Biofilms Flashcards
What % of microbial infections occur as biofilms
over 80%
What are microbial biofilms
group of microorganisms which are adherent both to eachother and to a surface
What are bacteria within biofilms embedded in
An extracellular matrix (made of proteins, sugars & extracellular DNA) that holds the organisms together
3 steps of biofilm formation
- Attachment
- Growth
- Detachment - due to running out of resources
What does the biofilm matrix consist of
Polymeric substances of bacterial origin - polysaccharides, proteins & nucleic acids
3 entry points for infectious microbial biofilms
- Catheter
- Hip replacement
- Periodontal disease (gum disease)
Can biofilms be polymicrobial in nature, and what does this mean?
- Yes - more commonly many species are found (mixed biofilms)
- May contain only one or two species but this is less common
What kinds of medical devices constitute an ideal surface for biofilm formation
Medical devices such as prostheses, catheters and endoscopes
How does vibrio cholerae form biofilms
Forms biofilms in aquatic environments prior to entry into host - more infectious after it leaves human host
Where does the opportunistic Pseudomonas aeruginosa form biofilms
Within the airways of cystic fibrosis patients
What is an example of a polymicrobial biofilm
Dental plaque
Can fungi also form biofilms - and with what structures
Yes
They form hyphae structures
Benefits of biofilms to the bacteria (3)
- Increases their survival
- Permits them to remain in a favourable niche
- Close proximity within biofilm - opportunities for nutrient & genetic exchange
How does biofilm formation promote bacterial survival
- Biofilms resist phagocytosis
- Bacteria within biofilms more tolerant to antimicrobial substances such as antibiotics, bleaches and host defense compounds
Effect of biofilms on antibiotics
- Some antibiotics have reduced penetration into biofilm structure
- Bacteria in biofilms have diff. patterns of gene expression with enhanced expression of genes conferring tolerance to antimicrobial substances - such as antibiotics
- Bacteria in biofilms grow slower than others - many antibiotics target fast growing bacteria
Steps in formation, maturation & dispersal of biofilms
- Attachment of planktonic cells (non attached cell - not part of a biofilm) to a surface
- Cell- cell adhesion by the extracellular matrix
- Proliferation & maturation - further matrix produced
- Dispersal to release planktonic cells
What do planktonic cells attach to a surface using
- Pili
- Flagella
- Adhesion proteins
Why does dispersal of planktonic cells from biofilm occur
Triggered by nutrient availability / other envirnmental factors
Strategies for control of biofilm formation
- Inhibition of regulatory systems that control biofilm formation through low molecular weight molecules
- Use of enzymes that degrade components of extracellular matrix (glue)
- Agents for disruption of biofilm formation
Why would rapid dispersal of biofilms be aggravating
Quickly disseminating large numbers of bacteria into bloodstream
What controls biofilm maturation in Pseudomonas aeruginosa
Quorum sensing by 3-oxo-C12 and 4-Alkylquinolones (PQS and HHQ)
What are biofilms a breeding ground for
Antibiotic resistance
What does Furanone C30 do
Potentiates the antibiotic effects of tobramycin on biofilms of Pseudomonas aeruginosa
