PMID:20086092

Citation	Mount, KL, Townsend, CA, Rinker, SD, Gu, X, Fortney, KR, Zwickl, BW, Janowicz, DM, Spinola, SM, Katz, BP and Bauer, ME (2010) Haemophilus ducreyi SapA contributes to cathelicidin resistance and virulence in humans. Infect. Immun. 78:1176-84
Abstract	Haemophilus ducreyi is an extracellular pathogen of human epithelial surfaces that resists human antimicrobial peptides (APs). The organism's genome contains homologs of genes sensitive to antimicrobial peptides (sap operon) in nontypeable Haemophilus influenzae. In this study, we characterized the sap-containing loci of H. ducreyi 35000HP and demonstrated that sapA is expressed in broth cultures and H. ducreyi-infected tissue; sapA is also conserved among both class I and class II H. ducreyi strains. We constructed a nonpolar sapA mutant of H. ducreyi 35000HP, designated 35000HPsapA, and compared the percent survival of wild-type 35000HP and 35000HPsapA exposed to several human APs, including alpha-defensins, beta-defensins, and the cathelicidin LL-37. Unlike an H. influenzae sapA mutant, strain 35000HPsapA was not more susceptible to defensins than strain 35000HP was. However, we observed a significant decrease in the survival of strain 35000HPsapA after exposure to LL-37, which was complemented by introducing sapA in trans. Thus, the Sap transporter plays a role in resistance of H. ducreyi to LL-37. We next compared mutant strain 35000HPsapA with strain 35000HP for their ability to cause disease in human volunteers. Although both strains caused papules to form at similar rates, the pustule formation rate at sites inoculated with 35000HPsapA was significantly lower than that of sites inoculated with 35000HP (33.3% versus 66.7%; P = 0.007). Together, these data establish that SapA acts as a virulence factor and as one mechanism for H. ducreyi to resist killing by antimicrobial peptides. To our knowledge, this is the first demonstration that an antimicrobial peptide resistance mechanism contributes to bacterial virulence in humans.
Links	PubMed PMC2825904 Online version:10.1128/IAI.01014-09
Keywords	Adult; Anti-Bacterial Agents/pharmacology; Antimicrobial Cationic Peptides/pharmacology; Bacterial Proteins/genetics; Bacterial Proteins/physiology; Chancroid/microbiology; Chancroid/pathology; Conserved Sequence; Drug Resistance, Bacterial; Female; Gene Deletion; Gene Expression Profiling; Genetic Complementation Test; Haemophilus ducreyi/drug effects; Haemophilus ducreyi/pathogenicity; Human Experimentation; Humans; Male; Microbial Sensitivity Tests; Microbial Viability/drug effects; Middle Aged; Skin/pathology; Virulence; Virulence Factors/genetics; Virulence Factors/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HAEDU:Q7VM01		GO:0009405: pathogenesis	ECO:0000315:		P		Table 3. Papule formation not affected, though sapA expression had a significant effect on the ability to progress to pustule formation in humans. Although precluded by biosafety regulations from testing complemented mutants in humans, the data suggest that SapA contributes significantly to the virulence in humans. No suggestions of cross-contamination.	complete
HAEDU:Q7VM01		GO:0030682: evasion or tolerance of host defense response	ECO:0000315:		P		Figure 3 shows the effect of sapA mutation on resistance to the mammalian defense LL-37. The plasmid-complemented mutant was not significantly different from the parent. No resistance was seen for alpha- and beta- defensins.	complete CACAO 5373
HAEDU:Q7VM01	involved_in	GO:0030682: evasion or tolerance of host defense response	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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