Micribiology - Endospores And Contol Of Microbial Growth (w20) Flashcards
What are endospores ?
Resting/dormant/inert form of some bacterial cells
Produced only by two Gram+ Genera: Bacillus and Clostridium
What is sporulation ?
The process of endospore formation
What is germination ?
The process in which endospores return to the vegetative state
What are the 4 terms used to describe antimicrobial control measures ?
- sterilization
- disinfection
- sanitisation
- antimicrobial chemotherapy
How is sterilization an antimicrobial growth measure ?
Sterilisation: Destroying all microbial life (including endospores)
A sterile object is totally free of viable microorganisms
How is disinfection an antimicrobial control measure ?
Disinfection: Reduces the number of pathogenic microorganisms (not endospores) to the point where they no longer cause diseases
Disinfectant: agents applied on inanimate objects/surfaces (toxic to human tissue)
Antiseptic: agents applied on living tissue
How is sanitisation an antimicrobial control measure ?
Sanitisation: reduces the microbes to safe levels by public health standards
How is antimicrobial chemotherapy an antimicrobial control measure ?
Antimicrobial chemotherapy: Drug treatment for specific infections used internally to SELECTIVELY kill or inhibit growth of microorganisms within host tissues, targeting a unique structure of the specific microbe
What are endospores resistant to ?
Desiccation, heat, chemicals and radiation
What are the three sequential steps of germination ?
1) activation
2) initiation
3) outgrowth
What happens during germination ?
During germination, the core is hydrated, spore coats are cracked and the cell metabolism is restored
What disease does clostridium botulinum cause ?
Botulism
What disease does clostridium perfingens cause ?
Gas gangrene
What disease does clostridium tetani cause ?
Tetanus
What disease does bacillus anthracite cause ?
Cutaneous or pulmonary anthrax
What is the goal of an sterilization process ?
The goal of any sterilisation process is the destruction of bacterial endospores, viruses and cellular organisms
What is sterilization and essential stage in ?
Sterilisation is an essential stage in the:
- processing of any product destined for parenteral administration
- for contact with broken skin, mucosal surfaces, or internal organs
Death of a whole population is not instantaneous but continues in a _________ manner as the time or concentration is _______ .
1) logarithmic
2) increased
What does effectiveness of the control agents depend on ?
Effectiveness of the control agents depends on:
- Time of exposure
- Microbial characteristics
- Number of microbes
- Environment (organic matter, temperature, biofilms)
What effects do treatments used to control microbial death have on the microbes ?
Effects on the microbes
- Alternation of membrane permeability
- Protein denaturation
- Damage to nucleic acids
What physical treatments are there to control microbial death ?
Physical treatments:
- Temperature
- Heat (moist and dry)
- Cold temperatures
- Filtration
- Radiations
- Osmotic pressure
What chemical treatments are there to control microbial death ?
Chemical treatments :
- Alcohols
- Halogens
- Iodine
- Chlorine
- Phenolics
- Aldehydes
- Quaternary ammonium compounds
- Sterilizing gases
- Heavy metals
What is more effective for controlling microbial death: moist or dry heat ?
Moist heat, which kills microbes by denaturing their proteins.
What is autoclave ?
Autoclave: preferred sterilisation method, unless material is damaged by heat, moisture, or high pressure
Closed chamber with hot saturated steam under pressure
What is pasteurization ?
Pasteurisation (moist heat disinfection): Developed by Louis Pasteur to prevent the spoilage of beverages. Used to reduce microbes responsible for spoilage of beer, milk, wine, juices, etc.
What are the three methods available for pasteurization ?
3 Methods:
1) Classic Method of Pasteurisation: 65 o C for 30 minutes
2) Flash Pasteurisation (HTST): Used today. 72 o C for 15 seconds
3) Ultra High Temperature Pasteurisation (UHT): 140 o C for 4 seconds and then cooled quickly in a vacuum chamber. This is a sterilising method
What do low temperatures do to microbes ?
- Low temperatures (< optimal temp.) slow down microbial growth
- Reduces metabolic rate of most microbes to stop their proliferation and toxin production, but often do not kill microbes
- Refrigeration temperatures (4-8 o C) are used for food preservation
What does filtration of microbes do ?
Filtration: Removal of microbes by passage of a liquid or gases through membrane material with defined small pores (< microbe size)
What is osmotic pressure in reference to microbial growth ?
Osmotic pressure: The use of high concentrations of salts and sugars in foods is used to increase the osmotic pressure and create a hypertonic environment.
What is plasmolysis ?
When the water leaves the cell, plasma membrane shrinks away from cell wall. The cell may not die, but usually stops growing.
