Lecture 8. Control Of Microbial Growth

1. What is meant by 'we live in an ocean of microbes'? Give examples.

- microbes are part of the natural environment; most are benign or benificial

gut microbes assist with digestion of carbs and proteins as well as synthesis of folic acid and vitamin K

microbes in sanitation systems decompose human wastes

microbes produce useful fermentation products (bread, beer, etc)

A. Microbes are harmful pathogens that should be avoided at all costs.

D. Microbes are only found in select environments and not everywhere.

C. Gut microbes do not play a role in digestion or synthesis of important nutrients.

B. Microbes have no impact on the environment and are therefore insignificant.

Microbes are not solely harmful pathogens and play various beneficial roles in the environment and human health, as outlined in the correct answer.

Explanation

Microbes are not solely harmful pathogens and play various beneficial roles in the environment and human health, as outlined in the correct answer.

2. Why is it important to understand mechanism of growth control?

The mechanism of growth control is only relevant for agricultural purposes.

Knowing about growth control is irrelevant as modern medicine can always treat any related issues.

Understanding growth control is not important as it doesn't have any impact on daily life.

-some microes are pathogens so it is important to understand how to effectively disinfect surfaces or equipment in a hospital setting; control foodborne illnesses; conduct safe honme canning; understand food, drug, home product labels

Understanding the mechanism of growth control is crucial for various aspects of public health and safety, including preventing the spread of pathogens, controlling foodborne illnesses, ensuring proper sterilization in healthcare settings, and interpreting information on consumer products.

Explanation

Understanding the mechanism of growth control is crucial for various aspects of public health and safety, including preventing the spread of pathogens, controlling foodborne illnesses, ensuring proper sterilization in healthcare settings, and interpreting information on consumer products.

3. Define sterilization, disinfection, antisepsis, degerming, and sanitization.

1destruction of all microbes including endospores

2destruction of most but not all microbes including endospores of Clostridium botulinum

3destruction of vegetative (non-endospore forming) pathogens on living tissue

4removal of microbes from a limited area

5treatment of lower microbial counts on eating and drinking utensils

1. preservation of microbes2. prevention of microbial growth3. neutralizing microbial odors

4. Define the following terms: 1. nosocomial infections 2. biocide or germicide 3. fugicide 4. virucide 5. tuberculocide 6. bacteriostasis 7. sepsismicrobial death rate.

10. a chemical that inhibits growth or kills off microorganisms

1. hospital-acquired infections

2. treatment or agent that kills microorganisms

3. teatment or agent that kills fungi

4. a treatment or agent that kills viruses

5. a treamtne or agent that kills Mycobacterium Tuberculosis (TB)

6. a treatment designed to stop growth (but doesn't sterilize). If you remove treatment, growth may resume

7. indicates bacterial contamination (from Greek for decay); also used to describe disseminated bacterial disease

8. number of dying cells per unit of time (usually per min)

8. number of dying cells per unit of time (usually per min)

9. a treatment or agent that kills parasites

The incorrect answers provided do not accurately define the terms listed in the question. Option 8. does not match with the term 'sepsismicrobial death rate.' Option 9. is incorrect because it does not match with any of the terms listed. Option 10. is inaccurate as it does not align with the definitions provided in the question.

Explanation

The incorrect answers provided do not accurately define the terms listed in the question. Option 8. does not match with the term 'sepsismicrobial death rate.' Option 9. is incorrect because it does not match with any of the terms listed. Option 10. is inaccurate as it does not align with the definitions provided in the question.

5. How do various factors influence microbial death rate?

7. Fats and proteins enhance the effectiveness of disinfectants

1. Low population load results in faster microbial death rates

1. high population load, longer period of time required to kill all the organisms

2. they inhibit death induced by antimicrobial agents

3. some disinfectants work better at warm temp

4. can protect the microorganisms from exposure to disinfectatnts

5. soem antimicobials work better at acid pH

6. ex. Pasteurization uses lower heat for a longer time to achieve the same effect that high heat for a shorter time can achieve in a destruction of microorganisms in food products

7. gram positive organisms are more susceptible to many agents than gram negative organisms.

