Lecture 5 Test 3

actions of microbial control agents

-Alteration of membrane permeability (disinfectants and antiseptics) -damage to proteins (static agents) -Damage to nucleic acids (UV and gamma radiation)

disinfectants

-Chemical agents used for disinfection -used on inanimate objects -not suitable for living tissue because they are harsh chemicals

Biguanides

-Chlorhexidine -Disrupt plasma membranes -Effective against Gram positive and Gram negatives -Used on skin and mucous membranes (mouth wash) -NOT phenols

phenol and phenolics

-Commonly used as laboratory and hospital disinfectants -Disrupt plasma membranes (good for bacteria hiding in tissue) -effective in presence of organic material, and long lasting -irritating properties -o-phenylphenol is active ingredient in lysol

Characteristics of an ideal chemical

-Disinfectant must be effective against wide variety of infectious agents at low concentrations (no chemical is effective against all) -must be effective in the presence of organic matter (biofilms, tissue) -should be stable in storage -Work in wide range of pH conditions -Take less time to kill bacteria

physical methods of control

-Heat (most common) -Low temperatures -High pressure -Desiccation (dehydrate) -Osmotic pressure (increase salt) -Radiation -Filtration

Dry Heat Sterilization

-Kills by oxidation & denatures proteins -flaming (kills endospores) -incineration (used in hospitals for bandages after patient) -hot-air sterilization (micro lab hot air oven) -not meant for heat sensitive substances and NO liquids

Thermal death point (TDP)

-Lowest temperature at which all cells in a culture are killed in 10 min. - must use same # of cells when comparing bacteria

effectiveness of treatment depends on

-Number of microbes (higher # = more time to kill) -Population composition (cells are in different phases) -Concentration or intensity of an antimicrobial agent (chemicals are agents are usually diluted to avoid skin damage) -Time of exposure -Temperature (chemicals work best at higher temperatures since they can easily diffuse through a population) -Environment (organic matter, temperature, biofilms)

peroxygens

-Oxidizing agents -Use: Contaminated surfaces -H2O2 (disinfectant and antiseptic) -peracetic acid (kills endospores at high concentrations, disinfectant) -Ozone (O3) (disinfectant) -enter membrane and ionize

High pressure denatures proteins

-disrupt membrane -endospores can tolerate high pressure -NOT sterilization -removes most vegetative cells but endospores remain (why when you open pressured fruit juices they must be kept in the fridge)

heavy metals

-good disinfectants -Ag, Hg, and Cu (some antiseptics) -Silver nitrate may be used to prevent gonorrheal ophthalmia neonatorum -Silver sulfadiazine used as a topical cream on burns -Copper sulfate is an algicide -Oligodynamic action (small quantities are sufficient to kill bacteria) -denature proteins -silver included in clothing to prevent bacterial growth

alcohols

-hand sanitizer and antiseptics; can disinfect -ethanol -isopropanol -Denature proteins, dissolve lipids -Require water to act -if used undiluted they don't work -water helps get alcohol into cell -if you use 100% then it destroys cell proteins which creates a shell not allowing the alcohol in -up to 70% alcohol is effective

Low temperature

-inhibits microbial growth (doesn't kill) -Refrigeration (8-10 C; psychotrophs still grow) -Deep-freezing (below 0 C) -Lyophilization (desiccation or freeze drying): remove water and freeze; bacteria won't grow but won't die either; inhibits endospores)

microwave radiation

-kill by heat -not especially antimicrobial -kills vegetative cells to some extent -not good for cooking, only heating

Disinfection

-killing, inhibition, or removal of disease causing (pathogenic) organisms

supercritical fluids

-liquid chemical with gas properties -CO2 with gaseous and liquid properties (kill bacteria and spores) -Use: Medical implants bc other chemicals leave toxic residue

Commercial sterilization

-lower temperature to prevent messing up food such as dairy or canned goods -killing C. botulinum endospores (found in soil, produces botulism toxin)

plasma

-mix of ions in gas form -Free radicals destroy microbes -Use: Tubular instruments bc it's good at diffusion -other chems can't be used bc they won't diffuse through the tube and will leave a residue

heat

-most pathogens are mesophiles that die because heat causes nucleic acids and proteins to denature as well as membrane lysis -used at home, for food, and in lab

Osmotic pressure causes plasmolysis

-pickling -inhibits growth -if endospores do germinate they will undergo plasmolysis

membrane filters

-porous membranes with defined pore sizes that remove microorganisms primarily by physical screening (pore is smaller than microbe) -have replaced depth filters for the most part

microbial characteristics

-prions- not living; proteins that cause disease (chemicals and autoclave can't kill -endospores (killed by ionization, radiation, autoclave, incineration, some chemicals, Cl dioxide and acid, some aldehydes) -mycobacteria- complex cell wall sensitive to autoclave and incineration

disk diffusion test

-qualatative method -bacteria exposed to various concentrations of chemical -evenly spread 100 cells -in center place filter paper soaked in chemical -at 37 C chemical diffuses out and as it goes out the concentration lessens -zone of inhibition: concentration is sufficient to kill bacteria -measure size of zone and compare

