d7b2d801__BRD_Testing____Cattle_Network__1
[0] Single polymerase chain reaction (PCR) on respiratory tract swabs [2] Provides specific evidence the virus or bacterium is present (or has been recently) [3] Can’t tell the relative contribution of the organism to disease severity, plus not useful to gauge antibiotic resistance [1] 
Detects the organism’s DNA in a sample
Have We Gotten a Little Too Smart on BRD Testing? | Cattle Network
1