title: The membrane as a target for controlling hypervirulent Clostridium difficile infections.
abstract: OBJECTIVE
  The stationary phase of Clostridium difficile, which is primarily responsible for diarrhoeal symptoms, is refractory to antibiotic killing. We investigated whether disrupting the functions of the clostridial membrane is an approach to control C. difficile infections by promptly removing growing and non-growing cells.
  
  
  METHODS
  The bactericidal activities of various membrane-active agents were determined against C. difficile logarithmic-phase and stationary-phase cultures and compared with known antibiotics. Their effects on the synthesis of ATP, toxins A/B and sporulation were also determined. The effect of rodent caecal contents on anti-difficile activities was examined using two reutericyclin lead compounds, clofazimine, daptomycin and other comparator antibiotics.
  
  
  RESULTS
  Most membrane-active agents and partially daptomycin showed concentration-dependent killing of both logarithmic-phase and stationary-phase cultures. The exposure of cells to compounds at their MBC resulted in a rapid loss of viability with concomitant reductions in cellular ATP, toxins A/B and spore numbers. With the exception of nisin, these effects were not due to membrane pore formation. Interestingly, the activity of the proton ionophore nigericin significantly increased as the growth of C. difficile decreased, suggesting the importance of the proton gradient to the survival of non-growing cells. The activities of the lipophilic antimicrobials reutericyclins and clofazimine were reduced by caecal contents.
  
  
  CONCLUSIONS
  These findings indicate that C. difficile is uniquely susceptible to killing by molecules affecting its membrane function and bioenergetics, indicating that the clostridial membrane is a novel antimicrobial target for agents to alleviate the burden of C. difficile infections.
authors.affiliation: Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA.
authors.forename: Xiaoqian
authors.initials: X
authors.lastname: Wu
authors.forename: Philip T
authors.initials: PT
authors.lastname: Cherian
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lee
authors.forename: Julian G
authors.initials: JG
authors.lastname: Hurdle
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D058491:Bacterial Load; D002432:Cecum / Q000382:microbiology; D002462:Cell Membrane / Q000187:drug effects*; D002991:Clofazimine; D016360:Clostridioides difficile / Q000187:drug effects*; D003015:Clostridium Infections / Q000188:drug therapy* / Q000382:microbiology; D006224:Cricetinae; D008647:Mesocricetus; D050296:Microbial Viability / Q000187:drug effects; D013720:Tenuazonic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; C416127:reutericyclin; D013720:Tenuazonic Acid; D002991:Clofazimine