Unit 3: Microbial Growth Control Flashcards
GROUP, Environment (Aerobic & Anaerobic), O2 Effect
_____ aerobe - Growth - No growth
Required (utilized for aerobic respiration)
_____
Growth if level not too high - No Growth
Required but at levels below 0.2 atm
_____ anaerobes
No growth - Growth
Toxic
_____
Growth - Growth
Not required for growth but utilized when available
_____ anaerobes
Growth - Growth
Not required and not utilized
Obligate aerobe
Microaerophile
Obligate anaerobes
Facultative anaerobes/aerobes
Aerotolerant anaerobes
_____: microbes were a possible cause of disease
Pasteur’s work
_____: developed aseptic techniques to prevent contamination of surgical wounds:
- Washing hands with microbe-killing
- chloride of lime Using the techniques of aseptic surgery
Ignaz Semmelweis and Joseph Lister
____ caused death in 10% of surgeries
Up to 25% of mothers delivering in hospitals died due to infection
Nosocomial infections
METHODS OF INHIBITING MICROBIAL GROWTH
_____: the killing or removal of all microorganisms (including viruses).
_____: a process that directly targets pathogens, although it may not eliminate all microorganisms.
_____: used to prevent contamination of surgical instruments, medical personnel, and the patient.
_____: the process of removing or neutralizing harmful substances from surfaces, people, or the environment.
Sterilization
Disinfection
Aseptic techniques
Decontamination
When bacterial populations are heated or treated with antimicrobial chemicals, they usually die at a constant rate.
One log disease = 90% of population killed
Several factors influence the effectiveness of antimicrobial treatment:
Number of microbes
Type of Microbes
Environmental influence
Time of exposure
Physical Methods of Microbial Control
- _____ kills microorganisms by denaturing their enzymes and other proteins.
- _____ Removal of microbes by the passage of a liquid or gas through a screen-like material with small pores.
- _____ effect depends on microbe and treatment applied
- _____ has various effects on cells, depending on its wavelength, intensity, and duration.
Heat Sterilization
Filtration
Low Temperature
Radiation
Physical Methods: HEAT STERILIZATION
_____ kills microorganisms by
coagulating their proteins.
Moist Heat
Physical Methods: HEAT STERILIZATION
I. Moist Heat
_____ Heat to 100°C or more at sea level.
Kills vegetative forms of bacterial pathogens, viruses, and fungi and their spores (10 min or less)
Boiling
_____: can survive up to 30
minutes of boiling
_____: up to 20 hrs or more of boiling
Hepatitis virus
Endospore
Physical Methods: HEAT STERILIZATION
I. Moist Heat
_____ use of chamber which is filled with hot steam under pressure.
- The temperature of steam reaches 121°C at twice atmospheric pressure.
- All organisms and endospores are killed WITHIN 15 MINUTES.
- Require more time to reach the center of solid or large volumes of liquid
Autoclaving
Physical Methods: HEAT STERILIZATION
I. Moist Heat
_____ developed by Louis Pasteur to prevent the spoilage of beverages.
- Employs MILD HEATING, sufficient to kill the organisms without seriously damaging the taste of the product.
Pasteurization
Types of Pasteurization
_____: milk was exposed to 65°C for 30 minutes.
_____: milk exposed to 72°C for 15 seconds
_____: milk is treated at 140°C for 3 seconds and then cooled very quickly in a vacuum chamber.
- Classic Method of Pasteurization
- High-Temperature Short time Pasteurization (HTST)
- UltraHigh-Temperature Pasteurization (UHT)
Physical Methods: HEAT STERILIZATION
_____: kills microorganisms by oxidation effects, denatures proteins and other cellular components.
Dry Heat
Physical methods: HEAT STERILIZATION
II. Dry Heat
_____: used to sterilize inoculating loops and needles.
_____: place objects in an oven
Require 1-2 hrs at 100°C.
Direct flaming
Hot air sterilization
Dry heat transfers heat less effectively to a cool body, than moist heat.
Physical methods: FILTRATION
_____ Used in operating rooms and burn units to remove bacteria from air.
_____ Use in industry and research.
Different sizes:
◦ _____ um pores: filter most bacteria
◦ _____ um pores: retain all viruses and some large proteins
High-Efficiency Particulate Air filters (HEPA)
Membrane filters
- 0.22 and 0.45 um pores
- 0.01 um pores
Physical methods: LOW TEMPERATURE
A. _____: temperatures from 0 to 7°C.
B. _____: temperatures below 0°C.
Refrigeration
Freezing
Reduces metabolic rate so they cannot reproduce or produce toxins
Bacteriostatic effect
Types of Freezing
_____: Does not kill most microbes
_____: more harmful to bacteria because ice crystals disrupt cell structure therefore inhibit microbes.
Flash freezing
Slow Freezing
Physical methods: RADIATION
Two Types:
- Ionizing Radiation
- Nonionizing Radiation
Physical methods: RADIATION
_____ Gamma rays, X-rays, electron beams or higher energy rays.
- Have short wavelengths (less than 1 nanometer)
- Penetrates human tissues and cause mutations in DNA and produce peroxides
- Used to sterilize pharmaceuticals and disposable medical supplies, for materials that cannot be autoclaved
Ionizing Radiation
Physical methods: RADIATION
_____ Ultraviolet (UV)
- Wavelength is longer than 1 nanometer.
- Damages DNA by producing _____, which causes mutations
- _____ - used to disinfect operating rooms, nurseries, cafeterias
- Damages skin and eyes
- Doesn’t penetrate paper, glass, cloth, and tissues.
Nonionizing Radiation
Thymine
Poor penetrating power
