Microbial Control and Chemical Agents

Vocabulary flashcards covering microbial resistance characteristics, peroxygens, gaseous chemosterilants, food preservatives, and aldehydes based on lecture notes.

Enveloped Viruses

Viruses that are easier to kill because lipid-soluble antimicrobials damage their outer envelope.

Non-enveloped Viruses

Viruses that are more resistant to chemical biocides because they possess only a protein coat, allowing fewer biocides to work against them.

Prions

Infectious proteins that cause neurological diseases (such as mad cow disease); they are extremely resistant to destruction, making normal autoclaving inadequate and requiring incineration of disposable instruments or specialized treatment such as NaOH combined with intensified autoclaving.

Gram-negative Bacteria (Biocide Resistance)

Bacteria that are generally harder to kill and more resistant to biocides than Gram-positive bacteria due to their outer lipopolysaccharide (LPS) membrane and selective porins.

Pseudomonas and Burkholderia

Gram-negative bacterial genera that are especially resistant to many biocides and can even grow in certain disinfectants and antiseptics, particularly quaternary ammonium compounds (quats).

Mycobacteria

A group of bacteria, including Mycobacterium tuberculosis, characterized by high resistance to chemical biocides due to a waxy, lipid-rich layer in their cell wall.

Tuberculocidal

A substance or agent capable of killing mycobacteria.

Bacterial Endospores (Chemical Resistance)

Highly resistant resting structures against which few biocides are effective; glutaraldehyde and chlorine show some effectiveness, alcohol, iodine, and phenolics show poor activity, while chlorhexidine, bisphenols, quats, and silver show none.

Peroxygens

A class of oxidizing agents used for microbial control, primarily represented by hydrogen peroxide and peracetic acid.

Hydrogen Peroxide ($H_2O_2$)

An oxidizing agent that damages cellular components; it is sporicidal at high concentrations, breaks down into harmless water and oxygen, and in vaporized form can sterilize rooms and surfaces, though it is not recommended for open wounds because it damages human cells.

Peracetic Acid (PAA)

One of the most effective liquid chemical sporicides and sterilants; it kills vegetative bacteria and fungi in $<15\,\text{min}$ and endospores and viruses within $30\,\text{min}$, leaves no toxic residue, and remains effective in the presence of organic matter.

Ozone ($O_3$)

An oxidizing agent used in water disinfection that is a stronger killing agent than chlorine, though it breaks down quickly.

Benzoyl Peroxide

An oxidizing agent used as a topical treatment for acne.

Gaseous Chemosterilants

Chemical agents used in a closed chamber for sterilization when physical or heat-based sterilization methods are inappropriate.

Ethylene Oxide (EtO)

A toxic and explosive gaseous sterilant that works at low or room temperature by alkylating and cross-linking proteins and nucleic acids, penetrating deeply to kill all microbes including endospores on heat-sensitive materials.

Chlorine Dioxide

A broad-spectrum chemical agent used in water treatment and food processing that kills bacteria and viruses, can act as an antiseptic at low concentrations, and inactivates cysts and endospores at high concentrations.

Plasma Sterilization

A low-temperature sterilization process that combines hydrogen peroxide with an electromagnetic field or vacuum to create free radicals, effectively destroying microbes and endospore-formers on complex medical and surgical instruments.

Supercritical Fluids

Substances such as supercritical $CO_2$ that possess both liquid and gas properties, used for low-temperature decontamination and sterilization capable of inactivating endospores at around $45\,^{\circ}\text{C}$.

Benzoate and Sorbate

Chemical food preservatives added to inhibit mold growth, particularly in acidic food products.

Propionate

An antifungal chemical preservative commonly incorporated into bread to prevent spoilage.

Nitrates and Nitrites

Preservatives used in processed meats to maintain color and prevent the germination and growth of Clostridium botulinum endospores, preventing botulism.

Nisin

An antibiotic preservative used in cheese to inhibit endospore-forming bacteria.

Natamycin

An antifungal antibiotic preservative utilized primarily in cheese.

Aldehydes

A class of chemical agents, including formaldehyde and glutaraldehyde, that inactivate microbial proteins through cross-linking.

Formalin

A $37\%$ aqueous solution of formaldehyde historically used for preserving biological specimens, now limited due to toxic and carcinogenic concerns.

Glutaraldehyde

A liquid chemical disinfectant and sterilizing agent that is more effective and less irritating than formaldehyde, capable of sporicidal high-level disinfection for hospital equipment such as endoscopes and respiratory devices.