Control of Microbial Growth

Question 1

A chemical or other agent that kills microbes or inhibits their growth.

Answer 1

Antimicrobial

Question 2

An antimicrobial chemical nontoxic enough to be used on skin.

Answer 2

Antiseptic

Question 3

Set of procedures used to help prevent the accidental introduction of unwanted microbes.

Answer 3

Aseptic Technique

Question 4

A chemical or other agent that kills bacteria.

Answer 4

Bactericide

Question 5

Describes a chemical or other agent that stops the growth of bacteria without killing them.

Answer 5

Bacteriostatic

Question 6

A chemical or other agent that kills or inactivates living cells.

Answer 6

Biocide

Question 7

A chemical that destroys many, nut not all, microbes on an inanimate surface or object.

Answer 7

Disinfectant

Question 8

A brief heat treatment that reduces the number of spoilage microorganisms and destroys pathogens in the product; a related term, ____ ________, refers to physical treatments that have the same outcome without using heat.

Answer 8

Pasteurization, cold pasteurization

Question 9

A treatment that inhibits Microbial Growth to delay spoilage.

Answer 9

Preservation

Question 10

Describes a product that is free of all viable microbes, including endospores and viruses.

Answer 10

Sterile

Question 11

The destruction or removal of all microbes on or from a product.

Answer 11

Sterilization

Question 12

Who introduced the first surgical antiseptic?

Answer 12

Joseph Lister (1879)
Remember Listerine is named after him.

Question 13

What does the term “sterile” not considered to be free of?

Answer 13

Prions

Question 14

What are the risk of chlorine use to disinfect water in treatment facilities?

Answer 14

The production of disinfection by-products (DBPs). Which are known to have long-term health risks, including kidney, liver, central nervous system damage, and cancer.

Question 15

How is sterilization different from disinfection? (MicroAssessment 5.1)

Answer 15

Sterilization is a higher level of microbial control than disinfection. Sterilization removes or destroys ALL viable microbial life, disinfection selectively removes or destroys most clinically important microbial life.

Question 16

Why is it important for a microbiology laboratory technician to use aseptic technique? (Micro Assessment 5.1)

Answer 16

Cross contamination can make an experiment useless.
Microbial escape when working with dangerous microbes is also a real risk.

Question 17

How would a company that makes lipsticks determine if a batch had been contaminated by microorganisms during the production process? (critical thinking, MicroAssessment 5.1)

Answer 17

This is a critical thinking question and does not have a direct answer.

Question 18

Name an ideal antimicrobial procedure that is multipurpose and non-toxic.

Answer 18

There is none. All antimicrobial procedures have drawbacks.

Question 19

What are genera of bacteria have the most resistance endospores typically encountered?

Answer 19

Bacillus, Clostridium, and related genera.

Question 20

Unlike endospores, how can protozoan cysts and oocysts be destroyed?

Answer 20

Heat: Giardia lamblia and Cryptosporidium hominis are easily destroyed by boiling.

Question 21

How are Mycobacterium species best controlled and why?

Answer 21

The hydrophobic cell walls of mycobacterium make them resistant to many chemical treatments. So strong, toxic chemicals are required to disinfect M. tuberculosis.

Question 22

Why is poliovirus resistant to disinfectants?

Answer 22

It lacks a lipid envelope, making it relatively resistant.

Question 23

How long would it take for an antimicrobial treatment to kill a 10^6 colony with a D value of 1 minute? With a D value of 5 minutes?

Answer 23

6 minutes
30 minutes

Question 24

Describe 3 groups of microbes that are resistant to certain chemical treatments. (there are many) (MicroAssessment 5.2)

Answer 24

1. Bacillus species have strong endospores.
2. Clostridium species also have strong endospores.
3. Mycobacterium species are hydrophobic and require very strong chemicals to disinfect
4. Poliovirus has no lipid envelope making them resistant to disinfectants.
5. Pseudomonas species are common but can actually survive and grow in some disinfectants.

Question 25

Why must critical instruments be sterile, whereas small numbers of endospores are permitted on semicritical instruments? (MicroAssessment 5.2)

Answer 25

Critical instruments come into direct contact with with body tissues that don’t have a normal microbiota.
Semicritical instruments, like endoscopes, come into contact with mucus membranes that do have a normal microbiota.

Question 26

Is it safe to say that if all bacterial endospores have been killed, then all other medically important microorganisms also have been killed? (Critical Thinking MicroAssessment 5.2)

Answer 26

Generally, yes. But it depends on how. If both extreme heat and chemical measures were used, then most likely yes. If only chemicals were used, depending on which chemicals, it is possible that bacteria with very thick casings, grease, or other inorganic compounds blocking chemical access may prevent sterilization. Then again, it could also be argued that endospores could be protected, incidentally, by the same measures.