L3 Normal flora and biofilms

Question 1

_____ more bacterial cells than human cells

Answer 1

10x

Question 2

where are the largest numbers of normal flora in the human

Answer 2

oral cavity and lower GI tract

Question 3

oral cavity microbiome

Answer 3

10^9

Question 4

lower GI tract microbiome

Answer 4

10^9-10^11

Question 5

anaerobes are found in greater/less numbers compared to aerobes in the human body

Answer 5

greater > 1000:1

Question 6

classification of bacteria

Answer 6

kindgom 
phylum
class
order
family
genus 
species

Question 7

gut microbiota in healthy adults ___________ 48% and __________ 51%

Answer 7

bacteroidetes; firmicutes

Question 8

breastfeeding babies influences their immune system and susceptibility to _________ and _______

Answer 8

asthma and allergies

Question 9

microbes are gathered from birth through

Answer 9

vaginal birth and breastfeeding

Question 10

normal flora occupy gut niches and therefore

Answer 10

prevent some pathogens from taking up residence (antibiotics can kill normal flora and therefore cause greater issues in some cases)

Question 11

C difficile is considered a firmicute/bacteroidete

Answer 11

firmicute

Question 12

antibiotic associated C difficile

Answer 12

part of the normal gut flora; spore are not metabolically active but extremely stable; antibiotic treatment wipes out normal gut flora allowing spores to take over

Question 13

what do our gut microbes do for us?

Answer 13

produce vitamin B and K, help digest food, occupy niches and exclude pathogens, and train our immune systems

Question 14

staphylococcus epidermidis

Answer 14

skin

Question 15

S. aureus

Answer 15

nose

Question 16

lactobacillus species

Answer 16

vagina

Question 17

bacteroidetes and firmicutes (gram +)

Answer 17

GI tract

Question 18

e coli and clostridium species

Answer 18

GI tract

Question 19

sessile

Answer 19

bacteria growing in a biofilm or attached to a surface

Question 20

planktonic

Answer 20

free-floating or mobile bacteria not attached to a surface

Question 21

polysaccharide capsule

Answer 21

extracellular, organized, covalently bound to bacterial surface

Question 22

lipopolysaccharide (LPS)

Answer 22

endotoxin, lipid A, saccharide core, integral part of gram negative bacterial outer membrane

Question 23

exopolysaccharides

Answer 23

secreted beyond the bacterial envelope into the environment, do not remain attached to individual bacteria; very important for biofilm production

Question 24

stages of biofilm formation

Answer 24

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

Question 25

> 99% of bacteria live in

Answer 25

biofilms

Question 26

> 80% of bacterial infections are thought to be caused by organisms growing as

Answer 26

biofilms

Question 27

bacteria in biofilms are/are not uniform, some are not rapidly dividing, influencing susceptibility to antibiotics

Answer 27

are not

Question 28

exopolysaccharides casing limits/increases penetration of host defenses and antibiotics

Answer 28

limits

Question 29

biofilms forming on implanted catheters can lead to increased /decreased infections

Answer 29

increased

Question 30

1. A person with a normal healthy immune system acquires a new strain of E. coli that now lives in his gastrointestinal tract. This individual is not ill. A second person with an acute leukemia and no white blood cells acquires the same organism, develops diarrhea followed by hypotension, bacteremia, sepsis, and death. Which of the following best describes this organism?
   A. Normal flora for both individuals
   B. A pathogen for both individuals
   C. One with a low degree of virulence

Answer 30

C. The E. coli have become part of the first person’s resident gut flora. As long as they stay there, and the person remains in good health, all is well. In the second person who has a severly compromised immune system, the organism is pathogenic. Because the organism has pathogenic potential, but is not causing disease in a person with a healthy immune system, we conclude that it has low virulence.

Question 31

2. A patient comes to the ED with a skin abscess on the right arm. A culture of the lesion grew several bacterial species. Which of the following organisms is the most likely cause of this infection?
   A. Escherichia coli
   B. Staphylococcus aureus
   C. Staphylococcus epidermidis

Answer 31

2. B. Both S. aureus and S. epidermidis are common among the normal flora of the skin, but the coagulase-positive S. aureus is more virulent and is more likely to cause tissue damage associated with skin abscesses.

Question 32

3. Indwelling catheters are often sources of nosocomial infections that are difficult to treat with antibiotics. Which of the following statements best explains this?
   A. Resistant bacteria are better than susceptible ones at forming biofilms.
   B. Extracellular bacterial polysaccharide reduces penetration of antibiotics.
   C. Bacteria growing in biofilms are rapidly-dividing.

Answer 32

3. B. Exopolysaccharides encasing bacteria in biofilms inhibit penetration of antibiotics. Even susceptible bacteria growing in biofilms are more resistant, due to slower growth characteristics.

Question 33

4. Match the following organisms with the anatomical location in which it is most likely to be found as part of the normal microbiota.
   A. Staphylococcus aureus GI tract
   B. Clostridium difficile Vagina
   C. Lactobacillus crispatus Skin

Answer 33

4. A. Skin; B. GI tract; C. Vagina