Normal Flora and Biofilms

Question 1

number of bacteria in oral cavity

Answer 1

10^9

Question 2

number of bacteria in lower GI tract

Answer 2

10^9 - 10^11

Question 3

which organisms outnumber the others

Answer 3

• anaerobes outnumber aerobes

Question 4

most gut microbiota that keep us healthy

Answer 4

• bacteroidetes

- firmicutes

Question 5

where do our gut microbes come from?

Answer 5

• transfer of microbes from mom gut to infant gut
• transfer of bacteria during vaginal birth
• fetus exposed to skin microbiota during breast feeding

Question 6

C. diff

Answer 6

• spore forming bacterium

- part of normal gut

Question 7

C. diff spores

Answer 7

• not metabolically active

- extremely stable

Question 8

antibiotic treatment and C. diff

Answer 8

• antibiotics wipe out normal gut flora

- allows spores to vegetate and C. diff to proliferate

Question 9

what do our gut microbes do for us?

Answer 9

• help digest food
• produce vitamins B and K
• occupy niches and exclude pathogens
• train our immune systems

Question 10

spectrum of relationships with our microbes

Answer 10

• normal flora
• colonization
• carrier state
• infectious disease

Question 11

colonization

Answer 11

• when organisms get a place to stay within the host without being washed away
• doesn’t mean that bad things are going to happen

Question 12

carrier

Answer 12

• further towards pathogenesis
• pathogen present and not causing disease in that person
• can be problematic in another person

Question 13

infectious disease

Answer 13

• presence of organism results in infectious disease in the host

Question 14

where is Staphylococcus epidermidis found?

Answer 14

• skin

Question 15

where is Staph aureus found?

Answer 15

• nose

- more virulent because is catalase positive

Question 16

where is Lactobacillus species found

Answer 16

• vagina

Question 17

where are Bacteriodetes and Firmicutes found

Answer 17

• gram positives

- GI tract

Question 18

where are E. coli and Clostridium species found

Answer 18

• gram negative

- GI tract

Question 19

sessile

Answer 19

• bacteria growth in a biofilm for attached to a surface

- most bacteria

Question 20

planktonic

Answer 20

• free-floating or motile bacteria not attached to a surface

Question 21

polysaccharide capsule

Answer 21

• extracellular
• organized
• bacterial virulence factor
• covalently bound to bacterial surface (gram + or -)

Question 22

LPS

Answer 22

• Lipid A + saccharide core + O-antigen side chains

- integral for gram neg outer bacterial membrane

Question 23

exopolysaccharides

Answer 23

• secreted beyond bacterial envelope into environment

- do not remain attached to individual bacteria

Question 24

stages in biofilm formation

Answer 24

• 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

Question 25

what percent of bacteria live in biofilms

Answer 25

• 99%

Question 26

what percent of bacterial infections are thought to be caused by organisms growing as biofilms

Answer 26

• more than 80%

Question 27

importance of exopolysaccharide casing in biofilms

Answer 27

• limits penetration of host defenses and antibiotics

Question 28

uniformity of bacteria in biofilms

Answer 28

• not uniform

- some not rapidly dividing

Question 29

division and susceptibility to antibiotics

Answer 29

• non rapid dividing bacteria not susceptible to antibiotics

Question 30

biofilms forming on medical devices

Answer 30

• problematic in healthcare settings

Question 31

infection rates of implanted catheters after:

• less than 7 days
• greater than 28 days

Answer 31

• 10-50%

- 100%

Question 32

acute bacterial infections caused by

Answer 32

• planktonic bacteria

Question 33

chronic bacterial infections caused by

Answer 33

• biofilm bacteria