L3 - Biofilms Flashcards
What is Planktonic
Free-living
What is Biofilm
Sessile
Adherent
bacteria linked by EPS
What is EPS?
Extracellular polymeric substance
What is ECM?
Extracellular matrix
What is the composition of a biofilm?
bacterial cells - 10-30%
EPS - 70-90%
How are biofilms organised?
dynamic
specific areas
channel to bring water/nutrients deep
low flowing = mushroom/tower
high flow = streamer
What are the stages of biofilm formation?
Initial attachment Irreversible attachment Maturation I Maturation II Dispersion
What triggers the biofilm developmental sequence?
dessication
antibiotics
HIGH CELL DENSITY
quorum sensing
PRODUCTION/DETECTION OF SIGNALLING MOLECULES
What signalling molecule trigger biofilm development?
N-acyl homoserine lactones
Oligopeptides
Autoinducer-2
high conc. = changes in bacterial gene expression
What are emergent properties?
behaviour the arise in a complex system - not predictable from study of individual components
What are the emergent properties of biofilms?
Slower growth
Altered gene expression
antibiotics do not clear
immune sys do no clear
Increased development of ‘true’ antibiotic resistance - mutability increases in biofilm state
What kind of organisms to biofilms contain?
non-growing
What helps to reduce biofilm hypermutability?
antioxidants
What factor is not involved in the REDUCED ability to detoxify ROS in the biofilm?
endogenous oxidative stress
What are human infections involving biofilms?
catheters, contact lenses, valves…
What are oral biofilms?
Gingivitis - plaque
Periodontitis - gum inflammation
What is the issue with biofilms and wounds?
wounds may take years to heal
amputation
debridement works better than antibiotics
How do device-associated biofilms occur?
colonise in medical devices
host inflammatory molecules
Surgical removal often required
What’s involved in staphylococcal biofilms?
MSCRAMMs
adhesion to cell surfaces coated with host plasma proteins:
- fibronectin adhesins
- collagen-binding protein
- fibrinogen-binding proteins
Biofilms and cystic fibrosis?
P.aeruginosa forms biofilm in lung - major cause of death
Pseudomonas cells covered with glycocalyx
What is the Calgary Biofilm Device?
stain biofilm with crystal violet
more purple = more dense biofilm
What is the use of repurposinng compounds with a history of human use?
look for anti-biofilm activity
redox-active agents
How are anti-biofilm compounds (RA - redox-active agents) categorised?
2 groups on how they exert their effect
Type 1 cell killers - kill cells within biofilm
Type 2 matrix killers - restructuring, cells disperse and become planktonic so can be killed by antibiotics
