EXAM 2: Microbial Control Flashcards
Antisepsis
The reduction in the number of microorganisms on living tissue
Aseptic
An environment or procedure free of pathogens
Degerming
The removal of microorganisms by mechanical means
Disinfection
The destruction of host microorganisms on non-living tissue
Pasteurization
The use of heat to destroy pathogens and reduce the number of spoilage microorganisms in food and beverages
Sanitization
The removal of pathogens from objects to meet public health standards
Sterilization
The destruction of all microorganisms in or on an object
Thermal death point
Lowest temperature that kills all cells in broth in 10 min
Thermal death time
Time taken to sterilize volume of liquid at set temperature
Decimal Reduction
Time required to destroy 90% of microbes in a sample
-cide meaning
suffix indicating that agent kills
include bactericides and everything else
-static meaning
suffix indicating that agent inhibits growth
include bacteriostatic and fungistatic
Discuss the significance of the selection criteria for microbial control agents
Ideally, agents should be:
Inexpensive
Fast-acting
Stable during storage
Capable of controlling microbial growth while being harmless to humans, animals, and objects
Describe factors that may affect the efficacy of antimicrobials
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
Differentiate between thermal death time and decimal reduction
Thermal death time: time to sterilize volume of liquid at set temperature
Decimal Reduction: time required to destroy 90% of microbes in a sample
Define the parameters for autoclaving and pasteurization
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)
Differentiate between biosafety levels
- Biosafety Level 1 (BSL-1)
- Nonpathogenic microbes - Biosafety Level 2 (BSL-2)
- Opportunistic agents - Biosafety Level 3 (BSL-3)
- True pathogens - Biosafety Level 4 (BSL-4)
- Microbes cause severe or fatal disease
Describe the methods of microbial control discussed in lecture and explain the mechanisms behind their functions
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)
Compare and contrast various physical methods and their mechanisms. (i.e. pasteurization vs.
autoclaving. Ionizing radiation vs. UV)
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
Compare and contrast various Chemical methods of Microbial Control and their mechanisms
(PHOSHAA)
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
