Micro Bio – Microbiology Flashcard Answers

·         Types

o   Phenols and phenolics

o   Biguanides

o   Alcohols

o   Halogens

o   Oxidizing agents

o   Surfactants

o   Heavy Metals

o   Food and cosmetic preservatives

o   Aldehydes

o   Gaseous agents

·         Kill microbes by damaging cytoplasmic membrane, proteins, DNA, or cell wall

·         Effectiveness depends on

o   Type of agent

o   Temp

o   Length of exposure

o   Amount of organic matter

o   pH

o   Concentration

o   Age of antimicrobial solution

More effective against lipid enveloped viruses and the vegetative cells of bacteria protozoa and fungi than endospores, naked viruses, and protozoan cysts

o   Are antibiotics, semi-synthetic antibiotics, or synthetic chemicals used to control microbial growth in body of a host

o   Some used outside body

·         Should be

o   Inexpensive

o   Fast acting

o   Stable during storage

o   Not affected by presence of organic material

o   Compatible with soaps, detergents and other chemicals

o   Able to control all microbial growth while being harmless to humans, animals, and objects

·         None exists

Have advantages and disadvantages

·         Few chemical antimicrobials achieve sterility

o   Kill vegetative pathogens and reduce microbes to safe levels

·         No one chemical agent can be used safely in all situations to kill all microbes

·         Differ in

o   Mechanism

o   Types of microbes it kills

o   Time and conditions of killing

o   Objects it can be used on

·         Selection: Need to know

o   Properties of chemical agent

o   Types of microbes to kill

o   How long it takes to kill

o   If agent can be used on material

·         Organic matter matters in agent and method

·         Manufacturers directions give concentration, temp, application time, and how long diluted can be stored

Must be followed to ensure disinfection

·         4 Methods

o   Phenol coefficient

o   Use-dilution tests

o   Filter paper disk diffusion methods

o   In-use tests

·         Phenol was standard of comparison

o   Doesn’t account for bacteriostatic or residual effects

·         Current standard by American Official Analytical Chemists is use-dilution method

·         Both phenol coefficient and use-dilution tests performed in many ways.

o   3 test microbes used

§  Staphylococcus aureus

§  Salmonella choleraesuis

Pseudomonas aeruginosa (gram negative microbe notorious for resistance to chemical antimicrobial agents)

·         Microbes in broth cultures exposed to various concentrations of phenol for specific time

·         Microbes plated

·         Test disinfectant measured compared to phenol

·         Ratio called phenol coefficient

Disinfectant more effective than phenol à coefficient will be greater than one

·         He said remember name not details

metal rings adsorbed live bacteria

·         Rings removed and dried

·         Rings placed in various dilutions of test disinfectant for 10 mins

·         Rings removed and incubated at 37 C

Acceptable use dilution kills test microbes 95% of time

·         Dip filter paper into antimicrobial agent and place onto inoculated medium

·         Effective agents will have a ring of no growth (clear zone) around paper

Unreliable for agents volatile or inactivated by organic compounds

·         Sample surface before and after use and inoculate agar medium

·         Count numbers of colonies

Expensive and time consuming but accurate

o   High – Sterilization. Kills or inactivates all life forms

o   Intermediate – Kills all life forms except endospores

o   Low – kills vegetative gram-positive bacteria, vegetative gram-negative bacteria, lipid enveloped viruses, but  not mycobacteria, endospores, non-lipid viruses, and some fungi

·         Hospital Level – low level EPA disinfectant

·         Hospital level with tuberculocidal activity – intermediate EPA

         Hospital level disinfectant with HIV, Hep B, Hep C activity will kill those viruses but not necessarily mycobacteria

