Читать книгу Diagnostics and Therapy in Veterinary Dermatology - Группа авторов - Страница 56

PCR is a molecular copying technique useful for detecting very small amounts of DNA in a sample. PCR makes millions to billions of copies of specific regions of DNA, referred to as amplicons, in order to amplify, quantify, and further study the molecule of interest (Waters and Shapter 2014). The basic steps of PCR involve denaturing the DNA of interest using heat, annealing oligonucleotide pairs (primers) to desired regions of the DNA, and making copies of this DNA template using DNA polymerase. Each time this reaction takes place, the DNA is doubled, so that at the end of 20 cycles there are more than one million copies of the template DNA. Once the DNA is amplified, additional laboratory techniques such as quantification of a molecule of interest, DNA sequencing, DNA cloning, and ELISA can be used to study the DNA further. PCR tests provide rapid and accurate results; however, the presence of DNA does not prove that the molecule of interest is functional or viable. Moreover, the presence of DNA does not prove causality of disease and may simply represent a contamination of the sample. In other words, finding dermatophytic fungal DNA on a host does not prove the fungal organism is alive and causing infection (Jacobson et al. 2018). Further diagnostics confirming fungal invasion of the host tissue (e.g. trichogram, cytology, or histopathology) would be required to confirm the presence of dermatophytosis.