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Title: Transfer of the virulence-associated protein A-bearing plasmid between field strains of virulent and avirulent Rhodococcus equi
Authors: Stoughton W, Poole TL, Kuskie K, Liu M, Bennentt K, Morrissey A, Takai S, Cohen N
Journal: J Vet Intern Med
Accepted date: 2013 Aug 12
Interpretive summary: A bacterium called Rhodococcus equi is the cause of severe pneumonia in newborn horses (foals). This bacterium has worldwide distribution and causes severe economic losses for the equine industry. Factors that contribute to the spread of this infectious disease have remained elusive. It is known that R. equi possesses a virulence gene called VapA that leads to the disease, and VapA is carried on a small circular piece of mobile DNA called a plasmid. Bacteria can share or transfer plasmids by a process called conjugation. Conjugation occurs when a bridge is formed between two bacterial cells and the plasmid migrates across the bridge. After this process is completed, the recipient cell that acquired the plasmid will display the genetic traits of the original bacterial cell if they were present on the plasmid. In this case, the recipient bacterium would be converted from a non-disease-causing causing bacterium to a disease-causing bacterium. Some plasmids transfer more easily than others, and some do not transfer at all. This study was done to determine if the VapA plasmid could be transferred. The results of this study showed that the VapA plasmid did transfer to two different recipient strains of R. equi. This provides insight into one mechanism of how the disease-causing forms of R. equi may spread and indicates that strategies to combat the disease may be more difficult than once thought.
Publication date: 2013 Nov
Volume: 27
Issue: 6
Pages: 155562