Fig. 1

Loss of SpxB reduces cytotoxtic potential of culture supernatants. a A549 human epithelial cells were exposed to culture supernatants from parental strain T4R and mutant strains lacking SpxB or PLY. Cytotoxicity was assesed by measuring propidium iodide uptake using flow cytometry. b Hemolytic effect of PLY released in culture supernatant. Serially diluted culture supernatants from T4R and mutant strains lacking SpxB were incubated with washed sheep red blood cells for 30 min and subsequently centrifuged. The absence of a red pellet at the bottom of well indicates lysis of RBCs. (+) indicates distilled water positive control for complete hemolysis and (−) received no PLY. Results are representative of duplicate experiments