Microbial Growth Control Flashcards
• Process of destroying unwanted microbes
Has improved throughout human history and today, many countries have clean drinking water, sterilized food and medical equipment
MICROBIAL CONTROL
Millennia before animalcules were viewed by Sir Anton van Leeuwenhoek and before the Germ Theory of Disease in Koch’s Postulates had been accepted, references to germicidal agents had been made in the ancient writings of_______
• Their_______ applied spices, vegetable oils, and gums to their dead
• Using techniques that have kept them in a superior state of preservation even today
Egyptians
embalmers
Persians, Greeks and Romans had legal documents requesting the use of _____ and_____ vessels for the storage of public drinking water
• Early civilizations practiced salting, smoking, pickling, drying, use of spices in cooking and exposure of food and clothing to sunlight to control microbial growth.
bright copper and silver
in the year 1847 at the Maternity Clinic of Vienna’s General Hospital requested that interns who had performed autopsies, washed their hands with chlorinated lime before examining expectant mothers
IGNAZ SEMMELWEIS
• In mid 1800s,______ and______ helped developed aseptic techniques to prevent contamination of surgical wounds by the use of ______on surgeon’s hands - and in the operating field, the surgical instruments used, the hospital environment in general
Ignaz Semmelweis and Joseph Lister
carbolic acid
• Before then:
Nosocomial infections caused death in
______of surgeries.
Up to_____ mothers delivering in hospitals died due to infection.
10%
25%
• is the most common method used to kill microorganisms, unfortunately, for the food industry, temperatures used to kill all living microbes will also result in degrading the quality of food during the cunning process
Instead, commercial sterilization is used
EXTREME HEAT
• Can be achieved by applications of heat, pressure, chemicals, radiation/ filtration
STERILIZATION
• Items to be_____ can be surfaces, equipment, food, medication, as well as biological culture media.
Sterilized
• Killing or removing all forms of microbial life (including endospores and prions-the most resistant forms)in a material or an object.
STERILIZATION
• Heat treatment that kills endospores of Clostridium botulinum, the causative agent of botulism, in canned food.
COMMERCIAL STERILIZATION
• Does not kill endospores of thermophiles, (not pathogens that may grow at temperatures above 45 degrees Celsius.)
COMMERCIAL STERILIZATION
• May use physical or chemical methods.
• Destruction of vegetative microorganisms by chemical or physical methods
DISINFECTION
• Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases.
• Usually involves the removal of vegetative or non-endospore-forming pathogens.
DISINFECTION
Does not destory bacterial endospores and can be achieved by chemicals
Ultraviolet radiation, boiling water, or steam
Disinfection
Applied to the use of a chemical to treat an inert surface or substance
DISINFECTANT
Applied to living tissue (antisepsis)
ANTISEPTIC
• Medical instruments require sterilization, but in other areas of life, microbes do not have to be completely eliminated-just reduced to insufficient numbers to prevent infection, disease, and the transmission of infection and disease
DEGERMING
Mechanical removal of most microbes in a limited area
• Example: when someone is about to receive an injection, the skin is swabbed with alcohol
DEGERMING
• reduction of the number of microorganisms to safe public health levels
SANITIZATION
• Minimizes the chances of disease transmission between users
• E.g.: Hot soup and water
• Glassware and other tableware in restaurants, institutions as well as the home environment
SANITIZATION
Indicates bacterial contamination, as in septic tanks for sewage treatment.
SEPSIS
Comes from Greek for decay or putrid.
SEPSIS
Absence of significant contamination.
Technique that prevents the entry of microorganisms into sterile tissues
ASEPSIS
• prevent contamination of surgical instruments, medical personnel, and the patient during surgery; prevent bacterial contamination in food industry.
ASEPTIC TECHNIQUES
Microbial growth is at a standstill.
• Suffix stasis: To stop or steady.
BACTERIOSTATIC AGENT/MICROBIOSTATIC
• An agent that inhibits the growth of bacteria, but does not necessarily kill them.
BACTERIOSTATIC AGENT/MICROBIOSTATIC
• Inhibit fungal growth
FUNGISTATIC AGENTS
-> an agent that kills certain microorganisms
Germicide
• -> an agent that kills bacteria. Most do not kill endospores.
