FIG. 1.

Sensitivities of wt, tagO, and tagO complemented strains to gIIA PLA₂, HBD-3, and Magainin II amide. S. aureus (wt, tagO, and complemented strains) at 1 × 10⁶/ml were incubated for 2 h as described in Materials and Methods in the presence of increasing concentrations of gIIA PLA₂ (A), HBD-3 (B), and Magainin II amide (C), as indicated. Bacterial viability was measured as CFU in TSA and is expressed as a percentage of the initial inoculum. The lowest doses tested of gIIA PLA₂, HBD-3, and Magainin II amide were 10 ng/ml, 1.25 μg/ml, and 0.4 μg/ml, respectively. Growth of all three bacterial strains during 2 h of incubation without gIIA PLA₂, HBD-3, and Magainin II amide was similar, resulting in >100% CFU. The results shown represent the means of three experiments ± standard errors of the means (error bars). Where indicated, the asterisks denote statistically significant (P < 0.05) greater resistance of the S. aureus tagO mutant to killing by gIIA PLA₂ and by HBD-3 versus that of the wt and S. aureus tagO complemented strains.