PMB 222: Principles of Sterilization and Disinfection

A collection of vocabulary flashcards covering the principles of physical and chemical sterilization, types of disinfectants, and methods for evaluating antimicrobial potency.

Sterilization

The removal or destruction of all forms of microbial life using physical or chemical methods.

Moist Heat (Autoclaving)

A physical sterilization method using steam under pressure at $121^{\circ}\text{C}$ for $15-20\,\text{minutes}$.

Dry Heat

A sterilization method using hot air ovens at $160^{\circ}\text{C}$ for $2\,\text{hours}$.

Filtration

A physical sterilization method used for heat-sensitive solutions where microbes are removed via membrane filters.

Ionizing Radiation

A form of radiation sterilization involving Gamma rays or X-rays.

Chemical Sterilization

The use of chemical agents such as Ethylene oxide gas, formaldehyde gas, or glutaraldehyde to destroy all microbial life including spores.

Disinfection

The process of eliminating most pathogenic microorganisms, excluding spores, on inanimate objects.

Settle plates

A microbiological sampling method used to monitor microorganisms in the air.

Broad-Spectrum Antimicrobial Activity

The ability of a disinfectant to kill or inactivate a wide variety of pathogens, including bacteria, viruses, and fungi.

Residual Effect

The prolonged activity of an ideal disinfectant that continues to work after application to offer ongoing defense.

Concentration of Disinfectant

The amount of active chemical agent present in a solution, which generally increases killing power but can cause material damage if too high.

Contact Time

The duration for which a disinfectant remains in contact with a surface or microorganism to ensure effective action.

Microbial Load

The number of organisms present; a higher load requires more disinfectant and longer exposure time.

Alcohols

Rapidly bactericidal and virucidal agents like Ethanol and isopropanol; they cause protein coagulation and are used at $50-70\%$ concentrations.

Aldehydes

Sporicidal chemical agents like Formaldehyde and glutaraldehyde used for high-level disinfection of medical equipment.

Halogens

Topical antimicrobial agents such as Chlorine and iodine that bind with protoplasm and oxidize proteins.

Phenolics

Bactericidal agents like Cresols and chlorhexidine that denature proteins; Joseph Lister was the first to use phenol.

Quaternary Ammonium Compounds (QACs)

Cationic surfactants like Benzalkonium chloride effective against bacteria and enveloped viruses.

Oxidizing Agents

Germicides like Hydrogen peroxide that release nascent oxygen to oxidize microbial protoplasm.

Extinction Time Method

A potency evaluation method that measures the time needed for complete killing of microorganisms added to a disinfectant.

Phenol Coefficient Method

A method comparing a disinfectant's effectiveness to phenol by determining the dilution that kills organisms like Salmonella typhi in $10\,\text{minutes}$ but not in $5\,\text{minutes}$.

Bacteriostatic Activity

The ability of an agent to inhibit bacterial growth without actually killing the organisms.

Agar Diffusion Test

Also known as the Kirby-Bauer test; it assesses effectiveness by measuring the zone of inhibition (clear area) around a disc on an inoculated agar plate.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism.

Germicide

A chemical used for non-selective killing or inhibiting growth of microbes on contact.

Antiseptic

A germicide specifically applied on living surfaces.

Formaline

An aqueous solution containing $38-40\%\,(\text{W/V})$ formaldehyde and $10\%$ methanol, used as a potent disinfectant.

Boric acid

A weak, non-irritating antiseptic used in $2-4\%$ aqueous solutions for eye infections or as a mouthwash.

Chlorhexidine (Savlon)

A powerful synthetic cationic biguanide used as a topical antiseptic and wound cleansing agent.

Acriflavine

An acridine dye that exists as an orange-red crystalline powder, used for treating chronic ulcers and burn dressings.

Nitrofurazone

A nitrofuran derivative bactericidal to aerobic and anaerobic bacteria, often used as a $0.2\%$ cream for burns.