Control of microbial growth chapter 7

sepsis

Bacterial contamination.

asepsis

The absence of significant contamination (e.g.

antiseptic

A chemical that destroys harmful microbes from living tissue.

bacteriostasis

Inhibition of microbial growth without killing the microbes.

degerming

Reducing microbial load on skin or tissue by mild chemicals. (soaps

decontamination

Reduction of microbial contamination from materials and surfaces using disinfectants.

sanitization

Removing and destroying all microbial life.

disinfection

Lowering or inhibiting microbial growth on non-living surfaces.

sterilization

Removing or destroying all microbial life on an object.

pasteurization

Destroying pathogens without altering the flavor of food.

3 main targets of microbial control agents

1. Plasma membrane 2. Proteins (enzymes) 3. Nucleic acids

damaging the plasma membrane

It causes leakage of cellular contents and interferes with growth.

damaging microbial proteins

Enzymes are denatured

damaging nucleic acids

Cells can't replicate or synthesize proteins.

moist heat

Kills microbes by denaturing proteins.

examples of moist heat

Boiling

autoclave

Sterilizing instruments using steam under pressure.

common pasteurization methods

1. 72°C for 15 seconds (HTST) 2. 140°C for 4 seconds (UHT)

dry heat

Kills microbes by oxidation (e.g.

refrigeration effects on microbes

Slows metabolism and growth (bacteriostatic).

types of microbial preservation using cold

Deep-freezing and lyophilization (freeze-drying).

filtration

Passage of a substance through a screen-like sheet

ionizing radiation

Causes mutations by breaking DNA strands.

examples of ionizing radiation

X-rays

ionizing radiation is used in

food industry and medical field

non-ionizing radiation

Forms thymine dimers in DNA

UV radiation is used in

Hospitals

UV radiation effectiveness

Only effective on surfaces

does not penetrate deeply.

microwaves effects on microbes

Kill by heat

not directly antimicrobial.

phenols

Injure lipid-containing plasma membranes.

phenolics

Phenol derivatives with reduced irritation and increased effectiveness.

bisphenols

Disrupt plasma membranes.

iodine

Impairs protein synthesis and alters membranes.

common iodine forms

Tincture (in alcohol) and iodophor (with detergent).

chlorine

Acts as an oxidizing agent

disrupts enzyme systems.

active ingredient in bleach

Hypochlorous acid (HOCl).

alcohols

Denature proteins and dissolve lipids.

alcohols effectiveness

Need water to be effective

water slows evaporation and helps protein denaturation.

alcohol concentration in hand sanitizer

Usually 62-70%.

alcohols and endospores

Do not kill endospores due to inability to penetrate their protective layers.

role of soaps in microbial control

Mechanical removal of microbes (degerming)

soaps antimicrobial properties

No