Biofilm
One-Sentence Definition
A biofilm is a surface-attached microbial community embedded in a self-produced extracellular matrix, showing altered growth and high tolerance to antimicrobials and immune clearance.
Simple Explanation
Bacteria build sticky cities on surfaces (catheters, valves, teeth) where drugs and immune cells struggle to reach them.
Detailed Scientific Explanation
- Stages: attachment → microcolonies → mature matrix → dispersal.
- Matrix: polysaccharides, proteins, eDNA.
- Quorum sensing coordinates density-dependent behaviors.
- Classic clinical: device infections, endocarditis vegetations, P. aeruginosa in CF airways, dental plaque.
Mechanism
Slow growth + matrix diffusion barrier + persister cells → antibiotic tolerance (often without new resistance genes). Distinct from genetic Mutation and Selection resistance, though both can coexist.
Clinical Importance
- Device removal often required for cure.
- Longer / combination regimens; relapse common if biofilm persists.
Diagnostic Relevance
- Standard AST on planktonic cells underestimates biofilm tolerance.
- Sonication of explanted devices improves culture yield.
AMR Relevance
- Biofilms are reservoirs for HGT and chronic selection under antibiotics.
Related MOCs
- MOC - Fundamentals of Microbiology · MOC - Clinical Microbiology · MOC - Antimicrobial Resistance (AMR)
Active Recall Questions
- Tolerance vs resistance in biofilms?
- Why do catheter infections often need device removal?
- Name two biofilm-associated clinical scenarios.