Bactericide
-> an agent that inactivates viruses
Virucide
-> an agent that kills fungi
• Fungicide
•-> an agent that kills bacterial endospores or fungal spores
Sporicide
When bacterial populations are heated or treated antimicrobial chemicals, they usually die at a..
constant rate
_______ is the PERMANENT LOSS of reproductive ability of microbes
• Permanent loss of all other vital activities
• Lethal agents do not always alter the appearance of a microbial cell even if the motility of the organism is gone.
• Therefore, the term ____can be used
ONLY if the reproduction cannot occur even if the organism is given the optimal growth conditions
Microbial death
• Destructive forces of chemical / physical agents act on the individual cells; and if exposed intensively and long enough, the cell structures become DYSFUNCTIONAL and the cells show irreversible damage
• In general, cells in a given culture or in a given environment vary in their susceptibility to antimicrobial agents
Microbial death
They die at some fractional rate per unit time
If 50% of microorganisms in a population die every minute, after 2 minutes, ___% will still be alive; after 3 minutes, ___% are still alive; and so on
If 50% of microorganisms in a population die every minute, after 2 minutes, 25% will still be alive; after 3 minutes, 12.5% are still alive; and so on
It is therefore safe to say that the total number of organisms present, when the disinfection process begun, determines the time required to eliminate all microbes
RATE OF MICROBIAL DEATH
SEVERAL FACTORS THAT INFLUENCE THE EFFECTIVENESS OF ANTIMICROBIAL TREATMENT
- Number of Microbes
- Type of Microbes
- Environmental influences
- Time of Exposure
a. Dictates the time required for the destruction of all contaminants
Number of Microbes
a. Nature of organisms to be destroyed - biofilms include a number of organisms and species-
b. other contaminants can include vegetative organisms such as spores, and any target population that contains more than 1 organism can present a broad spectrum of resistance
Type of Microbes
a. Presence of organic material (blood, feces, saliva) tends to inhibit antimicrobials, pH etc.
Environmental influences
a. Chemical antimicrobials and radiation treatments are more effective at longer times.
b. In heat treatments, longer exposure compensates for lower temperatures.
Time of Exposure
Order of resistance against biocidal process
Prions
Bacterials spores
Protozoal oocysts
Helminth eggs
Mycobacteria
Small non-enveloped viruses
Protozoal cysts
Fungal spores
Gram-negative bacteria
Vegetative fungi and algae
Vegetative helminths and protozoa
Large non-enveloped viruses
Gram-positive bacteria
Enveloped viruses
HIGHLY RESISTANT:
prions (Creutzfeldt-Jakob disease)
Kills microorganisms by denaturing their enzymes and other proteins.
Heat resistance varies widely among microbes.
Heat
Lowest temperature at which all of the microbes in a liquid suspension will be killed in ten minutes.
Thermal death point
Minimal length of time in which all bacteria will be killed at a given temperature.
Thermal death time
Time in minutes at which 90% of bacteria at a given temperature will be killed. Used in canning industry.
Decimal reduction time
Kills microorganisms by coagulating their proteins. In general, moist heat is much more effective than dry heat.
Has the ability to penetrate
microbial cells
Melt lipids in cytoplasmic
membranes
Moist heat
Heat to 100 degree Celsius or more at sea level. Kills vegetative forms of bacterial pathogens, almost all viruses, and fungi and their spores within 10 minutes or less.
Endospores and some viruses are not destroyed this quickly.
Boiling
can survive up to 30 minutes of boiling.
Hepatitis Virus
can survive up to 20 hours or more of
boiling (Clostridium, Bacillus spp.)
Endospores
Steam under pressure (Principle)
Autoclave
Water normally boils at 100 degrees Celsius; when put under pressure, it boils at a higher temperature
Autoclave
• During________, the materials to be sterilized are placed under 15 pounds per square inch of pressure in a pressure cooker-type of apparatus
When placed under 15 pounds of pressure-the boiling point of water is raised to______ in which it is a temperature sufficient to kill bacterial endospores
autoclaving
121 degrees Celsius
Developed by Louis Pasteur to prevent the spoilage of beverages.
