title: Rapid degradation of Streptococcus pyogenes biofilms by PlyC, a bacteriophage-encoded endolysin.
abstract: OBJECTIVE
  Streptococcus pyogenes, or Group A streptococcus (GAS), has a propensity to colonize human tissues and form biofilms. Significantly, these biofilms are a contributing mechanism of antibiotic treatment failure in streptococcal disease. In this study, we evaluate a streptococcal-specific bacteriophage-encoded endolysin (PlyC), which is known to lyse planktonic streptococci, on both static and dynamic streptococcal biofilms.
  
  
  METHODS
  PlyC was benchmarked against antibiotics for MIC, MBC and minimum biofilm eradication concentration (MBEC). A biomass eradication assay based on crystal violet staining of the biofilm matrix was also used to quantify the anti-biofilm properties of PlyC. Finally, conventional fluorescence microscopy and laser scanning confocal microscopy were used to study the effects of PlyC on static and dynamic biofilms of GAS.
  
  
  RESULTS
  PlyC and antibiotics had similar MIC (range 0.02-0.08 mg/L) and MBC (range 0.02-1.25 mg/L) values on planktonic GAS. However, when GAS grew in biofilms, the MBEC values for antibiotics rose to clinically resistant values (≥400 mg/L) whereas PlyC had MBEC values two orders of magnitude lower by mass and four orders of magnitude lower by molarity than the conventional antibiotics. Laser scanning confocal microscopy revealed that PlyC destroys the biofilm as it diffuses through the matrix in a time-dependent fashion.
  
  
  CONCLUSIONS
  Our findings indicate that while streptococcal cells within a biofilm rapidly become refractory to traditional antibiotics, the biofilm matrix is readily destroyed by the lytic actions of PlyC.
authors.affiliation: Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, MD 20850, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Thomas
authors.initials: T
authors.lastname: Köller
authors.forename: Bernd
authors.initials: B
authors.lastname: Kreikemeyer
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Nelson
mesh_terms: D001433:Bacteriolysis; D018441:Biofilms / Q000187:drug effects*; D010450:Endopeptidases / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D008853:Microscopy; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000502:physiology*; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D014764:Viral Proteins; D010450:Endopeptidases; C001143:endolysin
keywords: antimicrobial; cell wall hydrolase; enzybiotic; susceptibility