Establishment and application of dual isothermal amplification of <i>Pasteurella multocida</i> and <i>Streptococcus suis</i> in pigs.

Porcine respiratory disease complex is a clinically lethal condition and is the leading cause of mortality in weaned piglets as well as growing and fattening pigs. <i>Pasteurella multocida</i> (Pm) and <i>Streptococcus suis</i> (SS) are common respiratory pathogens in porcine respiratory disease complex. This study combined the recombinase polymerase amplification (RPA) technique with the lateral flow dipstick (LFD) technique. The dual Basic-RPA detection method for Pm and SS and the dual RPA-LFD rapid visualization detection method for Pm and SS were constructed, respectively. The detection limit of RPA-LFD was 10^-6 ng μL^-1, which was higher than the detection limit of RPA at 10^-5 ng μL^-1 and much higher than the detection limit of polymerase chain reaction at 10^-4 ng μL^-1. There was no cross-reactivity with other pathogens which indicated that the method had good specificity and high sensitivity. The detection rate of RPA-LFD was much higher than that of conventional Polymerase chain reaction in 60 clinical samples collected in 2023 with suspected Pm and SS. This method could avoid the complicated temperature cycling instruments and does not require professional laboratory skills, which makes it suitable for on-site detection.