9-4 IMM Normal Flora and Biofilms

Question 1

Areas with largest number of bacteria

Answer 1

Mouth and the lower GI tract (10^9)

Question 2

What makes up our gut microbiota?

Answer 2

• firmicutes (51%)
• bacteriodetes (48%)
• proteobacteria

Question 3

Where do our gut microbes come from?

Answer 3

Babies are colonized before and after birth by birth canal and breast feeding

Question 4

Problem with antibiotics

Answer 4

Normal flora occupy gut niches and antibiotics clear the way for pathogens

Question 5

Antibiotics and C. difficile

Answer 5

• 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

Question 6

Gut biota from day 1 to 2 years for a baby

Answer 6

• day 1: baby fecal flora resembles skin/vaginal flora

- year 2: baby fecal flora resembles normal fecal flora

Question 7

What do our gut microbes do for us?

Answer 7

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

Question 8

Study of fecal transplants among patients with C. difficile related disease

Answer 8

• resolution in 81% of patients receiving fecal transplant while only 31% resolution for patients receiving vancomycin

Question 9

Normal flora - Staphylococcus epidermidis is located…

Answer 9

on skin

Question 10

Normal flora - Staph aureus is located…

Answer 10

in nose

Question 11

Normal flora - Lactobacillus species is located…

Answer 11

in vagina

Question 12

Normal flora - bacteriodetes and firmicutes (gram +) is located…

Answer 12

in GI tract

Question 13

Normal flora - E. Coli and Clostridium species is located…

Answer 13

in GI tract

Question 14

Sessile bacteria

Answer 14

bacteria growing in a biofilm or attached to a surface

Question 15

Planktonic bacteria

Answer 15

free floating or motile bacteria not attached to a surface

Question 16

Gram-postive bacteria

Answer 16

• retain crystal violet dye during gram staining
• cell wall consists of several layers of peptidoglycan
• has teichoic acid in cell wall

Question 17

Gram-negative bacteria

Answer 17

• 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

Question 18

Polysaccharide capsule

Answer 18

extracellular and attached to both gram negative and gram positive surface

Question 19

Exopolysaccharides

Answer 19

secreted beyond the bacterial envelope into the environment

Question 20

Stages of biofilm formation

Answer 20

1) reversible attachment
2) irreversible attachment
3) polysaccharide production
4) growth and formation of 3D structure
5) dispersal

Question 21

___% of bacterial infections are caused by organisms growing in biofilms

Answer 21

more that 80%

Question 22

_______ casing limits penetration of host defenses and antibiotics

Answer 22

Exopolysaccharide

Question 23

Process of biofilm on implanted inert surface

Answer 23

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

Question 24

Infection rates of urethral catheter

Answer 24

10-50% if in for less than 7 days, 100% if in for more than 28 days