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MCIM 223 > Lecture 11 and 12 > Flashcards

Lecture 11 and 12 Flashcards

1
Q

Control of mircrobes in the environment 3

A

Control can mean
-killing of microbes on surface
-physical removal of microbes from a surface
-Preventing an increase in microbial number on a surface
(Control does not mean sterile environment)

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2
Q

Methods for controlling environmental microorganisms include: 2

A
  1. Physical Methods - heat, radiation, filtration
  2. Chemical Methods - antiseptics, disinfectants, preservatives
    (they do not discriminate between types)
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3
Q

Heat

A

Denature proteins and DNA, melts lipids = cell death

  • economical; easy to control and monitor
  • moist heat is better than dry heat (faster penetration, better protein denaturation, water helps disrupt chemical bonds)
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4
Q

Boil water (heat control)

A

10 minutes at 100°C kills bacteria & viruses, but not spores (ie. boiling does not guarantee sterility)

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5
Q

Pressurized Steam (via autoclave)

A

20 min. of steam @ 15 lbs / inch (= 121°C) kills bacteria and spores (ie. proper autoclaving guarantees sterility)

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6
Q

How do you know if your stuff has been through an autoclave

A

Heat sensitive autoclave tape

Autoclave pouches with indicator strips

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7
Q

Good Habits to develop when working with sterilized materials

A
  • check package integrity (rips, dmg)
  • Check expiry date
  • check indicator its been properly sterilized
  • treat the inside of package as sterile, the outside not
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8
Q

Radiation

A) Ultraviolet Light

A

(germicidal lamps)

  • Cross links bases in DNA (stops replication, causes mutations)
  • 5 to 45 second exposure kills most microbes (depends on intensity)

But
-Not all types of microbes are equally sensitive (spore require more exposure times)
-dmg to skin eyes
-poor penetration of liquids, plastic glass
(for surface or air sterilization only! OR)

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9
Q

Radiation

B) Ionizing Radiation

A
  • Dislodges electrons from atoms (disrupts chemical bonds, breaks DNA)
  • Much higher penetrative power than UV
  • Commercial uses only (cold sterilization)
  • Sterilize heat-sensitive products; plastics; wrapped objects
  • Food irradiation (to reduce bacterial numbers in foods)
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10
Q

Can a home microwave be used for sterilization

A

MW excite water molecules which release energy as heat
therefore killing of microbes is due to heat and needs water

Dry objects in a microwave will not sterilize it

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11
Q

Filtration

A
  • Physical removal of microbes (no killing)
  • Create filters with pores too small for (most) microbes to pass
membrane filters (cellulose fiber with pores 0.2 - 0.5 uM)
(Bacteria, fungi trapped on surface of filter but viruses can pass)

For heat-sensitive liquids and gasses

  • nutrients in bacterial growth media (vitamins)
  • injectable drugs, surgical gasses
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12
Q

Chemical Methods

Germicides

A

Germicides
-Chemicals used to kill microbes on surfaces

Antiseptics - use on biological surface (skin)
Disinfectants - use on inanimate surfaces (non-living)

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13
Q

Chemical Methods

Preservatives

A

-Chemicals which may kill microbes, but usually only inhibit microbial by creating unfavorable environment

No selective toxicity

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14
Q

Overview - Germicidal

A

> 300 Chemicals that have anti-microbial properties

  • > 8000 formulations
  • different agents for different uses

Mechanism of action is usually by:

  • Denaturing and coagulating cellular proteins
  • Dissolving lipids (in cell membranes)
  • Oxidizing cellular macro-molecules

Germicides are designed to:

  • Greatly reduce the microbial “load” on a surface (always)
  • create sterile surface (depends on agent)
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15
Q

Germicides - Factors affecting how well they work 5

Clean before disinfecting !!!

A

-Time of exposure (not all microbes killed at same rate)
-Temp of environment (less effective at lower temp)
-Concentration of germicide (higher is better, but more toxic)
-Presence of organic matter (soil, blood, pus form layer and weaken germicide)
-Number, type, and special characteristics of microbes present
(More germs more chemicals, spores hard to kill, biofilms resistant)

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16
Q

Germicides can be rated according to killing ability 2 level

Potency

choice of which

A
  • High-level (sterilant) - kill all microbes, including spores
  • Intermediate-level (everything except spores)
  • Low-level (kills most vegetative bacteria but not mycobacteria, spores and some viruses)

-Potent germicides are also disinfectants

Choice of germicide depends on application and result

  • biological vs inanimate surface
  • complete sterility vs. only reducing microbial load
  • risk category of device or surface being treated
17
Q

Germicides - some examples relevant to health care

Phenols (Triclosan)

A
  • earliest germicides (denatures proteins)[Lister/ carbolic acid used on skin]
  • Skin irritation, neurotoxicity (absorbed through skin)

Used as disinfectant (Lysol = O-phenylphenol)

  • high concentrations kill mycobacteria (not spores)
  • Hexachlorophene (pHisoHex®) - use on newborns in early 70’s resulted in cases of brain damage

Small doses in medicine

18
Q

Germicides - some examples relevant to health care

Phenols

Triclosan

A
  • Chlorinated phenol with an unusual mode of action (stop an enzyme req. for bacterial fatty acid synthesis)
  • Non irritating - used in consumer products (SUTURE THREAD, soap, toothpaste, deodorants, trash bags, utensils)
  • Toxic concerns with long term exposure
19
Q