·         Phenol (carbolic acid) first chemical to disinfect surgical wounds

·         Rarely used now

o   Unpleasant odor

o   Irritating to skin and mucous membranes

o   Toxic

·         Phenolics intermediate to low level disinfectant

o   Chemical derivatives of phenol

o   O-phenylphenol – Lysol

o   Orthocresol

o   Amylphenol – Amphyl

·         Intermediate to low level disinfectants

o   Less irritating and toxic to humans

o   Effective in killing mycobacteria but not always naked viruses

o   Kill cells by damaging plasma membrane and denaturing proteins

·         Usually dissolved in detergent solution to enhance ability to wet surfaces

o   Remain active in presence of organic compounds

o   Stable to dilutions and remain active on surfaces long after application

·         One of four general types of disinfectant recommended by EPA for med/dental facilities

o   Common in healthcare, labs, home (Lysol, triclosan)

·         Disadvantages

o   Odor

o   Irritate skin

o   Can accumulate to toxic levels

o   Require 10 minutes contact time

·         Bisphenols

o   Phenol derivatives with two phenolic groups

§  Intermediate to low level

o   Common bisphenols

§  Hexachlorophene (pHisoHex) effective in killing staphylococci and streptococci

·         Surgical scrub and on skin

·         Prescription only due to possible neurological damage if overuse

§  Triclosan

Antibacterial soaps, toothpastes, cutting boards, pillows

·         Low level disinfectants

·         Disinfect skin and mucous membranes

·         Related to phenolics or bisphenols

·         Chlorhexidine is best known

o   Kills vegetative microbes by disrupting plasma membrane

o   Effective against staphylococci and streptococci

o   Prescription only in US

o   Common surgical scrub

o   Mouthwash – Peridex

                      Antiplaque agent to treat caries and perio disease

o   Reactive non metallic iodine, chlorine, fluorine, and bromine

o   Intermediate level in pure elemental and in compound state

§  Iodine and chlorine compounds common disinfectants or antiseptics

§  Bromine and fluorine rarely used

·         More toxic

·         Expensive

o   Iodine

o   Chlorine

o   Bromine

·         Iodine (I₂) long used as antiseptic for skin and wounds

·         Kills microbes by combining with tyrosine groups and denaturing protein

·         Used in tincture or iodophor

o   Tincture – dissolved in 70% alcohol

§  Irritating to skin and stain objects

o   Iodophor – organic moecule-iodine complex that releases I₂ slowly

§  No staining and less irritating

§  Preferred

·         Betadine and Isodine

o   Iodophores commonly used for skin disinfection

o   Iodine binding organic molecule povidine also surface wetting agent

·         Wescodyne, IodoFive, and Biocide

o   Iodophors to disinfect hard surfaces

o   EPA- intermediate level

o   One of four recommended types for surface disinfection in med/dental settings

·         Disadvantages

o   Diluted iodophors lose iodine at slow, constant rate and half – shelf life 1-2 weeks

o   Inactivated by too much organic matter

o   Pseudomonas and protozoan cysts resistant

                10 minute contact time

·         Highly effective intermediate level disinfectants

·         Cl₂ – gas that combines with water to form HOCl – Hypochlorous acid

·         HOCl enters cells and oxidizes

o   Destroys proteins, lipids, nucleic acids and kills cell

·         Cl₂ disinfects drinking water

o   Disadvantages

§  Protozoan cysts resistant

·         Natural surface water often contaminated and needs filtered

§  Combines with organic matter à carcinogens

·         Small enough risk to be worth it

§  Cl₂ toxic and corrosive

·         5% Sodium Hypochlorite NaOCl – bleach

o   Common, inexpensive, effective household disinfectant for laundry and floors

o   1/10 dilution recommended by EPA for hard surfaces in med/dental settings

o   1/10 bleach not affected by organic material

o   Intermediate level – 5 minutes contact

o   Disadvantages

§  Corrosive for fabrics, aluminum, and other metals

§  Irritating to mucous membranes

§  Must be removed from sensitive materials with water

·         Calcium hypochlorite – solid form of chlorine that forms HOCl when mixed with water à lime water

