Disinfectants and Antiseptics Flashcards
What is the Classification of Disinfectants?
- Low level disinfectants
- Intermediate level disinfectants
- High level disinfectants (chemical sterilants)
Describe the Characteristics of Low Level Disinfectants
- Kill most vegetative bacteria and some fungi and viruses
- Don’t kill mycobacteria or bacterial spores
- Used to clean environmental surfaces
Describe the Characteristics of Intermediate Level Disinfectants
- Kill vegetative bacteria, most viruses and fungi
- Don’t kill resistant bacterial spores
Describe the Characteristics of High Level Disinfectants
- Destroys vegetative (growing) bacteria, mycobacteria, fungi and viruses
- Does not necessarily kills bacterial spores, must be capable of sterilisation when contact time is extended
What are the Factors Effecting the Effectiveness of Disinfectant?
- Number of Microbes
- Type of Microbes
- Material in Contact with
- Temperature
- Time of Exposure
- Presence of Excipients
- Chemical nature of disinfectant
- Concentration and Quanitity of Disinfectant
Factors Effecting the Effectiveness of Disinfectant: Number of Microbes
- The more microbes, the longer it takes to eliminate
Factors Effecting the Effectiveness of Disinfectant: Type of Microbes
- Mycobateria, spores and certain viruses can be very resistant to disinfection
- Vegetative cells are easiest to kill
Factors Effecting the Effectiveness of Disinfectant: Material in Contact With
- Presence of Organic Material (e.g. blood, saliva, faeces) inhibits antimicrobials
- High protein based materials absorb and neutralise some chemical disinfectants
Factors Effecting the Effectiveness of Disinfectant: Temperature
Cold temperatures inhibit disinfectant activity
Factors Effecting the Effectiveness of Disinfectant: Time of Exposure
Chemical antimicrobials are more effective at longer contact times
Factors Effecting the Effectiveness of Disinfectant: Presence of Excipients
Excipients e.g. surfactants may inactivate some
Disinfectant Susceptibility of Microbes: Gram-Negative Bacteria
Double membrane; more resistant
Disinfectant Susceptibility of Microbes: Growth Phase
Stationary-Phase bacteria more resistant than log-phase
Disinfectant Susceptibility of Microbes: Mycobacteria, endospores and protozoan cysts
Extremely resistant
Disinfectant Susceptibility of Microbes: Virus Envelope
Non-enveloped viruses are generally more resistant that enveloped viruses to disinfectants and antiseptics
What are the Modes of Action of Disinfectants and Antiseptics
- Damage lipids and/or proteins of the semi-permeable cytoplasmic membrane of microorganisms resulting in leakage of cellular materials needed to sustain life
- Denature microbial enzymes and other proteins, usually by disrupting the hydrogen and disulfide bonds (3D Shape) therefore blocks metabolism
What are the Types of Disinfectants?
- Alcohols
- Phenols and Phenolics
- Chlorhexidine (CH)
- Heavy Metal Compounds
- Quaternary Ammonium Compounds
- Aldehydes
- Peroxygens (oxidising agents)
- Paracetic Acid
Describe the Characteristics of Alcohols as a Disinfectant
- Kill bacteria and fungi, not endospores or non-enveloped viruses
- Act by denaturing proteins and disrupting cell membranes (kill in 30 secs)
- Examples: wipe microbes off skin before infections
- Not good for open wounds - cause proteins to coagulate
Describe the Characteristics of Phenols and Phenolics as a Disinfectant
-
Advantages:
- Stable; persist for long times after applied
- Remain active in the presence of organic compounds
-
Disadvantages:
- Skin irritant
- Neurological damage in infants
- E.g. throat sprays and lozenges, local anaesthetic
Describe examples of Chlorhexidine as a Disinfectant
- Preoperative bathing
- Prevent surgical site infection
- ICU: daily CHG washcloth intervention reduce bloodstream infections
Describe the Characteristics of Heavy Metal Compounds as a Disinfectant
- Hg and Ag significant germicides
- Small antimicrobial activity
- Bind onto functional groups of proteins and inactivate them
- Disadvantages
- Very toxic
- Cause allergic reactions
- Microbes can develop resistance
- Large quantities of biological fluids and wastes neutralise their actions
- E.g. silver nitrate: topical antiseptic, ophthalmic treatments, ointments, wart removal
Describe the Characteristics of Quaternary Ammonium Compounds as a Disinfectant
- Denatures protein and disrupts lipids in cell wall
-
Advantages
- Strong antimicrobial action
- Stable
- Non-toxic
- Colourless
- Odourless
-
Disadvantages
- Forms foam
- Organic matter interferes with effectiveness
- Neutralised by soaps and anionic detergents
Describe the Characteristics of Aldehydes as a Disinfectant
Gluteraldehyde
Formaldehyde
- Gluteraldehyde
- Less irritating and more effective than formaldehyde
- Sterilising agent
- Used to disinfect hospital instruments
- Formaldehyde
- Taurosept: treatment and prevention of catheter infections
- Broad antimicrobial, bactericidal and antifungal spectrum
- Prevention of biofilm formation
- Taurosept: treatment and prevention of catheter infections
Describe the Characteristics of Peroxygens (oxidising agents) as Disinfectant
- Hydrogen peroxide
- Used as antiseptic
- Not good for open wounds - quickly broken down by catalase
- Sporicidal at higher temperatures
- Benzoyl peroxide
- Acne medications
Describe the Characteristics of Paracetic Acid as Disinfectant
- Effective liquid sporicides available
- Sterilant
- Kills bacteria and fungi <5 mins
- Kills endospores and viruses within 30 mins
- Medical instruments because no toxic residue is left
Describe Drug Efflux Pumps
- Give resistance to disinfectants and antiseptics
- Efflux wide range of compounds = resistance to most disinfectants/antiseptics
