Introduction

Question 1

What is the purpose of peptidoglycan?

Answer 1

Gives rigid support and protects against osmotic pressure

Question 2

What is the purpose of the capsule?

Answer 2

To protect against phagocytosis and T cell mediated immune responses

Question 3

What is the structure of glycocalyx?

Answer 3

Polysaccharide

Question 4

What is the function of glycocalyx?

Answer 4

Mediates adherence to surfaces (especially foreign surfaces)

Question 5

What kind of bacteria contain an outer membrane?

Answer 5

Gram negative

Question 6

What are spores made out of?

Answer 6

Keratin-like coat, dipicolinic acid

Question 7

Describe the role of the outer membrane (present in gram negatives)

Answer 7

• It is made out of lipopolysaccharide which is a major surface antigen
• Lipid A induces TNF and IL-1

Question 8

Wat type of bacteria contain lipoteichoic acid?

Answer 8

Gram positives

Question 9

What kind of bacteria contain thinner peptidoglycan cell walls?

Answer 9

Gram negatives

Question 10

What kind of bacteria contain a larger periplasmic space?

Answer 10

Gram negatives

Question 11

What does the periplasmic space contain?

Answer 11

Contains enzymes necessary for bacterial virulence such as lipases, Beta lactamases, phosphatases and proteases (can inhibit penicillin)

Question 12

What structure can cause the release of TNF-alpha from macrophages? (causing toxic shock)

Answer 12

Lipopolysaccharide endotoxins on outer membranes of gram negatives

Question 13

What bacteria does not contain a cell wall? What do they contian instead?

Answer 13

Mycoplasma (gram positive organism)

- instead contain sterols

Question 14

What is unique about the cell wall of mycobacteria?

Answer 14

• Contains mycolic acid and has a high lipid content

Question 15

What is a gram stain made from?

Answer 15

• Crystal Violet and iodine cause a dark purple/blue colour in gram positives
• Safranin acts as a counter stain (causes gram negatives to stain pink)

Question 16

What organisms cannot be identified via gram staining?

Answer 16

• Treponema
• Rickettsia
• Mycobacteria
• Mycoplasma
• Legionella pneumophila
• Chlamydia

These Rascals May Microscopically Lack Colour

Question 17

Why can mycoplasma not be gram stained?

Answer 17

No cell wall

Question 18

Why can mycobacteria not be gram stained?

Answer 18

The cell wall has a high lipid content (requires acid-fast stain)

Question 19

What are mycobacteria visulaized with?

Answer 19

Acid-fast staining

Question 20

Why can Treponema not be gram stained?

Answer 20

Too thin

Question 21

Why can Rickettsia, Legionella pneumophila and Chlamydia not be visualised with gram staining?

Answer 21

They are all intracellular organisms (Chlamydia also lacks muramic acid in its cell wall)

Question 22

How are treponemes visualised?

Answer 22

Darkfield microscopy and fluorescent antibody staining

Question 23

What is legionella visualised with?

Answer 23

Silver stain (or immunofluorescent staining)

Question 24

What organisms can be visualised with immunofluorescent staining?

Answer 24

Intracellular parasites (Rickettsia, legionella pneumophila and chlamydia)

Question 25

What can a Giemsa stain be used to visualise?

Answer 25

- Borrelia - Plasmodium - Trypansomes - Chlamydia

Question 26

What can PAS (periodic acid Schiff) be used to identify? | And what does it stain specifically?

Answer 26

- Tropheryma whippelii (cause of Whipple's disease) | - Stains glycogen, mucopolysaccharides

Question 27

What does the Ziehl-Neelsen visualise?

Answer 27

Acid-fast organisms (such as mycobacteria e.g TB)

Question 28

What can the India ink stain be used to visualise?

Answer 28

Cryptococcus neoformans (mucicarmine can also be used to stain the thick polysaccharide capsule red)

Question 29

What can the silver stain be used to visualise?

Answer 29

- Fungi | - Legionella

Question 30

What media is used to grow haemophilus influenzae?

Answer 30

Chocolate agar with factors V (NAD+) and X (hematin)

Question 31

What media is used to grow Neisseria gonorrhoeae?

Answer 31

- Thayer-Martin media | - aka VPN media (Vancomycin, Polymyxin and Nystatin)

Question 32

What type of organisms turn pink on MacConkey's agar?

Answer 32

Lactose-fermenting enterics (e.g E. coli)

Question 33

What other than MacConkey's agar can E. coli be grown on?

Answer 33

Eosin-methylene blue (EMB) agar (grows as blue/black colonies with metallic sheen)

Question 34

What media is legionella grown on?

Answer 34

Charcoal yeast extract agar buffered with cysteine and iron

Question 35

What medium are fungi grown on?

Answer 35

Subouraund's agar

Question 36

What are examples of obligate aerobes? (organisms which require O2 to generate ATP)

Answer 36

- Nocardia - Pseudomonas aeruginosa - Mycobacterium tuberculosis - Bacillus Nagging Pests Must Breathe

Question 37

Where can psedomonas aeruginosa be found?

Answer 37

- Burn wounds - Nosocomial pneumonia - Pneumonias in cystic fibrosis patients

Question 38

Where can M. tuberculosis commonly reactivate? (e.g after immune compromise or TNF-alpha inhibitor use)

Answer 38

The apices

Question 39

What are examples of obligate anaerobes?

Answer 39

- Clostridium - Bacteroides - Actinomyces Can't Breathe Air

Question 40

What enzyme do obligate anaerobes lack?

Answer 40

Catalase and/or superoxide dismutase | - Makes them susceptible to oxidative damage

Question 41

Where can anaerobes be found as normal flora?

Answer 41

GI tract (foul-smelling)

Question 42

Why are aminoglycosides ineffective against anaerobes?

Answer 42

They require O2 to enter into the bacterial cell

Question 43

What are examples of obligate intracellular organisms?

Answer 43

- Rickettsia - Chlamydia Stay inside cells when its Really Cold

Question 44

What are examples of facultative intracellular organisms?

Answer 44

- Salmonella - Neisseria - Bruccella - Mycobacterium - Listeria - Francisella - Legionella - Yersinia pestis Some Nasty Bugs May Live FaculativeLY

Question 45

What are examples of encapsulated bacteria?

Answer 45

- Streptococcus pneumoniae - H. influenza type B - Neisseria Meningitidis - Salmonella - Klebsiella pneumoniae - Group B strep SHiN SKis

Question 46

What is a positive quellung reaction?

Answer 46

If encapsulated bug is present the capsule swells when specific anticapsular antisera are added

Question 47

What does catalase degrade?

Answer 47

H2O2 (hydrogen peroxide)

Question 48

What organisms are catalase positive?

Answer 48

- Staph aureus - Serratia - Pseudomonas - Actinomyces - Candida - E. coli you need SSPACE for your cats

Question 49

What kind of miccrobes are patients with chronic granulomatous disease vulnerabe to?

Answer 49

Catalase positive organisms as they reley on H2O2 to fight infection (they have a NADPH oxidase deficiency)

Question 50

What disease does Borrelia cause?

Answer 50

Lyme's disease