Used to reduce microbes responsible for spoilage of beer, milk, wine, juices, etc.
> does not kill all microorganism
MOIST HEAT
PASTEURIZATION
: Milk was exposed to 65 degree Celsius for 30 minutes
Classic Method of Pasteurization
Used today. Milk is exposed to 72 degree Celsius for 15 seconds. (Flash method)
• High Temperature Short Time Pasteurization
(HTST):
Milk is treated at 140 degree Celsius for 3 seconds and then cooled very quickly in a vacuum chamber.
• Advantage: Milk can be stored at room temperature for several months.
Ultra High Temperature Pasteurization (UHT):
• Kills by oxidation effects
Protein oxidation rather than protein coaqulation
DRY HEAT
EXAMPLE: DIRECT FLAMING
• Used to sterilize inoculating loops and needles.
Heat metal until it has a red glow.
Dry heat
Effective way to sterilize disposable items (paper cups, dressings) and biological waste.
INCINERATION
• Place objects in an oven. Require 2 hours at 170 degrees Celsius for sterilization.
121 degrees Celsius for 16 hours or longer, depending on the volume
• Used for sterilizing glasswares, metal instruments, and other inert materials (oils and powders not damaged by excessive temperature)
HOT AIR STERILIZATION
______is transfers heat less effectively to a cool body, than_____
• Dry heat
moist heat
Removal of microbes by passage of a liquid or gas through a screen like material with small pores.
Used to sterilize heat sensitive materials like vaccines, enzymes, antibiotics, and some culture media
FILTRATION
provide a useful way of steriliing materials such as vaccines, antibiotic solutions, animal sera, enzyme solutions and other solutions that may be damaged / denatured by high temperatures or chemical agents
It contain pores small enough to prevent the passage of microbes but large enough to allow the organism free-fluid to pass through
The liquid is then collected in a sterile flask
Microbiological membrane filters
Used in operating rooms and burn units to remove bacteria from air.
High Efficiency Particulate Air Filters (HEPA):
• Type of a pleated mechanical air filter
High Efficiency Particulate Air Filters (HEPA):
High Efficiency Particulate Air Filters (HEPA): can remove______% of dust, pollen, mold, bacteria and any airborne particles with a size of____ microns
• Diameter specification of ____ microns responds to the worst case + MOST PENETRATING PARTICLE SIZE (MPPS)
• Particles larger/smaller are chopped with higher efficiency using the WORST-CASE PARTICLE SIZE RESULTS in the worst case efficiency rating such as 99.97% or better for all particle sizes
99.97
0.3
0.3
• Uniform pore size.
• Used in industry and research.
-any organisms in the sample are concentrated on the surface of the membrane
trapped bacteria is placed in a special plate containing a pad saturated with the appropriate medium
Passage of nutrients to the filter during incubation facilitates the growth of organisms in the form of colonies on the upper surface of the membrane
Discrete colonies that form can be easily transferred to the confirmation media
MEMBRANE FILTERS
Membrane filters
: used to filter most bacteria. Don’t retain spirochetes, mycoplasmas and viruses.
: retain all viruses and some large proteins. Membrane filters are constructed out of a wide range of synthetic materials, including cellulose acetate, cellulose nitrate (collodion), polyamide (nylon), polycarbonate, polypropylene, and polytetrafluoroethylene (Teflon).
0.22 and 0.45 um pores
0.01 um pores
: Temperatures from 0 to Degrees Celsius. Bacteriostatic effect.
Reduces metabolic rate of most microbes so they cannot reproduce or produce toxins.
Refrigeration
: Temperatures below 0 degrees Celsius.
: Does not kill most microbes.
: More harmful because ice crystals disrupt cell structure. Over a third of vegetative bacteria may survive 1 year.
Freezing
Flash Freezing
Slow Freezing
In the absence of water, microbes cannot grow or reproduce, but some may remain viable for years.
After water becomes available, they start growing again.
Do not require refrigeration
Has a static effect on microorganisms
DESSICATION/DRYING
Susceptibility to desiccation varies widely:
: Only survives about one hour.
: May survive several months. Viruses are fairlv resistant to desiccation.
: May survive decades.
