biofilms Flashcards
(24 cards)
What is a biofilm?
Adhered bacterial community encased in a gel-like matrix of polymers secreted from the bacterial cell (extracellular polymeric substance)
Biofilms are recalcitrant to antimicrobial therapy and the actions of the immune system, representing the dominant form of microbial growth.
What are the stages of biofilm development?
- Reversible attachment
- Irreversible attachment
- Macrocolony formation
- Biofilm maturation
- Detachment and dispersal
Each stage involves specific processes and interactions among bacterial cells.
What is the first stage of biofilm development?
Reversible attachment
This stage includes the formation of a conditioning film and non-specific interactions such as Van der Waals and electrostatic interactions.
What occurs during irreversible attachment in biofilm development?
Binding of specific adhesins
Surface attachment deficient mutants (SAD) cannot form biofilms.
What triggers macrocolony formation in biofilms?
Extracellular polymeric substance production triggered by quorum sensing
This occurs after the initial attachment of bacteria.
What characterizes biofilm maturation?
Secondary colonizers adhere both non-specifically and specifically
Bacteria may co-aggregate before adhering to the macrocolony.
What factors can cause detachment and dispersal of cells in biofilms?
- Physical forces
- Nutrient limitation
- Enzyme activity
These factors can lead to cells leaving the existing biofilm and potentially initiating a new biofilm elsewhere.
What is the composition of extracellular polymeric substance (EPS)?
- Polysaccharides
- Globular glycoproteins
- Amino acids
- Sugars
- Nucleic acids/DNA fragments
- Lipids
- Phosphates
- Organic acids
- Ions
EPS has variable chemical and physical properties.
What functions does EPS serve in a biofilm?
- Aids adhesion to the surface
- Maintains a hydrated layer
- Provides channels for nutrient capture and waste removal
- Acts as a physical barrier against phagocytes
- Binds toxins and enzymes
EPS plays a critical role in the survival and functionality of biofilms.
What is dental plaque?
A community of microorganisms found on a tooth surface as a biofilm, embedded in a matrix of polymers of host and bacterial origin
Dental plaque serves as a model biofilm for studying microbial communities.
What are the stages of dental plaque formation?
- Pellicle Formation (conditioning film)
- Reversible adhesion
- Receptor-mediated attachment (Early colonizers)
- Co-adhesion (Late colonizers)
Each stage is critical for the establishment and maturation of dental plaque.
What pathogen is associated with dental caries?
Streptococcus mutans
This bacterium thrives under acidic conditions resulting from dietary carbohydrate fermentation.
What is Staphylococcus epidermidis?
Gram-positive coccus and coagulase-negative bacterium, considered a commensal skin flora
It is now recognized as a significant opportunistic pathogen associated with device-related infections.
What are the biofilm virulence factors of Staphylococcus epidermidis?
- MSCRAMMs (adhesins)
- Polysaccharide intercellular adhesin (PIA)
These factors play important roles in biofilm formation and contribute to its pathogenicity.
What is Pseudomonas aeruginosa known for?
Gram-negative, rod-shaped bacterium that can cause infections in compromised hosts
It is particularly notorious for its role in chronic lung infections in cystic fibrosis patients.
What are some biofilm-associated infections caused by Pseudomonas aeruginosa?
- Infection of wounds and burns
- Meningitis
- Chronic lung infection (cystic fibrosis)
- Ventilator-associated pneumonia (VAP)
These infections arise when the bacterium is introduced into areas lacking normal defenses.
What is the role of alginate in Pseudomonas aeruginosa biofilms?
It is an anionic polysaccharide that contributes to biofilm structure and immune response
High amounts of alginate in biofilms lead to chronic inflammation and tissue damage in cystic fibrosis.
What contributes to biofilm resistance to antibiotics?
- Poor antibiotic penetration
- Release of antibiotic-degrading enzymes
- Presence of persisters
- Activation of cellular stress responses
Biofilm cells are significantly more resistant to antibiotics than planktonic cells.
What are persisters in biofilms?
Small subpopulation of bacteria that are not drug-resistant mutants
They represent 0.1-10% of the population and can survive antibiotic treatment.
What is horizontal gene transfer in biofilms?
The exchange of genetic information due to the close proximity of bacteria
Transformation rates can be significantly higher in biofilms compared to planktonic cells.
What is quorum sensing?
Density-dependent control of gene expression that triggers biofilm formation and virulence factor production
High cell density is a key factor in the regulation of these processes.
What are common biofilm models used for study?
- Colony Biofilm Model
- Drip flow reactor
- Constant depth film fermenter system
These models aid in understanding biofilm behavior and responses to antimicrobial treatment.
What treatments are used against biofilms?
- Physical removal
- Biocide-coated biomedical devices
- Antibiotic therapy
- Quorum sensing inhibitors
- Bacteriophage therapy
These approaches aim to disrupt biofilm formation and eliminate established biofilms.
True or False: Biofilms are the dominant lifestyle of bacteria.
True
Biofilms cause a range of difficult-to-treat infections and contribute to antibiotic resistance.
