title: New role for human α-defensin 5 in the fight against hypervirulent Clostridium difficile strains.
abstract: Clostridium difficile infection (CDI), one of the most common hospital-acquired infections, is increasing in incidence and severity with the emergence and diffusion of hypervirulent strains. CDI is precipitated by antibiotic treatment that destroys the equilibrium of the gut microbiota. Human α-defensin 5 (HD5), the most abundant enteric antimicrobial peptide, is a key regulator of gut microbiota homeostasis, yet it is still unknown if C. difficile, which successfully evades killing by other host microbicidal peptides, is susceptible to HD5. We evaluated, by means of viability assay, fluorescence-activated cell sorter (FACS) analysis, and electron microscopy, the antimicrobial activities of α-defensins 1 and 5 against a panel of C. difficile strains encompassing the most prevalent epidemic and hypervirulent PCR ribotypes in Europe (012, 014/020, 106, 018, 027, and 078). Here we show that (i) concentrations of HD5 within the intestinal physiological range produced massive C. difficile cell killing; (ii) HD5 bactericidal activity was mediated by membrane depolarization and bacterial fragmentation with a pattern of damage peculiar to C. difficile bacilli, compared to commensals like Escherichia coli and Enterococcus faecalis; and (iii) unexpectedly, hypervirulent ribotypes were among the most susceptible to both defensins. These results support the notion that HD5, naturally present at very high concentrations in the mucosa of the small intestine, could indeed control the very early steps of CDI by killing C. difficile bacilli at their germination site. As a consequence, HD5 can be regarded as a good candidate for the containment of hypervirulent C. difficile strains, and it could be exploited in the therapy of CDI and relapsing C. difficile-associated disease.
authors.affiliation: Division of Immunity, Transplantation and Infectious Diseases, Emerging Bacterial Pathogens Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy furci.lucinda@hsr.it.
authors.forename: Lucinda
authors.identifier: http://orcid.org/0000-0002-8639-405X
authors.initials: L
authors.lastname: Furci
authors.affiliation: Division of Immunity, Transplantation and Infectious Diseases, Emerging Bacterial Pathogens Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Rossella
authors.initials: R
authors.lastname: Baldan
authors.affiliation: Division of Immunity, Transplantation and Infectious Diseases, Emerging Bacterial Pathogens Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Bianchini
authors.affiliation: Division of Immunity, Transplantation and Infectious Diseases, Emerging Bacterial Pathogens Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Alberto
authors.identifier: http://orcid.org/0000-0003-4494-5762
authors.initials: A
authors.lastname: Trovato
authors.affiliation: Department of Microbiology, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Ossi
authors.affiliation: Department of Microbiology, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Cichero
authors.affiliation: Division of Immunity, Transplantation and Infectious Diseases, Emerging Bacterial Pathogens Unit, IRCCS San Raffaele Scientific Institute, Milan, Italy.
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Cirillo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D016360:Clostridioides difficile / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D013293:Enterococcus faecalis / Q000187:drug effects / Q000648:ultrastructure; D004761:Enterocolitis, Pseudomembranous / Q000382:microbiology; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D021521:Ribotyping; D023084:alpha-Defensins / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; C500225:DEFA5 protein, human; D023084:alpha-Defensins; C406413:human neutrophil peptide 1