MicroBio 15: Control of Microorganisms Flashcards
the Control of Microorganisms is effective in two basic ways:
- by killing the microorganism
- by inhibiting the growth of microorganism
this control can be accomplished by physical and chemical means
Microbial Control
Physical Methods of Microbial Control
- Heat
a. Moist Heat
- Boiling
- Sterilization
- Pasteurization
- Tyndallization/ intermitent sterilization
b. Dry Heat
- incineration
- hot air
- low temperature
- filtration
- laminar flow/ biological safety cabinets
- radiation
this consists of boiling solid and liquid food, steam sterilization for culture media, pasteurization for milk and other liquid food, tyndallization.
Moist heat
usually done in a laboratory oven to sterilize glasswares
Dry heat
Exposure to _____ water for 10 minutes is sufficient to destroy vegetative cells and eukaryotic microorganisms
Boiling (100C)
Is boiling high enough to kill bacterial endospores? Yes or No
No
This kills or destroys all viable microorganisms
Sterilization
What equipment is used for using steam under pressure?
Pressure cooker or autoclave
what is the Sterilization temperature and pressure time?
121*C - 15lbs/in^2 - 15 minutes
involves brief heatiing at 55-72*C
Pasteurization
Used for substances that are destroyed by high temperature like milk, juice, beer and wine to preserve them for long periods at the same time retaining foods’flavor and value
Pasteurization
True or False: Pasteurization temp. does not kill microbes but reduce their population so they can be stored longer.
True
3 ways of Pasteurization
- Flash method (high temp short time)
- Batch method (low temp low time)
- Ultrahigh temperature
Pasteurization at 72*C for 15 sec
Flash method or HTST
Pasteurization at 63C - 66C for 30 min * A newer technique that produce milk that has a storage life of 3 months
Batch method or LTLT
Pasteurization that has temperature of 134*C for 1-2 sec
Ultrahigh temperature or UHT
This method is used for substances that can’t withstand the high temp. of steam under pressure
Tyndallization or intermitent sterilization
under Tyndallization, the materials are exporsed to free flowing steam for _________ min for 3 consecutive days
30 - 40 minutes
True or False: The temperature in Tyndallization does not get above 100*C
True
Type of Dry Heat method which involves in a flame or heating coil direct exposure to such intense heat ignites and reduces microorganisms to ashes
Incineration
Type of Dry Heat that is generally used to sterilize glasswares in the laboratory.
Hot air
- involves the use of a labooratory oven
- sterilization time is 160-170*C for 2-3 hours
- not suitable for heat sensitive materials like plastic and rubber items
Hot air
True or False: Most pathogenic microorganisms are mesophilic and do not grow at 5*C
False. They do not grow at 4*C
This inhibit the growth and reproduction of microorganisms; important in food microbiology and postharvest storage of fruits and vegetables to increase shell-life
Low temperature (freezing and refrigeration)
Involves fluid strained through a filter with openings large enough for the fluid to pass through but not the microorganisms
Filtration
True or False: Filtration is an effective method of removing microorganisms form liquids
True
This utilizes membrane filters made up of cellulose acetate, cellulose nitrate, polycarbonate or polyvinylidine fluoride
FIltration
Suitable for microbial control (e.g gamma rays, X-rays, UV rays) ; used to disinfect/sterilize the surface of the laminar flow hood, operating rooms to sterilize the air and any exposed surfaces
Radiation
These employ high efficiency particulate air (HEPA) filters ; prevents contamination in research labs ; used when culturing dangeroud microbes
e.g. Mycobacterium tuberculosis and tumor viruses
Laminar flow or biological safety cabinets
True or False: Ultraviolet radiation around 260 nm wavelength is quite lethal to microbes
True
In Chemical COntrol, this are agents aimed at killing microorganisms
Microbicidal agents
“cide” means what?
