9-4 IMM Normal Flora and Biofilms Flashcards
Areas with largest number of bacteria
Mouth and the lower GI tract (10^9)
What makes up our gut microbiota?
- firmicutes (51%)
- bacteriodetes (48%)
- proteobacteria
Where do our gut microbes come from?
Babies are colonized before and after birth by birth canal and breast feeding
Problem with antibiotics
Normal flora occupy gut niches and antibiotics clear the way for pathogens
Antibiotics and C. difficile
- C. difficile is a part of our normal guy flora
- spore forming bacteria: spores are not metabolically active and are extremely stable
- antibiotics knock out normal flora allowing spores to vegetate and C. difficile to predominate
Gut biota from day 1 to 2 years for a baby
- day 1: baby fecal flora resembles skin/vaginal flora
- year 2: baby fecal flora resembles normal fecal flora
What do our gut microbes do for us?
- help digest food
- produce vitamins B and K
- occupy niches and exclude pathogens
- help train our immune system
Study of fecal transplants among patients with C. difficile related disease
- resolution in 81% of patients receiving fecal transplant while only 31% resolution for patients receiving vancomycin
Normal flora - Staphylococcus epidermidis is located…
on skin
Normal flora - Staph aureus is located…
in nose
Normal flora - Lactobacillus species is located…
in vagina
Normal flora - bacteriodetes and firmicutes (gram +) is located…
in GI tract
Normal flora - E. Coli and Clostridium species is located…
in GI tract
Sessile bacteria
bacteria growing in a biofilm or attached to a surface
Planktonic bacteria
free floating or motile bacteria not attached to a surface
Gram-postive bacteria
- retain crystal violet dye during gram staining
- cell wall consists of several layers of peptidoglycan
- has teichoic acid in cell wall
Gram-negative bacteria
- don’t retain the violet dye from gram staining
- single layer of peptidoglycan surrounded by outer membrane
- has lipopolysaccharide (LPS or endotoxin) in outer membrane which is toxic to animals
Polysaccharide capsule
extracellular and attached to both gram negative and gram positive surface
Exopolysaccharides
secreted beyond the bacterial envelope into the environment
Stages of biofilm formation
1) reversible attachment
2) irreversible attachment
3) polysaccharide production
4) growth and formation of 3D structure
5) dispersal
___% of bacterial infections are caused by organisms growing in biofilms
more that 80%
_______ casing limits penetration of host defenses and antibiotics
Exopolysaccharide
Process of biofilm on implanted inert surface
1) planktonic bacteria
2) adherent bacteria cells form biofilm
3) frustrated phagocytosis, release of enzymes
4) enzymes damage tissue around biofilm and planktonic bacteria released causing dissemination and acute infection in nearby tissue
Infection rates of urethral catheter
10-50% if in for less than 7 days, 100% if in for more than 28 days
