Control of Growth

Question 1

Name some physical methods to remove, destroy, or inhibit microbial growth.

Answer 1

Physical control methods include the use of heat, cold, irradiation, and mechanical removal. An example is the use of heat to sterilize an inoculating loop.

Question 2

Name some chemical methods to remove, destroy, or inhibit microbial growth.

Answer 2

Chemical control methods involve the use of antimicrobial chemicals like alcohol or bleach. Some are appropriate for skin, like alcohol, while bleach would not be safe on human skin but could be used on inanimate objects.

Question 3

Briefly describe sterile or sterilization.

Answer 3

Sterilization is the destruction of ALL microbial life, including viruses and endospores. Either something is sterile or it is not. There is no in-between.

Question 4

Briefly describe when a sterile environment is not needed. Name the terms that describe two techniques less severe than sterilization.

Answer 4

When reducing the number of harmful microbes to a safe level can be sufficient. Disinfection or antisepsis creates a safe environment.

Question 5

Contrast disinfection and antisepsis.

Answer 5

The distinction between them has to do with whether the material involved is an object or body tissues. Antiseptics are safe to use on tissues; disinfectants are not.

Question 6

All control methods target a specific part of a microbe. Give some examples.

Answer 6

Targets include the cell wall, cell membrane, nucleic acid and protein synthesis, proteins, and specific metabolic pathways.

Question 7

Identify some microbes that have the highest levels of resistance to control methods.

Answer 7

prions, bacterial endospores

Question 8

Identify some microbes that have some resistance to control methods.

Answer 8

protozoan cysts, naked viruses, some (resistant) bacteria

Question 9

List some disinfectants mentioned in the labs.

Answer 9

Aldehydes, Chlorine compounds, phenolics, quaternary ammonium detergents

Question 10

Briefly describe aldehydes as disinfectants.

Answer 10

Aldehydes like formaldehyde have broad-spectrum effects on microbes and are good for use on surfaces.

Question 11

Give an example of chlorine compounds as disinfectants.

Answer 11

Chlorine compounds like bleach are found in many household cleaning products.

Question 12

Give examples of phenolics as disinfectants.

Answer 12

Phenolics like Lysol and Triclosan are also found in many household cleaning products, including antibacterial soap.

Question 13

Briefly describe quaternary ammonium detergents as disinfectants.

Answer 13

Quaternary ammonium detergents are effective in disrupting the membranes of microbes.

Question 14

Briefly define antiseptics.

Answer 14

Antiseptics are chemical compounds safe enough to use on human tissues.

Question 15

Give examples of antiseptics included in the labs.

Answer 15

Examples include alcohols, iodine compounds, silver drops and ointments, and chlorhexidine soaps.

Question 16

Describe some effects of inadequate control methods.

Answer 16

Without adequate control methods, lab results may show contamination, food would spoil more quickly, water and beverages would be undrinkable, and we would have less ability to prevent and treat infectious disease.

Question 17

Describe the diffusion assay technique used to test chemical control of microbial growth.

Answer 17

• Plates will be inoculated to form a bacterial lawn. Different chemicals will be applied to each filter paper disc, which will then be placed on the inoculated plates.
• Regions of no growth around the chemically treated disc will be measured in millimeters. The data on the zones of inhibition can then be used to determine the effectiveness of the chemical agent.

Question 18

After incubation, how does the diffusion assay technique reveal chemical inhibition of growth?

Answer 18

After incubation, clear zones will appear around the discs where the chemical agent was able to inhibit the growth of the inoculated organism.

Question 19

Describe the measurement taken with the diffusion assay techinque.

Answer 19

Measurements are taken from one edge of growth to the direct opposite edge of growth, including the diameter of the disc itself.

Question 20

With the diffusion assay technique, if there is no zone around the disc, how is this recorded?

Answer 20

If no zone appears around the disc, that agent was ineffective against that organism. The zone of inhibition is recorded as zero.

Question 21

Briefly describe antisepsis.

Answer 21

Chemical treatments to kill or inhibit the growth of all vegetative microorganisms on body surfaces.

Question 22

Briefly describe bacterial lawn.

Answer 22

Organisms heavily inoculated on an agar plate will form a uniform growth across the surface of the plate.

Question 23

Briefly describe disinfection.

Answer 23

The destruction of pathogenic nonsporulating microbes or their toxins, usually on inanimate surfaces.

