The present study was conducted to investigate serotype distribution and biofilm formation of Actinobacillus (A.) pleuropneumoniae isolated from pneumonic lungs of pigs. A total of 37 A. pleuropneumoniae were isolated between January 2009 and June 2010. Serotypes of A. pleuropneumoniae isolates were determined using two different PCRs. The majority of isolates belonged to serotype 5 (n=31, 83.8%), and the others belonged to serotype 1 (n=4, 10.8%), and 2 (n=2, 5.4%), respectively. The ability of biofilm formation of the isolates was also determined by quantitative microtiter plate assay. Biofilm formation was observed in both 23 (62.2%) of the 37 field isolates and seven (43.8%) of the 16 reference strains. On the other hand, biofilm formation was various according to the serotypes: 20 (64.5%) of serotype 5, and three (75.0%) of serotype 1. However, two isolates of serotype 2 did not produce the biofilm in this study. Consequently, A. pleuropneumoniae serotype 5 was the most frequently detected (83.8% of the isolates), and 23 (62.2%) of 37 isolates exhibited biofilm positive phenotype in this study.

Grossly, a lot of soft white nodules, 0.5～1.5 cm in diameter, were randomly scattered in liver of a slaughtered Korean Native Cattle. The surface of liver was roughened by those nodules. Histopathologically the nodules were consisted of numerous mature blood vessels, which had variable size and wall thickness, and which were encircled by much connective tissue. Masson's trichrome stain clearly revealed the proliferated blood vessels and perivascular stroma and, immunohistochemical staining revealed that endothelial cells of proliferated blood vessels were positive for Von Willebrand Factor. Based on gross and histopathological lesions, and immunohistochemical staining, the case was confirmed as hepatic vascular hamartoma and it is the first case report in Korea, as far as we know.