Disinfection, Antiseptics, and Decontamination

Disinfection

• A physical or chemical process that eliminates disease causing microorganisms, but not necessarily spores

Disinfectants

• Chemicals or mixtures that eradicate microorganisms, but not necessarily spores
• Usually applied to inanimate surfaces or objects

Properties of an Ideal Disinfectant/Preservative

• Exhibits a broad spectrum of activity
• Maintains high potency under various conditions
• Does not harm linen or metals
• Compatible with other formulation agents or container components
• Remains stable during storage and across a wide pH range
• Economical
• Lacks offensive odors
• Non-staining

Antiseptics

• Substances that inhibit microbial growth without necessarily killing microbes
• Typically applied to body surfaces

Decontamination

• Any process that removes or kills microorganisms
• Can neutralize hazardous chemicals and radioactive materials

Cleaning

• Process that removes dirt, organic matter, and stains that can interfere with decontamination
• Methods include brushing, vacuuming, dry dusting, and damp mopping with detergent

Pre-cleaning

• Necessary for effective disinfection or sterilization
• Should be performed carefully to prevent exposure to infectious agents
• Requires using materials compatible with subsequent germicides
• Often involves using the same chemical germicide as disinfection

Chemical Germicides

• Can be harmful to humans and the environment
• Must be carefully selected, stored, handled, and disposed
• Gloves, aprons, and eye protection are recommended when preparing dilutions

Chlorine

• Fast-acting, broad-spectrum chemical germicide
• Relatively harmless to human tissues, easy to handle, colorless, and non-staining
• Sold as bleach, a diluted aqueous solution of sodium hypochlorite (NaOCl)
• Solutions may last up to a week
• Solutions used with materials with high levels of organic matter should be changed daily
• Solutions:
  • General all-purpose laboratory disinfectant: 0.1% available chlorine
  • Biohazardous spillage: 0.5% available chlorine

Disinfecting Water with Chlorine

• Use a final concentration of 1–2 mg/l (1 – 2 ppm) available chlorine
• Bleach is not recommended as an antiseptic
• Chlorine gas poses significant health risks due to its toxicity, leading to respiratory distress and other serious health issues. Therefore, the unregulated and excessive application of bleach must be strictly avoided to prevent accidental exposure.

Iodine Iodophors

Act similarly to chlorine but are less inhibited by organic matter

Can stain fabrics and environmental surfaces

• Iodophors and tinctures of iodine are effective antiseptics
• Povidone-iodine is a reliable surgical scrub and skin antiseptic
• Organic iodine-based products should be stored at 4–10°C to prevent bacteria growth
• Iodine solution is effective against many protozoans
• Iodine can be toxic, but is safe for human tissue at proper concentrations

Tincture of Iodine Disadvantages

• Stains tissue
• Causes skin irritation
• Causes allergic reactions
• Can be intrinsically contaminated with Burkholderia cepacia & Pseudomonas aerogenosa
• Causes pseudobacteraemia and peritonitis

Glutaraldehyde

• Active against bacteria, spores, fungi, lipid and non-lipid viruses
• Non-corrosive and faster-acting than formaldehyde
• Requires several hours to kill bacterial spores
• 2% solution needs to be "activated" to be made alkaline
• Activated solutions can be reused for 1–4 weeks depending on use
• Discard solutions that become turbid

Glutaraldehyde Disadvantages

• Toxic and irritating to skin and mucous membranes, avoid contact
• Must be used in fume-hoods or ventilated areas
• Not recommended as a spray or solution for environmental surfaces

Cidex-OPA

• O-Phthalaldehyde
• Does not require activation
• Not an irritant to eyes and nasal passages
• Stable over a pH range of 3-9
• Requires no exposure monitoring
• Has a barely perceptible odor
• Effective against mycobacteria, including glutaraldehyde-resistant strains

Phenolic Compounds

• Earliest germecides used
• Germicides are essential for controlling infectious diseases by eliminating pathogenic microorganisms across various environments. They target bacteria, fungi, and viruses to ensure hygiene in medical, industrial, and domestic settings. Their effectiveness depends on factors like composition, concentration, and organic matter presence. Selecting the right germicide requires consideration of contact time, environmental impact, and safety. Proper usage, including dilution and safety precautions, maximizes benefits while reducing risks.
• Active against vegetative bacteria, lipid-containing viruses, and fungi
• Show activity against mycobacteria
• Inactive against spores
• Variable activity against non-lipid viruses

Phenolic Compound Disadvantages

• Inactivated by water hardness
• Incompatible with cationic detergents
• Not recommended for food contact surfaces or use around young children
• Absorbed by rubber and can penetrate skin

Triclosan

• Bisphenol compound
• Common in hand-washing products
• Active mainly against vegetative bacteria
• Safe for skin and mucous membranes
• Has anti-inflammatory properties

Dettol

• Contains halophenol (chloroxylenol)
• Widely used
• Bactericidal, but P. aeruginosa and many molds are highly resistant

Chlorhexidine

• A cationic bisguanide
• Available as a 4% solution in a detergent base
• Bactericidal against Gram-positive and Gram-negative bacteria
• Effective against HIV, herpes virus, and influenza virus
• Minimally affected by blood and organic materials
• Inactivated by soaps and anionic detergents

Alcohols

• Ethanol (ethyl alcohol) and 2-propanol (isopropyl alcohol) both have similar disinfectant properties
• 70–80% solutions are typically used
• Concentrations above 90% and below 50% are generally ineffective
• Isopropyl alcohol is effective up to 99%
• Leaves no residue on surfaces
• Kills vegetative cells, but not spores, after 10 minutes of exposure

