Biofilm powerpoint

1. Biofilms
• Communities of organisms attached to a solid surface
– Can be nonliving or living tissue surface
• Evolve over time consisting of many species
• Most important, they are a multiorganism cooperative population
• Two main types of biofilms
– Sessile
• Permanently anchored to a surface
• Covalently bonded to the surface
• Planktonic
– Free floating
• Movement to new habitats

2. Biofilms (Cont’d)
• Examples of biofilms
– Water pipes
– Ventilator system of airplanes or convention centers
– Wine casks causing spoilage
– Serious lung infections of CF patients
• Problems with susceptibility

3. Natural Biofilm on a Metal Surface

4. Environmental and Cultural Factors That
Affect Biofilm Development

5. Biofilms: Community of Cells
• Most important characteristics
– Attachment efficiency
– Nutritional resources
– Substrata
– Environment shear stress or force

6. Variables Important in Cell Attachment and
Biofilm Formation

7. Stage I – Development I
Stage II – Development II
• Reversible binding to
surface
• Increased attachment
via fimbriae and pili
• Irreversible binding and aggregate
formation
• Decreased motility
• Exopolysaccharide (EPS) trap nutrients
and planktonic bacteria
Stage III – Maturation I
Stage IV – Maturation II
• Colony thickness of
greater than 10 um
thick
• Colony thickness of greater than
100 um thick
• Some bacteria detach but are
trapped in the film
Stage V
Stage 0
• Breaking off of bacteria
leads to start of new
biofilms
• Planktonic state

8. Stages in Biofilm Formation (Cont’d)
• Active growing cells
• Persister cells
– Cells in a dormancy-like state
• Importance
– Cells not actively growing may not be affected by drugs
» Cell wall inhibitors
» Ribosome inhibitors
• Communication between bacteria
– Quorum sensing (QS)
• Pheromones
– Gram positive – low-molecular-weight homoserines
– Gram negative – peptides and proteins

9. Architecture of Biofilms
• Outer layer
– Most dynamic and metabolically active cells
• Intermediate layer
– Still active but less so
– Genetic reservoir for genes involving nutrient utilization and drug
resistance
• Inner surface layer
– Persister cells
• Dynamic system
– Defends itself as a group
• Freely exchanging traits and retaining resistance

10. Mechanisms of Pathogenicity

11. Biofilms as a Defense Mechanism
• When culturing organisms
– Catheter tips, artificial joints, etc.
– Isolation of individual organisms can be hard to culture
• Sessile
– Isolated colonies may not reflect the colonies permanently attached to
the plastic surface
• Planktonic
– Isolated colonies may not contain antibiotic resistance, but other
colonies in the group may contain resistance
• Look susceptible in a dish but not in the patient
– Treatment failure

12. Biofilms as a Defense Mechanism (Cont’d)
• Protect against pH changes
• Interference with immune function
– Prevent phagocytosis
– Prevent antigen exposure to antibodies
• Sticky EPS glues biofilm together; stops clearance
• Organization of biofilm
– Slow-growing organisms attached to surface show increase resistance
to antibiotics

13. Biofilms as a Defense Mechanism (Cont’d)
• Gene transfer
– Transformation
– Conjugation
• Greater genetic potential as a group than alone
– Eventually the virulence factors cluster, causing a worsening of disease

14. Diseases Associated with Biofilms
• Primarily indwelling medical devices
– Examples include
• Artificial heart valves
• Prostheses
• Catheters
• Can be tissue and vessels as well
– Some disease as it progresses from acute to chronic diseases

15. Dental Biofilms
• Plaque
– Caries (cavities)
– Periodontal disease
• Dental cleaning removes plaque
– Biofilm develops again
• Acquired pellicle
– Organisms produce
glycans to produce slime
layer
• Sugars
– Broken down to acids that damage
teeth

16. Laboratory Consequences Associated with
Biofilms
• Cultures
– Require growth to get colonies
• Problem is colonies won’t grow under normal conditions
• False negatives
– Improper sample collection
• Swabs or culturing outer surface of equipment
• Aggregates of organisms
– Single colonies can represent up to 100,000 bacteria of mixed origin
• Thus amounts of each organism are greatly underestimated or not
considered significant
• Antibiotic susceptibility
– Single isolates that are members of a biofilm may not represent the
genetic potential or resistance of a community

17. Detection of Biofilms
• PCR with pathogen-specific probes
• Confocal laser scanning microscopic imaging
– CLSM

18. Potential Interventions
• Establishing biofilms in 96 well plates
– Minimal biofilm elimination concentration (MBEC)
• Help select successful concentrations of drugs and appropriate
concentration
• Treatment outcomes
– Prevent metastasis
– Reduce bioburden
– Prevent attachment
• Other treatments
– Sonication to disrupt biofilm
– Toxic compounds (silver)