Abbot Patrick, Aviles Alena E, Eller Lauren, Durden Lance A
Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
Appl Environ Microbiol. 2007 Oct;73(19):6045-52. doi: 10.1128/AEM.00228-07. Epub 2007 Aug 10.
Coinfections within hosts present opportunities for horizontal gene transfer between strains and competitive interactions between genotypes and thus can be a critical element of the lifestyles of pathogens. Bartonella spp. are Alphaproteobacteria that parasitize mammalian erythrocytes and endothelial cells. Their vectors are thought to be various biting arthropods, such as fleas, ticks, mites, and lice, and they are commonly cited as agents of various emerging diseases. Coinfections by different Bartonella strains and species can be common in mammals, but little is known about specificity and coinfections in arthropod vectors. We surveyed the rate of mixed infections of Bartonella in flea vectors (Polygenis gwyni) parasitizing cotton rats (Sigmodon hispidus) in which previous surveys indicated high rates of infection. We found that nearly all fleas (20 of 21) harbored one or more strains of Bartonella, with rates of coinfection approaching 90%. A strain previously identified as common in cotton rats was also common in their fleas. However, another common strain in cotton rats was absent from P. gwyni, while a rare cotton rat strain was quite common in P. gwyni. Surprisingly, some samples were also coinfected with a strain phylogenetically related to Bartonella clarridgeiae, which is typically associated with felids and ruminants. Finally, a locus (pap31) that is characteristically borne on phage in Bartonella was successfully sequenced from most samples. However, sequence diversity in pap31 was novel in the P. gwyni samples, relative to other Bartonella previously typed with pap31, emphasizing the likelihood of large reservoirs of cryptic diversity in natural populations of the pathogen.
宿主体内的共感染为菌株间的水平基因转移以及基因型间的竞争相互作用提供了机会，因此可能是病原体生活方式的关键要素。巴尔通体属是寄生于哺乳动物红细胞和内皮细胞的α-变形菌。它们的传播媒介被认为是各种叮咬节肢动物，如跳蚤、蜱、螨和虱子，它们通常被认为是各种新出现疾病的病原体。不同巴尔通体菌株和种类的共感染在哺乳动物中很常见，但对于节肢动物传播媒介中的特异性和共感染情况却知之甚少。我们调查了寄生于棉鼠（刚毛棉鼠）的跳蚤传播媒介（格氏多蚤）中巴尔通体的混合感染率，此前的调查表明棉鼠的感染率很高。我们发现，几乎所有跳蚤（21只中的20只）都携带一种或多种巴尔通体菌株，共感染率接近90%。一种先前被确定在棉鼠中常见的菌株在它们的跳蚤中也很常见。然而，棉鼠中另一种常见菌株在格氏多蚤中不存在，而一种在棉鼠中罕见的菌株在格氏多蚤中却相当常见。令人惊讶的是，一些样本还与一种在系统发育上与克拉氏巴尔通体相关的菌株共感染，克拉氏巴尔通体通常与猫科动物和反刍动物有关。最后，从大多数样本中成功测序了巴尔通体中典型存在于噬菌体上的一个基因座（pap31）。然而，相对于其他先前用pap31分型的巴尔通体，格氏多蚤样本中pap31的序列多样性是新的，这强调了该病原体自然种群中存在大量隐秘多样性库的可能性。
