Control of Microorganisms by Physical and Chemical Agents

Vocabulary flashcards covering key terms and definitions from the lecture notes on the control of microorganisms by physical and chemical agents.

Sterilization

The process by which all living cells, spores, and acellular entities are destroyed or removed from an object or habitat.

Sterilant

A chemical agent capable of achieving sterilization.

Disinfection

The killing, inhibition, or removal of microorganisms that may cause disease; primarily used on inanimate objects and may not destroy all spores.

Disinfectant

A chemical agent used to carry out disinfection; usually applied to inanimate objects and may not sterilize.

Sanitization

Reduction of the microbial population to levels considered safe by public health standards; the object is cleaned as well as partly disinfected.

Antisepsis (antiseptic)

The prevention of infection by applying antiseptics to living tissue, killing or inhibiting pathogen growth and reducing the overall microbial population; less toxic than disinfectants.

Chemotherapy

Chemicals used internally to kill or inhibit the growth of microorganisms within host tissues.

Endospore

A highly resistant, dormant form produced by some bacteria that survives harsh conditions and is difficult to destroy with common disinfectants.

Germicide

An agent that kills pathogens (and many non-pathogens) but may not kill endospores.

Bactericide

An agent that kills bacteria.

Bacteriostatic

An agent that inhibits the growth of bacteria but does not necessarily kill them.

pasteurization

Controlled heating (usually around 55–60°C) to destroy pathogens and reduce spoilage in foods and beverages; does not achieve sterilization.

Autoclave

A device that uses saturated steam under pressure (typical: 121°C, 15 psi) to sterilize; conditions kill vegetative cells and endospores in minutes; requires proper air removal and time.

Moist heat

Sterilization or disinfection using steam or boiling water; more effective than dry heat due to protein and nucleic acid damage.

Dry heat

Sterilization using dry air/heat (e.g., ovens, incineration); slower and often less effective than moist heat but suitable for heat-stable materials.

D value

Decimal reduction time; the time required at a specific temperature to kill 90% of the microorganisms in a suspension.

z value

The temperature increase needed to reduce the D value by tenfold (i.e., to shift the lethality curve).

F value

The time (in minutes) at a specified temperature needed to achieve a prescribed level of lethality.

12D concept

Heating to achieve a 12-log reduction (e.g., from 10^12 spores to 1 spore) under defined conditions.

Biofilm

A structured community of microorganisms attached to a surface, embedded in an extracellular matrix, which often protects microbes from antimicrobials.

Depth filter

A thick layer filter (e.g., diatomaceous earth, Chamberlain filters) that removes microorganisms by physical screening and adsorption.

Membrane filter

A thin porous membrane (about 0.2 μm pores) that removes microorganisms by size exclusion; used for sterilizing heat-sensitive liquids.

HEPA filter

High-efficiency particulate air filter that removes 99.97% of 0.3 μm particles.

Laminar flow biological safety cabinet

A cabinet that forces air through HEPA filters to create a sterile curtain across the opening, protecting the worker and the product.

Ethylene oxide

A gaseous sterilant used to sterilize heat- and moisture-sensitive items, capable of destroying endospores.

Vaporized hydrogen peroxide

A gaseous sterilant used to achieve sterilization of equipment and rooms.

Ultraviolet (UV) radiation

Radiation around 260 nm that is lethal to microorganisms but has poor penetration; used for sterilizing air and exposed surfaces in specific settings.

Ionizing radiation

Gamma or other high-energy radiation that penetrates materials and sterilizes by destroying DNA; effective against endospores and many organisms; used to sterilize drugs, sutures, and some foods.

Aerosol

A gaseous suspension of liquid or solid particles that can be generated during laboratory work and may pose infection risks.

Aseptic technique

A set of practices to prevent contamination by microorganisms during handling and experiments.