Abstract
Objective
To determine whether Pasteurella haemolytica and P trehalosi isolates possess the structural gene for Pasteurella leukotoxin IktA and whether β-hemolytic activity of these isolates correlated with detection of the IktA gene.
Sample Population
147 P haemolytica isolates from 21 biovariant groups and 101 P trehalosi isolates from 7 biovariant groups. In addition, P multocida and organisms from 7 other genera were tested to establish specificity of the procedure.
Procedure
Isolates were observed for β-hemolysis. A polymerase chain reaction (PCR) procedure was used to amplify the RTX domain of the Pasteurella IktA gene.
Results
The IktA gene was detected in 108 (44%) isolates, including 15 associated with respiratory tract disease. All but 2 (98%) of the isolates that had the IktA gene were β-hemolytic when grown on sheep blood agar. The remaining 140 isolates were negative for the IktA gene and hemolytic activity.
Conclusions and Clinical Relevance
Hemolytic activity of P haemolytica and P trehalosi isolates correlated with detection of the IktA gene for all but 2 isolates. However, 56% of isolates tested were negative for the IktA gene and β-hemolytic activity. Leukotoxin production and secretion is a major virulence factor when other conditions are favorable for disease development. Therefore, identification of strains that possess the IktA gene may aid in the evaluation of the pathogenic potential of Pasteurella strains carried by wild and domestic animals. (Am J Vet Res 1999;60:1402–1406)
