Deja Review Usmle Step 1 Microbiology

Front 1

Two genera of gram-positive cocci?

Back 1

1. Streptococcus
2. Staphylococcus

Front 2

Four genera of gram-positive bacilli?

Back 2

1. Clostridium
2. Listeria
3. Bacillus
4. Corynebacterium

Front 3

Which gram-positive bacilli are spore-forming?

Back 3

1. Clostridium
2. Bacillus

Front 4

Which gram-positive cocci are catalase positive?

Back 4

Staphylococcus

Front 5

Which gram-positive cocci are coagulase positive?

Back 5

Staphylococcus aureus

Front 6

Streptococci that typically show alpha/green hemolysis?

Back 6

Streptococcus pneumoniae and viridians group (mutans)

Front 7

Streptococci that typically show beta/clear hemolysis?

Back 7

Group A (pyogenes) and group B (agalactiae)

Front 8

Streptococci that typically show gamma/no hemolysis?

Back 8

Group D (enterococcus and peptostreptococcus)

Front 9

How are S. pneumoniae and viridians streptococci differentiated in the laboratory?

Back 9

S. pneumo is bile soluble and optochin sensitive

Front 10

How can capsulated S. pneumo bugs be detected in the laboratory?

Back 10

Quellung positive (capsule swells when antisera is added)

Front 11

What determines the Lancefield grouping of streptococci?

Back 11

C-carbohydrate in the bacterial cell wall

Front 12

How are groups A and B differentiated in the laboratory?

Back 12

Group A is bacitracin sensitive

Front 13

How are spores from gram-positive rods killed?

Back 13

Autoclave (spores are resistant to heat and most chemicals)

Front 14

Three pathogenic gram-negative cocci?

Back 14

1. Neisseria meningitides
2. Neisseria gonorrhea
3. Moraxella catarrhalis

Front 15

Six gram-negative coccobacilli?

Back 15

1. Haemophilus influenzae
2. Pasteurella
3. Brucella
4. Bordetella pertussis
5. Francisella
6. Legionella

Front 16

Three clinically important gram-negative rods that are typically lactose fermenting?

Back 16

1. Enterobacter
2. Escherichia coli
3. Klebsiella (all implicated in UTIs)

Front 17

Two obligate intracellular organisms?

Back 17

1. Chlamydia (steals ATP from host)
2. Rickettsia (lacks CoA and NAD->can't produce own ATP)

Front 18

Four obligate aerobes?

Back 18

1. Nocardia
2. Pseudomonas
3. Mycobacterium tuberculosis
4. Bacillus

Front 19

Three obligate anaerobes?

Back 19

1. Clostridium
2. Bacteroides
3. Actinomyces (no catalase and/or superoxide dismutase->susceptible to oxidative damage)
How are the pathogenic Neisseria species differentiated in the laboratory?

Front 20

How can Pseudomonas be rapidly differentiated from many lactose nonfermenters in the laboratory?

Back 20

Pseudomonas is oxidase positive.

Front 21

Culture requirements of Corynebacterium diptheriae?

Back 21

Tellurite agar or Loeffler media

Front 22

Culture requirements of Bordetella pertussis?

Back 22

Bordet-Gengou potato blood agar

Front 23

Culture requirements of Neisseria gonorrhoea?

Back 23

Thayer-Martin (VCN-Vancomycin, Colistin, Nystatin) and a selective medium

Front 24

Culture requirements of Legionella pneumophila?

Back 24

Charcoal yeast agar with iron and L-cysteine

Front 25

Culture requirements of Mycoplasma pneumoniae?

Back 25

Eaton agar

Front 26

Culture requirements of Mycobacterium tuberculosis?

Back 26

Lowenstein-Jensen agar

Front 27

Culture requirements of Vibrio species?

Back 27

Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) agar

Front 28

Culture requirements of Enterococcus?

Back 28

40% bile and 6.5 % NaCl

Front 29

Culture requirements of Haemophilus influenzae

Back 29

Chocolate agar (contains factor V (NAD) and X (hematin)

Front 30

Culture requirements of lactose fermenters (Kelbsiella, Escherichia, etc.)?

Back 30

MacConkey agar->pink colonies

Front 31

Culture requirements of fungi?

Back 31

Sabouraud agar

Front 32

Which cell membrane structure is unique to gram-positive organisms?

Back 32

Teichoic acid

Front 33

Which molecule, unique to the bacterial cell wall, provides rigid support and resistance against osmotic pressure?

Back 33

Peptidoglycan

Front 34

Which heat stable LPS is found in the cell wall of gram-negative bacteria?

Back 34

Endotoxin

Front 35

Which is the only gram-positive organism with LPS-lipid A?

Back 35

Listeria monocytogenes

Front 36

Name five important systemic effects of endotoxin (particularly lipid A).

Back 36

1. Increased IL-1->fever
2. Increased Tissue Necrosis Factor (TNF)->hemorrhagic tissue death
3. Increased nitric oxide->hypotension and shock
4. Activation of alternate complement pathway->increased C3a (edema) and C5a (PMN chemotaxis)
5. Activation of factor XII->coagulation cascade->DIC

Front 37

Which has a higher toxicity, endotoxins or exotoxins?

Back 37

Exotoxins: fatal dose on the order of 1 microgram (vs hundreds of micrograms for endotoxins)

Front 38

Name the mechanism of DNA transfer:
DNA is taken up directly from the environment by competent cells...

Back 38

Transformation (can occur in eukaryotic cells, too)
Medically important natural transformers:
HHSNG (Here, Have Some New Genes)
H. pylori
H. influenzae
S. pneumoniae
N. gonorrhoea

Front 39

Name the mechanism of DNA transfer:
Plasmid or chromosomal DNA transferred from one bacterium to another via cell-to-cell contact...

Back 39

Conjugation

Front 40

Name the mechanism of DNA transfer:
DNA transferred by a virus from one cell to another; can be generalized or specialized...

Back 40

Transduction

Front 41

Name the mechanism of DNA transfer:
DNA segments able to excise and reincorporate into different locations...

Back 41

Transposons