Sanitization

-reduction of microbial population to levels deemed safe (based on public health standards) -applied to public spaces -not sterilization because not all organisms are eliminated

Chemical Food Preservatives

-static agent -Organic acids (ionize weakly in water) -unionized form can get into cells and slowly ionize, releasing H+ and lowering pH -Inhibit metabolism (doesn't kill) -Sorbic acid, benzoic acid, and calcium propionate -Control molds and bacteria in foods and cosmetics -nitrite prevents endospore germination -antibiotics (Nisin (bacteriocin) and natamycin (anti-fungal) prevent spoilage of cheese)

-static

-suffix indicating that agent inhibits growth -include bacteriostatic and fungistatic -when taken away bacteria will start to grow again -antibiotics work because they stop the growth and the immune system eliminates the microbes

-cide

-suffix indicating that agent kills -include bactericides, fungicides, algicides, and viricides

filtering air

-surgical masks -cotton plugs on culture vessels -high-efficiency particulate air (HEPA) filters (used in laminar flow biological safety cabinets)

decimal reduction time (DRT)

-time to kill 90% of a population at a given temperature -Measure of agent's killing efficiency

Chemotherapy

-use of chemicals to kill or inhibit growth of microorganisms within host tissue -include agents that kill microorganisms or inhibit their growth (cidal and static) ex. antibiotics, disinfectants, antiseptics

Ultra-high-temperature: 140°C for <1 sec

-used for dairy creamers which are kept at room temperature -mix hot air steam with milk droplets in chamber

depth filter

-water cleaned but can't remove bacteria and endospores -why they're being replaced by membrane filters -however they are faster and better for large quantities of water

When the local drinking water is believed to be contaminated, area residents are advised to boil their water before drinking. Often, however, they are not told how long to boil it. As a student of microbiology, what is your recommendation?

10 minutes

growth rate

2 fold exponential rate

static agents

chemicals that inhibit growth but don't kill

cidal agents

chemicals that kill microbes

high concentrations of this solution can destroy endospores

chlorine dioxide

which of the following is effective even at very low concentrations?

copper

which of the following methods is used to preserve food by slowing the metabolic processes of food-borne microbe? a) non-ionizing radiation b) gamma irradiation c) filtration d) freezing e) pasteurization

d) freezing

an iodophor is a/an a) agent that reduces oxygen b) phenol c) a detergent d) iodine attached to an organic compound e) quaternary ammonium compound

d) iodine attached to an organic compound

The label on the container of a product in the dairy case proudly proclaims, "This dairy product is sterilized for your protection". However, a statement in small letters below reads: "Use within 30 days of purchase." Should this statement arouse your suspicion about the sterility of the product? Why?

dairy products are not sterilized but pasteurized

surface-active agents/surfactants

degerming- remove bacteria from surface but doesn't effect growth

which of the following disinfectants act by disrupting plasma membrane? a) aldehydes b) hydrogen peroxides c) soaps d) halogens e) bisphenols

e) bisphenols

gonorrheal ophthalmia neonatorum

eye infection of infant that resulted from natural birth and getting mom's bacteria

which is best suited for sterilizing intravenous liquids?

filtration

which chemical is used in kitchen cutting boards and handles of knives?

triclosan

cells in log phase

very sensitive and die quickly

Antisepsis

prevention of infection of living tissue by microorganisms

filtration

-Reduces microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms from liquid or air -not used for solids -membrane filters

Pasteurization

-Reduces spoilage organisms and pathogens (doesn't sterilize; doesn't kill endospores) -63°C for 30 min or High-temperature short-time: 72°C for 15 sec are equivalent treatments -Thermoduric organisms survive -phosphatase test checks if pasteurization is complete -Ultra-high-temperature: 140°C for <1 sec (used for dairy creamers)

Degerming

-Removing microbes from a limited area -on tissue or inanimate objects ex. rubbing alcohol before injection or iodine based agents before surgery

steam sterilazation: autoclave

-Steam under pressure -temperature of steam is raised above boiling due to increased pressure (Boyle's Law) -121°C at 15psi (1 atmosphere) for 20 min -effective against all types of microorganisms including spores -Steam must contact item's surface -indicator strips are used to show sterilization -only heat resistant substances can be autoclaved ex. can't sterilize dairy or it would be destroyed

Why control microorganisms in the environment?