5. Exposure time to agents does not influence microbial death rates

4. pH has no impact on the effectiveness of antimicrobials

2. Organic matter in human waste and bodily fluid enhances the effect of antimicrobial agents

3. Disinfectants work better at colder temperatures

6. Gram negative organisms are more susceptible to antimicrobial agents than gram positive organisms

6. What are the mechanisms of action of antimicrobial control agents?

2. promotion of viral replication

1. inhibition of cell wall synthesis

1. damage to PM
2. damage to enzymes and other structural proteins
3. damage to nucleic acids

3. enhancement of microbial growth

Antimicrobial control agents work by causing damage to the cell membrane, enzymes, and nucleic acids of microorganisms, leading to their destruction or inhibition of growth.

Explanation

Antimicrobial control agents work by causing damage to the cell membrane, enzymes, and nucleic acids of microorganisms, leading to their destruction or inhibition of growth.

7. What methods fall under the category of moist heat? How does this method kill? What type of organisms are killed under boiling? Pressure cooker or autoclave?

1. steaming and microwaving 2. kills by suffocating the organisms 3. all types of organisms 4. autoclave only

1. boiling, autoclaving (canning is a subset), and pasteurization

2. kills primarily by coagulating (denaturing) proteins

3. most organisms (including viruses and fungi) 10 minute

4. most heat resistant organisms and bacterial endospores are killed by moist heat under pressure

1. grilling and frying 2. kills by freezing the organisms 3. only bacteria and parasites 4. neither pressure cooker nor autoclave

1. smoking and pickling 2. kills by dehydrating the organisms 3. only fungi and protozoa 4. pressure cooker only

Moist heat methods like boiling, autoclaving, and pasteurization are commonly used to kill a wide range of organisms through protein coagulation. These methods are effective against most types of organisms, including viruses and fungi, when used correctly. While pressure cookers and autoclaves are both used for moist heat sterilization, pressure cookers are more effective at killing heat resistant organisms and bacterial endospores.

Explanation

Moist heat methods like boiling, autoclaving, and pasteurization are commonly used to kill a wide range of organisms through protein coagulation. These methods are effective against most types of organisms, including viruses and fungi, when used correctly. While pressure cookers and autoclaves are both used for moist heat sterilization, pressure cookers are more effective at killing heat resistant organisms and bacterial endospores.

8. Autoclaving: What is the relationship between pressure and temperature? How do sterilization occur? What pressure and temperature kills all organisms? What works well for autoclaving? How do you sterilize surfaces and instruments?

1. The lower the pressure, the greater the temperature.

3. Steam at a pressure of 5 pounds per square inch (psi) kills all organisms.

2. Sterilization occurs by exposure to sunlight.

1. the higher the pressure, the greater the temperature

2. by contact of the organism to steam or in liquids

3. seam at a pressure of 15 pounds per square inch (psi) thus 121 C kills all organisms and endospores in 15 minutes

4. small volumes. large volumes require more time

5. steam in an autoclave must contact all surfaces; instruments are wrapped in paper that can be wetted and allow the steam to contact them.

Autoclaving relies on the relationship between pressure and temperature for effective sterilization. The incorrect answers provided are common misconceptions that do not accurately reflect the process of autoclaving.

Explanation

Autoclaving relies on the relationship between pressure and temperature for effective sterilization. The incorrect answers provided are common misconceptions that do not accurately reflect the process of autoclaving.

9. What are some important considerations for home canning?

3. Skipping the step of driving off cold air before sealing is okay

1. Canning in glass jars is not safe

2. Using expired ingredients won't affect the canning process

1. heat under pressure can effectively preserve food

2. ball canning guide

3. need to drive off cold air

4. solid such as meat and larger sizes (ie quarts require more time than pints)

When home canning, it's crucial to follow proper instructions, including using a pressure canner, following guides like Ball canning guide, ensuring no cold air is trapped in the jar before sealing, and knowing that solid items require more heat exposure to can properly.

Explanation

When home canning, it's crucial to follow proper instructions, including using a pressure canner, following guides like Ball canning guide, ensuring no cold air is trapped in the jar before sealing, and knowing that solid items require more heat exposure to can properly.

