Deletion of mtrC in Haemophilus ducreyi increases sensitivity to human antimicrobial peptides and activates the CpxRA regulon.

ABSTRACT: Haemophilus ducreyi resists killing by antimicrobial peptides encountered during human infection, including cathelicidin LL-37, ?-defensins, and ?-defensins. In this study, we examined the role of the proton motive force-dependent multiple transferable resistance (MTR) transporter in antimicrobial peptide resistance in H. ducreyi. We found a proton motive force-dependent effect on H. ducreyi's resistance to LL-37 and ?-defensin HBD-3, but not ?-defensin HNP-2. Deletion of the membrane fusion protein MtrC rendered H. ducreyi more sensitive to LL-37 and human ?-defensins but had relatively little effect on ?-defensin resistance. The mtrC mutant 35000HPmtrC exhibited phenotypic changes in outer membrane protein profiles, colony morphology, and serum sensitivity, which were restored to wild type by trans-complementation with mtrC. Similar phenotypes were reported in a cpxA mutant; activation of the two-component CpxRA regulator was confirmed by showing transcriptional effects on CpxRA-regulated genes in 35000HPmtrC. A cpxR mutant had wild-type levels of antimicrobial peptide resistance; a cpxA mutation had little effect on defensin resistance but led to increased sensitivity to LL-37. 35000HPmtrC was more sensitive than the cpxA mutant to LL-37, indicating that MTR contributed to LL-37 resistance independent of the CpxRA regulon. The CpxRA regulon did not affect proton motive force-dependent antimicrobial peptide resistance; however, 35000HPmtrC had lost proton motive force-dependent peptide resistance, suggesting that the MTR transporter promotes proton motive force-dependent resistance to LL-37 and human ?-defensins. This is the first report of a ?-defensin resistance mechanism in H. ducreyi and shows that LL-37 resistance in H. ducreyi is multifactorial.

SUBMITTER: Rinker SD 

PROVIDER: S-EPMC3125844 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature