Cooperation between LepA and PlcH Contributes to theIn VivoVirulence and Growth ofPseudomonas aeruginosain Mice
ABSTRACTPseudomonas aeruginosa-derived large extracellular protease (LepA) and hemolytic phospholipase C (PlcH) are considered to play an important role in the pathogenicity of this organism. Although bacterial growth appears to be closely related to virulence, little is known about whether LepA and PlcH participate in the growth and virulence ofP. aeruginosa. In this study, we investigated whether LepA and PlcH contribute to the virulence and growth ofP. aeruginosausing a wild-type strain and mutants. The growth rate of the isogeniclepAsingle mutant was lower than that of the wild-type strain in a minimal medium containing serum albumin or hemoglobin as the sole carbon and nitrogen source. Furthermore, the growth rate of thelepA plcHdouble mutant decreased greatly compared with that of the wild-type strain in a minimal medium containing erythrocytes as a sole nutrient source for growth. Thus, these results indicate that cooperation between LepA and PlcH would contribute to the utilization of erythrocytes as a sole nutrient source for the growth ofP. aeruginosa. In addition, mouse infection experiments demonstrated that the virulence of thelepAandplcHsingle mutants was attenuated, and the numbers of the mutants were lower than the numbers of the wild-type strain in peritoneal lavage fluid and whole-blood specimens. In particular, the virulence and growth rate of thelepA plcHdouble mutant were markedly lower than those of the wild-type strain. Collectively, these results suggest that LepA and PlcH contribute to thein vivovirulence and growth ofP. aeruginosa.