Lecture 6: Growth Control

Question 1

What methods are available to control microbial growth?

Answer 1

Sterilization: Kill all microbes

Disinfection: Inhibit growth on inanimate surface

Antisepsis: Inhibit growth on living tissue

Question 2

What are the methods of sterilization?

Answer 2

Heat, Radiation, Filters

Question 3

What is the heat sterilization?

Answer 3

Denatures macromolecules making them lose structure/function

• Decimal Reduction Time: 10-fold reduction
• Thermal death time: Time to KILL ALL microbes

Question 4

What equipment will you use for heat sterilization?

Answer 4

Autoclave

• Up to 121 degrees Celsius
• Uses steam to get endospores to hatch (endospores resistant to 150 degrees celsius)

Question 5

What method is used for heat growth control?

Answer 5

Pasteurization
-Rapid heating/cooling

Does not KILL ALL microbes but REDUCES number

Question 6

What are the types of radiation sterilization?

Answer 6

UV Radiation
-mutates DNA

Ionizing Radiation
-Radicals tear proteins/lipids apart

Question 7

What is UV radiation sterilization?

Answer 7

Expose to UV waves

Advantage: Practical and Safer
Disadvantage: Sterilize surface only

Question 8

What is Ionizing radiation sterilization?

Answer 8

Expose to Electromagnetic radiation

Advantage: Cold sterilization penetrate solid/liquid
Disadvantage: DANGEROUS

Question 9

What is filter sterilization?

Answer 9

Sterilization without heat that uses filters

Advantage: Safe and useful for heat sensitive microbe
Disadvantage: Cant use on solids

Question 10

What are Depth Filters?

Answer 10

Filter sterilization uses glass fibers to make 3d spiderweb

Question 11

What are membrane and nucleopore filters?

Answer 11

Filter sterilization uses strong polymers to trap microbe

Nucleopore filters use polycarbonate film with specific and controllable pore sizes to trap microbe

Question 12

What is a chemical that kills or inhibits microbial growth?

Answer 12

Antimicrobial agent

Question 13

What are the classifications of antimicrobial agents?

Answer 13

Target Organism
-Bacterio-, Fungi-, Viri-

Action

• static= stop growth (plateau total+viable cell count)
• cidal= kills cells (decrease viable cell count)
• lytic=kills+lyses cells (decrease total cell count)

Question 14

What is targeted by bacteriostatic, bateriocidal, and bateriolytic antimicrobial agents?

Answer 14

Bacteriostatic-ribosomes, prevent protein synthesis

Bacteriocidal-bins specific cellular targets

Bacteriolytic-cell wall+membranes=lysis

Question 15

What is the Minimum Inhibitory Concentration (MIC)?

Answer 15

Amount of chemical needed to inhibit growth

Question 16

What kinds of antimicrobial agents would you use on inanimate surfaces and external body surfaces?

Answer 16

Inanimate surfaces
-Sterilants and Disinfectants

External Body Surfaces
-Antiseptics (germicides)

Question 17

What do sterilants do? What would you use them for?

Answer 17

KILL ALL microbial cells and endospores

Use on heat-sensitive equipment

Question 18

What do Disinfectants do? What would you use them for?

Answer 18

Kill ALL microbial cell but NOT endospores

Used on home surfaces

Question 19

What do Antiseptics (germicides) do? What would you use them for?

Answer 19

Kill Microbial cells or inhibit growth (non-toxic)

Used in Handwashing soaps

Question 20

What are the different structural classes of antimicrobial drugs which kill and inhibit microbial growth INSIDE the body?

Answer 20

B-Lactam = 52%
Fluoroquinolones = 24%
Macrolide = 20%
Other = 4%

Question 21

What class of drug is penicillin?

Answer 21

B-Lactam

Question 22

What are some of the targets of antimicrobial drugs?

Answer 22

DNA translation

RNA Elongation

DNA Gyrase (only in bacteria)

Folic Acid Synthesis

Cell Wall Synthesis

Question 23

Who is Paul Ehrlich and what is selective toxicity?

Answer 23

Paul Ehrlich responsible for magic bullet approach to antimicrobial drugs

Selective toxicity is the goal of antimicrobial drugs
-inhibit or kill microbial pathogens and don’t harm human

Question 24

What are Sulfa antimicrobial drugs? What is its mechanism and spectrum?

Answer 24

Synthetic Antimicrobial Drug

• Mechanism: Interfere with folic acid synthesis (DNA)
• Spectrum: Broad, Gram + and Gram -

Question 25

What are QUINILONES antimicrobial drugs? What is its mechanism and spectrum?

Answer 25

Synthetic Antimicrobial Drug

• Mechanism: Interfere with DNA Gyrase
• Spectrum: Broad, Gram + and Gram -

Question 26

What are ISONIAZID antimicrobial drugs? What is its mechanism and spectrum?

Answer 26

Synthetic Antimicrobial Drug

• Mechanism: Interfere with Mycolic Acid
• Spectrum: Mycobacterium (Broad)

Mycolic Acid makes waxy cell wall, hard for other drugs to penetrate

Question 27

What are the types of Natural antimicrobial drugs?

Answer 27

Antibiotics

• Produced by microbes
• Many know, few useful (selective toxicity)

Semi-Synthetic
-Artifically modified antibiotics

Question 28

What are B-Lactam antibiotics?

Answer 28

Semi-Synthetic Antibiotic, Example: Penicillin

• Mechanism: Interfere w/ cell wall
• Spectrum: Gram +, Gram -. Intracellular (broad)

prevents peptidoglycan synthesis

Question 29

What are Macrolides?

Answer 29

Semisynthetic Antibiotic, Example: Erythromycin

• Mechanism: Interfere with protein synthesis (translation)
• Spectrum: Gram +, Gram -, broad

Question 30

What is the problem with Anti-viral and Anti-Fungal drugs?

Answer 30

Can also affect host cells

Question 31

What is an example of antiviral drug?

Answer 31

Azidothymidine (AZT)

• HIV Treatment
• Resembles nucleotide Thymidine
• prevents reverse transription (RNA->DNA)

Question 32

What are the types of antifungal drugs and what is an example of each?

Answer 32

Topical Drugs
-Surface application

Fungi Specific Drugs
-target specific processes/structures

Ergosterol Inhibitors prevent synthesis of this cholestrol found in fungi cytoplasmic membranes