Unit 6.1: Control of Microbial Growth

Why do we bother controlling microbial growth?

We control microbial growth because it can cause food spoilage, disease, and contamination

What are the two general categories that control microbial growth?

• Physical methods

• Chemical methods

What is the definition of sterilization?

Sterilization is the destruction of all living microorganisms, including endospores

What is commercial sterilization?

Commercial sterilization destroys microorganisms that would cause spoilage in canned or packaged foods

What is disinfection and disinfectant?

Disinfection destroys vegetative pathogens on inanimate objects / surfaces

• Disinfectant is an agent that disinfects

What is antiseptic?

Antiseptics are disinfectants used for living tissue

What is Degerming? What is an example of degerming?

Degerming is the mechanical removal of microbes from a small area of living tissue

• An example of degerming would be washing hands

What is Aseptic?

Aseptic refers to techniques that are used to prevent contamination by microbes

What is preservation?

Preservation is the use of mechanisms to delay the spoilage of perishable items

What is Biocide?

Biocide is a treatment that can kill microbes

What is Bacteriocide?

Bacteriocide is a treatment that can kill bacteria

What is bacteriostatic?

Bacteriostatic is a treatment that can only inhibit the growth of bacteria

What are some examples of Critical items (sterile)

• Surgical instruments

• IV fluids

What are some examples of Semi-critical items (high level of disinfection)

• Dental mirror

• Respiratory equipment

What are some examples of Non-critical items? (light disinfectant)

• Crutches

• Wheelchairs

What does AMA stand for?

AMA = anti-microbial agent

What rate do bacteria generally die off when exposed to an AMA?

Bacteria generally die off at a constant rate when exposed to an AMA

What is the D-Value?

The D-Value is the time needed to reduce the number of microbes by 90%

What is an example of the D-Value?

Based on the table, the D-Value would be 1 minute because 90% of the population is killed every minute

What can alter the effectiveness of AMA?

1. Number of microbes: the higher the number, the longer it takes

2. Time of exposure

3. Environmental influences: Temperature, presence of organic matter may prevent the action of some AMAs

4. Microbial characteristics: Bacteria being gram positive vs. gram negative, Viruses being enveloped vs. non-enveloped

What type of bacteria do Biocides tend to be more effective against? Why?

Biocides tend to be more effective against Gram-positive bacteria (Staph & Strep) because they lack Gram-negative’s outer membrane

What specifically do we do to microbes to kill them?

1. Alter cell membranes and cell walls (physical damage): Change in membrane permeability can cause cellular contents to leak out leading to cell lysis

What specifically do we do to microbes to kill them? pt. 2

2. Disruption of cellular metabolism and reproduction: Protein damage leads to loss of function, affecting metabolic pathways. DNA/RNA damage prevents reproduction