Normal Flora and Biofilms

Question 1

Classification schemes

Answer 1

Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 2

Most common gut microbacteria in healthy adults

Answer 2

1. Firmicutes (51%)

2. Bacteroidetes (48%)

Question 3

Antibiotic-associated Clostridium difficile disease

Answer 3

C. diff is normal part of gut flora; spore-forming bacterium, not metabolically active, stable.
Antibiotic Tx wipes out gut flora, allows C. diff to predominate

Question 4

What do our gut microbes do? (4)

Answer 4

1. Help digest food
2. Produce Vitamins B & K
3. Occupy niches, exlude pathogens
4. Train immune systems

Question 5

Important bacteria in microbial communities: Skin (1)

Answer 5

Staphylococcus epidermidis

Question 6

Important bacteria in microbial communities: Nose (1)

Answer 6

Staphylococcus aureus

Question 7

Important bacteria in microbial communities: Vagina (1)

Answer 7

Lactobacillus species

Question 8

Important bacteria in microbial communities: GI tract (4)

Answer 8

1. Bacteroidetes (G+)
2. Firmicutes (G+)
3. E. Coli
4. Clostridium species

Question 9

Polysaccharide capsule

Answer 9

extracellular, organized capsule, covalently bound to bacterial surface. Makes a halo. G+/-

Question 10

Lipopolysaccharide

Answer 10

Integral part of G- outer membrane

Question 11

Exopolysaccharides

Answer 11

Secreted beyond bacterial envelope, do not remain attached to bacteria

Question 12

5 Stages of Biofilm formation

Answer 12

1. Reversible attachment
2. Irrreversible attachment
3. Polysaccharide production
4. Growth/formation of 3D structure
5. Dispersal

Question 13

Sessile vs. Planktonic bacteria

Answer 13

Sessile: growing in biofilm/attached to a surface
Planktonic: free-flowing/motile

Question 14

% of bacteria living in biofilms

Answer 14

> 99%

Question 15

% of bacterial infections caused by organisms growing as biofilm

Answer 15

> 80%

Question 16

Exopolysaccharide casing limits:

Answer 16

limits penetration of host defenses and antibiotics

Question 17

Bacteria in biofilms susceptibility to antibiotics influences

Answer 17

1. Non-uniformity

2. Not all are rapidly dividing

Question 18

Foreign body infection steps (4)

Answer 18

1. Planktonic bacteria
2. Adherent cells form biofilm
3. Frustrated phagocytosis, release of enzymes
4. Enzymes damage tissue around biofilm, release planktonic bacteria –> dissemination/acute infection in neighboring tissue