|HOLMAN, DEVIN - US Department Of Agriculture (USDA)|
|Bearson, Bradley - Brad|
Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2017
Publication Date: 12/19/2017
Citation: Lippolis, J.D., Holman, D.B., Brunelle, B.W., Thacker, T.C., Bearson, B.L., Reinhardt, T.A., Sacco, R.E., Casey, T. 2017. Genomic and transcriptomic analysis of Escherichia coli strains associated with persistent and transient bovine mastitis and the role of colanic acid. Infection and Immunity. 86(1):e00566-17. https://doi.org/10.1128/IAI.00566-17.
Interpretive Summary: Strains of Escherichia coli can cause transient or persistent mastitis in dairy cattle. Understanding the molecular mechanisms that cause these different type of infections is important. We sequenced the DNA and messenger RNA to understand which genes were differentially regulated between transient and persistent E. coli strains. DNA and mRNA analysis revealed that transient strains lacked genes that help protect the bacteria from an innate immune defense system called complement mediated killing.
Technical Abstract: Escherichia coli is a leading cause of bacterial mastitis in dairy cattle. This infection is most often transient in nature, causing an infection that lasts 2–3 days. However, E. coli has been shown to cause a persistent infection in a minority of cases. The mechanisms that allow for a persistent E. coli infection are not fully understood. The goal of this work was to determine differences between E. coli strains originally isolated from dairy cattle with transient and persistent mastitis infections. Using RNA sequencing on isolates grown in milk culture, we show gene expression differences in nearly 200 genes when comparing bacteria from the two clinical phenotypes. In addition, we sequenced the genomes of the E. coli strains and report genes unique to the transient and persistent phenotypes. Differences in the wca operon, which encodes for colanic acid, was identified by DNA as well as RNA sequencing and differentiated the two phenotypes. Previous work demonstrated that E. coli strains that cause persistent infections were more motile than those that cause transient infections. Deletion of genes in the wca operon from a persistent strain resulted in a reduction of motility as mearsured in swimming and swarming assays. Furthermore, colanic acid has been shown to protect bacteria from complement-mediated killing. Here, we show that transient E. coli strains were more sensitive to complement mediated killing. In addition, the deletion of genes from the wca operon caused a persistent E. coli strain to become sensitive to complement mediated killing. This work identifies important differences between E. coli strains that cause persistent versus a transient mammary infection in dairy cattle.