Infections - Lecture 1

Question 1

What are the typical features of a Gram Positive bacteria?

Answer 1

1) simple structure
2) 50% peptidoglycan
3) 40-45% acidic polymer
4) 5-10% proteins and polysaccharides

Question 2

What are the features of a gram negative bacteria?

Answer 2

1) more complex
2) periplasmic space
3) peptidoglycan layer 5%
4) OUTER MEMBRANE
5) complex polysaccharides

Question 3

Gram positive contain high levels of peptidoglycan in the cell wall and DON’T stain PINK with gram staining technique. True or false?

Answer 3

True

Gram positive don’t stain pink and have lots of peptidoglycan (50%)

Question 4

Name some gram positive cocci shapes and examples

Answer 4

Cocci can be either clusters or chains/pairs

With cocci clusters- staphylococci
Cocci chains/pairs - streptococci (which can be heamolytic or non-haemolytic)

Question 5

Name the shape of gram positive bacilli and give examples

Answer 5

Shape; sporeforming, non-sporeforming, branching, acid fast

Examples of;

1. Sporeforming- aerobic (bacillus), anaerobic (clostridium - c.difficile, c.perfingens)
2. Non-sporeforming - molite (listeria), non-moline (lactobacilli)
3. Acid fast - mycobacterium (m. Tuberculosis)

Question 6

Gram negative bacteria contain high levels of peptidoglycan in cell walls and stains pink with gram staining technique. True of false?

Answer 6

False.
Gram negative has low levels of peptidoglycan (5%). (Gram +ve has high levels of peptidoglycan)
But yes, it does stain pink

Question 7

Give the type of cocci and bacilli with examples of gram negative bacteria

Answer 7

Cocci - Neisseria - N. meningitis; Moraxella - N. caterehalis

Bacilli - Shortrods - acinobacter; brucella, Boardatella
Long rods - enterobacteria
Curved/spiral rods - helicobacter, vibrio

Question 8

Mechanism of action of antibiotics:
CELL WALL SYNTHESIS
Give examples of antibiotics that follow this mechanism

Answer 8

Penicillin 
Cephalosporins 
Vancomycin 
Beta-lactamase inhibitors 
Carbapenems 
Aztreonam
Bacitracin

Question 9

Name antibiotics that follow the mechanism of:

PROTEIN SYNTHESIS

Answer 9

1. 30s subunit - ahminoglycosides, tetracycline, glycyclcyclines (tigecycline)
2. 50s subunit -
   Macrolides, chloramphenicol, clindamycin,
3. 70s complex -
   Oxazolidinones (linezolid)

Question 10

MoA of antibiotics:

DNA SYNTHESIS

Answer 10

Fluroquinolones

Metronidazole

Question 11

MoA of antibiotics

RNA SYNTHESIS

Answer 11

Rifampicin

Macrocycyclines (fidaxomicin) [this is a new drug which is used to treat C.difficile]

Question 12

MoA of antibiotics

FOLIC ACID SYNTHESIS

Answer 12

Sulfonamides

Trimethoprim

Question 13

MoA of antibiotics

CELL MEMBRANE FUNCTION

Answer 13

Polymyxins

Daptomycin

Question 14

MoA of antibiotics

MYCROLIC ACID SYNTHESIS

Answer 14

Isoniazid (mycobacteria)

Question 15

Can you name a few new mellinelial drugs?

Answer 15

1. Linezolid (class - oxazolidonone gram +ve)
2. Ertapenem (carbapenem gram +ve/-ve)
3. Tedizolid (oxazolidonone gram +ve)
4. Doripenem (carbapebem gram +ve/-ve)

Question 16

Name the 3 mechanisms of resistance

Answer 16

1. Antibiotic degrading enzyme
2. Antibiotic altering enzyme
3. Antibiotic efflux pump

(Changes in MEMBRANE permeability to antibiotics, alteration of bacterial proteins that are antimicrobial targets, enzymatic degradation of antibacterial drugs)

Question 17

What is natural resistance?

Answer 17

1. Bacteria have a selective advantage
2. You then take antibiotics and everything dies off, but some survive
3. These survivors then multiply and so when you use the same antibiotic it’s no longer effective as they have become resistant

Question 18

What is acquired resistance?

Answer 18

This is where you gain DNA material via direct contact, through the environment

Question 19

How is there resistance to penicillin and cephalosporin

Answer 19

Because the bacteria contains beta lactamase which breaks down the beta lactam ring in the penicillin

Question 20

What are the methods being developed to overcome beta lactamase antibiotics?

Answer 20

Via

1. Development of new antibiotics that are stable to beta lactamase attack
2. Coadministration of beta lactamase inhibitors with beta lactamase drugs

Question 21

How does resistance to methicillin, which is stable to gram +ve beta lactamase, occur?

Answer 21

Through alteration of an antibiotic target protein, penicillin binding protein 2.

Question 22

Production of antibiotic modifying enzymes and SYNTHESIS of antibiotic insensitive bacterial targets are primary resistance mechanisms for:

Answer 22

Trimethoprim 
Sulfonamides 
Amino-glycosides 
Chloramphenicol 
Quinolones

Question 23

Reduced antibiotic penetration is a resistance mechanism for

Answer 23

Beta lactam drugs
Amino-glycosides
Chloramphenicol
Quinolones