Micro Chapter 7
Reliable sterilization with moist heat requires... which are most commonly achieved by steam under pressure in an _____.
temperatures above that of boiling water, autoclave
Is rapid freezing to slow freezing most effective for harming bacteria
slow (ice crystals are disruptive)
Heat requires extra time to reach the center of ___ materials. Why?
solid, they do not have the convection currents liquids do
can bacteria grow at several degrees below freezing?
some can
Review the chart on page 186? physical agents of microbial control
eh
The resistance of viruses to biocides largely depends on the presence or absence of an _____.
envelope
What is the most familiar example of a gaseous chemosterilant?
ethylene oxide
bacteriocin
a protein formed by one bacterium to inhibit another
Most foods remain unfrozen until _____ deg C or lower.
-2
What disadvantages might heat have as a microbial control?
-it could inactivate certain vitamins or antibiotics in a solution -damage of materials (rubber and latex) -costly
Explain how the nature of the suspending medium might decrease the effectiveness of heat treatments?
-medium rich in proteins or fats will protect the microbes
What is a major disadvantage to UV light as a disinfectant?
-th radiation is not very penetrating so the organisms to be killed have to be directly exposed -can damage human eyes -can cause burns and skin cancer in humans
What could influence the effectiveness of antimicrobial treatments?
-the number of microbes (time) -environmental influences (warmth)
At the temperatures of ordinary refrigerators (_____), the metabolic rate of most microbes is so reduced that they cannot reproduce or synthesize toxins. In other words, ordinary refrigeration has a ______ effect. Yet, ___ do grow slowly in these temperatures and will alter the appearance and taste of food over time. _______ bacteria generally will not grow at refrigerator temperatures, but _______ is one important exception.
0-7 deg C bacteriostatic psychrotrophs Pathogenic Listeria
High-efficeincy particulate air (HEPA) filters remove almost all microbes larger than about ______ micrometers in diameter.
0.3
Name the autoclave setting required to kill ALL organisms and their endospores (besides prions).
15 psi 121 deg 15 minutes
Name and describe some of the ways chemical antimicrobial agents may work:
ALTERATION OF MEMBRANE PERMEABILITY: -causes cellular contents to leak into the surrounding medium and interfere with the growth of the cell DAMAGE TO PROTEINS AND NUCELIC ACIDS: -breaking of hydrogen and covalent bonds to denature protein -damage to amino acids results in no replication or protein synthesis
vegetative
non-endospore-forming
What is the organism that commercial sterilization is worried about?
Clostridium botulinum
Iodophor
Combination of iodine and an organic molecule from which the iodine is released slowly (don't stain, less irritating)
UV light damages the ______ of exposed cells by causing bonds to form between adjacent ________- bases, usually ______, in DNA chains. These ____ _____ inhibit correct replication of the DNA during reproduction.
DNA, pyrimidines, thymines, thymine dimers,
Name and describe some physical methods of microbial control:
DRYING (DESSICATION): SALTING (OSMOTIC PRESSURE): HEAT: -denatures enzymes -
______ are relatively resistant to high pressure.
Endospores
T or F: Most disinfectants work somewhat better in cold solutions.
F, warmer
Name the physical methods of microbial control:
Heat Filtration Cold High Pressure Desiccation Osmotic Pressure Radiation
Name and describe the two types of sterilizing radiation
IONIZING RADIATION: -shorter wavelengths (less than 1 nm) so more energy -gamma, X-ray, high E electron beams -ionization of water (forming toxic hydroxyl radicals) -adopted by food, medical, and postal services NONIONIZING RADIATION: -longer wavelength (more than 1 nm) -UV (260 nm)
What was the first to use phenol to control surgical infections?
