FIG 5.

Sensitivity of AMPR mutants to antimicrobial peptides. Wild-type S. Enteritidis (ZM100) and S. Enteritidis virK (ZM112), ybjX (ZM114), virK pWSKVirK (ZM112C), and ybjX pWSKYbjX (ZM114C) were tested for their sensitivity to antimicrobial peptides. (A) S. Enteritidis strains were exposed to a general, potent antimicrobial peptide, polymyxin B, for 1 h and then plated for CFU enumerations. Results are presented as the log reduction in CFU. virK and ybjX mutants showed significantly increased susceptibility. (B) S. Enteritidis strains were exposed to a host-specific antimicrobial peptide, AvBD-6, using a microbroth dilution method. Sensitivity to AvBD-6 is expressed as percent growth inhibition. Both the virK mutant and the ybjX mutant had increased susceptibility to AvBD-6. Data shown are from three independent experiments, and the average values are shown in parentheses. A single asterisk denotes significant differences (P < 0.05).