Biofilms & Polymicrobial Infections II

• What kind of substance is hydroxyapatite and what does it mean?

  Amphipathic substance so it enables the components present in the acquired pellicle (e.g. proteins & glycoproteins) to bind to the surface of the tooth via electrostatic interactions

  
• What happens once the acquired pellicle is present?


  It's then colonised by early colonisers, usually bacteria from Streptococcus and there's usually a sequential deposition of different microbes

  e.g.A. naeslundii, F. nucleatum, P. gingivalisThe late colonisers such asT. denticola&T. forsythiathen join

  
• What do the bacterial colonisers physically interact with each other through?

  Adhesins which are expressed on their surface
• What are mature biofilms encased in and what is it important for?


  Encased in extra polymeric substances (EPS)

  
  

  This helps biofilms with:

  
  

  -Mechanical stability

  -Facilitates cell-cell interactions

  -Reduced efficacy of anti microbials/immune cells

  
• What are the advantages biofilms offer over planktonic growth?

  Increased metabolic fitness: nutritional cooperation

  Increased genomic diversity: horizontal gene transfer, antibiotic resistance

  Increased stress resistance:(biological/chemical/physical) e.g. aerobic bacteria can lower oxygen tension providing the means for anaerobic species to survive

  Recalcitrance: reduced antibiotic penetrance/diffusion into the biofilm
• What Is the dynamics of biofilm maturation like?

  There is an increase in community complexity from adhesion to a mature biofilm

  
  

  As the age of biofilm increases, we get more gram negative anaerobes

  
  

  CHANGES IN BIOFILM COMPOSITION CAN LEAD TO DYSBIOSIS (microbial imbalance)

  
• What kind of infection is periodontitis?

  Polymicrobial infection of the subgingival crevice, associated with a shift in gram status of the microbiota & chronic inflammation of the gums

  
• What are some more examples of biofilm-related infections?

  Medical plastics, prosthetic heart valve endocarditis, contact lens keratitis, diabetic foot ulcers

  
• Describe polymicrobial infections with the biofilm.

  They're numerous, dynamic & complex and classified into 3 major types:

  
  

  Physical: e.g. co-aggregation

  Chemical: e.g. quorum sensing

  Nutritional: e.g. digestive consortiums
• What is co-aggregation?


  Process whereby genetically distinct bacteria attach to each other via specific molecules called adhesins
• Where are co-aggregates derived from & what can it influence?

  Co-aggregates are derived from planktonic cells & co-aggregates can influence the development & composition of polymicrobial biofilms

  
• Can bacteria also physically interact with fungi?

  Yes,Candida albicansis a fungus that can produce pathogenic invasive filaments called 'hyphae' andS. aureuscan physically attach to the hyphae

  
• What is denture stomatitis?

  Polymicrobial biofilm-mediated condition

  Biofilm accumulates on dentures (haven't been cleaned properly) & is colonised by fungi (typicallyCandidaspecies) and this biofilm is in constant contact with the oral mucosa.

  The oral mucosa becomes inflamed, because of that & because of virulence factors which are secreted by both microbes