Detection of PCR and colony spots in situ hybridization for HPI irp1, irp2, irp3, irp4, irp5 gene (A-E, genetic test results of HPI irp1, irp2, irp3, irp4, irp5 in turn; F, colony spot hybridization for irp2 gene; M, DL 2000 Marker; 1, negative control; 2, positive strain; 3, experimental strain).