Question 24

Briefly describe Heavy (or dominant) growth.

Answer 24

Descriptor indicating the organism was present in high numbers or in all inoculum regions, dilutions, or concentrations.

Question 25

Briefly describe Intermediate (or moderate) growth.

Answer 25

Descriptor indicating the organism was present in noticeable (medium) numbers or in at least half of the inoculum regions, dilutions, or concentrations.

Question 26

Briefly describe Scant (or scanty) growth

Answer 26

Descriptor indicating the organism was present in low numbers or only in certain inoculum regions, dilutions, or concentrations.

Question 27

Briefly describe Vegetative cell

Answer 27

A metabolically active and growing cell.

Question 28

Briefly describe Zone of Inhibition

Answer 28

Clear zone around a site where chemical agents were able to inhibit the growth of the inoculated organism.

Question 29

What are antibiotics?

Answer 29

Antibiotics are natural compounds produced by microorganisms that can be used to inhibit the growth of other microorganisms.

Question 30

Briefly describe the meaning of antibiotic being synthetic or semi-synthetic.

Answer 30

Some antibiotics are synthetic or semi-synthetic, meaning they are completely or partially synthesized to have similar effects on microbial growth.

Question 31

In the labs, there are three classifications of the strength of effect of an antibiotic on the growth of a particular organism. What are they?

Answer 31

Sensitive
Intermediate
Resistant: Cells can tolerate the drug and grow in its presence.

Question 32

Briefly describe term sensitive as it relates to the effect an antibiotic has on microbial growth.

Answer 32

Cells are affected by the drug and growth is inhibited.

Question 33

Briefly describe term intermediate as it relates to the effect an antibiotic has on microbial growth.

Answer 33

Drug has some effect on the cells (less than sensitive, more than resistant).

Question 34

Briefly describe term resistant as it relates to the effect an antibiotic has on microbial growth.

Answer 34

Cells can tolerate the drug and grow well in its presence.

Question 35

Name or phrase that indicates an antibiotic that works only against a small range of microorganisms.

Answer 35

narrow-spectrum.

Question 36

Name or phrase that indicates an antibiotic that works against a wide range of microbial classes

Answer 36

broad-spectrum.

Question 37

Describe the consequences of administering the wrong antibiotic?

Answer 37

• If the wrong antibiotic is used, it may kill off the harmless bacteria, leaving the pathogens with a greater opportunity to multiply and make the symptoms even worse.
• resistance to antimicrobial drugs has become a major concern. Because of this drug resistance issue, it is very important to choose antimicrobial treatments based on the effectiveness of these agents against specific pathogens.

Question 38

Name the method used in the labs to determine the effectiveness of antibiotics against a specific bacteria.

Answer 38

The Kirby-Bauer test is a commonly used method to determine the effectiveness of several different antibiotics against a particular bacterial agent.

Question 39

For the Kirby-Bauer method, identify and describe the plate media used to grow the sample.

Answer 39

a plate of Mueller-Hinton agar.
* allows for the growth of any microorganism, it does not promote or inhibit the growth of any specific organism.
* It also has an agar concentration that promotes the diffusion of drugs through the medium leading to a larger zone of inhibition.

Question 40

For the Kirby-Bauer method, when is it time to place antimicrobial discs?

Answer 40

Once a lawn of bacteria is created.

Question 41

For the Kirby-Bauer method, describe how antibiotics are applied to the plate.

Answer 41

a dispenser places antimicrobial discs containing different concentrations of specific antibiotics onto the surface of the lawn of bacteria

Question 42

For the Kirby-Bauer method, what is the next step after incubation?

Answer 42

After incubation, the zones of inhibition are measured in millimeters for comparison to determine the susceptibility of the organism to the different antimicrobial drugs used in the test.

Question 43

For the Kirby-Bauer method, what can be said for the largest zone of inhibition?

Answer 43

The largest zone of inhibition is not automatically assumed to be the best. (diffusion of the drugs from each disc will vary which would impact the results.)

Question 44

For the Kirby-Bauer method, how are the results evaluated?

Answer 44

Charts are available to compare the measured zone of inhibition with its effectiveness. Sizes are given for susceptible and resistant. If the result is in between then the effect is described as intermediate.

Question 45

Briefly describe antimicrobial drug.

Answer 45

Compounds that can be used to inhibit or destroy microbial growth.