Chalter 9: Chemical Control of Microbes (Down to before Phenol)

For chemical control what state can it occur at? What is the range of chemical controls? What are the two types of dissolved chemicals used?

• Occur in the liquid, gaseous, or solid state

• Range from disinfectants and antiseptics to sterilants and preservatives

• Aqueous: chemicals dissolved in pure water as the solvent (“Aqueous of Iodine”)

• Tinctures: chemicals dissolved in pure alcohol or alcohol-water mixtures (“Tincture of Iodine”)

What are the 5 factors affecting the germicidal activity of chemicals?

• Nature of the microorganisms being treated

• Nature of the material being treated

• Degree of contamination

• Time of exposure

• Strength and chemical action of the germicide

What are the desirable qualities in a chemical germicide?

• Rapid action, even in low concentrations

• Solubility in water or alcohol and long-term stability

• Broad-spectrum microbicidal action without being toxic to human and animal tissues

• Penetration of inanimate surfaces to sustain a cumulative or persistent action

• Resistance to becoming inactivated by organic matter

• Not corrosive and nonstaining

• Sanitizing and deodorizing properties

• Affordability and availability

What is the 4 point scheme of chemical methods of control?

1. Does it achieve sterilization

2. Use/forms

3. Mode of action

4. Special characteristics

What are the two halogens? What are the targets of halogens/Do they kill Endospores reliable? What does this mean?

The two halogens are chlorine and iodine

• Can kill endospores but very slowly and unreliably (also kill all other microbes)

• This means they can sterilize sometimes but not always and it’s not reliable

What is the 4 point scheme of chlorine (Halogen)?

1. Does it achieve sterilization: Can kill endopores and sterilize but it’s very slow and unreliable

2. Use/forms: 2a. Gaseous or Liquid chlorine (Cl2): disinfect drinking water, sewage and waste water

2b. Hypochlorite: used in health care to treat wounds (antiseptic), disinfect bedding and instruments, sanitize food equipment and in restaurants, pools, and spas (use changes based on concentration)

3. Mode of action:

4. Special characteristics: Less effective if exposed to light, alkaline pH, and organic matter

What is the 4 point scheme of Iodine (Halogen)?

1. Does it achieve sterilization: Can kill endopores and sterilize but it’s very slow and unreliable

2. Use/forms: 2a. Iodine aqueous solution: used as a topical antiseptic; higher concentration used as a disinfectant for plastic and rubber instruments

2b. Iodophors (complexes of iodine and alcohol): iodine released slowly; used to prepare skin for surgery, in surgical scrubs, to treat burns, and as a disinfectant

3. Mode of action

4. Special characteristics: Extremely irritating to the skin and is toxic when absorbed (can be safe based on diff. contractions); many iodophors banned in consumer products in 2017

What is the 4 point scheme of oxidizing agents?

1. Does it achieve sterilization: Can kill endospores but only in high concentrations, unreliable (sometimes but not always)

2. Use/forms: 2a. Peracetic acid

   2b. Hydrogen peroxide: 3% hydrogen peroxide used for skin (antiseptic) and wound cleansing, mouth washing, bedsore care; used to treat infections caused by anaerobic bacteria; 35% hydrogen peroxide used for sterilizing delicate instruments

3. Mode of action:

4. Special characteristics: Can kill endospores only in high concentrations (not a reliable sterilizing

   agent)

What are the two forms of oxidant agents? Describe the differences in concentration for hydrogen peroxide. What does the anaerobic bacteria do?

1) Peracetic acid

2) Hydrogen peroxide: 3% hydrogen peroxide used for skin and wound cleansing, mouth washing, bedsore care; used to treat infections caused by anaerobic bacteria; 35% hydrogen peroxide used for sterilizing delicate instruments

• The anaerobic bacteria eat on dead tissue; this prevents growth b/c the cells product O2 which is problematic for anaerobic bacteria

What is the 4 point scheme for Aldehydes?

1. Does it achieve sterilization: reliably kills Endospores

2. Use/forms: Glutaraldehyde: kills rapidly and is broad-spectrum (kills many types of bacteria); used to sterilize respiratory equipment, scopes, kidney dialysis machines, dental instruments

3. Mode of action

4. Special characteristics: Glutaraldehyde is somewhat unstable

What is the 4 point scheme of Ethylene Oxide gas?

1. Does it achieve sterilization: Reliably kills endospores: gaseous sterilant (only reliable sterilization as a gas)

2. Use/forms: Ethylene oxide gas: used to sterilize syringes, surgical supplies, and medical devices that are prepackaged

3. Mode of action

4. Special characteristics: Ethylene oxide is explosive, it can damage lungs, eyes, and mucous membranes if contacted directly; ethylene oxide is rated as a carcinogen