Lister
betadine
Most commonly used in iodophor/iodine, skin prep and wound treatment
Name and describe the types of disinfectants:
PHENOLS AND PHENOLICS phenols: -irritates skin and disagreeable odor -low concentration: throat pain relief (anesthetic) -concentrations above 1%: significant antibacterial effect (throat sprays) phenolics: -chemically altered phenol (reduced irritating qualities) -injure lipid-containing plasma membranes (effective of mycobacterium) -remain active in the presence of organic compounds -stable -persist -suitable for disinfecting pus, saliva, and feces -cresols (O-phenylphenol), Lysol, surface disinfectant - BISPHENOLS -derivatives of phenol containing two phenolic groups -hexachlorophene (antimicrobial lotion, staph and strep, newborns) -triclosan (soap and toothpaste, kitchenware, so used there is resistance popping up), inhibits enzyme used for lipid synthesis BIGUANIDES -cell membranes -chlorhexidine (skin and mucous membranes, skin preparation) -alexidine (rapid) HALOGENS -iodine and chlorine -iodine (antiseptic, protein synthesis and cell membranes), tincture, iodophor -chlorine (disinfectant, germicidal bc forms acid with water, enzymes, disinfects water, bleach (chlorox) ALCOHOLS -effectively kill bacteria and fungi but not endospores or enveloped viruses -denatures proteins -dissolves lipids -used for deferring but not effective enough for treating wounds -ethanol -isopropanol (rubbing alcohol) -hand sanitizers (not effective against endospores or viruses in lipid envelopes) HEAVY MEATLS AND THEIR COMPOUNDS -silver, mercury, copper -metal ions combine with sulfhydryl groups and denaturation happens -silver: antiseptic (1% silver nitrate solution) surfacine, -mercury: bacteriostatic, use limited bc toxicity corrosiveness and ineffective in organic matter, control mildew in paints -copper: destroy green algae, Bordeaux control fungal diseases, new lotion sanitizer -zinc: mouthwashes, shampoos SURFACE-ACTIVE AGENTS -decrease surface tension among molecules of a liquid CHEMICAL FOOD PRESERVATIVES -added to retard spoilage -sulfur dioxide (winemaking) -sodium benzoate, sorbic acid, and calcium propionate -simple organic acids or salts of organic acids -sodium nitrate and nitrite: added to meats ANTIBIOTICS -useful for injection or ingestion to treat disease -nisin: added to cheese -natamycin: antifungal antibiotic, cheese ALDEHYDES -some of the most effective antimicrobials -inactivate proteins by forming covalent cross-links with other functional groups on proteins -formaldehyde gas (glutaraldehyde is less irritating and more effective, one of the few liquid chemical disinfectants that can be considered a sterilizing agent) CHEMICAL STERILIZATION PLASMAS - a state of matter in which gas is excited (in this case by an electromagnetic field) to make a mixture of nuclei with assorted electrical charges and free electrons -can sterilize metal and plastic devices like long tubes with a very thin diameter -have many free radicals which quickly destroy even spore-forming microbes -elements of both physical and chemical sterilization -requires only low temperatures -relatively expensive SUPERCRITICAL FLUIDS -combines chemical and physical methods -"supercritical"= properties of both a liquid and a gas PEROXYGENS AND OTHER FORMS OF OXYGEN -peroxygens: a group of oxidizing agents that includes hydrogen peroxide and per acetic acid
______ _____ is one of the most effective liquid chemical spermicides available and can be used as a sterilant.
Peracetic acid
Which two gram-negative genera are unusually resistant to biocides and many antibiotics?Why?
Pseudomonas Burkholderia selective porins (mycobacteria also exhibit greater than normal resistance to chemical biocides)
Name and describe the different surface-active agents:
SOAPS AND DETERGENTS: -mechanical removal of microbes through scrubbing -little value as an antiseptic -emulsification (breaks oils into droplets) -good determine agents -effective sanitation method ACID-ANIONIC SANITIZERS: -clean food processing equipment (esp dairy) -anion of the molecule reacts with plasma membrane QUATERNARY AMMONIUM COMPOUNDS (QUATS) -most widely used surface-active agents: cationic detergents (quats) -cation is important part -fungicidal, amebicidal, virucidal -dont kill endospores or mycobacteria -probably affect the plasma membrane -Zephiran and Cepacol: mouthwash -Pseudomonas actively grow in quats
hot-air sterilization
Sterilization by the use of an oven at 170°C for approximately 2 hours
T of F: once a bacteriostatic agent is removed, growth might resume.
T
T or F: Bacteria are sometime thought of as "little bags of enzymes."