10. Dry Heat Sterilization kills how and what are examples?

1. through dehydration 2. pasteurization and boiling

1. by oxidation

2. flaming and hot-air sterilization (place in oven at 170 C for 2 hrs

1. by denaturation 2. autoclaving and irradiation

1. by carbonization 2. chemical sterilization and filtration

Dry Heat Sterilization primarily works by oxidation, which destroys microorganisms. Flaming and hot-air sterilization are common examples where high temperatures are used to achieve sterilization. The incorrect answers provide alternative methods and misconceptions about the process of dry heat sterilization.

Explanation

Dry Heat Sterilization primarily works by oxidation, which destroys microorganisms. Flaming and hot-air sterilization are common examples where high temperatures are used to achieve sterilization. The incorrect answers provide alternative methods and misconceptions about the process of dry heat sterilization.

11. Other physical methods of microbial control Filtration1. removes what?2. necessary when?3. what type/size filters are used?

1. viruses or small molecules

1. bacteria or other large cells

2. to sterilize heat-sensitive media, protein solutions, etc.

3. filters are .22 um and .45um in size; HEPA (high efficiency particulate air filters) in biosafety hoods remove bacteria from air.

3. filters are 1um and 10um in size; basic air filters in homes remove bacteria from air

2. to sterilize heat-resistant media only

12. Other physical methods of microbial controlLow Temperatures 1. Name the machinery and describe its function. 2. What is the temperature range of an ordinary refrigerator and what does it do to most microbes? 3. At what temperature do freezers operate and how does it affect organisms? 4. Name one important human pathogen that can grow in refrigerators.

1. ordinary refrigeration temperature (0-7 C) is bacteriostatic (reduce the metabolic rate of most microbes is so reduced that hey cannot reproduce or synthesize toxiins) not bacteriocidal

2. inhibits growth of most pathogens but not the rpsychrotropic organisms

3. freezer temperatures are bacteriostatic not bacteriocidal, but some organisms such as parasitic worms are killed by freezing.

4. Listeria Monocytogenesis

2. Refrigeration temperature (1-5 C) is virucidal not bacteriostatic.

3. Freezer temperatures below -10 C are bacteriocidal not bacteriostatic.

1. Industrial refrigeration temperature (20-30 C) is bactericidal not bacteriostatic.

The correct answer highlights the effects of ordinary refrigeration temperature, the temperature range of freezers, and an example of a pathogen that can grow in refrigerators.

Explanation

The correct answer highlights the effects of ordinary refrigeration temperature, the temperature range of freezers, and an example of a pathogen that can grow in refrigerators.

13. Other physical methods of microbial control include:

2. UV light exposure

1. Exposure to extreme temperatures

3. Chemical disinfection

1. high salt to preserve meat

high sugar to preserve fruits

2. bacteriostatic

3. drying out

4. bacteriostatic

Physical methods of microbial control include high salt and sugar for preservation, bacteriostatic function, and dessication. Exposure to extreme temperatures, UV light, and chemical disinfection are other methods, but they are not specifically mentioned in the original question.

Explanation

Physical methods of microbial control include high salt and sugar for preservation, bacteriostatic function, and dessication. Exposure to extreme temperatures, UV light, and chemical disinfection are other methods, but they are not specifically mentioned in the original question.

14. Other physical methods of microbial control radiation: ionizing radiation1. uses what type of radiation2. how does it work...include energy use in explanation3. used for?4. and may become an important method for what?

2. Long wave lengths that are greater than 1 nm and carry low energy waves

3. Used for personal hygiene products, clothing, and electronic devices

1. UV rays, infrared radiation, and microwaves

1. gamma rays, electron beams, and x-rays
2. short wave lengths that are less than 1 nm and carry high energy waves, penertrate deeply and ionize water molecules in microorganisms and form reactive hydroxyl radicals (OH*) that are toxic to the cells
3. sterilize pharmaceuticals, laboratory plastic ware, disposable medical supplies
4. sterilization of food (meats and vegetables)

Ionizing radiation includes gamma rays, electron beams, and x-rays with short wavelengths that ionize water molecules in microorganisms. This process is used for sterilizing various items like pharmaceuticals, laboratory tools, and even food. UV rays, infrared radiation, and microwaves do not have enough energy to penetrate deeply and ionize water molecules. The mentioned incorrect items do not align with the correct principles of ionizing radiation for microbial control.

