0520 - Biofilms and Abscesses Flashcards
What is a biofilm?
Structured community of microbial (generally bacterial) cells enclosed in a self produced polymeric matrix and adherent to an inert or living substance.
What is an abscess? What is its pathogenesis?
A condition that occurs when an organism enters a sterile site, and is not cleared by that site. A massive influx of neutrophils follows, and infected site is walled off (with lots of pus). Organisms grow and generate an anaerobic environment within the abscess. Implications/symptoms vary depending on location.
What are the steps involved in biofilm formation?
Reversible adsorption of bacteria - requires appropriate millieu
Irreversible attachment of bacteria - adhesins required
Growth and division of bacteria - sense quorum
Exopolymer production and biofilm formation - Number increases, forming biofilm.
Attachment of other organisms to biofilm - full-on community.
Once fully mature, can send out more single cells, disseminating infection.
Biofilm needs a quorum of individual organisms to form.
Why are biofilms important in human infection?
They are difficult to treat - Resistant to antibiotics and immune system due to physical structure.
They serve as a Nidus of infection after treatment, constant source of reinfection. AB’s etc can kill these planktonic cells, but not the sessile cells in the biofilm, meaning infection will recur after cessation of therapy.
Why are biofilms difficult to treat?
They are protected from the immune system and from antibiotics.
Secrete a mucin-like substance, which effectively agglutinates them, preventing phagocytosis, and impenetrable to antibiotics.
Phagocytes are attracted to the biofilms, release enzymes that damage our surface, increasing damage.
Individual cells are released at maturity and with phagocytic tissue damage. Re-infection.
How are biofilms resistant to antibiotics?
Depends on type, but could be one or many of:
Unable to penetrate
Trapped and inactivated by ECM
Inactive against non-growing cells.
Ejected via biofilm-produced efflux pumps
Inactivated by biofilm-specific resistance factors.
Why are biofilms a particular problem with prostheses?
Don’t want to have to take them out, but can’t leave them in as they’ll constantly re-infect the patient.
Also a major problem for indwelling catheters.
Describe the general principles involved in the management of infections associated with biofilms and abscesses.
Biofilm - Needs physical removal.
Abscess - needs surgery or drainage.
In both case, it is resistant to AB’s and immune system due to a ‘physical’ barrier, but maintain the ability to seed infection. Need to get rid of it.
What is the standard checklist for when infections are not responding to treatment? (8 steps)
Is it actually an infection?
Is there pus that needs draining? (abscess)
Is there a blockage that needs unblocking?
Is there a hole that needs fixing?
Is there a foreign body that needs removing? (biofilm)
Is the patient on the right antibiotic?
Is the patient on the right dose of antibiotic?
Is the patient compliant with treatment?
