title: Moraxella catarrhalis is susceptible to antimicrobial photodynamic therapy with Photofrin.
abstract: OBJECTIVE
  Moraxella catarrhalis is a significant cause of pediatric otitis media (OM), which is the most prevalent bacterial infection in children and primary reason for antibiotic administration in this population. Moreover, biofilm formation has been implicated as a primary mechanism of chronic or recurrent OM disease. As bacterial biofilms are inherently resistant to most antibiotics and these complex structures also present a significant challenge to the immune system, there is a clear need to identify novel antimicrobial approaches to treat OM infections. In this study, we evaluated the potential efficacy of antibacterial photodynamic therapy (aPDT) with porfimer sodium (Photofrin (PF)) against planktonic as well as biofilm-associated M. catarrhalis.
  
  
  METHODS
  The bactericidal activity of aPDT with PF was assessed against multiple recent clinical isolates of M. catarrhalis grown planktonically as well as in biofilms. The bactericidal activity of PF-aPDT was quantified by enumeration of colony forming units post-treatment. The effect of aPDT on M. catarrhalis biofilms was further investigated with scanning electron microscopy (SEM) imaging.
  
  
  RESULTS
  aPDT with PF significantly reduced M. catarrhalis viability. Although PF-aPDT caused higher killing in planktonic grown organisms (5-6 log kill), biofilm grown bacteria also demonstrated a statistically significant reduction in viable organisms (3-4 log decrease in recoverable bacteria) following treatment as compared to saline only controls (P < 0.01). SEM studies indicated the PF-aPDT treated bacteria exhibited prominent morphological changes with visibly distorted cell membranes.
  
  
  CONCLUSIONS
  aPDT with PF elicits significant bactericidal activity against both planktonic and biofilm-associated M. catarrhalis, suggesting this technology warrants further analysis as a potential novel antimicrobial treatment for acute or recurrent OM.
authors.affiliation: Department of Microbiology and Immunology, State University of New York at Buffalo, Buffalo, New York.
authors.forename: Nicole R
authors.initials: NR
authors.lastname: Luke-Marshall
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Mang
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Hansen
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Campagnari
mesh_terms: D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development / Q000528:radiation effects; D017323:Dihematoporphyrin Ether / Q000494:pharmacology*; D054025:Lasers, Dye; D053844:Lasers, Solid-State; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D001936:Moraxella catarrhalis / Q000187:drug effects* / Q000254:growth & development* / Q000528:radiation effects; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology*
chemical_list: D017319:Photosensitizing Agents; D017323:Dihematoporphyrin Ether
keywords: antimicrobial photodynamic therapy; biofilm; gram-negative bacteria; otitis media; photofrin