title: The effects of propidium monoazide treatment on the measured composition of polymicrobial biofilms after treatment with chlorhexidine.
abstract: BACKGROUND
  The treatment of polymicrobial biofilms with antimicrobial compounds results in not only an overall loss of viability, but also compositional shifts. While DNA-based technologies may be more appropriate for the assessment of bacterial composition than culturing, these techniques amplify DNA from both live and dead cells. Propidium monoazide (PMA) has been used to discriminate between live and dead cells by blocking the DNA from membrane-damaged cells from being amplified.
  
  
  OBJECTIVE
  This study evaluated the use of PMA in a saliva-derived polymicrobial biofilm model subjected to a single chlorhexidine (CHX) treatment.
  
  
  METHODS
  The effects of PMA on viable cells were tested using both untreated and PMA-treated saliva as an inoculum. Viability was determined by plate counts, metabolic activity was determined by lactic acid production, and biofilm composition was assessed by 16S rRNA gene amplicon sequencing.
  
  
  RESULTS
  Exposure to a 0.2% CHX rinse (meridol® perio) reduced the viability and metabolic activity of 48-hour biofilms. The shift in biofilm composition observed after the CHX exposure was enhanced after a post-rinse PMA treatment. PMA treatment had a small effect on the measured composition of water-rinsed biofilms. Treating saliva with PMA reduced bacterial viability and shifted the bacterial composition of saliva and saliva-derived biofilms.
  
  
  CONCLUSIONS
  The removal of DNA from non-viable cells with PMA treatment was shown to elicit an improvement in the detection of shifts in in vitro polymicrobial biofilms after antimicrobial treatment. However, PMA also influenced the ability of cells to grow, indicating that PMA should be used with caution.
authors: R A M
authors: RA
authors: Exterkate
authors: E
authors: E
authors: Zaura
authors: M J
authors: MJ
authors: Buijs
authors: J
authors: J
authors: Koopman
authors: W
authors: W
authors: Crielaard
authors: J M
authors: JM
authors: ten Cate
mesh_terms: D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001386:Azides / Q000494:pharmacology*; D058491:Bacterial Load / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002710:Chlorhexidine / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000032:analysis; D006801:Humans; D007364:Intercalating Agents / Q000494:pharmacology*; D019344:Lactic Acid / Q000096:biosynthesis; D050296:Microbial Viability / Q000187:drug effects; D011419:Propidium / Q000031:analogs & derivatives* / Q000494:pharmacology; D012463:Saliva / Q000382:microbiology
chemical_list: D000891:Anti-Infective Agents, Local; D001386:Azides; D004269:DNA, Bacterial; D007364:Intercalating Agents; C533957:propidium monoazide; D019344:Lactic Acid; D011419:Propidium; D002710:Chlorhexidine