Explanation

Ionizing radiation includes gamma rays, electron beams, and x-rays with short wavelengths that ionize water molecules in microorganisms. This process is used for sterilizing various items like pharmaceuticals, laboratory tools, and even food. UV rays, infrared radiation, and microwaves do not have enough energy to penetrate deeply and ionize water molecules. The mentioned incorrect items do not align with the correct principles of ionizing radiation for microbial control.

15. Nonionizing radiation uses what type of radiation, and what is the wavelength most effective for killing microorganisms?

1. X-ray radiation; 2. 100 nm; these wavelengths are specifically absorbed by cellular DNA.

1. Infrared light; 2. 400 nm; these wavelengths are specifically absorbed by cellular DNA.

1. ultraviolet light
2. 260 nm; these wavelengths are specifically absorbed by cellular DNA
3. UV light damages DNA
4. doesnt penetrate, kills only on surface; harmful to the eyes and skin
5. no, most of the germicidal wvlengths are filtered out by ozone in the atmosphere

1. Visible light; 2. 600 nm; these wavelengths are specifically absorbed by cellular DNA.

Nonionizing radiation specifically refers to ultraviolet light, with a wavelength of 260 nm being the most effective for killing microorganisms as these wavelengths are absorbed by cellular DNA.

Explanation

Nonionizing radiation specifically refers to ultraviolet light, with a wavelength of 260 nm being the most effective for killing microorganisms as these wavelengths are absorbed by cellular DNA.

16. What is the germicidal effectiveness of a microwave?

Highly effective in killing germs due to the heat produced during microwaving.

Completely sterilizes food and surfaces when used for cooking.

1. not effective for germicidal treatment because the food is cooked by the heated moisture in food, but suraces are not sterile inside a microwave oven

Acts as a disinfectant by eliminating all types of bacteria and viruses in the microwave.

Microwaves are not effective for germicidal treatment as they primarily cook food through heated moisture, but do not sterilize surfaces within the appliance.

Explanation

Microwaves are not effective for germicidal treatment as they primarily cook food through heated moisture, but do not sterilize surfaces within the appliance.

17. What are some key considerations for chemical methods for microbial control?

2. Concentration is not important in using chemical methods for microbial control

1. very few chemical methods are capable fo sterilization, but most reduce the number of microbes
2. concentration (use as directed)
3. organics; pH; should you wash then disinfect?; each agent is useful in a specific setting. It is essential to understand which one

3. Any type of interference does not affect the effectiveness of chemical methods

1. Chemical methods are always capable of sterilization

18. What are two methods used to test the effectiveness of chemical control methods?

The Gram-staining test and the Acid-fast staining test.

The ELISA test and the PCR test.

The streak-plate test and the pour-plate test.

It test the effectiveness of each agent on 3 species of pathogenic bacteria
1. salmonella choleraesuis- a serovar of salmonella typhimurium that binds to blood vessels
2. staphylococcus aueus- a skind pathogen that often infects surgical wounds
3. pseudomonas aeruginosa- a skin pathogen that is an opportunist, problem for burn patients

1. so a metal ring isdipped in the bacteria, dried at 37 C, exposed to the disinfectant for 10 min at 20 C, washed, and transfered to culture medium. the degree of growth gives you a measure of the effectiveness of the disinfectant

2. a disk of filter paper is soaked in teh disinfectant, placed on a "lawn" of bacteria on an agar plate of each bacteria, and the effectiveness is judged by zone of inhibition

The use-dilution test involves exposing a metal ring dipped in bacteria to a disinfectant, while the disk-diffusion test involves placing a disk soaked in disinfectant on a lawn of bacteria on an agar plate.

Explanation

The use-dilution test involves exposing a metal ring dipped in bacteria to a disinfectant, while the disk-diffusion test involves placing a disk soaked in disinfectant on a lawn of bacteria on an agar plate.

19. Who first used chemical disinfectants like phenol and phenolics?

Alexander Fleming with the use of phenolics in penicillin

1. Joseph Lister with the use fo phenol in carbolic acid
2. rarely used now
3. at concentration above 1%
4. stable long-lasting, active in presence of organic compounds
5. pus, saliva, feces
6. Lysol; a derivative of phenol called O-phenylphenol is the main ingredient
7. acts by disturbing the PM

Marie Curie with the use of phenolics in radium

Isaac Newton with the use of phenol in calculus

Joseph Lister pioneered the use of phenol in carbolic acid for disinfection purposes.

