Lecture 4

Question 1

Culture medias

Answer 1

Selective = favor growth
Differential = Visually distinguish

Question 2

Selective Media

Answer 2

Additives toxic to some bacteria

MacConkey Enteric Media= Prevent growth of gram positive bacteria

Question 3

Differential Media

Answer 3

Differentiate between species based on their appearance on media

Question 4

Blood Agar Media

Answer 4

Shows differences

Hemolytic(produce hemolysin and destroys RBC) vs non-hemolytic

Question 5

Culture Based Diagnostic

Answer 5

Collect , Grow, Identify

Question 6

Antibiotics

Answer 6

Supress or kill bacteria (not fungi or antivirals)

Question 7

Sources of Antibiotics

Answer 7

Soil
Synthetic
Semi synthetic (modified)

Question 8

Selective Toxicity

Answer 8

Kill bacteria without harming host

Question 9

Therapeutic Index (T.I)

Answer 9

= Toxic Dose (to human) / Therapeutic dose (Kills bacteria)

The larger the dose the safer the drug

Question 10

Spectrum of Activity

Answer 10

Narrow = Few
Broad = Many

No drug can be effective against all species of bacteria

Question 11

Bactericidal

Answer 11

Kills bacteria

Question 12

Bacteriostatic

Answer 12

Inhibits growth

Question 13

Quinolones (prokaryotic)

Answer 13

Inactivates DNA gyrase (no super coiling = no dna replication)

Question 14

Rifampin (prokaryotic)

Answer 14

Binds to RNA polymerase = Blocks messenger RNA synthesis

Question 15

Block Protein Synthesis

Answer 15

Bind to the bacterial ribosome to interference with protein synthesis

Eukaryotic cells have different ribosome

Question 16

Inhibition of Metabolic Pathways

Answer 16

Sulfonamide (and Sulfa drugs)

Blocks synthesis of bacterial folic

Similar to PABA, but doesn’t create folic acid

Euc = Get PABA from diet

Question 17

Disrupt Bacterial Cell Membranes

Answer 17

Polymyxins - Bind to Phospholipids and becomes part of membrane

Result in loss of membrane function

Last resort due to not being selectively toxic

Usually an external cream

Question 18

Block Peptidoglycan synthesis

Answer 18

Large and diverse group of AB
High Selective toxicity because PG is unique to bacteria

Lactams=
Interfere with enzymes required for PG = Lysis of walls

Requires cell is be active

Question 19

AB in Combo

Answer 19

Avoid Antagonism = Drug blockage

Achieve synergism = Enhanced effect (attack different pathways)

Costly

Question 20

Reaction to AB use

Answer 20

1. Toxicity
2. Allergic reactions (rare), more intolerance
3. Disruption of normal flora

Question 21

Super Infection

Answer 21

Overgrowth of drug-resistant bacteria

Clostridium Difficle (resistant to AB)
 = Causes bacteria