Question 1

Alcohols are more effective at inactivating enveloped viruses than naked viruses.

Accepted Answer

Enveloped viruses have a lipid envelope that is vulnerable to disruption by alcohols, while naked viruses do not have this vulnerability. Therefore, alcohols are more effective at inactivating enveloped viruses.

Question 2

Chlorine and ethylene oxide are sterilizing gases.

Accepted Answer

This is true, chlorine and ethylene oxide are commonly used as sterilizing agents in medical and industrial settings.

Question 3

Which of the following is an advantage to using phenolics as antimicrobial agents?

Accepted Answer

Phenolics maintain their antimicrobial activity in the presence of organic matter, making them effective in situations where other agents might be inactivated. This characteristic is particularly useful in environments where blood, vomit, or feces are present, as these substances can deactivate some other disinfectants.

Question 4

Your aim is to sterilize prosthetic devices like heart valves and arti?cial joint structures before being used in the patient. Considering where they will be placed and the probable composition of the devices, what would be the best chemical to use?

Accepted Answer

Quaternary ammonium compounds are commonly used for sterilizing medical devices because they are effective against a wide range of microorganisms and are relatively non-toxic to human cells.

Question 5

Which of the following represents microbial control by osmotic pressure?

Accepted Answer

Salting meats creates a hypertonic environment, drawing water out of microbial cells through osmosis, thus inhibiting their growth.

Question 6

Chlorine compounds remain stable and effective in the presence of excess organic matter.

Accepted Answer

Chlorine compounds can become less effective as disinfectants in the presence of excess organic matter because the organic matter can react with and consume the chlorine, reducing its availability to kill harmful organisms.

Question 7

Which of the following is true regarding the use of osmotic pressure as an antimicrobial agent?

Accepted Answer

Exposing a microbe to a hypertonic environment, such as one with high concentrations of salt or sugar, draws water out of the cell through osmosis. This process, known as plasmolysis, can inhibit the growth of the microbe or kill it by causing dehydration and disrupting cellular processes.

Question 8

The difference between thermal death time and thermal death point in microbicidal activity is that _______.

Accepted Answer

Thermal death time refers to the shortest period needed to kill a specific organism under specific conditions at a certain temperature, while thermal death point (or temperature) is defined as the lowest temperature at which all organisms in a particular liquid suspension will be killed in 10 minutes.

Question 9

Your friend Joe recently visited the doctor for steroid injections into his knee to reduce swelling due to a previous knee injury. Within a couple of days, he had an infection caused by Pseudomonas, a very pathogenic and drug resistant bacterium. Luckily, Joe went to the doctor immediately and received antibiotics. The doctor tells him that the same problem has occurred to many other people across the United States. Predict the most likely cause of this situation.

Accepted Answer

The most likely cause of widespread infections across different locations would be contamination at the source, in this case, the production plant where the steroid was made. This would explain how multiple patients, presumably in different areas, all received injections contaminated with Pseudomonas.

Question 10

Hydrogen peroxide is used in the process of sterilizing instruments such as endoscopes.

Accepted Answer

Hydrogen peroxide is commonly used in the process of sterilizing instruments such as endoscopes due to its effectiveness in killing microorganisms.

Question 11

Which antimicrobial method does not sterilize?

Accepted Answer

Pasteurization does not sterilize; it reduces the number of viable pathogens to a level that is considered safe for consumption, but it does not eliminate all microorganisms.

Question 12

Which of the following is a disadvantage of dry heat methods such as using a Bunsen burner to incinerate microbes from an inoculating loop and the use of a hot air oven?

Accepted Answer

Dry heat methods, such as using a Bunsen burner and hot air ovens, have disadvantages including the danger associated with open flames and the longer time required for hot air ovens to sterilize compared to autoclaves.

Question 13

Organisms in the genus Pseudomonas are resistant to quats.

Accepted Answer

Organisms in the genus Pseudomonas are commonly known to be resistant to quaternary ammonium compounds (quats), which are commonly used as disinfectants and sanitizers.

Question 14

Soaps and detergents are very effective as sterilants.

Accepted Answer

Soaps and detergents are not effective as sterilants. They are used for cleaning and removing dirt and grime, but are not capable of killing all microorganisms, including spores and viruses. Sterilants are specifically designed to eliminate all types of microorganisms.

Question 15

You have inherited some old glass baby milk bottles from your grandmother, and you would like to use them instead of plastic bottles. The bottles are placed into a large metal container and placed in the oven at 325oF for about 2 hours. What factor would you change if you wanted the sterilization to occur much quicker?

Accepted Answer

Using a pressure cooker to sterilize the bottles with steam is a method of autoclaving, which is much quicker and more effective at sterilizing than dry heat from an oven.

Question 16

Isopropyl alcohol wiped across a skin site can sterilize it.

Accepted Answer

Isopropyl alcohol can disinfect a skin site by killing many types of bacteria and viruses, but it does not sterilize it, as sterilization requires killing or removing all forms of life and other agents like bacteria, viruses, and spores from a surface.

Question 17

When considering time and temperature as factors in microbicidal activity, _______.

Accepted Answer

Time and temperature are inversely proportional in microbicidal activity, meaning that as the temperature increases, the time required to achieve the same level of microbial kill decreases, and vice versa.

Question 18

You have some old plastic Petri dishes that you would like to use for pouring bacteriological agar plates. The only method of physical sterilization is ultraviolet radiation sterilization with your UV light (you cannot use the autoclave because it will dis?gure and melt the plastic). After sterilizing the
Plates, pouring the sterilized agar medium, and then leaving the plates out at room temperature for a day or two to let them solidify and dry, you ?nd contaminating bacterial colonies growing on the agar. Predict what has happened in this situation.

Accepted Answer

UV light sterilization is effective only on surfaces directly exposed to the UV light. If the lids were left on the Petri dishes during sterilization, the UV light would not penetrate the lids, leaving the inside surfaces of the dishes, including the agar, unsterilized and susceptible to bacterial contamination.

Question 19

Continued widespread use of the phenolic compound triclosan is advantageous in that it is important to remove as many organisms as possible from our hands and there is little risk of resistant organisms evolving.

Accepted Answer

Continued widespread use of triclosan has actually been shown to contribute to the development of antibiotic-resistant bacteria, also known as "superbugs." Additionally, there are concerns about the environmental impact of triclosan and its potential negative effects on human health. Therefore, the statement is false.

Question 20

Surgeons preparing for an invasive surgical procedure will scrub their hands thoroughly, and then they use a strong alcohol-based hand sanitizer which renders their hands sterile.

Accepted Answer

While surgeons do scrub their hands thoroughly and may use alcohol-based hand sanitizers, these practices reduce the microbial load to a very low level but do not render the hands completely sterile.

Quiz 11: Physical and Chemical Control of Microbes