1. Microbes and Multicellularity: The Biofilm Concept
Professor Adriano G Duse
Chief Specialist, Chair & Academic Head: Division of Clinical Microbiology and Infectious Diseases
NHLS & Wits School of Pathology

2. Objectives for this Lecture:
By the end of this lecture, students must be able to:
Define a bacterial biofilm
Describe the composition, and interrelationship of bacterial cells, within a biofilm
Briefly discuss the interactions of microbial cells within a bacterial biofilm with particular reference to cell-to-cell signaling (quorum sensing)
Understand the mechanisms of resistance of biofilm-embedded cells to antimicrobial agents
Discuss the clinical relevance of bacterial biofilms in infective processes and medical device associated infections
Illustrate all of the above by describing the “foreign body” effect and infection

3. The Biofilm Concept
NOT NEW – A van Leeuwenhoek, 1683 !

4. The Biofilm Concept
Assemblage of microbial cells, irreversibly associated with a surface, enclosed in matrix of mainly polysaccharide material
Sessile versus planktonic microbial cells
Biofilm matrix may also contain non-cellular materials
Form on a variety of surfaces: living tissues, medical devices, industrial / natural aquatic systems

5. The Biofilm Concept
Assemblage of microbial cells, irreversibly associated with a surface, enclosed in matrix of mainly polysaccharide material
Sessile versus planktonic microbial cells
Biofilm matrix may also contain non-cellular materials
Form on a variety of surfaces: living tissues, medical devices, industrial / natural aquatic systems

6. The Biofilm Concept
Assemblage of microbial cells, irreversibly associated with a surface, enclosed in matrix of mainly polysaccharide material
Sessile versus planktonic microbial cells
Biofilm matrix may also contain non-cellular materials
Form on a variety of surfaces: living tissues, medical devices, industrial / natural aquatic systems

9. Biofilms And Antimicrobial Resistance

10. Biofilms And Hospital-Acquired Infections
Main nosocomial infections (NIs) acquired by biofilms are:
Bacteremia
87% of (N) bacteremias have an indwelling vascular device
England: 0.6/1000 pt days; ICUs: 9/1000 pt days; > 40% S aureus, 17% CoNS, ~ 9% enterococci
US: ~ cases of CR-bacteremia in 2001
Urinary tract infections – account for ~ 30% of all NIs
95% of (N) UTIs are catheter-related
Of all patients with a urinary catheter: 30% bacteriuria % clinical UTI
Risk of UTI increases by 5% for each day catheter is in situ
Pneumonia
Occurs in ~ 1% of all patients, accounting for 40% of all surgical ICU infections
Incidence of VAP ranges from 7 to > 40% (mono- / polymicrobial, Gram – ves & + ves
Surgical wound infections: not necessarily a biofilm infection per se but relevant

11. Biofilms In Infectious Diseases
Two types of medically important biofilms:
Those that develop on surfaces of implanted medical devices
Those that form directly on host tissues

12. Biofilms And Device-Related Infections
Central venous catheters (CVCs)
Urinary catheters
Endo tracheal tubes and ventilator tubing
Prosthetic heart valves
Orthopaedic devices
Endoscopes & post-disinfection rinsing tanks

13. The Foreign Body Effect