Sterlization and Disinfection

Body’s own defenseive mechanisms

Field of immunology

Chemotherapeutic Agents

Antibiotics

Public Health Measures

National, state, and local guidelines for air, water, food safety, health clinics, and epidemiology

Sterilization and Disinfection

Control of infectious agents by physical and chemical means

Sterilization

The destruction of all forms of life, including bacterial spores. All or nothing

Free of viable organisms

Absolute state

cide/cidal

To kill, make nonviable

Stasis/static

prevent multiplication without killing

Disinfection

Process that eliminates a defined scope of microorganisms, including some spores

Disinfectant

Chemical agent used on inanimate objects such as medical instruments to destroy microorganisms

Antiseptics

Chemical agents applied to skin to eliminate or reduce the number of bacteria present. Spores unaffected

Sepsis

A toxic condition resulting from the presence of microbes or microbial products (toxins) in body

Asepsis

Condition free of viable microorganisms

Goal or technique

Health Care-Associated Infections

Infection acquired during a hospital stay or from other healthcare providers

Surfactants

Compounds that lower surface tension between two liquids, a gas, and a liquid, or between liquid and solid.

Detergent

Surfactant or mix of surfactant with cleansing properties when in dilute solutions.

Soap

Salt or fatty acid used for cleaning and lubricating. Soaps are surfactants

To be effective, need to be used with handwashing.

Primary purpose is to remove organic matter such as oils and dead skin cells that may harbor microorganisms.

Surgical Aspetic Techniques

Practices that prevent microorganism from gaining access to surgical wounds and tissues of patients.

Prevention starts before patient enters operating room.

Cleaning and disinfecting skin area to be opened

Medical Aspetic Techniques

Practice designed to keep objects, personnel, patients, and hospital environment free from agents that cause disease

Involved in every individual involved in hospital work.

Change gloves frequently

10-40 lbs of solid waste per patient per day

Body Substance Precautions

System of isolation in which barrier techniques are used for specific patient interactions rather than specific diagnoses

All body fluid needs to be considered infectious

Specification for body substance precautions

1. Body substance precautions shall be standard of care for all patients
2. Gloves shall be worn
3. Face protection
4. Gowns or aprons shall be worn
5. Private room assigned if patient soils general room environment with moist body substances

HIgh-virulence Airborne Disease

TB and Covid

Special precautions are taken for patients

Infection Control Committee

Establish and operate practical system for reporting and evaluating infections in patients, personnel, and discharged patients.

Universal Precautions

Bio-safety precautions in lab = universal precaution

Assume all specimen are infectious for blood-borne pathogen such as Hepatitis B

Place every specimen in well-constructed secure lid

Wear gloves and face shield

Never pipette by mouth. Use pipetting aids

Decontaminate all lab work

Limit use of needles and syringes

Decontaminate materials used before reprocessing

Always wash hand

Cleaning a Bio-Hazardous Spill

1. Contain spill


1. Cover with absorbent material- paper towels
2. Saturate towels with appropriate disinfectant solution


1. 1:10 bleach
2. Pour or squirt from outer edge toward center to create barrier
3. Wait 10 - 15 minutes
4. Discard everything into an appropriate container

Level of Disinfection

Sterilization

High-Level

Intermediate-Level

Low-Level

Critical Items

Require sterilization

Surgical instruments and needles

Semi-critical items

Touch intact mucous membranes.

Require high-level disinfection

Endoscopes cytoscopes

Non-critical items

Touch unbroken skin.

Intermediate to low-level disinfection

BP cuff

Factors Influencing degree of killing

Type of bug

Number

Surface

Contact Time

Temperature

pH

Biofilms

Concentration of disinfecting agent

Presence of organic material like blood

Interfering Matter

Soil

pH

Soil

Organic matter such as blood, urine

Provides protection for microorganisms against disinfectants

pH

Acid foods are easier to sterilize than when alkaline conditions exist

Variation within a population

Microorganism within population are subjected to antimicrobial agents or processes don’t all die at once. In different states.

Problem Microorganism

Bacterial endospores

Mycobacteria

Blood Borne Agents

Environmental Organisms

Bacterial Endospores

Most resistant forms of life. Some can withstand 20 hours in boiling water.

Mycobacteria

Resistant to aqueous disinfectants of waxy cell hydrophobic.

Blood-Borne Viruses

Problem agent because of inapplicability of sterilizing measures for situations in transmission most frequently occurs

Environmental Organisms

Found everywhere and are often resistant to chemical disinfections.

Heat to achieve sterility

1. Moist Heat - at least 60 C for 30 minutes
2. Steam under pressure (autoclave) 15 lb. 121 C for 15 min or more
3. Dry Heat 170 C for 2 hours
4. Pasteurization - similar to moist heat, above. Kill vegetative organisms without damaging taste
5. Open Flames/incinerators - inoculating loops, tweezers
6. Cold is never method of sterilization

Filter to Achieve Sterility

1. Membrane Filter Used extensively in preparing media that cannot withstand autoclaving and solutions for patient use
2. High-efficiency particulate air filters used to filter air in operating suites and rooms of burn patients.
3. Filters fail when it comes to viruses

Radiation to achieve sterility

1. Ionization radiation - sterilize plastics more suggested
2. Ultra-Violet - has little penetration and can only kill organisms suspended in air or on surfaces. Cannot penetrate shadows

Chemical Agents

Few chemical agents achieve sterility.

No one appropriate for all circumstances.

Diluted may be better

Chlorine

Bleach

Chlorine Gas treated for swimming pools

Sodium hypochlorite: most effective for HIV.

Inexpensive

1:10 dilution

Aldehydes

1. Formalin, a 37% aqueous solution of formaldehyde gas, used to preserve biological specimens and inactivate bacteria and viruses in vaccines
2. Glutaraldehyde, less irritating and better disinfectant. Bacterilcidal, tuberculocidal, and virucidal in 10 minutes and sporicidal in 3 to 10 hours.

Phenol

1. Phenol (carbolic acid) first antiseptic. Good at killing bacteria but not viruses
2. Phenolics (lysol) prepared in combination with soap or detergent

Chlorohexidine

Frequently in healthcare

Broad antimicrobial activity and persistent activity

Alcohols

Effectively kill vegetative bacteria (including TB) and fungi, but not endospores and nonenveloped viruses

Nontoxic, tend to dry

Inactivated by organic matter

Iodine

1. Iodine Tincture - solution in aqueous alcohol
2. Iodophor - Betadine and Isodine
3. Excellent skin antiseptic agents.

Heavy Metals as Disinfectants

Silver

Mercuric Chloride

Copper Sulfate

Zinc Chloride

Oxidizing Agent

Ozone

Hydrogen Peroxide

Benzoyl Peroxide (for anaerobic pathogens)

Quaternary Ammonium Compounds

Low-level disinfectant with detergent properties that is bactericidal, fungicidal, and virucidal against lipid viruses

Not effective against TB or viruses without envelope

Not compatible with soap

Gaseous Chemosterilizers

Gases used in closed chamber like autoclave

Ethylene oxide kills all microbes and endospores but requires longer exposure peroid of 40 to 18 hours but is toxic and explosive

Used for medical supplies and equipment