Microbiology: The Control of Microbial Growth

Vocabulary practice flashcards covering terminology, physical methods, evaluation techniques, and chemical agents used for microbial control from Chapter 7 of Tortora, Funke, and Case's Microbiology: An Introduction (11th Edition).

Sepsis

Microbial contamination; derived from the Greek word for decay or putrid.

Asepsis

The absence of significant microbial contamination; aseptic techniques prevent contamination of surgical wounds and medical equipment.

Sterilization

The destruction or removal of all forms of microbial life, including bacterial endospores (with the possible exception of prions).

Commercial Sterilization

A heat treatment sufficient to kill endospores of Clostridium botulinum in canned food without degrading product quality.

Disinfection

The destruction or removal of vegetative pathogens on inanimate objects or surfaces using chemical or physical methods.

Antisepsis

The destruction or removal of vegetative pathogens from living tissue, almost always accomplished using chemical antimicrobials.

Degerming

The mechanical removal of microbes from a limited area, such as scrubbing skin with soap and water or an alcohol swab prior to an injection.

Sanitization

A treatment intended to lower microbial counts on eating and drinking utensils or environmental surfaces to safe public health levels.

Biocide (Germicide)

A chemical or physical agent that directly kills microorganisms, usually with certain exceptions such as bacterial endospores.

Bacteriostasis

A treatment or condition that stops or inhibits bacterial growth and multiplication without killing the cells.

Thermal Death Point (TDP)

The lowest temperature at which all microorganisms in a particular liquid suspension are killed in $10\,\text{min}$.

Thermal Death Time (TDT)

The minimal length of time required to kill all microorganisms in a particular liquid culture at a given temperature.

Decimal Reduction Time (DRT)

The time in minutes required to kill $90\%$ of a microbial population at a specific temperature.

Autoclave

An apparatus that utilizes moist heat in the form of steam under pressure (typically $121^\circ\text{C}$ at $15\,\text{psi}$ for $15\,\text{min}$) to denature proteins and achieve complete sterilization.

Pasteurization

The application of mild heat (such as $72^\circ\text{C}$ for $15\,\text{sec}$) to reduce spoilage organisms and eliminate pathogens in milk and beverages without damaging flavor.

Membrane Filtration

The passage of heat-sensitive liquids (such as vaccines or enzymes) through a screenlike cellulose or plastic filter with pores typically $0.22\,\mu\text{m}$ in diameter to remove bacteria.

High-Efficiency Particulate Air (HEPA) Filter

A specialized air filter designed to remove microorganisms and particles larger than $0.3\,\mu\text{m}$ from the surrounding environment.

Desiccation

The removal of water from microorganisms, which halts cellular metabolism and produces a primarily bacteriostatic effect.

Plasmolysis

The shrinkage of a microbial cell's cytoplasm caused by the osmotic outflow of water in a hypertonic environment created by high concentrations of salt or sugar.

Ionizing Radiation

High-energy radiation (including gamma rays, X-rays, and high-energy electron beams) that ionizes water into reactive hydroxyl radicals ($\cdot\text{OH}$) to destroy microbial DNA.

Nonionizing Radiation

Radiation with longer wavelengths, specifically ultraviolet (UV) light around $260\,\text{nm}$, that damages DNA by inducing the formation of thymine dimers.

Use-Dilution Test

A standard method for evaluating disinfectant effectiveness wherein bacteria-coated metal carrier rings are dried, submerged in disinfectant at $20^\circ\text{C}$ for $10\,\text{min}$, and incubated in culture broth to monitor bacterial survival.

Disk-Diffusion Method

A laboratory assay where paper filter disks impregnated with specific antimicrobial chemicals are placed onto an inoculated agar plate to evaluate efficacy by observing zones of inhibition.

Phenolics

Chemically altered derivatives of phenol that reduce skin irritation and increase antimicrobial action; they disrupt plasma membranes, denature proteins, and remain active in the presence of organic matter.

Bisphenols

Phenol derivatives consisting of two phenolic groups bridged together (e.g., hexachlorophene and triclosan) that inhibit bacteria by disrupting lipid plasma membranes.

Biguanides

Broad-spectrum chemical disinfectants and antiseptics (such as chlorhexidine) that disrupt microbial plasma membranes, widely used for skin disinfection before surgery.

Tincture

An antimicrobial preparation consisting of an active chemical compound (such as iodine) dissolved in an aqueous alcohol solution.

Iodophor

A complex of iodine and an organic carrier molecule (e.g., povidone-iodine) that slowly releases iodine, providing antiseptic action without staining or severe irritation.

Quaternary Ammonium Compounds (Quats)

Cationic detergent surface-active agents that denature proteins and disrupt plasma membranes; strongly bactericidal against gram-positive bacteria, fungicidal, and virucidal against enveloped viruses.

Oligodynamic Action

The ability of minute amounts of heavy metals (such as silver, mercury, zinc, and copper) to exert antimicrobial effects by denaturing cellular proteins.

Bacteriocin

An antibacterial peptide or protein synthesized by one bacterium that inhibits or kills other closely related bacteria (e.g., nisin used in food preservation).

Aldehydes

Potent chemical antimicrobial agents (such as formaldehyde and glutaraldehyde) that cross-link functional groups ($-\text{NH}_2$, $-\text{OH}$, $-\text{COOH}$, $-\text{SH}$) on cellular proteins, inactivating them.

Ethylene Oxide

A gaseous chemical sterilant that replaces labile hydrogen atoms in microbial proteins with alkyl radicals, achieving sterilization of heat-sensitive materials at ambient temperatures.

Plasma (Microbial Control)

A luminous, excited state of gas filled with free electrons and ions that produces reactive free radicals to rapidly sterilize narrow, hollow tubular surgical devices.

Supercritical Fluid

A state of matter combining the properties of a gas and a liquid (such as supercritical $\text{CO}_2$), capable of penetrating materials and cellular boundaries to sterilize medical implants.

Peroxygens

A class of powerful oxidizing agents (including ozone, hydrogen peroxide, and peracetic acid) used to decontaminate surfaces and sterilize medical instruments.