Control of Microbial Growth: Key Concepts and Definitions

sepsis

Bacterial contamination.

asepsis

The absence of significant contamination (e.g., during surgery).

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, alcohol)

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. 140 degrees for 4 sec

pasteurization

Destroying pathogens without altering the flavor of food. 72 degrees for 15 sec

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, stopping vital functions.

damaging nucleic acids

Cells can't replicate or synthesize proteins.

moist heat

Kills microbes by denaturing proteins.

examples of moist heat

Boiling, autoclaving, pasteurization.

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., flaming, hot-air ovens).

refrigeration effects on microbes

inhibits 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, gamma rays, electron beams.

ionizing radiation is used in

food industry and medical field

non-ionizing radiation

Forms thymine dimers in DNA, preventing replication.

UV radiation is used in

Hospitals, nurseries, operating rooms, labs.

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, causes leaks

phenolics

Phenol derivatives with reduced irritation and increased effectiveness.

bisphenols

Disrupt plasma membranes.

iodine

Impairs protein synthesis and alters membranes. Also used in water treatment

chlorine

Acts as an oxidizing agent; disrupts enzyme systems. Also used in water treatment

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), not killing.

do soaps have antimicrobial properties

No, they do not kill microbes.

what are the 3 physical methods for controlling microbial growth

temp, filtration, and kinda radiation