90 samples of pigs infected with porcine reproductive and respiratory syndrome (PRRS) in Bac Giang province were investigated, and the studied result showed that: - The average ratio of the pigs infected with PRRS (and from these pigs had found A. pleuropneumoniae) was 17.78 percent, in which the highest ratio was in the post weaning pigs from 1.5 to 3 months of age (28.00 percent). - The isolated bacteria strains had typically biological, chemical characteristics, corresponding to the papers published at home and abroad, they were high virulence strains. Of which, there were 7/10 strains caused 100 percent of experimental mice died after 12-36 hours and 3/10 strains caused 50 percent of experimental mice died after 18-48 hours. - The isolated bacteria strains were strongly susceptive with florphenicol, ceftiofur, amoxicilline and resistant to neomycine, erythromycine, lincomycine, colistine.