245 samples in pigs positive with PRRSV in Bac Giang province were collected, investigated and the testing results showed that: - Percentage of samples isolated bacterial species (P. multocida) was rather high accounting for 17.14 percent
Of which the highest ratio (22.6 percent) was samples in piglets after weaning (from 1.5 to 3 months old). - 31 bacterial species of P. multocida belonging to serotype A (account for 73.81 percent) and 11 bacterial species of P. multocida belonging to serotype 0 (account for 26.19 percent) were isolated. - P. multocida bacterial species were isolated having typically biological characteristics, which were similar with the descriptions for them in the papers/documentation in the country and foreign countries. - P. multocida bacterial species were isolated having high toxicity, of which 8/12 bacterial species caused 100 percent of experimental mice died after 12-36 hours and 4/12 bacterial species caused 50 percent experimental mice died after 24-36 hours.