Microbiology Exam 4 Control of Microbial growth

List nine types of disinfectants than can be used to control microbial growth and indicate which of these nine disinfectants can be considered as sterilants.

1. Halogens 2. Phenols & Phenol Derivatives 3. Biguanides 4. Alcohols 5. Heavy Metals 6. Surfactants sterilants: 7. Aldehydes 8. Peroxygens 9. Ethylene Oxide Gas

List seven physical methods for controlling microbial growth.

1. Heat 2. Low temperature 3. desiccation 4. high pressure 5. osmotic pressure 6. filtration 7. radiation (ionizing/nonionzing)

List three methods that employ moist heat to control microbial growth. Which of these three methods is the only reliable means of sterilization?

1. boiling 2. steam under pressure (reliable source) 3. pasteurization

List the two forms of dry heat sterilization. Aside from denaturation how else doe dry heat destroy microbes?

1. direct flaming or incineration 2. Hot-air sterilization oxidation effects/dehydration

Name the three key bacterial components/structures that a bactericidal agent may target.

1. inner plasma membrane 2. bacterial proteins 3. nucleic acids

List what needs to be considered before purchasing a disinfectant.

1. shelf life 2. type of microbes 3. time of contact 4. type of material 5. harmful/toxic to user 6. affordable/available 7. can it be inactivated by organic matter like blood 8. concentration/dilutions 9. corrode or stain

List five factors that can influence the rate at which a bactericidal agent can kill a bacterium.

1. time 2. agent concentration 3. # of microbes 4. type of bacteria 5. environmental influences

Name and briefly describe the two types of tests than can be used to evaluate disinfectants.

1. use-dilution test: expose stainless steel cylinders to microbe and allow microbe to dry on to cylinder. Expose to disinfectant for 10 minute. Transfer cylinders to sterile broth, incubate and check for growth. 2. disk-diffusion method: little pieces of filter paper that have dried with disinfectant. add your "discs" to the plate with the bacteria on it. If you see clearing around disc that means it couldn't grow

Who is the father of modern antisepsis and what type of disinfectant did he employ?

Dr. Josheph Lister; phenol

What is a chemiclave?

ETO sterilizers; use chemicals to sterilize (ethylene oxide)

Name two types of alcohol that are commonly used as disinfectants. Which of these two types has greater microbicidal activity and which of these two types is more toxic?

Ethanol and Isopropanol (rubbing alcohol). Isopropanol is more microbicidal and more toxic

What does the HTST pasteurization process involve? What does HTST stand for?

High-Temperature Short-Time: pasteurization of milk involves exposure at 72C for 15 seconds (no pressure)

Can low temperature be used for sterilization? What does low temperature achieve?

Low temperature usually does kill; but will slow microbial growth

Is pasteurized milk sterile? What does pasteurization achieve?

No it is not serial, reduces bacterial numbers and kills pathogenic microbes.

What is phenol? How does phenol destroy microbes and how effective is it against bacterial endospores? Why is phenol seldom used in hospitals today?

Phenol is a carbolic acid (toxic). Destroy many types of bacteria by DENATURING ENZYMES and DISRUPTING the plasma membrane. Effectiveness against bacterial endospores is poor

What happens if bacteria are exposed to a chemical agent that causes bacteriostasis?

a chemical that prevents bacterial growth but does not kill the organism

Define the term sanitization.

a cleaning technique that lowers the number of microbes to reduce contamination and maintain safe public health levels

How do surfactants destroy/damage microbes?

act by inserting into and disrupting plasma membranes

What are the two major types of surfactants?

anionic and cationic

How does high pressure treatment destroy microbes and can this process be used for sterilization?

applying high pressures alters the structure of proteins, can destroy vegetative bacteria but endospores are resistant to pressure alone and cannot be destroyed

What is formalin?

aqueous form of formaldehyde gas excellent disinfect and preservative. toxic

What are surfactants?

are surface-active agents like soaps and detergent; acts by inserting into and disrupting plasma membranes

Under what circumstances can hydrogen peroxide be sporicidal or a sterilant?

at high concentration

What is a bactericide, a fungicide, a virucide and a sporicide?

bactericide: chemical that destroys bacteria except endospores fungicide: a chemical that destroys fungal spores, hyphae, and yeast virucide: chemical that inactivates viruses sporicide: chemical that can destroy endospores

How does nonionizing radiation destroy microbes? What are the disadvantages of using nonionizing radiation to disinfect/sterilize items?

because nonionzing radiation poorly penetrates through liquids or solids direct exposure must be used. thymine dimers

How do alcohols destroy microbes and how effective are alcohols against bacterial endospores?

by denaturing proteins and disrupting the plasma membrane; ineffective against bacterial endospores.

