Paper I — 2023 January (Supplementary) (2019 Scheme) — Q10
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Paper I
2023 January (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
Importance of biofilms in management of infections.
Q104 marksShort Answers
Answer
Biofilms are structured communities of microorganisms adherent to a surface (biological or inert/device), encased within a self-produced extracellular polymeric matrix (glycocalyx) — a mode of growth fundamentally different from, and clinically far more resistant than, planktonic (free-floating) bacteria.
Importance in management of infections:
Markedly increased antibiotic resistance/tolerance — organisms within a biofilm can tolerate antibiotic concentrations many times (often 10–1000-fold) higher than the same organism growing planktonically, due to restricted antibiotic penetration through the matrix, reduced metabolic activity of deeply embedded cells, and the presence of dormant “persister” cells — meaning standard antibiotic dosing/duration is frequently inadequate for biofilm-associated infection.
Device-associated infections — biofilms readily form on indwelling medical devices (intravascular catheters, prosthetic joints, heart valves, urinary catheters, endotracheal tubes), making these a major and difficult-to-treat source of hospital-acquired infection; classic organisms include Staphylococcus epidermidis and S. aureus on catheters, and Pseudomonas aeruginosa in cystic fibrosis lung infection.
Need for device removal — biofilm-associated infections often cannot be cured by antibiotics alone, and definitive treatment frequently requires removal of the infected device/foreign material in addition to antibiotic therapy, an important management principle directly stemming from biofilm biology.
Protection from host immune defences — the biofilm matrix also impairs penetration and effectiveness of host antibodies, complement, and phagocytic cells, contributing to chronic, relapsing infection despite an intact immune system.
Diagnostic challenge — biofilm-embedded organisms may not be efficiently released into surrounding fluid, sometimes causing false-negative cultures despite ongoing device-associated infection, complicating diagnosis.
Chronic wound infections — biofilms in chronic non-healing wounds (e.g., diabetic foot ulcers) similarly impair healing and antibiotic efficacy.
Clinical significance: understanding biofilm biology directly informs clinical practice — minimizing unnecessary device use/duration, considering device removal early in refractory device-associated infection, and recognizing that prolonged/combination antibiotic regimens are often needed when device removal is not immediately feasible.
