Exam 2: Microbial control

Question 1

Antisepsis

Answer 1

The reduction in the number of microorganisms on living tissue

Question 2

Aseptic

Answer 2

An environment or procedure free of pathogens

Question 3

Degerming

Answer 3

The removal of microorganisms by mechanical means

Question 4

Disinfection

Answer 4

The destruction of host microorganisms on non-living tissue

Question 5

Pasteurization

Answer 5

The use of heat to destroy pathogens and reduce the number of spoilage microorganisms in food and beverages

Question 6

Sanitization

Answer 6

The removal of pathogens from objects to meet public health standards

Question 7

Sterilization

Answer 7

The destruction of all microorganisms in or on an object

Question 8

Thermal death point

Answer 8

Lowest temperature that kills all cells in broth in 10 min

Question 9

Thermal death time

Answer 9

Time taken to sterilize volume of liquid at set temperature

Question 10

Decimal Reduction

Answer 10

Time required to destroy 90% of microbes in a sample

Question 11

-cide meaning

Answer 11

suffix indicating that agent kills
include bactericides and everything else

Question 12

-static meaning

Answer 12

suffix indicating that agent inhibits growth
include bacteriostatic and fungistatic

Question 13

Discuss the significance of the selection criteria for microbial control agents

Answer 13

Ideally, agents should be:
Inexpensive
Fast-acting
Stable during storage
Capable of controlling microbial growth while being harmless to humans, animals, and objects

Question 14

Describe factors that may affect the efficacy of antimicrobials

Answer 14

Physical & Environmental:
Temperature
- High Temps denature proteins & interfere with membrane fluidity. Heat can increase efficacy and activity

pH
- Changes in pH modify the ionization of functional groups and disrupt hydrogen bonding. This affects the stability of the agent

Susceptibility of microorganisms:
- Germicides classified as high, intermediate, or low effectiveness (most resistant to most susceptible)
- High-level kill all pathogens, including endospores
- Intermediate-level kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria
- Low-level kill vegetative bacteria, fungi, protozoa, and some viruses

Question 15

Differentiate between thermal death time and decimal reduction

Answer 15

Thermal death time: time to sterilize volume of liquid at set temperature

Decimal Reduction: time required to destroy 90% of microbes in a sample

Question 16

Define the parameters for autoclaving and pasteurization

Answer 16

a. Autoclave
- Pressure applied to boiling water prevents steam from escaping
- Boiling temperature increases as pressure increases
- 121 C 15psi, 15 min
- Sterilizes
- Will kill endospores
b. Pasteurization
- Flash pasteurization: 72C – for 15 seconds
- Ultra High temp. Pasteurization: 138C – for 2 seconds
- Batch method: 63*C – for 30 minutes

Question 17

Differentiate between biosafety levels

Answer 17

BSL - 1: nonpathogenic microbes
BSL - 2: Moderately hazardous agents (opportunistic)
BSL - 3: True pathogens
BSL - 4: Handling of microbes that cause severe or fatal disease

Question 18

Describe the methods of microbial control discussed in lecture and explain the mechanisms behind their functions

Answer 18

review chart

Question 19

Compare and contrast various physical methods and their mechanisms. (i.e. pasteurization vs.
autoclaving. Ionizing radiation vs. UV)

Answer 19

• Boiling:
  Kills vegetative cells of bacteria, fungi, protozoan, trophozoites, and viruses
  Boiling time is critical as different elevation require different boiling times
  Endospores, protozoan cysts, and some viruses survive in boiling

-Autoclaving:
Pressure applied to boiling water prevents steam from escaping
Boiling temp increases as pressure increases
Sterilizes and will kill endospores

-Pasteurization:
Used for milk, ice cream, yogurt, and fruit juices
Used instead of boiling because boiling would affect taste
Heat tolerant microbes survive – not sterilization
Flash pasteurization used for extended shelf life

Ultrahigh-temperature sterilization
140*C for 1 second, then rapid cooling
Treated liquids can be stored at room temperature

Dry Heat:
Used for materials that cannot be sterilized with moist heat
Denatures proteins and oxidizes metabolic and structural chemicals
Requires higher temps for longer time than moist heat
Incineration is ultimate means of sterilization

Refrigeration and Freezing:
Decrease microbial metabolism, growth, and reproduction
Slower chemical reactions
Liquid water not available
Refrigeration halts growth of most pathogens
Psychrophilic microbes can multiply in refrigerated foods
Slow freezing more effective than quick freezing
Organisms vary in susceptibility to freezing

Filtering air:
Surgical masks
Cotton plugs on culture vessels
High efficiency particle air filters (HEPA)
Used in biological safety cabinets

Osmotic Pressure:
High concentrations of salt or sugar in foods to inhibit growth
Curing and Brining
Cells in hypertonic solution of salt or sugar lose water
Fungi have greater ability than bacteria to survive hypertonic environments

Non-ionizing Radiation:
Wavelength greater than 1nm
Excites electrons, causing them to make new covalent bonds (affects 3D structure of proteins and nucleic acids)
UV light causes pyrimidine dimers in DNA
UV light does not penetrate well
Suitable for disinfecting air, transparent fluids and surfaces of objects

Ionizing radiation:
Wavelengths shorter than 1nm (electron beams, gamma rays)
Ejects electrons from atoms to create ions
Ions disrupt hydrogen bonding, oxidize double covalent bonds and create hydroxide ions (denature DNA)
Electron beams (effective at killing but do not penetrate)
Gamma Rays (penetrate well but require hours to kill microbes)

Question 20

Compare and contrast various Chemical methods of Microbial Control and their mechanisms
(PHOSHAA)

Answer 20

memorize chart