Neisseria gonorrhoeae
Mycobacterium tuberculosis
Clostridium spp. and Bacillus spp.
The use of high concentrations of salts and sugars in foods is used to increase the osmotic pressure and create a hypertonic environment.
OSMOTIC PRESSURE
: As water leaves the cell, plasma membrane shrinks away from cell wall.
Cell may not die, but usually stops growing.
Plasmolysis
: More resistant to high osmotic pressures.
.: that live on skin are fairly resistant to high osmotic pressure.
Yeasts and Molds
Staphylococci spp
- a method of treating Infectious waste
Burning hazardous material to ashes at temperatures______
Ensure no infective materials remain in samples or containers when disposed (including prions, infective proteins)
Disadvantage/limitation of its use: toxic air emissions and the presence of heavy metals in ash
Incineration
870° to 980°C
used to sterilize biohazardous trash and heat-stable objects; an autoclave is used for this purpose
Moist heat (steam under pressure)
Is in the form of saturated steam under 1 atmosphere (15 pounds per square inch [psi] of pressure causes the irreversible denaturation of enzymes and structural proteins
Two common sterilization temperatures:
Moist heat (steam under pressure)
121°C and 132°C
Moist heat (steam under pressure)
CDC advises that;
Wrapped instruments be exposed for 30 minutes at_____ and 15 minutes at_____, with a dry time of 15-30 minutes
121°C (250°F)
132 °C (270 °C)
: hot steam under pressure.
• 121°C at 15 psi for 15 minutes.
AUTOCLAVE
• biological indicators used in a sterilizing cycle
• spores of Geobacillus stearothermophilus
• (+)growth : turbid , changes color from purple to yellow (Bromcresol Purple)
Kilit ampules or Paper strips
- kills by oxidation effects; used to sterilize iterns such as glassware, oll, petrolatum, or powders; an oven is use for this purpose
Requires longer exposure times (1.5 to 3 hours) and higher temperatures, 160°C to 180°C
Dry heat
- method of choice for antibiotic solutions, toxic chemicals, radioisotopes, vaccines, and carbohydrates, which are all heat sensitive
Filtration
Requires passing the substance through a cellulose acetate or cellulose nitrate membrane with a vacuum
Sterile membrane filters (pore: 0.22 um, 0.45um, 0.01 um)
Filtration
- kills by degrading/altering DNA and protein;
destroys bacterial endospores and vegetative cells;
used for sterilizing disposables such as plastic syringes, catheters, or gloves before use.
Ionizing Radiation
_____ and _____ machines is composed of short wavelength and high energy gamma rays
Gamma rays (radioisotopes: Caesium-137 and cobalt-60),
X-ray machines, Cathode rays (electron-beam radiation, UV rays (150nm)
Microwaves and radiograph
Advantages: high penetrating power, rapidity in action, temperature-not raised, flexibility (any phase)
Disadvantages: high capital costs, handling/disposal of radioactive
material
Ionizing Radiation
Chemical Methods of Sterilization
Ethylene oxide (EO, EtO)
Vapor-phase hydrogen peroxide (oxidizing agent)
- kills by denaturing proteins replacing functional groups with alkyl groups
Ethylene oxide (EO, EtO)
Most common sterilant, gaseous form, for sterilizing heat-sensitive objects; disadvantages: lengthy cycle times (4-18h) and produces potential health hazards (toxic and explosive in pure form)
Ethylene oxide (EO, EtO)
• sterilize HEPA filters in BSCs, metal, and nonmetal devices such as medica instruments (e.g. scissors)
• Advantage: no toxic by-products produced
Vapor-phase hydrogen peroxide (oxidizing agent)
Physical methods
•____ at 100°C for 15 minutes kills vegetative bacteria.
•____ at 70°C for 30 minutes kills food pathogens without damaging the nutritional value or flavor.
• Using nonionizing radiation such as_____
• UV rays have long wavelength and low energy.
Boiling
Pasteurizing
UV light
SPASTEURIZATION
63°C for 30 mins.
72°C for 15 secs.
