Microbiology Basics

Front 1

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

Back 1

Beta-lactamases are found in the periplasm of gram negative bacteria. The enzyme hydrolyzes beta-lactam antibiotics, conferring resistance.

Front 2

Which gram-positive organism lacks a polysaccharide capsule and has a capsule made of something else?

Back 2

Bacillus anthracis - has D-glutamate instead of polysaccharide

Front 3

What are spores made of and what do they do?

Back 3

Keratin-like coat, dipicolinic acid. Provide resistanceto dehydration, heat and chemicals

Front 4

What helps organisms adhere to indwelling catheters?

Back 4

The glycocalyx (composed of polysaccharide)

Front 5

What is the major surface antigen of gram-positive cell walls and what does it do?

Back 5

Teichoic acid - unique to gram-positive bacteria. Induces TNF and IL-1

Front 6

What is specific to gram-negative bacterial cell membranes?

Back 6

Endotoxin/LPS (lipopolysaccharide)

Front 7

Describe the four phases of bacterial growth.

Back 7

1) Lag phase of metabolic activity without division. 2) Log phase of rapid cell division. 3) Stationary phase in which nutrient depletion slows growth. 4) Death due to prolonged nutrient depletion and buildup of waste products.

Front 8

What are exotoxins and endotoxin chemically?

Back 8

Exotoxins are polypeptides, while endotoxins are lipopolysaccharides.

Front 9

Where do bacteria keep their exotoxin or endotoxin genes?

Back 9

Exotoxin genes on plasmids or bacteriophages; endotoxin genes on bacterial chromosomes.

Front 10

Which is more fatal – exotoxin or endotoxin?

Back 10

Exotoxin is highly fatal (~1 microgram), while you need 100’s of micrograms for endotoxin to prove lethal.

Front 11

Which has greater heat stability – endotoxin or exotoxin?

Back 11

Endotoxin – stable at 100°C for 1 hour, while endotoxin is rapidly destroyed at 60°C (EXCEPT Staph enterotoxin)

Front 12

True or False: We can vaccinate against exotoxins and endotoxins.

Back 12

False: We do have toxoids vaccines against exotoxins for diseases like tetanus, botulism and diphtheria, but there are no vaccines against endotoxins.

Front 13

Which bugs have Exotoxin that acts by ADP ribosylation?

Back 13

Corynebacterium diphtheriae (which then inactivates EF-2). Also Escherichia coli, Vibrio cholerae, and Bordetalla pertussis (all these then stimulate adenylate cyclase).

Front 14

Which bug has exotoxin that blocks the release of acetylcholine? What symptoms does that cause?

Back 14

Clostridium botulinum. Anticholinergic symptoms, CNS paralysis, floppy baby, and a wrinkle-free forehead if injected!!

Front 15

Which bug has exotoxin that blocks glycine release? What does that cause?

Back 15

Clostridium tetani. Causes “lockjaw”.

Front 16

How does Staph aureus cause toxic shock syndrome?

Back 16

The toxin is a superantigen that binds to MHC II protein and T-cell receptor à induces IL-1 and IL-2 à TSS

Front 17

How could bacterial infection cause disseminated intravascular coagulation?

Back 17

Endotoxin can activate Hageman factor --> initiates coagulation cascade --> DIC

Front 18

How could bacterial infection cause hypotension?

Back 18

Endotoxin activates macrophages to release nitric oxide (--> vasodilationà hypotension); can also activate alternate complement pathway C3a, --> hypotension (N.B. also edema).

Front 19

How does bacterial infection cause fever?

Back 19

Endotoxin activates macrophages to release IL-1 and TNF --> fever.

Front 20

Gram Stain Limitations: --- are too thin to be visualized. Use darkfield microscopy and fluorescent antibody staining instead.

Back 20

Treponema

Front 21

Gram Stain Limitations: --- lack a cell wall

Back 21

Mycoplasma

Front 22

Gram Stain Limitations: --- stain with silver

Back 22

Legionella pneumophila

Front 23

What are the two Neisseria species?

Back 23

N. meningitidis, N. gonorrhoeae

Front 24

How are the Neisseria species differentiated?

Back 24

MeninGococci ferment Maltose & Glucose; Gonococci ferment only Glucose

Front 25

Pigment-producing Bacteria: --- produces a yellow pigment

Back 25

Staphylococcus aureus (Latin aureus = gold)

Front 26

Pigment-producing Bacteria: --- produces a blue-green pigment

Back 26

Pseudomonas aeruginosa

Front 27

Pigment-producing Bacteria: --- produces a red pigment

Back 27

Serratia marcescens (think red marachino cherry)

Front 28

IgA proteases allow organisms to…

Back 28

… colonize mucosal surfaces

Front 29

Name 4 organisms with IgA proteases

Back 29

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

Front 30

What are the lab steps for ID'ing Staphylococcus aureus?

Back 30

1st gram stain --> get purple/blue cocci (= positive); 2nd catalase test --> positive (staphylococcus clusters); 3rd coagulase test --> positive (differentiates S. aureus from the coagulase-negative S. epidermidis and S. saprophyticus)

Front 31

What are the 4 types of gram-postive rods?

Back 31

Corynebacterium, Listeria, Bacillus, Clostridium

Front 32

When do you test for bacitracin sensitivity or resistance?

Back 32

For beta-hemolytic strep. Bacitracin-sensitive --> Group A beta-hemolytic Strep pyogenes. Bacitracin-resistant --> Group B (Bad!) beta-hemolytic Strep agalactiae

Front 33

Name 4 laboratory features of Streptococcus pneumoniae

Back 33

alpha hemolytic (green – partial hemolysis), positive Quellung reaction, optochin-sensitive, and bile-soluble

Front 34

When would you do the optochin test?

Back 34

When you have alpha hemolytic strep

Front 35

0

Back 35

0

Front 36

Once you see gram-negative rods under the microscope, what is your next diagnostic test?

Back 36

test lactose fermentation

Front 37

What are the 3 fast lactose fermenters:

Back 37

Klebsiella, E. coli, and Enterobacter

Front 38

How do you distinguish among lactose non-fermenters?

Back 38

Perform an oxidase test

Front 39

Which are oxidase-positive?

Back 39

Pseudomonas

Front 40

Which are oxidase-negative?

Back 40

Shigella, Salmonella, or Proteus

Front 41

What are the gram-negative cocci?

Back 41

Neisseria

Front 42

What are the gram-negative coccoid rods?

Back 42

H. influenzae, Pasteurella, Brucella, Bordetella pertussis

Front 43

Which gram negative coccoid requires factors V and X for growth?

Back 43

H. flu

Front 44

Use chocolate agar and factors V & X for ---

Back 44

Hemophilus influenzae

Front 45

Factor V has --- and Factor X has ---

Back 45

NAD, hematin

Front 46

Thayer-Martin (VCN) media to culture ---

Back 46

Neisseria gonorrhoeae

Front 47

Bordet-Gengou (potato) agar to culture ---

Back 47

Bordetella pertussis

Front 48

Tellurite plate, Loffler's medium, blood agar for ---

Back 48

Corynebacterium diphtheriae

Front 49

Lowenstein-Jensen agar for growing ---

Back 49

Mycobacterium tuberculosis

Front 50

Pink colonies on MacConkey's agar are ---

Back 50

Lactose-fermenting enterics (Klebsiella, Eschericihia, or Enterobacter

Front 51

Charcoal yeast extract agar buffered with increased iron and cysteine to grow ---

Back 51

Legionella pneumophila

Front 52

Sabouraud's agar to culture ---

Back 52

Fungi