What are the disadvantages of using ethylene oxide gas as a disinfectant/sterilant?

cancer hazard, reproductive hazard, can kill us

How does exposure to ionizing radiation result in microbial death?

causes direct damage of DNA that results in microbial death

Name a common biguanide used in many hospital operating rooms.

chlorhexidine

What type of halogen was used to decontaminate the Hart Senate Offices after the 2001 anthrax attacks?

chlorine dioxide gas

What industry are canning retorts used in? What does commercial sterilization mean with respect to the food canning industry?

commercial sterilization: process meant to destroy Clostridium botulinum endospores but will NOT completely sterilize product

What are bisphenols? How do bisphenols destroy microbes and how effective are they against bacterial endospores?

derivates of phenol that contain two phenolic groups connected by a bridge. less irritating to skin, destroy gram -positvie and gram negative bacteria by disrupting the plasma membrane. Ineffective against bacterial endospores and mycobacteria

What are phenolics? How do phenolics destroy microbes and how effective are they against bacterial endospores? Name a product that uses a phenolic compound as its active ingredient.

derivatives of phenol, in which the phenol molecules has been chemically altered. destroys many types of bacteria by DENATURING ENZYMES and DISRUPTING the plasma membrane. Effectiveness against bacterial endospores is poor. Lysol

What is desiccation and what is lyophilization? Can either of these processes be used for sterilization?

desiccation involves the removal of water. In the absence of water microbes cannot grow but will remain viable. Lyophilization (freeze drying) actually a process used to preserve bacterial samples

How do heavy metals destroy microbes and what is the specific antimicrobial effect caused by heavy metals known as?

destroy microbes by binding to specific chemical groups on amino acids thereby inactivating the protein. Oligoynamic action, minute quantities of these compounds have an antimicrobial effect

How do biguanides destroy microbes and how effective are biguanides against bacterial endospores?

destroys bacteria by disrupting the plasma membrane. Not effective against bacterial endospores.

How does ethylene oxide gas destroy microbes and how effective is it against bacterial endospores?

effective as both a SPORICIDAL agent and a STERILANT causes cross-linking of both DNA and proteins which results in microbial death highly penetrating but slow acting

How effective is peracetic acid and what is it commonly used to disinfect?

effective liquid SPORICIDAL agent and STERILANT. used for disinfection of food-processing & medical equipment

What are the inherent problems with using heavy metals as disinfectants?

expensive; toxic to humans; allergic reactions; biological fluids and wastes can neutralize their activities; microbes can develop resistance

What are the two most common aldehydes used as disinfectants?

formaldehyde and glutaraldehyde

Filtration can be used to physically remove microbes from what two general types of samples?

fungi and protozoa

Which is a better disinfectant formaldehyde or glutaraldehye and why?

glutaraldehyde: more effective and less irritating than formaldehyde, sterilizing age, remains active in presence of organic material, non corrosive, and safe for plastics

What ways are reliable for sterilization?

heat (autoclaving), radition, and filtration

Why is ionizing radiation referred to as "cold sterilization"?

heat is not used

How does osmotic pressure destroy microbes and can it be used for sterilization?

high concentration of sugar and salt can prevent bacterial growth and/or destroy bacteria, Molds, yeasts, and endospores more resistant to high osmotic pressure. not very reliable

What is the general relationship between pressure and the temperature of steam?

higher pressure, higher temperature

Name the tow most common peroxygens used for disinfection?

hydrogen peroxide and per acetic acid

Chlorine combined with water produces what common disinfectant? How does this disinfectant destroy microbes and how effective is this disinfectant against bacterial endospores?

hypochlorous acid (bleach). Bleach is a strong oxidizing agent that causes other compounds to lose electrons, disrupts enzyme function. Effectiveness of bleach against endospores is fair

Name two common halogen disinfectants.

iodine and chlorine

What are the two types of sterilizing radiation? Which type has a longer wavelength, which type has a higher energy emission and which type is more penetrable? Give an example of each type of sterilizing radiation.

