Comparative analysis of plant and animal models for characterization of Burkholderia cepacia virulence.

A simple alfalfa model was developed as an alternative infection model for virulence studies of the Burkholderia cepacia complex. Symptoms of disease were observed in wounded alfalfa seedlings within 7 days following inoculation of 10(1) to 10(5) CFU of most strains of the B. cepacia complex. Strains from seven genomovars of the B. cepacia complex were tested for virulence in the alfalfa model, and the degree of virulence was generally similar in strains belonging to the same genomovar. Strains of Burkholderia multivorans and some strains of Burkholderia stabilis did not cause symptoms of disease in alfalfa seedlings. Representative strains were also tested for virulence using the rat agar bead model. Most of the strains tested were able to establish chronic lung infections; B. stabilis strains were the exception. Most of the strains that were virulent in the alfalfa infection model were also virulent in the lung infection model. The B. cepacia genomovar III mutants K56pvdA::tp and K56-H15 were significantly less virulent in the alfalfa infection model than their parent strain. Therefore, this alfalfa infection model may be a useful tool for assessing virulence of strains of the B. cepacia complex and identifying new virulence-associated genes.