T
What is a germicidal lamp?
a UV lamp that is found in hospital rooms, nurseries, operating rooms, and cafeterias
asepsis
absence of significant contamination
Heat is a lot more effective under ______ conditions.
acidic
Steam under pressure fails to sterilize when the ____ is not completely exhausted. This can happen with the premature closing of the autoclave's automatic ____ ____.
air, ejector valve
When a disinfectant is directed at living tissue it is called an _______.
antiseptic
What is the concept of equivalent treatments?
as the temperature is increase much less time is needed to kills the same number of microbes
sepsis
bacterial contamination
Another oxidizing agent is ______ _____, which is probably most familiar as the main ingredient in over-the-counter medications for acne.
benzoyl peroxide
One type of moist heat "sterilization" is _______. ________-______ _____ is essentially the same temperature. Although these methods kill most pathogens, what do they have trouble killing quickly?
boiling, free-flowing steam, endospores and viruses
______ is a type of food poisoning resulting from improper canning methods.
botulism
phenol
carbolic acid
Few _____ agents achieve sterility.
chemical
_____ agents are used to control the growth of microbes on both living tissue and inanimate objects.
chemical
Moist heat kills microorganisms primarily by irreversible ________ (denaturation) of proteins (ex: ____ ________)
coagulation, egg frying
chloramines
combined chlorine and ammonia, release chlorine over time, purify water, disinfect equipment
Sterilization in an autoclave is most effective when the organisms are either _____ by the ___ directly or are contained in a small volume of ______ liquid.
contacted by the steam directly, aqueous
disinfection
control directed at destroying harmful microorganisms (usually vegetative)
__________ is the destruction of vegetative pathogens on inanimate objects. ______ is the destruction of pathogens on living tissue.
disinfection, antisepsis
Difference in method between disinfection and antisepsis?
disinfection: physical or chemical methods antisepsis: mostly chemical methods
The ______-______ method is used in teaching labs to evaluate the efficacy of a chemical agent.
disk-diffusion
What is an example of an important covalent bond that hold proteins together and could be targets for antimicrobial agents?
disulfide bridges
Liquids or gases can be sterilized by ________.
filtration
_______ is used to sterilize heat-sensitive materials such as some culture media, enzymes, vaccines, and antibiotic solutions.
filtration
One of the simplest methods of dry heat sterilization is direct _______.
flaming
In general, disinfection is a ______ process.
gradual
Peroxygens
group of oxidizing agents that includes hydrogen peroxide and peracetic acid
most common method for sterilization
heat (can even kill endospores if high enough)
Most milk pasteurization today uses temperatures of at least 72 deg for only 15 seconds. This treatment is known as ____-_____ ___-_____ ______ (______).
high-temperature short-time pasteurization (HTST)
nosocomial infection
hospital acquired infection
Chlorine has germicidal action because of the _____ ____ that forms when chlorine is added to water.
hypochlorous acid
tincture
in solution in aqueous alcohol (ex: iodine)
______ is an effective way to sterilize and dispose of contaminated paper cups, bags, and dressings.
incineration
What happens to the temperature of the free-flowing steam when pressure is increased? How hot does 100 deg C steam get under 15 psi?
it increases, 121 deg
Why does hot-air sterilization take longer than moist sterilization?
it takes air longer to transfer heat to a cool body than it does water
-cide
kill
If you want a comprehensive list of disinfectants there is a big table on pages 196 & 197
kk
If the death curve is plotted logarithmically, the death rate is shown by a _____ line, which means that cells die at a ______ rate.
linear, constant
What types of food are most susceptible to spoilage by molds?
low pH (5.5 or lower)
sanitization
lowering microbial counts to safe public health levels to minimize disease transmission ex: high-temperature washing of dishes
determine/degermination
mechanical removal (rather than the killing) of most of the microbes in a limited area ex: swabbing skin with alcohol before an injection
_______ _____ are composed of such substances as cellulose esters or plastic polymers. They are only about ______ mm think and the pores are either ___ micrometers or _____ micrometers. Some ____ bacteria such as _______ or _____ will sometimes pass through these filters. Some of these filters come with pores that are ______ micrometers, which will retain even viruses and large protein molecules.
