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

Autoclaving: used for sterilization of medical and lab supplies that can tolerate heat and moisture
- Pressure applied to boiling water prevents steam from escaping
- Boiling temp increases as pressure increases
Autoclave conditions:
- 121 ̊C, 15 pso, 15 min
- Sterilizes & will kill endospores

Pasteurization: the use of heat to destroy pathogens and reduce the number of spoilage microorganisms in food and beverages
- Used for milk, ice cream, etc.
- Heat-tolerant microbes survive - NOT sterilization

Pasteurization of milk:
- Flash pasteurization: extended shelf life (ESL) High Temperature Short time (HTST) 72 ̊C for 15 sec
- Ultrahigh-temperature pasteurization (138 ̊C for 2 sec)
- Batch method ( 63 ̊C for 30 min)

Question 17

Differentiate between biosafety levels

Answer 17

1. Biosafety Level 1 (BSL-1)
   - Nonpathogenic microbes
2. Biosafety Level 2 (BSL-2)
   - Opportunistic agents
3. Biosafety Level 3 (BSL-3)
   - True pathogens
4. Biosafety Level 4 (BSL-4)
   - Microbes 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

Heat-related
moist heat (PABU)
- More effective than dry heat
- Used to disinfect, sanitize, and sterilize
- denature proteins and disrupt cell membranes
dry heat
- Denatures proteins & oxidizes metabolic and structural chemicals
- Requires higher temperatures for longer time than moist heat to sterilize

Refrigeration & Freezing
- Denatures proteins and disrupt cell membranes
- Decreases/slows down microbial metabolism, growth, and reproduction
- Slow freezing is more effective than quick freezing due to crystal orientations

Filtration
- Pores of filters are mechanically blocking the microorganisms from passing through
- Think of N95 masks

Osmotic pressure
- High concentrations of salt or sugar in foods to inhibit growth
- Hypertonicity (ex. slim jerky)

Radiation
- ions disrupt H bonding, oxidize double covalent bonds & create hydroxide ions
non-ionizing
- Wavelengths 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

ionizing (UV, sunlight, etc)
- Wavelengths shorter than 1nm
- Ejects electrons from atoms to create ions
- Ions disrupt H bonding, oxidize double covalent bonds, and create hydroxide ions
- Hydroxide ions denature other molecules (DNA)

Question 19

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

Answer 19

Autoclaving: pressure is applied to boiling water to prevent steam from escaping. Boiling temperature increases as pressure increases. Sterilizes & will kill endospores

Pasteurization: use of heat to destroy pathogens and reduce the number of spoilage microorganisms in food and beverages. Used for milk, ice cream, yogurt, & fruit juices (boiling would affect taste). Heat-tolerant microbes survive (will eventually spoil, bc it’s not sterilization)

Ionizing radiation:
- Wavelengths shorter than 1nm
- Ejects electrons from atoms to create ions
- Ions disrupt H bonding, oxidize double covalent bonds, and create hydroxide ions
- Hydroxide ions denature other molecules (DNA)

Non Ionizing radiation:
- Wavelengths 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

Question 20

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

Answer 20

Phenols & Alcohols
- denature proteins and disrupt cell membranes

Halogens
- oxidation or denature proteins

Oxidizing Agents
- oxidation

Surfactants
- reduce surface tension of solvents

Heavy metals
- unknown

Aldehydes and Gaseous Agents
- denature proteins and inactivate nucleic acids

Antimicrobials
- various