Normal Flora and Biofilms Flashcards
number of bacteria in oral cavity
10^9
number of bacteria in lower GI tract
10^9 - 10^11
which organisms outnumber the others
- anaerobes outnumber aerobes
most gut microbiota that keep us healthy
- bacteroidetes
- firmicutes
where do our gut microbes come from?
- transfer of microbes from mom gut to infant gut
- transfer of bacteria during vaginal birth
- fetus exposed to skin microbiota during breast feeding
C. diff
- spore forming bacterium
- part of normal gut
C. diff spores
- not metabolically active
- extremely stable
antibiotic treatment and C. diff
- antibiotics wipe out normal gut flora
- allows spores to vegetate and C. diff to proliferate
what do our gut microbes do for us?
- help digest food
- produce vitamins B and K
- occupy niches and exclude pathogens
- train our immune systems
spectrum of relationships with our microbes
- normal flora
- colonization
- carrier state
- infectious disease
colonization
- when organisms get a place to stay within the host without being washed away
- doesn’t mean that bad things are going to happen
carrier
- further towards pathogenesis
- pathogen present and not causing disease in that person
- can be problematic in another person
infectious disease
- presence of organism results in infectious disease in the host
where is Staphylococcus epidermidis found?
- skin
where is Staph aureus found?
- nose
- more virulent because is catalase positive
where is Lactobacillus species found
- vagina
where are Bacteriodetes and Firmicutes found
- gram positives
- GI tract
where are E. coli and Clostridium species found
- gram negative
- GI tract
sessile
- bacteria growth in a biofilm for attached to a surface
- most bacteria
planktonic
- free-floating or motile bacteria not attached to a surface
polysaccharide capsule
- extracellular
- organized
- bacterial virulence factor
- covalently bound to bacterial surface (gram + or -)
LPS
- Lipid A + saccharide core + O-antigen side chains
- integral for gram neg outer bacterial membrane
exopolysaccharides
- secreted beyond bacterial envelope into environment
- do not remain attached to individual bacteria
stages in biofilm formation
- reversible attachment of planktonic bacteria
- irreversible attachment to host proteins (first committed step)
- polysaccharide production
- growth and formation of structure
- dispersal and planktonic bacteria go to another site
what percent of bacteria live in biofilms
- 99%
what percent of bacterial infections are thought to be caused by organisms growing as biofilms
- more than 80%
importance of exopolysaccharide casing in biofilms
- limits penetration of host defenses and antibiotics
uniformity of bacteria in biofilms
- not uniform
- some not rapidly dividing
division and susceptibility to antibiotics
- non rapid dividing bacteria not susceptible to antibiotics
biofilms forming on medical devices
- problematic in healthcare settings
infection rates of implanted catheters after:
- less than 7 days
- greater than 28 days
- 10-50%
- 100%
acute bacterial infections caused by
- planktonic bacteria
chronic bacterial infections caused by
- biofilm bacteria
