FA - Micro - Basic Bacteriology (2016)

Question 1

Outer membrane of Gram(-):

Answer 1

1. Endotoxin: Lipid A induces TNF+IL-1/ O polysaccharide component antigenic.
2. Most OMPs are antigenic.
3. Porins: Transport across outer membrane.

Question 2

1st-line lab test in bacterial identification:

Answer 2

GRAM STAIN.

Question 3

Gram stain - Bacteria with THICK PEPTIDOGLYCAN LAYER retain …?

Answer 3

CRYSTAL VIOLET DYE (Gram(+)).

Question 4

Gram stain - Bacteria with THIN PEPTIDOGLYCAN layer turn …?

Answer 4

RED or PINK (Gram(-)) WITH COUNTERSTAIN.

Question 5

Chlamydia lack classic peptidoglycan because of …?

Answer 5

DECREASED MURAMIC ACID.

Question 6

Ziehl-Neelsen stain (carbol fuchsin) - Alternative:

Answer 6

AURAMINE-RHODAMINE STAIN for screening = INEXPENSIVE, more sensitive, but LESS specific.

Question 7

Fluorescent antibody stain - Used to identify …?

Answer 7

Many BACTERIA + VIRUSES.

Question 8

Example of fluorescent antibody stain:

Answer 8

FTA-ABS FOR CONFIRMING SYPHILIS.

Question 9

Properties of growth media:

Answer 9

1. Selective media.
2. Indicator (differential) media.
   - -> The SAME type of media can possess BOTH (or NEITHER) of these properties.

Question 10

Selective media:

Answer 10

Favors the growth of particular organism while preventing growth of other organisms.
(eg Thayer-Martin).

Question 11

Indicator (differential) media:

Answer 11

Yields a color change in response to be the metabolism of certain organisms.
–> MacConkey agar contains a pH indicator; a lactose fermenter like E.coli will convert lactose to acidic metabolites –> Color change.

Question 12

Special culture requirements - E.coli:

Answer 12

Eosin-Methylene blue (EMB) agar –> Colonies with green metallic sheen.

Question 13

What serves as an antigen in vaccines?

Answer 13

Capsular polysaccharides + Protein conjugate.

Question 14

Asplenics have …?

Answer 14

DECREASED OPSONIZING ABILITY and thus INCREASED RISK for severe infections.
–> Give S.pneumo + H.flu + N.meningitidis vaccines.

Question 15

Encapsulated bacteria vaccines:

Answer 15

Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein, enhancing immunogenicity by promoting T-cell activation and subsequent class switching.

Question 16

Encapsulated bacteria vaccines - A polysaccharide antigen alone cannot …?

Answer 16

BE PRESENTED TO T CELLS.

Question 17

Pneumococcal vaccine:

Answer 17

1. PCV = Pneumococcal conjugate vaccine, ie, Prevnar.

2. PPSV = Pneumococcal polysaccharide vaccine with no conjugated protein, ie, Pneumovax.

Question 18

H.flu type B - Vaccine:

Answer 18

CONJUGATE VACCINE.

Question 19

Meningococcal vaccine:

Answer 19

CONJUGATE VACCINE.

Question 20

Catalase-positive organisms - Catalase degrades …?

Answer 20

H2O2 into H2O + Bubbles of O2 –> Before it can be converted to microbicidal products by the enzyme MPO.

Question 21

In vivo biofilm-producing bacteria:

Answer 21

1. S.epidermidis.
2. Viridans strep = S.mutans + S.sanguinis.
3. P.aeruginosa.
4. Nontypeable (unencapsulated) H.influenza.

Question 22

Biofim of S.epi:

Answer 22

1. Catheter.

2. Prosthetic device infections.

Question 23

Biofilm of Viridans strep (S.mutans, S.sanguinis):

Answer 23

1. Dental plaques.

2. Infective endocarditis.

Question 24

Biofilm of P.aeruginosa:

Answer 24

1. Respiratory tree colonization in CF patients.

2. Contact lens-associated keratitis.

Question 25

Biofilm of Nontypeable (unencapsulated) H.influenza:

Answer 25

OTITIS MEDIA

Question 26

Protein M - Shares …?

Answer 26

Similar epitopes to human cellular proteins (molecular mimicry).
–> POSSIBLY, underlies the autoimmune response seen in acute rheumatic fever.

Question 27

Type III secretion system - Also known as …?

Answer 27

“Injectisome”.

Question 28

Type III secretion system - What is it?

Answer 28

Needle-like protein appendage facilitating direct delivery of toxins from certain gram(-) bacteria to eukaryotic host cell.

1. Pseudomonas.
2. Salmonella.
3. Shigella.
4. E.coli.

Question 29

Bacterial genetics - Transformation - DNA that can be used?

Answer 29

ANY DNA CAN BE USED.

Question 30

What inhibits transformation?

Answer 30

Adding DEOXYRIBONUCLEASE to environment will degrade naked DNA in medium –> NO TRANSFORMATION SEEN.

Question 31

Example of TRANSPOSITION:

Answer 31

vanA gene from vancomycin-resistant Enterococcus to S.aureus.

Question 32

Spore-forming bacteria - When?

Answer 32

At the END OF STATIONARY PHASE when nutrients are limited.

Question 33

Spores - Features:

Answer 33

1. Highly resistant to heat and chemicals.
2. Have dipicolinic acid in their core.
3. Have no metabolic activity.
4. Must autoclave to potentially kill spores (as is done to surgical equipment) by STEAMING AT 121C for 15min.

Question 34

AB toxin - Examples:

Answer 34

1. Diphtheria toxin.
2. Exotoxin A.
3. Shiga toxin (ST).
4. Shiga-like toxin (SLT).
5. Heat-labile toxin (LT).
6. Heat-stable toxin (ST).
7. Edema toxin.
8. Cholera toxin.
9. Pertussis toxin.
10. Tetanospasmin.
11. Botulinum toxin.

Question 35

AB toxin is a 2-component toxin. Exception?

Answer 35

3-Component toxin for anthrax.

Question 36

A is for …

B is for …?

Answer 36

B = Enabling BINDING + triggering uptake (endocytosis).
A = Active A component.

Question 37

The active A components of the AB toxin are usually …?

Answer 37

ADP ribosyltransferases.

Question 38

Endotoxin - LPS found in …?

Answer 38

Outer membrane of gram(-) bacteria (both cocci + rods).

Question 39

Endotoxin - LPS composed of …?

Answer 39

1. O antigen.
2. Core polysaccharide.
3. Lipid A (the toxic component).

Question 40

Endotoxin is released upon …?

Answer 40

Cell lysis or by living vells by blebs detaching from outer surface membrane (vs exotoxin, which is actively secreted).

Question 41

Bacterial structures - Specialized structures - Spore - FUNCTION:

Answer 41

SURVIVAL - Resist:

1. Dehydration.
2. Heat.
3. Chemicals.