复感染。对来自 15 只动物的 47 个 PCR 阳性样本中的 8 个基因位点进行了测序。在牛群中检测到五种不同的序列类型（ST）和四种 ankA 等位基因。三种不同的 ST 在原发感染动物中引起临床明显的蜱传发烧。 ST和ankA等位基因之间的一致性为100%。因此，将用于 MLST 的管家基因和高度可变的 ankA 基因连接起来以提高分辨率。由于包含了按时间顺序排列的接近收集日期的样本，因此可以证明共同感染。共感染 A. phagocytophilum 菌株存在 14 至 18 个单核苷酸多态性 (SNP) 差异。大多数重复感染变体与之前的菌株有 14 个 SNP 差异，并且在 31 天的自由间隔后出现在中值。因此，双重感染菌株不太可能是由动物进化产生的。假定牛具有针对再感染或重复感染的免疫力，因为牛仅在初次感染期间出现临床症状。考虑到频繁发生的共同感染、再感染和重复感染事件，蜱-病原体-脊椎动物宿主相互作用可能比以前想象的要复杂得多。 这种复杂的情况无法在实验感染中轻易模拟，这凸显了现场研究的价值。