Lippolis John D, Holman Devin B, Brunelle Brian W, Thacker Tyler C, Bearson Bradley L, Reinhardt Timothy A, Sacco Randy E, Casey Thomas A
Ruminant Diseases and Immunology Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa, USA
Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa, USA.
Infect Immun. 2017 Dec 19;86(1). doi: 10.1128/IAI.00566-17. Print 2018 Jan.
is a leading cause of bacterial mastitis in dairy cattle. It is most often transient in nature, causing an infection that lasts 2 to 3 days. However, has been shown to cause a persistent infection in a minority of cases. Mechanisms that allow for a persistent infection are not fully understood. The goal of this work was to determine differences between strains originally isolated from dairy cattle with transient and persistent mastitis. Using RNA sequencing, we show gene expression differences in nearly 200 genes when bacteria from the two clinical phenotypes are compared. We sequenced the genomes of the strains and report genes unique to the two phenotypes. Differences in the operon, which encodes colanic acid, were identified by DNA as well as RNA sequencing and differentiated the two phenotypes. Previous work demonstrated that strains that cause persistent infections were more motile than those that cause transient infections. Deletion of genes in the operon from a persistent-infection strain resulted in a reduction of motility as measured in swimming and swarming assays. Furthermore, colanic acid has been shown to protect bacteria from complement-mediated killing. We show that transient-infection strains were more sensitive to complement-mediated killing. The deletion of genes from the operon caused a persistent-infection strain to become sensitive to complement-mediated killing. This work identifies important differences between strains that cause persistent and transient mammary infections in dairy cattle.
是奶牛细菌性乳腺炎的主要病因。它在本质上通常是短暂的，引发持续2至3天的感染。然而，已证实在少数情况下会导致持续性感染。导致持续性感染的机制尚未完全了解。这项工作的目标是确定最初从患有短暂性和持续性乳腺炎的奶牛中分离出的菌株之间的差异。通过RNA测序，我们发现当比较来自两种临床表型的细菌时，近200个基因存在基因表达差异。我们对这些菌株的基因组进行了测序，并报告了两种表型特有的基因。通过DNA以及RNA测序鉴定出编码柯氏酸的操纵子中的差异，并区分了两种表型。先前的研究表明，导致持续性感染的菌株比导致短暂性感染的菌株更具运动性。从持续性感染菌株中删除操纵子中的基因导致在游泳和群游试验中测得的运动性降低。此外，已证明柯氏酸可保护细菌免受补体介导的杀伤。我们发现短暂性感染菌株对补体介导的杀伤更敏感。从操纵子中删除基因会使持续性感染菌株对补体介导的杀伤变得敏感。这项工作确定了导致奶牛持续性和短暂性乳腺感染的菌株之间的重要差异。
