Principles of Bacteriology

Question 1

What is present in the wall of a gram + bacteria that is not present in a gram negative bacteria?

Answer 1

thick peptidoglycan layer

teichoic acid in wall

Question 2

T/F: Spores are metabolically active.

Answer 2

false

Question 3

How does bacterial infection cause fever?

Answer 3

endotoxin activates macrophages to release IL-1 and TNF, causing fever

Question 4

Name 5 common zoonotic bacteria.

Answer 4

Borrelia burgdorferi, Brucella, Francisella tularensis, Yersinia pestis, Pasteirella multocida

Question 5

Enterobaceriaceae: describe O, K, and H antigens

Answer 5

O - somatic, polysaccharide of endotoxin

K - capsular, related to virulence

H - flagellar, found in motile species

Question 6

What kind of bacteria form spores and when?

Answer 6

certain gram + rods when nutrients are limited

Question 7

Where is beta-lactamase in bacteria? What does it do?

Answer 7

periplasm of gram - bacteria

enzyme hydrolyzes beta-lactam antibiotics, conferring resistance

Question 8

What molecule is specific to gram - bacterial cell membranes?

Answer 8

LPS

Question 9

What are exotoxins and endotoxins, chemically speaking?

Answer 9

exotoxins tend to be polypeptides, while endotoxins are usually lipopolysaccharides

Question 10

How could bacterial infection cause hypotension?

Answer 10

endotoxin induces macrophages to release nitric oxide -> vasodilation, hypotension

can also activate alternate complement pathway C3a, causing hypotension

Question 11

Which organisms have exotoxin that acts by ADP ribosylation?

Answer 11

Corynebacterium diphtheriae, Escherichia coli, Vibrio cholerae, and Bordetalla pertussis

Question 12

What helps organisms adhere to indwelling catheters?

Answer 12

glycocalyx (composed of polysaccharide)

Question 13

Name the dominant normal flora on the teeth.

Answer 13

strep. mutans

Question 14

Being in a newborn nursery is a risk factor for which two pathogens?

Answer 14

CMV and RSV

Question 15

Name the dominant normal flora in the oropharynx.

Answer 15

strep. viridans

Question 16

Name the dominant normal flora in the vagina.

Answer 16

Lactobacillus, E. coli, group B strep.

Question 17

What disinfecting procedure kills spores?

Answer 17

autoclaving

Question 18

Which pathogen is most associated with total parenteral nutrition?

Answer 18

Candida albicans

Question 19

Where do bacteria keep their exotoxin or endotoxin genes?

Answer 19

exotoxin genes on plasmids or bacteriophages

endotoxin genes on bacterial chromosomes

Question 20

T/F: we can vaccinate against exotoxins and endotoxins

Answer 20

false

we have toxoid vaccines against exotoxins for diseases like tetanus, botulism and diphtheria, but there are no vaccines against endotoxins

Question 21

T/F: Spores are highly resistant to destruction by heat and chemicals.

Answer 21

T

Question 22

Gram for gram, which is more fatal: exotoxin or endotoxin?

Answer 22

exotoxin

Question 23

Name the dominant normal flora in the colon.

Answer 23

Bacteriodes fragilis > E. coli

Question 24

How is catalase a virulence factor?

Answer 24

it degrades H2O2, an antimicrobial product of PMNs

Question 25

Name the dominant normal flora of the nose.

Answer 25

Staph. aureus

Question 26

Are vaccines available for encapsulated bacteria?

Answer 26

yes

Question 27

What are two of the most common causes of nosocomial infections?

Answer 27

E. coli (UTI) and Staph. aureus (wound infection)

Question 28

What are spores made of? What do they protect from?

Answer 28

keratin-like coat, dipicolinic acid provide resistance to dehydration, heat and chemicals

Question 29

What is the major surface antigen of gram + cell walls and which two cytokines does it induce?

Answer 29

teichoic acid - unique to gram + bacteria induces TNF and IL-1

Question 30

Spores have ___ acid in their core.

Answer 30

dipicolinic

Question 31

What are the two pathogens most commonly associated with urinary catheterization?

Answer 31

E. coli, Proteus mirabilis

Question 32

What is the most likely pathogen when a water source (water aerosols) is involved?

Answer 32

Legionella

Question 33

Name four organisms with IgA proteases.

Answer 33

Strep. pneumoniae, N. meningitidis, N. gonorhoeae, H. influenzae

Question 34

What pathogen is often found on respiratory therapy equipment?

Answer 34

Pseudomonas aeruginosa

Question 35

What is the main virulence factor of encapsulated bacteria and how does it confer virulence?

Answer 35

polysaccharide capsule is antiphagocytic

Question 36

Which has greater heat stability: endotoxin or exotoxin?

Answer 36

endotoxin

Question 37

Name the dominant normal flora in the skin.

Answer 37

Staph. epidermidis

Question 38

How might a bacterial infection cause disseminated intravascular coagulation?

Answer 38

endotoxin can activate Hageman factor which initiates coagulation cascade, causing DIC

Question 39

Compare and contrast the cell walls of Gram +/-

Answer 39

Both have peptidoglycan (Gram+ is thicker layer) Gram - has LPS and LOS Gram + has Lipoteichoic acid

Question 40

Compare and contrast antigenic variation and shift

Answer 40

Antigenic variation is the process by which bacteria alter the expression of certain genes in response to environmental stressors to promote survival and increase virulence. This process is faster than random mutation. An example of this is the changing of surface protein expression to avoid detection by host immune cells. Antigenic shift is the exchange of genetic material between two subtypes of viruses to create progeny that is more virulent. This is commonly seen in influenza viruses.

Question 41

What is a plasmid

Answer 41

Plasmids can contain genes for antibiotic resistance or toxins. These plasmids can be freely replicated and transmitted between bacteria.

Question 42

If a bacteria is "competent" what does that mean? 3 examples

Answer 42

can facilitate the process of transformation (i.e., uptaking free genetic material from the environment and integrating it into the bacterial genome). Neisseria species, Haemophilus influenzae type b, and Streptococcus pneumoniae.

Question 43

Generalized vs. specialized transduction

Answer 43

Generalized - phage DNA not integrated into bacterial chromosome Specialized - specifically integrated into the chromosome

Question 44

Purpose of vanA gene?

Answer 44

Vancomycin resistance Mostly seen in enterococcus species.

Question 45

Endotoxins are made of __ found on the __ of ___

Answer 45

LPS on the outer cell membranes of Gram - bacteria.

Question 46

MHCs bind ___ but not ___ , therefore they cannot present ___ to ___

Answer 46

bind peptide antigens, but not polysaccharides therefore they cannot present endotoxins (made of polysaccharides) to TCRs (T cell receptors)

Question 47

AB toxins are part of ___ how do they work?

Answer 47

Exotoxins 1) Component A, the active component, enters the cell and exerts a toxic effect. 2) Component B, the binding and uptake component, binds to the target cell to facilitate entry of the toxin into the cell.

Question 48

Describe reassortment what agent is best at this?

Answer 48

different strains of segmented viruses can combine to create a new viral subtype Influenza - human + animal strain