Microbiology

Question 1

Peptidoglycan cell wall

Answer 1

+ thick

- thin

Question 2

Teichoic acid

Answer 2

+ present

- absent

Question 3

Periplasmic space

Answer 3

+ absent

- present

Question 4

Outer membrane

Answer 4

+ absent

- present

Question 5

LPS

Answer 5

+ absent

- present

Question 6

Porin

Answer 6

+ absent

- present

Question 7

Why is gram - bacterial infection harder to treat?

Answer 7

Bc gram - bacteria have outer membrane

Question 8

What is color of gram - bacteria when stained?

Answer 8

Pink

Question 9

What is color of gram + bacteria when stained?

Hint: thick cell wall

Answer 9

Violet-blue

Question 10

Characteristics of atypical bacteria

Answer 10

1. Lack cell wall e.g., mycoplasma

2. Composition of cell wall is atypical

Question 11

Acid-fast staining stains A acid on cell wall of mycobacterium tuberculosis. The resulting color is B.

Answer 11

A: mycolic
B: yellowish-red

Question 12

Mycolic acid makes mycobacterium tuberculosis A & B resistant.

Answer 12

A: chemical
B: aridity

Question 13

Why is mycoplasma resistant to B-lactam?

Answer 13

Bc it has no cell wall & B-lactam kills bacteria by inhibiting synthesis of cell wall

Question 14

E.g. of B-lactam

Answer 14

Penicillin

Question 15

Pathogenicity

Answer 15

Ability - organism - cause disease

Question 16

What make an organism pathogenic/have pathogenicity?

Answer 16

1. Transmissibility: ability - transfer - host to host
2. Infectivity: ability - breach - defense
3. Invasiveness: spread - diff parts of body
4. Virulence: capacity - cause disease (quantitative measure of pathogenicity)

Question 17

How can pathogen invade/spread to diff parts of body?

Answer 17

1. Direct extension: adjacent wound/infection
2. Lymph
3. Blood
4. Nerves

Question 18

As LD & ID50 increase, virulence ___.

Answer 18

decreases

Question 19

Bacterial pili & fimbriae

Answer 19

Adherence

Question 20

Bacterial capsule

Answer 20

Anti-phagocytic allowing survival in host cell

Question 21

Endospores are only formed by gram ___ bacteria but not all gram ___ bacteria can form endospores.

Answer 21

+

Question 22

Clinical effects of LPS are (systemic/local)?

Answer 22

systemic

Question 23

Effects of endotoxin/LPS

Answer 23

1. Activates macrophages via CD14/TLR4 –> TNF-a, IL-1, IL-6 & NO released
2. Alternatively activates complement system –> histamine released & neutrophil recruited
3. Activation of coagulation cascade –> disseminated intravascular coagulation (DIC)

Overall: hypotension, fever, septic shock, edema & DIC

Question 24

Clinical effects of exotoxin are ___ for each toxin.

Give an e.g..

Answer 24

specific

E.g., botulinum exotoxin causes muscle paralysis

Question 25

List 6 differences between endotoxin/LPS & exotoxin

Answer 25

1. LPS: lipopolysaccharide; exotoxin: protein 2. LPS: heat-stable; exotoxin: heat-labile (protein denatures at 60 'C) 3. LPS: component of outer membrane; exotoxin: synthesized in cytoplasm & secreted 4. LPS: gram - bac; exotoxin: gram + bac 5. LPS not as toxic as exotoxin 6. LPS: can't; exotoxin: can be used as toxoid vaccine bc protein

Question 26

List 6 differences between endotoxin/LPS & exotoxin

Answer 26

1. LPS: lipopolysaccharide; exotoxin: protein 2. LPS: heat-stable; exotoxin: heat-labile (protein denatures at 60 'C) 3. LPS: component of outer membrane; exotoxin: synthesized in cytoplasm & secreted 4. LPS: gram - bac; exotoxin: gram + bac 5. LPS not as immunogenic & toxic as exotoxin 6. LPS: can't; exotoxin: can form toxoid which can be modified into toxoid vaccine bc protein

Question 27

Components of exotoxin

Answer 27

A: A for active B: B for binding

Question 28

Immunogenic component of LPS

Answer 28

O antigen

Question 29

Toxic component of LPS

Answer 29

Lipid A

Question 30

Modes of transmission

Answer 30

1. Zoonoses (animals) 2. Vector transmission (arthropods like mosquitoes) 3. Aerosol (respiratory tract diseases like diphtheria, Legionnaire's disease & TB) 4. Indirect (food, water & surgical instruments) 5. Direct (sex & transplacental)

Question 31

Incubation period

Answer 31

Time between encounter w/ pathogen & onset of symptoms

Question 32

Subclinical infection

Answer 32

No symptoms

Question 33

Carrier state

Answer 33

During incubation period or subclinical infection where pathogen is latent/dormant in both states