Microbial Growth in the Environment

Vocabulary flashcards covering key terms and concepts from the lecture notes on microbial control methods.

Botulinum toxin

Exotoxin that blocks motor neurons and causes flaccid paralysis; toxin is heat-labile.

Flaccid paralysis

Paralysis due to inhibition of motor neuron function, seen with botulinum toxin.

Heat-labile toxin

A toxin that is destroyed by heat

Thermal death point

Lowest temperature that kills all cells in a broth within 10 minutes.

Thermal death time

Time required to sterilize a given volume of liquid at a specified temperature.

Commercial sterilization

Limited treatment that destroys pathogens but not all bacteria.

Disinfection

Process that removes pathogens from inanimate objects

Disinfectant

Chemical used to disinfect inanimate objects.

Degerming

Physical removal of microbes from a surface.

Sanitize

Cleansing to reduce microbial count to a safe level on inanimate objects.

Antisepsis

Removal or inhibition of pathogens from living tissue.

Aseptic

Prevention of contamination by microorganisms

Bactericidal

Kills microorganisms.

Bacteriostatic

Inhibits growth of microorganisms but does not kill them.

High level germicide

Kills all pathogens and bacterial endospores

Intermediate level germicide (4)

Kills fungal spores, protozoan cysts, virus, and pathogenic bacteria (not endospores)

Low level germicide (4)

Eliminate vegetative bacteria, fungi, Protozoa, and some viruses

Microbial death rate

Rate at which a population of microbes dies under a given antimicrobial treatment.

Alter membrane permeability

Disruption of lipid or protein components of the cell membrane leading to leakage and impaired growth.

Damage to proteins

Disruption of enzymes and structural proteins

Damage to nucleic acids

Damage that prevents transcription/translation

Effectiveness of treatment factors (4)

Depends on microbe numbers, environment, exposure time, and microbial traits.

Thick lipid coats

Outer membranes of some microbes that resist antimicrobial penetration.

Protozoan cysts

Resistant dormant forms of protozoa that are hard to eradicate.

Use-Dilution Testing

Method to assess disinfectants by testing with bacteria attached to metal rings and observing survival.

Disk-Diffusion

Method using filter paper disks with disinfectant on an agar plate to measure inhibition zones.

Kelsey-Sykes Capacity Test

Standard test to evaluate a chemical disinfectant’s capacity to control microbes.

In-use Test

Swabs from objects before and after disinfection tested for microbial growth to verify efficacy.

Disk-Diffusion Method

A disk soaked with chemical agent placed on a plate to measure a death/inhibition zone.

Cold method of control

Refrigeration, deep freezing, lyophilization

Desiccation

Drying to remove water and inhibit microbial metabolism.

Filtration

Physical removal of microbes from liquids or air through barriers.

Osmotic pressure method

High pressure denatures proteins and causes plasmolysis

Radiation

Use of ionizing or nonionizing radiation to inactivate microbes.

Ionizing radiation

X-rays, gamma rays, or electron beams that ionize water to form reactive species and damage DNA.

Nonionizing radiation

UV light (260 nm) that damages DNA by forming thymine dimers.

Ultraviolet Radiation 260 nm

Wavelength that damages DNA; used to sterilize air and surfaces.

Phenol & Phenolics

Early disinfectants that denature proteins and disrupt membranes

Bisphenols

Phenol derivatives that disrupt membranes.

Alcohols

Intermediate-level disinfectants that denature proteins and disrupt membranes (e.g., 70% ethanol).

Halogens

Disinfectants including iodine and chlorine that disrupt proteins and membranes.

Iodine

Tinctures or iodophors that disrupt protein synthesis and membranes.

Chlorine

used as oxidizing disinfectants.

Oxidizing agents

Kill microbes by oxidizing cellular components; include peroxides and ozone.

Surfactants

Compounds that disrupt membranes

Quaternary ammonium compounds

Low-level disinfectants that disrupt membranes

Heavy metals

Low-level antimicrobials that can denature proteins.

Aldehydes

Highly reactive compounds that cross-link proteins and nucleic acids

Glutaraldehyde

A high-level disinfectant/sterilant used for medical equipment.

Formalin

A formaldehyde solution used for embalming and disinfection.

Gaseous agents

used to sterilize heat-sensitive materials

Ethylene oxide

Gaseous sterilant that reacts with cell proteins

Biguanides

disrupts membranes and binds to skin

Chlorhexidine

Biguanide antiseptic with strong membrane-disrupting action and low toxicity.

Lysozyme

Enzyme that digests peptidoglycan

Prionzyme

Enzymes used to remove prions on medical instruments.

What organisms are the easiest to treat? (5)

Enveloped viruses, gram positive bacteria, nonenveloped viruses, fungi, and gram negative bacteria

What organisms are the most resistant to treat? (5)

Prions, bacterial endospores, mycobacteria, cysts of Protozoa, and active-stage protozoa(trophozoites)

What are the 5 ways to test chemical cleaner?

Use-dilution, disk-diffusion, Kelsey-Sykes capacity test, in-use test, and disk-diffusion method.

What are the 6 physical methods of control?

Heat, cold, desiccation, filtration, osmotic pressure, and radiation

What are the 9 chemical methods of control?

Phenol, alcohols, halogens, surfactants, heavy metals, aldehydes, gaseous agents, biguanides, and enzymes