Paratuberculosis (PTB) or Johne's disease is one of the most serious chronic debilitating diseases of ruminants worldwide that is caused by Mycobacterium avium subsp. paratuberculosis (MAP). MAP is a slow-growing bacterium that has very long latent periods, resulting in difficulties in diagnosing and controlling the disease, especially regarding the diagnosis of fecal shedders of MAP without any clinical signs. Based on this situation, attempts were made to identify biomarkers that show early responses to MAP infection in a macrophage cell line, RAW 264.7. In response to the infection with the bacterium, a lot of genes were turned on and/or off in the cells. Of the altered genes, three different categories were identified based on the time-dependent gene expression patterns. Those genes were considered as possible candidates for biomarkers of MAP infection after confirmation by quantitative RT-PCR analysis. To the best of our knowledge, this is the first attempt at discovering the host transcriptomic biomarkers of PTB, although further investigation will be required to determine whether these biomarker candidates are associated within the natural host.

: Paratuberculosis caused by Mycobacterium avium subsp. paratuberculosis (MAP) has extended latent periods of infection. Due to this property, difficulties in the detection of fecal shedder have been raised. A newly designed method for DNA extraction from fecal specimens, mGITC/SC was evaluated in terms of diagnostic efficiency. The detection limit of IS900 real-time PCR was about 50 MAP (1.5 cfu) in 250 mg of feces (6 cfu per g). Also, this DNA extraction method was faster and cheaper than that using commercial kit or other methods. Consequently, the mGITC/ SC is an economical DNA extraction method that could be a useful tool for detecting MAP from fecal specimens.