o   Commonly disinfects equipment and floors in agriculture

·         Sodium dichloroisocyanurate

o   Stable solid organic compound that slowly releases chlorine

o   Used with NaBr in swimming pools and hot tubs

o   Hospital disinfectant under name MicroStat

§  Disinfects in 5 mins

§  Tuberculocidal

§  Diluted solutions stable for 1 week

·         Chlorine Dioxide ClO₂

o   Highly reactive gaseous form of chlorine

o   Disinfects large objects in sealed chambers

o   Safely inactivated by pumping through sodium bisulfite

·         Chloramines

o   Stable ammonia and chlorine compounds that release chlorine slowly

o   Disinfect more slowly than other forms

Hospital disinfectants and drinking water

§  Disinfect hot tubs because evaporates slower than chlorine

§  Used with chlorine in swimming pools

·         Ethanol and isopropanol considered intermediate level in 50-95% solutions with water

o   Kills vegetative microbes but not naked viruses and fungal spores

·         Denatures proteins, dissolve lipids, and disrupts membranes

·         Pure alcohol ineffective and needs water to denature protein and disrupt cell membranes

·         Used on hard surface and skin but not on wounds because they denature proteins in wound healing

·         No residue

·         Non toxic

·         Disadvantages

o   Evaporates quickly in thin film which may not be enough contact time

o   Odor

·         Enhances efficacy of other disinfectants

o   Used in combo with iodine or quarternary ammonium compound

Alcohol-antimicrobial solutions called tinctures

·         Ions denature proteins in low concentrations – oligodynamic action

o   Mercury

o   Silver

o   Zinc

o   Lead

o   Copper

·         Long used as antiseptics and antimicrobials

o   1% silver nitrate in eyes of newborns prevents opthalmia neonatorum caused by Neisseria gonorrhoeae

o   Mercuric chloride and mercurochrome used as topical for years, no more

o   Thimersol w/mercury used as preservatives in vaccines. Supposed link to autism

o   Copper sulfate algicide in pools, fish tanks, paints

o   Zinc chloride in mouthwashes

o   Zinc oxide antifungal agent in body powders and creams and paints

o   Lead used in paints and gas but no longer

·         Heavy metal ions kill cells by combining with SH groups in proteins and denaturing

·         Killing efficacy reduced by organic material

             Clutathione protects cells from heavy metals

·         Soaps, anionic detergents, cationic detergents

·         Decrease surface tension of water

·         Allow water to wet solid surfaces fully

·         Dissolve dirt, fats, grease

·         Soaps – sodium salts of fatty acids

o   Not effective antiseptics or disinfectants because they don’t kill most microbes

o   Yet hand washing is one of most effective ways to prevent cross infections in hospitals

·         Scrubbing hands with soap followed by mechanical rinse removes surface microbes by emulsifying microbes, skin cells, and skin oils in micelles

o   Normal flora stay attached deeper

o   Abnormal bacteria more readily removed

o   Alcohol gels good substitute for handwashing and reduce infections by 50% because they are used more often than washing

·         Hospital infections

o   12.2 per 1000

o   Mortality 12.9% compared to 2.3%

o   Average charges for infections 185K rather than 31K

>2 billion in extra charges

§  Stronger surfactants than soaps due to sulfonic acid at end of hydrocarbon chain rather than carboxyl

§  Good surfactants and sanitizers, but not disinfectants

·         Don’t work against many gram negative

·         Anionic agents disrupt plasma membrane and denature proteins of some gram positive

·         Called quats or Quaternary Ammonium Compounds

·         Cepacol and Zephiran most commonly used quats

·         Good sanitizers and good surfactants

o   Odorless

o   Tasteless

o   Non-toxic

o   Common in toothpastes, body powders, and other products

·         Quats poor disinfectants by themselves

·         Zephiran ineffective against E. coli

·         Pseodomonas can grow in quat solutions

·         Zephiran tinctures kill E. coli

·         Quat tinctures – Intermedate level

o   EPA recommended for hard surfaces in med/dental setting but don’t work against naked viruses

o   Disinfect in 5 mins, non toxic, good wet ability, and no need to wipe up

·         Kill by disrupting cell membrane and denaturing proteins

·         Disadvantages

o   Organic matter, soaps, detergents interfere

Ineffective against Pseodomonas, many other gram-negative bacteria, and naked viruses

