biofilms Flashcards
biofilms
cause damage and disease
what sort of sieges to biofilmscause
chronic infections on heart valves, implants, dental decay, catheters
biofilms act as
reservoirs of contimination/ infection
biofilms are difficult to control since
they require a higher dose of antibiotics
biofilms are economically costly
e..g NHS costs/ steel pipers under the north sea which are corroded by sulphate reducing bacterial biofilsm
cistern 2001
best that 65% of infections may be biofilm related
approx 60% of….
HAIs are biofilm related
biofilm
“matrix associated microbial populations adherent to each other and or to surfaces ir interfaces” Casterton et al
medical infections
implants/ contact lenses
domestic
drains/ toilets
main infections causes by biofilms in tissues/ fluids are
Bacteremia (blood stream infection). UTIs, pneumonia
biofilm microorganisms are
more successful than planktonic
advantages of biofilms include
- increased resistance to antimicrobial agents
- increased resistance to host defences e.g TB, intracellular salmonella, reduced capacity for clearing by phagocytosis)
- enhanced genetic interaction e.g. movement of resistance plasmids
when antimicrobials diffuse into the biofilm
reaction hiitions leads to tolerance: sub lethal cones lead to selection for resistance e.g. reaction eiwth EPS, chelation, enzymatic degradation, precipitation, volatilisation as alkylated metal compounds.
uninhibited diffusion of antimicrobials
tolerance by slow growth e.g. VBNC and persisters. transfer of resistance genes- due to all being in close proximity.
biofilms are destroyed using
biocides
which microflora was the first to be studied
the mouth
over…. species have been identified in the oral cavity
700
toothpaste and fluoride the fluoride in it
is used to control biofilm formation
why is oral health so important
infections in the mouth can pass through the blood system and cause infection in organs
how do plaques form
1) primar colonisers- on the surfaces of teeth and soft tissues
2) secondary colonisers- attach to primary colonisers
3) mutation of plaque- growth in situ and attachment and detachment to the existing biofilm
4) disease causation-pathogenic effect include release of toxins/acids
which biofilm causes disease
the mature bioilms
three main groups of plaque bacteria
aerobes, facultative anaerobes and obligate anaerobes
aerobes
high proportion of young plaque. usually does not cause harm e.g. Neisseria subflaa
facultative naerobes
these are the majority of microbes in the mouth. able to survive and grow with high/ low oxygen concentration- usually gram positive e.g. Streptococcus mutants - usually gram neg
obligate anaerobes
high number in mature plaque- O2 is toxic or inhibitory to grothw. some of these species are harmful and associated with gum disease e.g.fusobacterium nucleotum
example of an aerobe
Neisseria subflave
example of a facultative anaerobe
Streptococcus mutans
example of an obligate anaerobe
Fusobacterium nucelotum.
examples of surfaces in healthcaree where pathogens survive
instruments, bed line, the floor
which pathogens survive well on healthcare surfaces
MRSA, salmonella, entrococci, Pseudomons aeruginosa, E.coli, Fusarium
% of UTIs caused by biofilms
95
% of bateremia cases
87%
86$ of pneumonia cases are
ventilator associated
prophylaxis
treatment to prevent disease
example of public prophylaxis
fluoride use in water- no consent, but very effective in reducing dental decay. only medical treatment give passively without consent
mode of action of fluoride
reduction in enzyme activity reduces acid production from carbohydrates. pathogens are outcompeted
biofilms cells in comparison to planktonic cells are generally much more
resistant to antibiotics and biocides
urinary catheters
quickly acquire organisms on the surge- 5-10% colonisation within 7 days (MRS may achieve a depth up to 5-6 ells in 2h) e.g. proteus spp
orthopaedic devices
external fixation from open fractures are out likely to be colonised. Often penetration of antibiotics into biofilms on stainless steel may fail to eradicate the infection
prosthetic joint infections
sometimes impossible to cure using antibiotics alone- this may lead to more surgery of even amputations.
basic stages of biofilm formation
attachment, growth ,detachment
attachment
free floating or planktonic bacteria encounter a submerged surface and within minutes become attached
Growth
Extracellular polymeric structure (EPS) production allows the emerging biofilm community to develop a complex, three dimensional structure
detachment
biofilms can propagate through detachment of small or large clumps of cells, or by a type of ‘seeding dispersal’ that releases individuals cells
biofilms can move in numerous ways
collectively by rippling or rolling across the surface, or by detachingin clubs or individuals by swarming and seeding
emergent properties fo biofilms and habitat formation
1) localised gradients- provide habitat diversity
2) sorption- resource capture
3) enzyme retention-external digestion system
4) cooperation- synergistic micro-consortia
5) competition- continous regeeration
6) tolerance and resistance- biofilm as a fortress
localised gradients
provide habitat diversity i.e. different bacteria will survive better at diff oxygen cones/ nutrients conc
a key resource of biofilms
calcium
cooperation
due to there being a variety of different bacteria which have different biochemical abilities, bacteria are able to use each others products to benefit themselves
competition
keeps all bacteria active
copiotrophs
an organism found in environments rich in nutrients particularly carbon. tend to grow iim high organise substrate conditions
oligotrophs
organisms that live in environments that offer very low levels of nutrients. characterised by slow growth, low rates of metabolism and generally low population density
copiotrophic biofilm
creates an oxygen gradient, producing niches for aerobes, fermenters and anaerobes
oligotrophic biofilm
nutrient gradients- some cell are more metabolically active, are starving, formation, VNBC, persister and dead cells.
communication
chemic and electrical communication
cooperation
nitrification- some cells are ammonia oxidisers and other nitrite oxidizers- syngerisist
competition
antibiotic, bacteriocins, killer vesicles, biosurfactants, inhibition of quorum sensing, nutrient depletion, cheating
