Chapter 7: Control of Microbial Growth

you got this!!! big healthcare field baddie

define sterilization

Removing all microbial life

Define disinfection

Removing pathogens

Define antisepsis

Removing pathogens from living tissue

Define sepsis

Refers to microbial contamination

Define asepsis

Absence of significant contamination

Define sanitization

Lowering microbial counts to safe levels

Define biocide/germicide

Kills microbes

Define bacteriostasis

Inhibiting, not killing, microbes

Define degerming

Removing microbes from a limited area

Describe the patterns and rate of microbial death caused by microbial control agents

- follows a constant logarithmic rate
- fixed percentage of remaining population dies over specific time interval
- not a fixed number of cells

Explain how microbial control agents affect membranes, proteins, and nucleic acids

- alteration of membrane permeability
- damage to proteins
- damage to nucleic acids

Compare moist heat, dry heat, and pasteurization methods for microbial control

Moist heat- denatures proteins (autoclave)
Dry heat- kills by oxidation (incineration)
Pasteurization- reduces spoilage of organisms and pathogens (thermoduric organisms survive)

Describe the role of filtration in microbial suppression

- suppresses microbes by physically removing them from liquids or gases instead of killing them
- effectiveness depends on pore size of filter

Describe the role of low temperature in microbial suppression

- slows or stops metabolic processes
- reduce efficiency of enzymes
- decreases fluidity of cell membranes
ex. refrigeration and deep freezing

Describe the role of high pressure in microbial suppression

denatures proteins

Describe the role of desiccation in microbial suppression

prevents metabolic processes

Describe the role of osmotic pressure in microbial suppression

causes plasmolysis (cells lose water)

Explain how different types of radiation are used to kill microorganisms

Ionizing and Non-ionizing radiation: Damages DNA
Microwaves: kill by heat; not especially antimicrobial

Identify factors influencing the effectiveness of chemical disinfectants

- concentration of disinfectant
- organic matter
- pH
- time

What doe the results from a use-dilution test tell us?

- ideal results show high percentage reduction or complete absence of microbial growth
- demonstrates the disinfectants effectiveness on a surface

What do the result from a disk-diffusion test tell us?

large clear areas (zone of inhibition) around disks:
-means bacteria are susceptible to antibiotic

small/no zones:
- indicate resistance

Differentiate between halogens used as antiseptics and those used as disinfectants

-antiseptics (iodine) are safe for living organisms
- disinfectants (chlorine) are more potent and intended for inanimate objects

What is the use of surface-active agents in microbial control?

- reduce surface tension
- emulsifying substances
- damaging cell membranes

(cleaning products, shampoo/body wash, cosmetics)

What is the use of food preservatives in microbial control?

-inhibit microbial growth
- lowering water activity or directly killing microbes
(prevents spoilage, off-flavors, toxicity)

List the advantages of glutaraldehyde over other chemical disinfectants

inactivate proteins by cross linking with functional groups
- used to disinfect medical equipment
- high level disinfectant and sterilization

tissue fixation in histology and pathology labs

Explain how the type of microbe affects the control of microbial growth

Depends on structure and life cycle of cell