·         Commonly used as preservatives in food, cosmetics, soft drinks

o   Sorbic acid and potassium sorbate inhibit molds in acidic foods

o   Benzoic acid and sodium benzoate inhibit molds in soft drinks and acidic foods

o   Para-aminobenzoic acids (parabens) inhibits mold in cosmetics and shampoos

§  People allergic to parabens often allergic to local anesthetic procaine because of structurally similarity

Calcium propionate inhibits molds in bread

o   Sodium bisulfite forms sulfur dioxide when dissolved

§  Disinfects bottles and equipment for making wine

§  Kills wild yeasts in fresh grape juice

o   Sodium nitrate and nitrite commonly preserve meats – hot dogs, sausage, and lunch meats

§  Nitrite inhibits Clostridum botulinum

§  Nitrite forms nitrous acid (mutagen). Also reacts with amines to form nitrosamines (carcinogens).

§  Botulism risk greater than cancer risk

·         Organic compounds with carbonyl end group

·         Highly reactive

·         High level disinfection

·         React with aldehyde, amino, hydroxyl, sulfhydryl, and carboxyl groups on other molecules

·         Formaldehyde and gluteraldehyde (Cidex) commonly used

o   Alkylate amino, hydroxyl, sulfhydryl, and/or carboxyl groups on proteins and nucleic acids, inactivating molecules and causing cell death

o   Gluteraldehyde has two aldehyde groups and can crosslink proteins or nucleic acids

·         Formaldehyde

o   Water soluble and sold in 37% solution (Formalin)

o   Preserves specimins and cadavers

o   Volatile, irritating to mucous membranes, allergenic, and carcinogenic

o   Needs ventilation and handling care

·         Gluteraldehyde (allergen and carcinogen)

o   Less volatile and irritating

o   Skin contact to be avoided

o   Used to disinfect med/dental instruments before sterilization

o   Cold sterilize non-autoclavable instruments (respiratory or dialysis equip)

o   2% solution

§  bacteriocidal in 10 mins

§  sporicidal in 10 hours

o   Disadvantages

§  Long contact time needed

§  Must be rinsed off

                                 Allergenic and carcinogenic to skin

·         Gases that sterilize in closed chambers

o   Ethylene oxide

o   Popylene oxide

o   B-propiolactone

o   Chlorine dioxide

·         Ethylene oxide, B-propiolactone, and propylene oxide are akylating agents with reactive 3 or 4 member rings with oxygen

o   Ring reacts with amino, hydroxyl, or sulfhydral groups in proteins and nucleic acids, alkylating  and inactivating, and causing cell death

·         Highly penetrating but slow to sterilize

o   18 hours to sterilize then 24 hours of ventilation

o   Fumes highly irritating, allergenic, poisonous, carcinogenic

                       Sterilize heat and water sensitive items

·         Peroxides, Ozone, and Peracetic acid – strong oxidizing agents

·         Intermediate to high level

·         Kill by denaturing proteins, destroying lipids, and breaking DNA molecules

·         Ozone highly reactive and formed by O₂ from electrical charges or UV lights

o   Some countries use to disinfect water

o   Doesn’t form carcinogens

o   More expensive and lasts shorter

·         H₂O₂ kills bacterial cells and disinfects/sterilizes inanimate objects or surfaces

o   Some books say inactivated by catalase from microbes

o   3% solution contains enough of excess

o   Heated and sterilizes containers for ultra-high temp sterilized products

·         Benzoyl peroxide in OTC acne meds

·         Paracetic acid – high level disinfectant used for med equipment

o   Corrosive

o   Irritating to skin/mucous membrane

·         Oxidizing agents effect against obligate anaerobes

Irrigate deep wounds to prevent clostridia and obligate anaerobes from causing gas gangrene

o   Steam

o   Formalin-alcohol vapor

o   Dry Heat

o   Ethylene Oxide

o   Gluteraldehyde

Phenols(intermediate to low)

Iodophors (intermediate)

Quat tinctures (intermediate)

Sodium Hypochlorite NaOCl- bleach at 1/10 solution (intermediate)