Explanation

Joseph Lister pioneered the use of phenol in carbolic acid for disinfection purposes.

20. What are bisphenols and how do they differ from phenols?

3. it is a synthetic compound not found in nature

1. its molecular structure has 2 phenolic groups
2. -hexachlorophene; pHisohex; used for control of microbes in surgical wards
-tricolosan; agents in antibacterial soaps; this agent has widespread use and triclosan resistant bacteria and appearing
3. good agent to kill gram positive staphylococci and streptococci
4. inhibits an enzyme needed for teh biosynthesis fatty acids (lipids), which mainly affects the integrity of the PM
5. broad spectrum activity on a lot of type of microorganism

1. its molecular structure has 1 phenolic group

2. it is a type of alcohol with a single phenol group

Bisphenols have a molecular structure with 2 phenolic groups, which distinguishes them from phenols that contain only 1 phenolic group.

Explanation

Bisphenols have a molecular structure with 2 phenolic groups, which distinguishes them from phenols that contain only 1 phenolic group.

21. Biguanides acts on?

Only bacteria

Only mycobacteria

Only viruses

1. a broad spectrum ( bacteria, fungi, some enveloped viruses, but not mycobacteria, endospores, or protozoa
2. as antimicrobial for skin (surgical hand scrub)
3. chlorohexidine
4. acts by distrubing PM of bacteria

Biguanides are antimicrobial agents that have a broad spectrum of action against bacteria, fungi, and some enveloped viruses, but they do not work against mycobacteria, endospores, or protozoa.

Explanation

Biguanides are antimicrobial agents that have a broad spectrum of action against bacteria, fungi, and some enveloped viruses, but they do not work against mycobacteria, endospores, or protozoa.

22. Halogens: Iodine (I2) act on?

Specific types of bacteria only

Only fungi

None of the above

1. broad specrum (bacteria, fungi, some viruses, many endospores are killed
2. alcohol solution (tincture [iodine in aqueous alcohol] of iodine)
3. iodine is combined with organic molecules as iodophor that release iodine more slowly; brand name: Betadine and Isodine
4. disinfect skin
5. inhibits protein functions; strong oxidizing agent

Iodine has a broad spectrum of action, affecting various microorganisms.

Explanation

Iodine has a broad spectrum of action, affecting various microorganisms.

23. What is the most effective form of chlorine (Cl2)?

Chloramine (NH2Cl)

Chlorine gas (Cl2) in its pure state

1. hypochlorous acid (HOCl) is formed when Cl gas is combined with water
2. disinfection of drinking water, swimming pools, sewage
3. Calcium hypochloride; used by semmelweis in 1840s to control childbirth fever
4. sodium hypochlorite; chlorox bleach
5. emergency disinfection of drinking water---2 drops bleach per liter of water for 30 minutes and water is safe for drinking
6. strong oxidizing agent, alters cells

Chlorine dioxide (ClO2)

The most effective form of chlorine is hypochlorous acid (HOCl), which is formed when Cl gas is combined with water. This compound is widely used for disinfection purposes and has strong oxidizing properties.

Explanation

The most effective form of chlorine is hypochlorous acid (HOCl), which is formed when Cl gas is combined with water. This compound is widely used for disinfection purposes and has strong oxidizing properties.

24. What do alcohols kill, what form are they most often used in, which is the more effective solution and why, what additional function do they have, and what is their mechanism of action?

1. Alcohols kill only endospores. 2. Ethanol and methanol are the most often used forms of alcohol. 3. 90% alcohol is more effective than 70% due to higher concentration. 4. Alcohols primarily act as anticoagulants. 5. Alcohols work by interfering with cellular respiration.

1. Alcohols kill viruses but not bacteria. 2. Rubbing alcohol is the most often used form of alcohol. 3. 50% alcohol is more effective than 70% for disinfection. 4. Alcohols primarily act as deodorizers. 5. Alcohols work by disrupting cell wall synthesis.