membrane filters, 0.1, 0.22, 0.45, 0.01
As a general rule, ______ and _____ are much more capable than bacteria of growing materials with low moisture/high osmotic pressure.
mold and yeasts
Why do molds more often cause the spoilage of fruits and grains than bacteria?
mold can grow in low-moisture and acidic environments
Do microwaves have much direct effect on microorganisms?
no
Is hydrogen peroxide a good antiseptic for open wounds? Why or why not?
no, quickly broken down into water and gaseous oxygen by the action of catalase
Should you wrap dry material in aluminum foil to autoclave?
no, steam won't reach, use paper
Are desiccated cells dead?
no, they are not growing or reproducing but they remain viable for years
The presence of ______ _______ often inhibits the action of chemical antimicrobials.
organic matter
The use of high concentrations of salts and sugars to preserve food is based on the effects of _____ _____.
osmotic pressure
Dry heat kills by _____ effects.
oxidation
The ____ of a medium often has a great effect on a disinfectant's activity.
pH
______ are not commonly used because they are irritating and aren't very effective at low concentrations. Chemically altered derivatives of these chemical are called ______, and they are less irritating and more effective as antimicrobials when combined with soaps or detergents.
phenols. phenolics
________ sterilization and ______ _____ sterilization are mixtures between physical and chemical sterilization.
plasma, supercritical fluid
Many biocides tend to be more effective against gram ______ bacteria. Why?
positive, the gram-negative LPS offers protection
Sterilization with liquid chemicals is possible, but even sporicidal chemicals are usually not considered to be ___________ sterilants. However, _______ chemosterilants are frequently used as substitutes for _______ sterilization.
practical, gaseous, physical
What is an advantage to high pressure treatments?
preserves flavors/colors/nutrients
How would autoclaving in Colorado be affected?
pressure higher than 15 psi
aqueous
primarily water
alkylation
process by which ethylene oxide destroys microorganisms, resulting in the inability of the cell to normally metabolize, reproduce, or both (replacement of hydrogen atom with chemical radical)
large industrial autoclaves are called...
retorts
a sterilizing agent is called a...
sterilant
commercial sterilization
sufficient heat treatment to kill endospores of Clostridium botulinum in canned food (but not to degrade food)
______ ____ ______ has been used to decontaminate medical implants such as bone, tendons, or ligaments taken from donor patients.
supercritical carbon dioxide
What is the most damaging part of the freeze-thaw cycle?
thaw
oligodynamic action
the ability of small amounts of a heavy metal compound to exert antimicrobial activity
thermal death point
the lowest temperature at which all organisms in a particular culture will be killed in 10 minutes
in addition to killing pathogens, pasteurization lowers bacterial counts, so...
the milk keeps well under refrigeration
thermal death time
the minimal length of time for all bacteria in a particular culture to be killed at a given timperature
filtration
the passage of liquid or gas though a screen like material with poorer small enough to retain microorganisms
What test does the dairy industry use to test whether a product has been pasteurized adequately?
the phosphatase test phosphatase is an enzyme found in milk, it will be inactivated if pasteurization occurred
sterilization
the removal or destruction of all living microorganisms
decimal reduction time
the time (mins) in which 90% of a population of bacteria at a given temperature will be killed
Many relatively heat-resistant (_______) bacteria survive pasteurization, but these are _____ to cause disease or cause refrigerated milk to spoil.
thermoduric, unlikely
Why is it okay if more resistant endospores of thermophilic bacteria survive commercial sterilization?
they won't germinate or grow under normal storage conditions
-stat or -stasis
to stop or steady the growth/multiplication of bacteria
review table on pg 177!!!!! u. need it!!
ugh
Milk can also be sterilized (different from pasteurization) by ____-____ _______ ______ (____).
ultra-high-temperature (UHT) treatments
What is the current standard for evaluating the effectiveness of disinfectants?
use-dilution test (contaminated cylinders left in disinfectant for 10 mins at 20 deg C and then surviving bacteria grow on medium)
_____ are generally resistant to desiccation, but they are not as resistant as ______, some of which have survived for centuries.
viruses, endospores
Does hydrogen peroxide effectively disinfect inanimate objects?
yes
Could sterilization be done by a gas?
yes, ethylene oxide