Detection of toxigenic Pasteurella multocida directly from nasal swabs with a nested PCR assay

A nested polymerase chain reaction(N-PCR) assay for direct detection of toxigenic Pasteurella multocida(T+ Pm) in nasal swab specimens collected from pigs was developed using 2 pairs of primers that were designed according to the published sequences of T+ Pm toxA,The size of amplicons were 864 and 447 bp,respectively.The assay could detect 26 CFU microorganisms.Mean while,no false amplification in detection of Escherichia coli,Streptococcus,Staphylococcus,Bordetella bronchiseptica,Nontoxigenic Pasteurella multocida,Haemophilus parasuis and Actinobacillus pleuopheumoniae could be observed.The nested PCR and bacterial isolation were employed simultaneously to examine 146 nasal swabs collected from 5 herds known to be infected with toxigenic Pasteurella multocida,44 and 97 specimens were positive and negative for both isolation and nested PCR,respectively,5 were positive for nested PCR only.The coincidence between bacterial isolation and nested PCR is 96.58%.These results indicated that the developed nested PCR might be a promising approach in clinical screening and detection of toxigenic Pasteurella multocida in a large number of swine swabs.