140°C for 3 secs. then vacuum-cooled
Classic Method
High T° Short Time Method
Ultra High T° Method
NON-IONIZING Radiation _______
• _______for 30 minutes) - disinfection of clean surfaces in operation theaters, laminar flow hoods, and water treatment.
UV rays
260-300 nm wavelength
• Infrared, ultraviolet radiation
• Inhibition of DNA replication, leads to mutation and death of exposed organisms
• Disadvantages: damages skin and eyes, does not penetrate paper, glass, and cloth
NON-IONIZING Radiation
Use of Low Temperatures
: 0 to 7°C; microbiostatic
: below 0°C; inactivation of bacteria; Flash/slow Freezing
REFRIGERATION
FREEZING
Desiccation:
No growth nor reproduction, some may remain viable for years
: Only survives 1 hr
: survives several months
: resistant to desiccation
: May survive for decades
Neisseria gonorrheae
M. tuberculosis
Viruses
Clostridium , Bacillus spp.
Osmotic Pressure:
A_____ environment is created by increasing concentrations of solute in substances.
______on skin are fairly resistant to high osmotic pressure.
hypertonic
Staphylococci spp.
Chemical Methods of Disinfection
• Alcohols
• Aldehydes
• Halogens (chlorine and chlorine compounds)
• Peracetic acid
• Hydrogen peroxide
• Quaternary ammonium compounds
• Phenolics
• Kill bacteria, fungi, but not endospores or naked viruses
• Dissolves plasma membrane
• Skin antiseptic, disinfects thermometers, injection vial rubber septa
ALCOHOLS:
•: Drinking alcohol. Optimum
concentration is 70%.
•: Rubbing alcohol; better
disinfectant; less volatile.
Ethanol
Isopropanol
ALDEHYDES:
• Excellent disinfectant; formalin (37% aqueous solution)
• Irritates mucous membranes, strong odor
Formaldehyde gas
• Less irritating, more effective than formaldehyde
° Sporicidal (kills endospores in 3-10 hours), sterilizing agent; cold sterilization
• Commonly used to disinfect hospital instruments, e.g.
bronchoscopes
Glutaraldehyde
: Effective alone or in compounds
• The most common hypochlorite solution, household bleach (NaOCI, 5.25%-6.15%);
HALOGENS
• Bactericidal, virucidal, fungicidal, mycobactericidal, and sporicidal;
• Inactivates proteins essential for microbial growth;
• Disinfect drinking water, pools, sewage
HALOGENS
Disadvantage: cause minor ocular, oropharyngeal, esophageal irritation when exposed to high concentrations without proper ventilation, discolors fabrics, and can produce toxic gas if improperly mixed with ammonia or acid in other cleaning agents.
Halogens
Halogens
• CDC: after blood spills, clean tabletops with a ____dilution of bleach
1:10
:effective liquid sporicidal even in the presence of organic material; sterilant for the surface sterilization of surgical instruments; does not leave toxic residues
Peracetic Acid
• effective in disinfection of inanimate objects; sporicidal at higher temperatures
Hydrogen Peroxide
• Disrupt membranes and proteins; example - Ozone, highly reactive form of O2
Used along with chlorine to disinfect water; more effective than chlorine, but less stable and more expensive
Peroxygens (Oxidizing Agents)
• surface active agents; cationic detergents.
• destroy fungi, amoebas, enveloped viruses
• Used on floors, furniture, and walls
QUATERNARY AMMONIUM NH
COMPOUNDS (Quats):
Best against GPB than against GNB.
QUATERNARY AMMONIUM NH
COMPOUNDS (Quats):
: Rarely ysed, skin irritant, strong odor
: chemical derivatives of phenol
Phenol
Phenolics
„: o-phenylphenol! (Lysol: benzalkonium chloride)
„: Triclosan
Cresols
Bisphenols
Antisepties
lodine
1% silver nitrate
3% Hydrogen peroxide, benzoyl peroxide, chlorhexidine gluconate, etc.
• As a tincture with alcohol or as an iodophor -
70% alcohol followed by an iodophor = most common skin
disinfection before drawing blood specimens for culture
lodine
• (replaced with erythromycin ointment or povidone iodide)
Placed in the eyes of newborns to prevent infections with
Neisseria gonorrheae
1% silver nitrate
