Block 6 Review

Question 1

Virulence Encoded on Plasmids

Answer 1

= autonomous and replicate outside of the chromosome
“PASTE”
Pestis: Yersinia pestis adherence and invasion
Anthrax: pOX1 toxins, pOX2 capsule
Shigella: invasion
Tetani toxin
ETEC: adhesions and toxins and E. coli hemolysis
*often encode abx resistance too!

Question 2

Transposons

Answer 2

=insertion sequences flanking carious genes and recombinases/transposases

• Step pyrogenes - exotoxins
• Staph aureus - STSS
• also responsible for bacterial resistance

Question 3

Pathogenicity Islands

Answer 3

=large regions of DNA usually found in tRNA operons 
H. pylori
UG E. coli 
EHEC 
EPEC

Question 4

Three types of resistance mechanisms

Answer 4

1) natural resistance
2) acquired resistance
3) mutational resistance

Question 5

Natural Resistance

Answer 5

• gram-ve membrane - inaccessibility of target
• multi-drug efflux pumps (TYPE 1)
• drug inactivation (proteases)

Question 6

Acquired Resistance

Answer 6

• plasmids/transposons
• conjugation
• target site modification (VRE)
• efflux pumps (specific and non-specific)
• drug inactivation/destruction (B-lactamases)

Question 7

Mutational Resistance

Answer 7

• changes in the chromosome
• target site modification (PBS changes)
• metabolic bypass (TMP resistance)
• de-repression of efflux pump

Question 8

Bacterial Energy Generation

Answer 8

1) Group Translocation - substrates (sugars) transported into cell by PTS (phosphotransferase system) and phosphorylated.
2) Glycolysis (NAD->NADH + H)
3) fermentation = alcohols or acids
or
4) respiration = TCA cycle and ETC

Question 9

Catalase and Superoxide Dismutase

Answer 9

protect bacteria from insult by radical oxygen species.

Question 10

Bacterial Growth

Answer 10

1) lag
2) log
3) stationary (nutrient limits slow growth, spore formation)
4) death phase
- impacts type of Abx rx and the effectiveness

Question 11

Bacterial Secretion Systems

Answer 11

1- ATP used, non-specific, pumps out abx
2- general secretory pathway, common
3- delivery of toxins to eukaryotic cells!!!
4- ATP-dependent transporter- important for transfer of DNA during conjugation.

Question 12

MIC

Answer 12

minimal inhibitory concentration- lowest abx needed to stop bacterial growth

Question 13

MBC

Answer 13

minimal bactericidal concentration- lowest abx concentration where no growth is seen after removal of abx.

Question 14

Disk diffusion assy

Answer 14

Kirby Bauer assay- provides clear zone based on concentration of abx gradient.

Question 15

Bacteriophage

Answer 15

Lysogenic (specialized) - integrate into chromosome
Lytic (generalized) - phage particles released by lysis of cell.
- Staph toxins
- C. dipheria toxin
- Strep pyogenes toxin
- EHEC shiga-like toxin
- V. Cholera toxin

Question 16

SCCmec

Answer 16

Staphylococcal chromosomal cassette

• MRSA methicillin resistance
• Type IV SSCmec encodes ACME gene that enhance MRSA’s colonization of the skin

Question 17

Urease (+)

Answer 17

HNCK

H.pylori
Nocardia
Crypotcoccus
Klebsiella

Question 18

ADP- ribosylating toxins

Answer 18

Diphtheria toxin (EF-2)
Pseudomona Exotoxin A (EF-2) 
ETEC Heat Labile Toxin (CAMP)
Cholera Toxin (CAMP)
Pertussis Toxin (CAMP)

Question 19

Transformation (naturally “competent”)

Answer 19

S.pneumonia
H.influenza
Nisseria