It has also been shown by a recent study on P. pneumotropica, an opportunistic bacterium of rodent pasteurellosis also able to cause severe infection in immunodeficient mice, and also a potential source for human contamination, that the mechanism of resistance to human complement system is through binding of FH and C4BP regulatory factors.22 For P. multocida the mechanism of resistance has not been cleared, tough similar resistance mechanism of FH and C4BP are quite expectable. This evidence concerns the gene FH and pasteurellosis.