1. bacteria and fungi, enveloped virues, but not endospores
2. ethanol and isopropyl alcohol most often used
3. 70% is more effective than 100% because denaturation requires water
4. enhances activity of other agents like benzalkonium chloride
5. protein denaturation and disruption of PM

1. Alcohols kill only endospores. 2. Methanol is the most often used form of alcohol. 3. 100% alcohol is more effective than 70% due to higher concentration. 4. Alcohols have no additional functions. 5. Alcohols affect DNA replication as their mechanism of action.

25. What are some examples of heavy metals, their past use, current use, use of copper sulfate and zinc chloride, and mechanism of action?

1. aluminum, iron, zinc 2. aluminum foil was used in the past to protect food 3. iron supplements are now used for anemia 4. in paint; in pesticides

1. lead, cadmium, nickel 2. lead-based paint was used in the past for buildings 3. cadmium is now found in rechargeable batteries 4. as a food preservative; in nail polish

1. silver, mercury, copper
2. 1% silver nitrate was used in the past to disinfect newborn babies eyes to protect against acquired Neisseria gonorrhaea
3. silver-sufadiazine is now used to treat antibiotic resistant bacteria
4. as a algaecide; in mouthwash
5. combines with sulfhydryl groups of proteins to denature proteins

1. gold, platinum, palladium 2. gold leaf was used in the past for art decoration 3. platinum-based drugs are now used in cancer treatment 4. as a catalyst; in electronic devices

Each of the incorrect answers provides a set of heavy metals that do not align with the correct examples provided. The incorrect past uses, current uses, and uses of copper sulfate and zinc chloride are also unrelated to the information provided in the correct answer. Additionally, the mechanism of action given in the correct answer is not present in any of the incorrect options.

Explanation

Each of the incorrect answers provides a set of heavy metals that do not align with the correct examples provided. The incorrect past uses, current uses, and uses of copper sulfate and zinc chloride are also unrelated to the information provided in the correct answer. Additionally, the mechanism of action given in the correct answer is not present in any of the incorrect options.

26. Surface Active agents: 1. Define 2. Provide examples 3. What are they used for? 4. What is a common ingredient found in many soaps?

3. Surface active agents are primarily used for preserving food products.

4. The common ingredient found in many soaps is alcohol.

1. decrease surface tension among moleducel so a liquid such as water
2. soaps and detergents
3. not useful as antiseptic, but remove microbes by scrubbing so its a good degerming agent
4. triclosan: active against gram positive bacteria

2. Examples of surface active agents are vinegar and baking soda.

1. Surface active agents increase surface tension among molecules in liquids.

Surface active agents, such as soaps and detergents, function by decreasing surface tension to facilitate the removal of dirt and microbes. Triclosan is a commonly used ingredient in soaps for its antimicrobial properties against gram positive bacteria.

Explanation

Surface active agents, such as soaps and detergents, function by decreasing surface tension to facilitate the removal of dirt and microbes. Triclosan is a commonly used ingredient in soaps for its antimicrobial properties against gram positive bacteria.

27. Quaternary Ammonium Compounds (Quats) are active on?

Water

Skin

Air

1. surface
2. cationic (positvely charged)
3. gram positive and some gram negatibe bacteria, fungi, protozoa, and enveloped viruses
4. endospores or mycobacteria or pseudonomas
5. Zephiran which is benzalkonium Chloride and Cepacol which is cetylpridinium chloride
6. disrupt PM: denatures proteins

Quaternary Ammonium Compounds are primarily used on surfaces for disinfection purposes.

Explanation

Quaternary Ammonium Compounds are primarily used on surfaces for disinfection purposes.

28. What inhibits mold growth in food?

Baking powder

Sucrose

Sorbic acid; potassium sorbate; sodium benzoate; calcium propionate

Vinegar

Mold growth in food can be inhibited by using preservatives such as sorbic acid, potassium sorbate, sodium benzoate, and calcium propionate. Sucrose, vinegar, and baking powder do not have the same mold inhibiting properties.

Explanation

Mold growth in food can be inhibited by using preservatives such as sorbic acid, potassium sorbate, sodium benzoate, and calcium propionate. Sucrose, vinegar, and baking powder do not have the same mold inhibiting properties.