Alcohol Uses

• Can be used on skin, laboratory benches, biosafety cabinets, and surgical instruments
• Alcohol-based hand-rubs are used to decontaminate lightly soiled hands when hand-washing is not possible

Alcohol Precautions

• Alcohols are volatile and flammable, do not use near open flames
• Label alcohol-containing bottles to avoid autoclaving

Hydrogen Peracids

• Hydrogen peroxide (H2O2) and peracids are strong oxidants
• Can be potent broad-spectrum germicides
• Safer than chlorine for humans and the environment

Hydrogen Peroxide

• 3% solution is a harmless but weak antiseptic
• Primarily used clinically for wound cleansing
• An effective disinfectant for inanimate materials
• Used for decontamination of laboratory benches and biosafety cabinets

Stronger Solutions of Hydrogen Peroxide

• Suitable for disinfecting heat-sensitive medical and dental devices
• Using vaporized hydrogen peroxide or peracetic acid for heat-sensitive devices requires specialized equipment like a plasma sterilizer
• Hydrogen peroxide and peracids can corrode metals like aluminum, copper, brass, and zinc
• Can decolorize fabrics, hair, skin, and mucous membranes
• Treated articles must be rinsed before contact with eyes and mucous membranes
• Should be stored away from heat and protected from light

Surface-Active Agents

Detergent substances divided into three groups: anionic compounds, soaps, and sodium or potassium salts

Cationic Substances

• Cationic detergents are equally effective against Gram-positive and Gram-negative bacteria

Quaternary Ammonium Compounds (QACs)

• Used in mixtures and with other germicides, like alcohols
• Effective against vegetative bacteria
• Affect lipid-enveloped viruses (e.g., HIV and HBV) but not non-enveloped viruses
• Benzalkonium chloride is used as an antiseptic

QAC Disadvantages

• Germicidal activity is reduced by organic matter, water hardness, and anionic detergents
• Potentially harmful bacteria can grow in quaternary ammonium compound solutions
• Low biodegradability may cause them to accumulate in the environment

Spill Clean-Up Procedures

• Wear gloves and protective clothing
• Cover the spill with cloth or paper towels
• Pour 5–10% bleach solution around the spill area
• Apply disinfectant concentrically, working towards the center of the spill
• After 30 minutes, clear away materials
• Use a dustpan for broken glass or sharps, dispose in a puncture-resistant container

Decontamination of Skin

• Wash the area thoroughly with soap and water
• Do not use detergents or abrasive materials to avoid skin damage

Decontamination of Cuts/Eyes

• Irrigate with water, preventing cross-contamination between areas

Decontamination of Clothing

• Remove contaminated garments immediately and place in a container
• Do not remove garments from the spill location until contamination is monitored

Appropriate Solutions for Different Matters

• For most organic matter and bacteria: clear soluble phenolics, diluted according to manufacturers' recommendations
• For blood or viruses: 1% hypochlorites
• Do not use hypochlorite solutions in centrifuges
• Use activated glutaraldehyde (2%) on surfaces for decontamination

Local Environmental Decontamination

• Laboratory areas, furniture, and equipment: sodium hypochlorite with 1 g/l available chlorine
• High-risk situations: stronger solutions (5 g/l)
• For routine environmental decontamination: 3% hydrogen peroxide (H2O2) can substitute for bleach solutions

Fumigation

• Rooms and equipment can be decontaminated by fumigation with formaldehyde gas, generated by heating paraformaldehyde or boiling formalin
• Use 150gm KMnO4 and 280 ml Formalin per 1000 cu ft area
• Conduct fumigation at a temperature of at least 21°C and 70% relative humidity

Post-Fumigation

• Ventilate the area thoroughly before allowing personnel to enter

Neutralize formaldehyde with gaseous ammonium bicarbonate

Choice of Disinfection

• Medical devices, equipment, and surgical materials are divided into three general categories: critical, semi-critical, and noncritical items

Critical Items

• Instruments or objects introduced directly into the bloodstream or sterile areas of the body
• Includes surgical instruments, cardiac catheters, implants, heart-lung oxygenator components, and blood compartments of hemodialyzers
• Require sterility at the time of use

Semi-critical Items

• Noninvasive flexible and rigid fiberoptic endoscopes, endotracheal tubes, anesthesia breathing circuits, and cystoscopes
• Require meticulous physical cleaning followed by high-level disinfection

Non-critical Items

• Do not ordinarily touch the patient or only touch intact skin, such as crutches, bed boards, and blood pressure cuffs
• These items rarely transmit disease
• Washing with a detergent may be sufficient

Disinfection Policies in Four Main Areas of Usage

• Skin and Mucous Membranes: phenols, diaguanides, QACs, iodine preps, and alcohols
• Instruments or Equipment: alkaline, glutaraldehyde, formaldehyde, phenolics, and disaguinides
• Potentially Contaminated Items: phenolics, disaguinides, chlorinated cyanurates, hypochlorites/detergents, and formaldehyde
• Relatively Clean Surfaces: phenolics, disaguinides, hypochlorites

Pharmacists Role

• Ensure disinfectants are properly diluted
• Prepare disinfectants fresh
• Ensure disinfectants are used as directed
• Select the correct disinfectants for the circumstances
• Establish protocols for disinfectant use throughout hospital areas