Germicides - some examples relevant to health care

Alcohols (ethanol, isopropanol) 5

A
  • Dissolves lipids and denatures proteins (effective against bacteria, viruses, fungi and not spores)
  • Non-toxic and non irritating (antiseptic use)
  • Mostly used as 70% solution in water (water aids protein denaturing and slows evaporation
  • May not remove everything (deep in pores survive, and if bacteria present)
  • Used as hand sanitation
20
Q

Germicides - some examples relevant to health care

Peroxides-

Hydrogen peroxide (H2O2)

Accelerated Hydrogen Peroxide (PerCept)

A

Hydrogen peroxide (H2O2)

  • Strong oxidizing agent breaks into water and oxygen killing anaerobic bacteria
  • antiseptic, bedsores

contact lens solution

Accelerated Hydrogen Peroxide (PerCept)

  • H2O2 + proprietary additives which give stability, and effectiveness
  • used in hospitals to clean pt care areas
21
Q

Germicides - some examples relevant to health care

Heavy Metals 5

A

Bind strongly to cellular proteins

  • inactivates cellular enzymes and inhibits membrane functions
  • antiseptic
Selenium -anti-fungal activity  (topical creams)Silver sulfadiazine (burn wound ointment)
Zinc compounds  (mouthwashes, etc.)Thimerosal (mercury derivative) 
Copper
22
Q

Germicides - some examples relevant to health care

Halogens (protein denaturation)

Chlorine
Iodine

A

Chlorine

  • Bleach (javex) = sodium hypochlorite
  • kills most microbes(and spores)
  • inactivated by organic matter; poor long-term stability

Iodine

  • less toxic and more stable than chlorine (antiseptic)
  • Tincture (iodine plus alcohol)
  • Iodophore (iodine + hydrocarbon carrier = carrier slows and prolongs iodine release)
    eg. Betadine (Iodine + polyvinylpyrrolidone) = skin antiseptic
23
Q

Germicides - some examples relevant to health care

Chlorhexidine

A

Disrupts membranes and denatures proteins

One of three antiseptics on WHO Essential medicines list

Low toxicity, none-irritable, sticks to skin and mucous membranes

  • coating on catheters and implanted medical devices
  • antiseptic skin creams and wipes (pre op skin care)
24
Q

Germicides - some examples relevant to health care

Alkylating Agents

Glutaraldehyde
Ethylene Oxide, Propylene Oxide

A

Highly effective at denauting proteins nucleic acids
high level sterilant if given long exposure times (5-10 hours)

Glutaraldehyde

  • Used in presence of organic material (medical/dental equipment/ tattoo parlors)
  • Kills vegetative bacteria in 10 minutes and spores in 10 hours

Ethylene Oxide, Propylene Oxide

  • Gaseous state lets penetration into hard to reach areas (equipment, implants, heat sensitive materials)
  • Very toxic, explosive and carcinogenic (treated equipment must be flushed with sterile air before use)
25
Q

When things go wrong

Outbreaks of hospital-acquired infections blamed on “failure” of a
germicide are instead usually due to:

A
  • Not following procedures and manufactor instructions
  • improper cleaning before use (not removing organic material)
  • Using wrong agent for situation
“Soap, water, and common sense are yet the best antiseptics”
	                                        William Osler (1849-1919)
26
Q

Germicidal Chemicals in household (consumer products)

A
  • contain chemical to make them antibacterial
  • modest amounts

Concerns:

  • resistance building
  • removal of normal flora
27
Q

Chemicals used as Preservatives 4

A

A product is microbiologically spoiled if:

  • Microbes with pathogenic potential present
  • Toxic microbial metabolites (eg LPS) present
  • Microbial growth caused deterioration

Chemical can be added to products to prevent spoilage

  • minimize risk of microbes introduced during making
  • keep product safe after making

Chemicals sometimes kill microbes directly, but usually just alter environment so they cant grow (high acidity and low water activity)

Main requirement is that chemical be completely non toxic

28
Q

“Aseptic” Techniques & Procedures

A

Practices & procedures to protect a patient from infection and prevent the spread of pathogenic microbes

29
Q

Medical Asepsis (AKA CLEAN techniques) 5

A
  • Reduce the number, or growth, or spread of germs on an object or environment
  • Cleaning environment (disinfecting also)
  • Proper handling and disposure of contaminated materials
  • Handwashing
  • Barrier precautions as needed (gloves)

Applied in all areas

30
Q

Surgical Asepsis (AKA STERILE Techniques) 2

A

Eliminate all microbes and low risk of new ones

High risk areas

  • Operatings rooms, labor and delivery
  • Lab Diagnostic area (cariac cath lab)
  • At Bedside in 3 main situations
    1. Where skin is punctured
    2. If skin is exposed because of burns/open wounds
  • Medical device inserted into sterile body
31
Q

Setting up and working in a sterile field 5 steps

A
  1. Sterile touch sterile
  2. 1 inch from sterile is not sterile
  3. Arms and hands remains above waist and below shoulders
  4. If you cant see it, its not sterile so don’t turn your back
  5. Sterile field becomes contaminated as it is exposed to air (don’t talk or move)

Situational awareness” is key (ie. constantly be aware of your surroundings and think about what you’re doing)

MCIM 223 (21 decks)

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