-To destroy pathogens and prevent their transmission. -To reduce or eliminate microorganisms responsible for the contamination of water, food and other substances

Nonionizing radiation

-UV, 260 nm -Damages DNA -UV limited to surface sterilization because it does not penetrate glass, dirt films, water, plastic -endospores are resistant so they require long exposure

Ionizing radiation

-X rays, gamma rays, electron beams (high energy, low wavelength) -Ionizes water to release OH• (toxic to vegetative cells -Damages DNA (phosphodiester bonds) -Effective against endospores (penetrates wall) -used for sterilization of sutures, plastic disposable supplies and food -liquids and antibiotics are damaged by this

Halogens: Iodine

-antiseptics -Tinctures: In aqueous alcohol (wounds and cuts) -Iodophors: In organic molecules, slow release of Iodine (help with burning sensation of alcohol) -Minimizes skin burns -Alter protein synthesis and membranes (binds to ribosomes)

gaseous sterilants

-can easily diffuse through small spaces -Denature proteins -Use: Heat-sensitive material that can't be sterilized by any other method -Ethylene oxide (highly toxic, used to kill ppl in WW2, sterilize hospital bedding) -Chlorine dioxide (fumigation) -used under certain conditions for certain materials

BPA

-catalyst for making plastic -toxic in large consumption and causes disease

Phosphatase test

-checks if pasteurization is complete -enzyme is denatured so if pasteurization is successful the enzyme won't be present

antiseptics

-chemical agents that kill or inhibit growth of microorganisms when applied to tissue -not suitable to consume for infection as they are nonspecific -won't remove everything, just superficial layer ex. sanitizer and listerine

aldehydes

-cidal agents -Inactivate proteins by cross-linking with functional groups (-NH2, -OH, -COOH, -SH) -Use: sterilize Medical equipment -Glutaraldehyde, formaldehyde, and orthophthalaldehyde -harsh chemicals that can damage skin

bisphenols

-derivative of phenol -Hexachlorophene (antiseptics: lotion for surgery, opportunistice pathogens killed) -triclosan (antiseptic in toothpaste and kitchen appliances; inhibits fatty acid biosynthesis) -Disrupt plasma membranes -Present in hand sanitizers -BPA

moist heat

-destroys viruses, fungi, and bacteria -boiling will not destroy spores and does not sterilize (need higher temp to destroy spores) -degrades nucleic acids, denatures proteins, and disrupts membranes -water is medium to transfer heat

Sterilization

-destruction or removal of all viable organisms (including endospores) -ex. autoclave (120 C)

dilution test

-determines concentration required to kill bacteria in 10 minutes -quantitative method -Metal rings dipped in test bacteria are dried -Dried cultures are placed in disinfectant for 10 min at 20°C -Rings are transferred to culture media to determine whether bacteria survived treatment

halogens: chlorine

-disinfectant; some antiseptics -Oxidizing agents (highly electronegative) -Bleach: Hypochlorous acid (HOCl, when suspended in water) -destroys vegetative bacteria and fungi -react with organic matter to form carcinogenic compounds (chloroform) -Chloramine: Chlorine + ammonia (slowly releases so it doesn't react with organic matter) -enters cell neutral then ionizes and releases Cl to oxidize

Thermal death time (TDT)

Minimum time required to kill all the bacteria in liquid culture at a given temperature

which of the following is a limitation of autoclave?

it cannot be used with heat-sensitive materials

microbial death curve

after 1 minute: 5 = 100,000 cells survive after 2 minutes: 4 = 10,000 cells survive DRT = i minute (10 fold difference b/t 4 and 5 after 1 minute)

filtering air in operating rooms

air conditioner dust can cause infection

Nisin

antibiotic made by bacteria

germicide

kills pathogens and many nonpathogens but not necessarily endospores

disk diffusion doesn't tell you

how much chemical should be used, just compares different chemicals

trisclosan in cosmetics

if you use too much it can cause neurological effects

which is most likely to be bactericidal?

ionizing radiation

boiling

isn't enough to kill endospores

staph epi

make biofilms

cells in stationary phase

more resilient to treatment

staph aureus

most common skin bacteria

which of the following is the active ingredient in Lysol?

o-phenylphenol

Population death

occurs exponentially by 10 fold

The water in your home aquarium always seems to resemble pea soup, but your friend's is crystal clear. Not wanting to appear stupid, you avoid asking him his secret. But one day, in a moment of desperation, you break down and ask, whereupon he knowledgably points to a few pennies among the gravel. What is the secret of the pennies?

pennies contain copper, a good disinfectant

which chemical is rarely used as an antiseptic?

phenol

which agent is most suitable for sterilizing narrow, long tubular instruments?

plasma

which chemical is safer to consume?

sodium benzoate

which chemical is best suited for sterilizing bones, tendons, and ligaments?

supercritical carbon dioxide