ionizing and non ionizing. Non ionizing has a longer wavelength and lower energy. The ionizing has a high energy emission and short wavelength. Ionizing: x rays, gamma rays Nonionzing: UV light

What two types of heat can be used to control microbial growth and what happens to proteins/enzymes when exposed to high heat?

moist and dry heat

How effective are heavy metals against bacterial endospores?

not effective

How effective is soap as a disinfectant?

not the best, hands will never be sterile. Very weak bactericidal activity

What are peroxygens?

organic peroxide that are strong oxidizing agents

What is microbial death?

permanent loss of reproductive capabilities, growth

What are the two main methods for controlling microbial growth?

physical and chemical methods

Why is hydrogen peroxide considered a poor antiseptic but a good disinfectant?

poor antiseptic because rapidly broken down to water and oxygen by human catalase good disinfectant on inanimate objects because bacteria cannot neutralize high concentrations of peroxide

What are the most common types of cationic detergents and how effective are these compounds against bacterial endospores?

quaternary ammonium compounds, not the best. limited bacterial activity, ineffective against bacterial endospores, used to clean laboratory benches, floors, clothing, etc.

Define the term degermation

scrubbing and/or swabbing the skin in chemical to reduce the number of microorganisms by mechanical removal

Prior to the advent of antibiotics, what heavy metal was applied to a newborn baby's eyes and why was this done?

silver nitrate, to prevent contracting gonorrhoea

Give an example of an anionic detergent.

soap

How does iodine destroy microbes and how effective is this type of disinfectant against bacterial endospores?

strong oxidizing agent that inhibits protein/enzyme function. At proper concentration and exposure times can kill all types of bacteria but is poor for endospores

Which is more effective as a disinfectant, a 100% solution of alcohol or a 70% solution of alcohol and why?

the 70% solution is more effective because they have greater microbicidal activity. Using 100% will only dehydrate bacteria

Define the term disinfection,

the destruction of most microbial life on inanimate surfaces (disinfectant) usually not including bacterial endospores

Define the term antisepsis,

the destruction of most microbial life on living surfaces not including bacterial endospores

Define the term sterilization

the removal/destruction of all microbial life including endospores

Define the following: the thermal death point, the thermal death time and the decimal reduction time.

thermal death point: lowest temperature at which all the bacteria in a liquid suspension will be killed in 10 minutes thermal death time: minimum length of time for all bacteria in a liquid suspension to be killed at a given temperature decimal reduction time: time (in minutes) in which 90% of a bacterial population will be killed at a given temperature

Name the mercury-based compound that was used as a preservative in vaccines and what disease was in wrongly claimed to be linked with?

thimerosal; autism

What are the three critical parameters that must be monitored during autoclaving?

time, temperature, pressure

Explain the difference between tincture of iodine and an iodophor. Which of these two types of disinfectants is more likely to be used in hospitals today and why?

tincture is used more in the past as an antiseptic, likely to irritate skin and is prone to staining, still used as a disinfectant for water in emergency or camping. Iodophors is a mixture of iodine and an organic molecules which allows slow release of the iodine, does not stain skin and less irritating to skin, most common is iodophor used is medical antisepsis, used to prepare skin for surgery.

Formaldehyde gas and formalin are excellent disinfectants but what is the major disadvantage with using these compounds?

toxic to humans

What are the advantages and disadvantages of using glutaraldehyde as a disinfectant/sterilant?

toxic, sensitizer, irritant. Can be harmful to us if not handled properly. Use greater safety precautions

What bisphenol is the active ingredient in "antibacterial" soaps and what is the potential problem associated with overuse of products that contain this compound?

triclosan, no proof that it was any more effective than using plain soap, the chemical is associated with antimicrobial resistant

How do aldehydes destroy microbes and how effective are aldehydes against bacterial endospores?

very effective against all microbes including bacterial endospores, inactivate proteins by causing crosslinks between chemical groups on amino acids

What is the best way to graphically represent microbial death from a bactericidal agent and why is this approach the most appropriate?

with time as the x axis, and the y as the log of number of viable cells

What does the UTH pasteurization process involve? What does UTH stand for?

Ultra-High-Temperature (UHT) involves exposure at 134C for 1-2 sec (no pressure)

Why is moist heat more effective in killing microbes compared to dry heat?

Water conducts heat better than air so moist heat can penetrate material more rapidly than dry heat (less time required for sterilization)