Week 14- controlling microbial growth

Question 1

Describe the following terms as they relate to controlling microbial growth in the environment:

pasteurization

Answer 1

use of heat to remove of pathogenic microorganisms in liquids

Question 2

Describe the following terms as they relate to controlling microbial growth in the environment:

degerming

Answer 2

physical removal of microorganisms

Question 3

Describe the following terms as they relate to controlling microbial growth in the environment:

sterilization

Answer 3

Should remove all microorganisms

like spores, endospores, cysts

Question 4

Describe the following terms as they relate to controlling microbial growth in the environment:

aseptic

Answer 4

an environment that is completely free of microorganisms

Question 5

Describe the following terms as they relate to controlling microbial growth in the environment:

antisepsis

Answer 5

remove all pathogenic microorganisms on human tissue

like e.coli

Question 6

Describe the following terms as they relate to controlling microbial growth in the environment:

disinfection

Answer 6

Remove all pathogenic microorganisms on objects

like ecoli

Question 7

Describe the following terms as they relate to controlling microbial growth in the environment:

sanitation

Answer 7

disinfectant at public health standard

Question 8

What is the difference between an agent that is “cidal” versus “static” (i.e. bactericidal versus
bacteriostatic agent or fungicidal versus fungistatic

Answer 8

Static- will slow down mo

cidal- will kill mo

Question 9

Define microbial death.

Answer 9

A microorganisms inability to reproduce under ideal conditions

Question 10

What are the two general methods of controlling microbial growth?

Answer 10

Physical- heat, refrigeration/freezing, desiccation, osmotic pressure, radiation

chemical-

Question 11

What specific structures/components of microbes do the modes of action of antimicrobial agents
affect?
How does the damage to each of these structures (from question above) affect the microbe adversely?

Answer 11

Cell wall-cells burst

cell membrane-contents leak out

viral envelope-disable attachment and prevent replication

protein-denature proteins-cause death

nucleic acids-halt protein synthesis through action on rna

Question 12

Describe the main factors that need to be considered when choosing an antimicrobial agent/method and
how they affect the efficacy of an agent/method

Answer 12

Site

organic materials-ex-feces vomit and tissue
typically remove organic material before using antimicrobial agent

Question 13

How can you adjust time to affect the effectiveness of antimicrobial methods/agents

Answer 13

some agents take longer times to be more effective

time needed to sterilize volume of liquid

(like 30 sec vs 5 min for a spray)

Question 14

Which types of microbes are more susceptible to antimicrobial agents

Answer 14

enveloped virus

gram positive/gram negative

Question 15

Which types of microbes are more resistant to antimicrobial agents

Answer 15

Bacteria endospores

cysts

protozoa

Tuberculosis

Question 16

High level germicide

Answer 16

used on mo that are hard to kill

resistant

Question 17

intermediate level germicide

Answer 17

used on some mo that are intermediate to kill

Question 18

low level germicide

Answer 18

Used on Mo that are easy to kill

susceptible

Question 19

How does high heat affect microbes?

Answer 19

denatures proteins

disrupts with structure and function of nucleic acids

Question 20

What is moist heat used for and give several examples.

Answer 20

Used to disinfect, sanitize, sterilize, and pasteurize

Denatures proteins and destroys cytoplasmic membran

more affective then dry heat

Boiling, Autoclaving, Pasteurization, Ultrahigh-temperature sterilization

Question 21

How are time and heat related when determining effectiveness of a heat method?

Answer 21

Typically with increased heat—time using the method can decrease

time needed to sterilize at a set temperature

Question 22

When would you use dry heat?

Answer 22

powders or incineration of biological tissue

Question 23

How do refrigeration and freezing harm microbes?

Answer 23

will slow down metabolism

ice crystal could form in freezing and kill

Question 24

How does filtration work? What is it used for?

Answer 24

will filter mo because of pores-

like liquids that are heat sensitive and air quality

pores size will determine what size of mo can filter through

Question 25

How does osmotic pressure work to kill microbes and what is it used for?

Answer 25

water follows solutes/salts

will put m.o in a hypertonic solution(more solute outside then inside) and can kill mo because water follows the salts out

Question 26

How does radiation harm microbes?

Answer 26

damage and denature nucleic acids

Question 27

What are the 2 types of radiation used?

Answer 27

ionizing (X-rays)

non ionizing (uv light)

Question 28

Name 2 uses for radiation

Answer 28

sterilization of medical equipment/ preservation of food

disinfect surfaces and transparent fluids

Question 29

Describe the use-dilution test

Answer 29

-metal cylinders are dipped into broth culture of bacteria

-Contaminated cylinder immersed into dilution of disinfectant

-Cylinders removed, washed, and placed into tube of
medium

-Most effective agents entirely prevent growth at highest dilution

Question 30

Describe how resistant microbes can develop due to excessive use of antiseptics and disinfectants.

Answer 30

overuse of antimicrobial methods- weaker killed and stronger survive

Question 31

Surfactants

Answer 31

Soaps and detergents. Soaps decrease surface tension and destroy cell membranes. Detergents are
positively charged organic surfactants—quaternary ammonium compounds are examples which are
antimicrobial

Question 32

Oxidizing agents

Answer 32

high level disinfectants and antiseptics that release oxygen radicals and work well against anaerobes; includes peroxides, ozone and peracetic acid

Question 33

Alcohol

Answer 33

Isopropanol or drinking alcohol (ethanol). Evaporate rapidly – both advantageous and disadvantageous. Can be used in tinctures (other antimicrobial agents dissolved in alcohol). Swabbing of skin with 70% ethanol prior to injection. More effective than soap

Question 34

Heavy Metals

Answer 34

Low-level bacteriostatic and fungistatic agents, control algae in water; arsenic, zinc, mercury, silver,
and copper; silver used in creams to treat burns. Thimerosal used to preserve vaccines

Question 35

Phenols

Answer 35

Intermediate to low level. Effective in presence of organic matter and remain active for prolonged
time. Commonly used in health care settings, labs, and homes (Pine and clove oils, Lysol, triclosan)

Question 36

Halogens

Answer 36

Iodine tablets, iodophores (Betadine®), chlorine treatment of drinking water, bleach, chloramines in wound dressings, and bromine disinfection of hot tubs

Question 37

Gaseous agents

Answer 37

used for sterilization in hospital settings and equipment that are heat and water sensitive but can be explosive and highly poisonous; denature proteins and DNA; ethylene oxide is commonly used—used in chambers in hospitals. Can be extremely hazardous to people using them

Question 38

Aldehydes

Answer 38

Glutaraldehyde both disinfects (short exposure) and sterilizes (long exposure). Formalin used in embalming and disinfection of rooms and surgical or dental instruments.