To kill
Examples of Microbicidal Agents
- Bactericide
- Fungicide
- Algicide
- Viruscide
- Viricide
- Nematicide
agents that temporarily prevent microorganisms from multiplying but not killing them
Microbistatic Agent
Statis/static means
to stand still
Examples of Microbistatic Agents
- Bacteriostatic
- Fungistatic
a. Disinfectant
b. Antiseptic
- Agents used to destroy vegetative pathogens
ex: ethyl alcohol, isopropyl alcohol, Chlorine gas Cl2, phenols)
Disinfectant
- normally used in inanimate objects and externally on skin because the concentration required to be effective is toxic to human and animal tissues
Disinfectant
from the term “asepsis”
Antiseptic
refers to any practice preventing entry of infectious agents into sterile tissues; preventing infection
Antiseptic
a water-soluble cleansing agent which combines with impurities and dirt to make them more soluble, and differs from soap in not forming a scum with the salts in hard water.
Detergent
Agents applied directly to exposed body surfaces like skin, wounds, surgical incisions to destroy or inhibit vegetative pathogen.
E.g Tincture of Iodine and Betadine
Antiseptic
agents that mechanically remove microorganisms (along with food debris) to reduce level of contaminants
e.g. germicidal soaps, plain soaps, hand sanitizers
Sanitizer
Modes of Action of Antimicrobial Agents
- Cell wall
- Cell membrane
- Biosynthetic pathways (e.g. protein synthesis)
- enzyme function
When combined with water, this releases hypochlorous acid which causes denaturation of enzymes thus suspending metabolic activities
Chlorine and its compounds
this ensured safety of water for drinking
chlorination of drinking water (0.6 to 1 part of chlorine per million parts of water)
rapidly penetrates cells of microorganisms and interfere with hydrogen and disulfide bonding of proteins thereby disturbing a variety of metabolic function in microbes
Iodine and its compounds
Chemical control where only ethyl and isopropyl are suitable for microbial control; 50% or higher dissolve lipids, denature protein, disrupt cell surface
Alcohols
Mercury, silver, and most other metals inactivate proteins bringing metabolism into a stand still
Heavy Metals
acts as surfactants making them good wetting agents, cleansing agents and emulsifiers
Soaps and detergents
these are chemicals used in treatment, relief or prophylaxis of diseases.
may also come as:
1. Antibiotics
2. Synthetic agents
Chemotherapeutic Agents
Substances produced by microorganisms that can inhibit or kill other microorganisms
Antibiotics
Sources of penicillin:
Penicillium chrysogenum, Penicillium notatum
e.g. penicillin, ampicillin, amoxicillin
An antibiotic with characteristic B(Beta) - lactam ring, inhibiti cell wall synthesis, and broad spectrum
B-Lactam antibiotics
e.g. Penicilins and Cephalosporins
Source of cephalosporins
Cephalosporium acremonium
e.g. cephalothin, cefazollin, cefaclor
- with 2 or more amino sugars and an aminocyclitol ring reffered to as amino-glycoside
- inhibits protein synthesis
- broad spectrum
e.g.g streptomycin - Streptomyces griseus
Aminoglycoside drugs
- named for their regular group of 4 rings
- block protein synthesis
- broad system
e.g. aureomycin - Streptomyces aureofaciens
Tetracyline antibiotics
- with large lactone rings connected to sugar moieties
- inhibit protein synthesis
- broad spectrum
e.g. erythromycin - Streptomyces erythraeus
chloramphenicol - Streptomyces venezuelae
Macrolide antibiotics
drugs derived in the laboratory from dyes or other organic compounds
Synthetic Drugs
- 1st widely used growth factor analog to specifically inhibit growth of bateria
Sulfa Drugs
- blocks synthesis of folic acid, a nucleic acid precursor
sulfanilamide
- a nicotanimide (vitamin) analog effective only againt Mycobaterium tuberculosis
- interferes with the synthesis of the mycobacterial-specific mycolic acid wall material
Isoniazid
- a class of synthetic antibacterial compound
- interact with bacterial DNA gyrase preventing it from supercoiling the bacterial DNA which is required for packaging of the DNA in the bacterial cell
Quinolones
- effective for treating both G+ and G- (Gram) bacterial inefction and Urinary Tract Infection (UTI)
Fluoroquinolones
