Transcript Microbial control agents

Microbial control of postharvest diseases has been one of the most
extensively studied alternatives and appears to be a viable
technology
Control of microbial growth can be by inhibition of growth,
killing the microorganisms or removing them from an
environment. Antimicrobial agents can be divided into agents
that kill microorganisms (bactericidal) and agents that inhibit
growth (bacteriostatic) of the microbes.
Electromagnetic irradiation is another effective way to sterilize
or reduce microbial burden of almost any substance.
Microwaves, ultraviolet (UV) radiation, X-rays, gamma rays and
electrons are used although each type of irradiation has a
specific mechanism.
Control of microbes is important in the
food industry because some microbes spoil
food or their growth in food produces
toxins. The susceptibility of a product to
food spoilage is a consequence of its
suitability as a growth medium. Therefore,
foods with low water activity are less
susceptible to microbial spoilage.
Antibiotics Introduction
Antibiotics are among the most frequently prescribed
medications in modern medicine. Antibiotics cure
disease by killing or injuring bacteria. The first antibiotic
was penicillin, discovered accidentally from a mold
culture. Today, over 100 different antibiotics are
available to doctors to cure minor discomforts as well as
life-threatening infections.
Although antibiotics are useful in a wide variety of
infections, it is important to realize that antibiotics only
treat bacterial infections. Antibiotics are useless against
viral infections (for example, the common cold) and
fungal infections (such as ringworm). Your doctor can
best determine if an antibiotic is right for your
condition.
• Chemotherapy, or the use of chemical agents to destroy
cancer cells, is a mainstay in the treatment of
malignancies. The possible role in treating illness was
discovered when the bone marrow suppressive effect of
nitrogen mustard was noted in the early 1900's. Since
that time, the search for drugs with anticancer activity
has continued, and the goal of treatment with
chemotherapy has evolved from relief of symptoms to
cure. A major advantage of chemotherapy is its ability to
treat widespread or metastatic cancer, whereas surgery
and radiation therapies are limited to treating cancers
that are confined to specific areas.
• Chemotherapy is the use of drugs that kill rapidly
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dividing cells to treat cancer. Chemotherapy drugs are
toxic to cancer cells, which take in the drugs as they
multiply. Once inside the cells, the drug kills the cell or
prevents it from dividing and forming new cells.
Chemotherapy may consist of a single medication or a
combination of drugs administered intravenously or
orally. Most patients with active, symptomatic myeloma
(stage II or III) are initially treated with some form of
chemotherapy.
There are several chemotherapy regimens that myeloma
patients may receive, including:
Conventional chemotherapy
High-dose chemotherapy with stem cell transplantation
Salvage therapy
• Almost all chemotherapy agents currently
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available kill cancer cells by affecting DNA
synthesis or function, a process that occurs
through the cell cycle. Each drug varies in the
way this occurs within the cell cycle.
The major categories of chemotherapy agents
are alkylating agents, antimetabolites, plant
alkaloids, antitumor antibiotics, and steroid
hormones. Each drug is categorized according to
their effect on the cell cycle and cell chemistry.
• Alkylating agents kill cells by directly attacking DNA. Alkylating
agents may be used in the treatment of chronic leukemias,
Hodgkin's disease, lymphomas, and certain carcinomas of the lung,
breast, prostate and ovary. Cyclophosphamide is an example of a
commonly used alkylating agent.
• Nitrosoureas act similarly to akylating agents and also inhibit
changes necessary for DNA repair. These agents cross the bloodbrain barrier and are therefore used to treat brain tumors,
lymphomas, multiple myeloma, and malignant melanoma.
Carmustine (BCNU) and lomustine (CCNU) are the major drugs in
this category.
• Antimetabolites are that drugs block cell growth by interfering
with certain activities, usually DNA synthesis. Once ingested into the
cell they halt normal development and reproduction. All drugs in this
category affect the cell during the "S" phase of the cell cycle.
Antimetabolites may be used in the treatment of acute and chronic
leukemias, choriocarcinoma, and some tumors of the
gastrointestinal tract, breast and ovary. . Examples of commonly
used antimetabolites are 6-mercaptopurine and 5-fluorouracil (5FU).
• Antitumor antibiotics are a diverse group of compounds. In
general, they act by binding with DNA and preventing RNA
synthesis. These agents are widely used in the treatment of a
variety of cancers. The most commonly used drugs in this group are
doxorubicin (Adriamycin), mitomycin-C, and bleomycin.
• An antiseptic is a substance which inhibits
the growth and development of
microorganisms. For practical purposes,
antiseptics are routinely thought of as
topical agents, for application to skin,
mucous membranes, and inanimate
objects, although a formal definition
includes agents which are used internally,
such as the urinary tract antiseptics.
• Antiseptics are a diverse class of drugs which are applied
to skin surfaces or mucous membranes for their antiinfective effects. This may be either bacteriocidal or
bacteriostatic. Their uses include cleansing of skin and
wound surfaces after injury, preparation of skin surfaces
prior to injections or surgical procedures, and routine
disinfection of the oral cavity as part of a program of oral
hygiene. Antiseptics are also used for disinfection of
inanimate objects, including instruments and furniture
surfaces.
• Disinfectants
•are antimicrobial agents that are applied to
non-living objects to destroy microorganisms,
the process of which is known as disinfection.
Disinfectants should generally be distinguished
from antibiotics that destroy microorganisms
within the body, and from antiseptics, which
destroy microorganisms on living tissue.
Sanitizers are substances that reduce the
number of microorganisms to a safe level. The
main difference between a sanitizer and a
disinfectant is that at a specified use dilution, the
disinfectant must have a higher kill capability for
pathogenic bacteria compared to that of a
sanitizer. Bacterial endospores are most
resistant to disinfectants, however some viruses
and bacteria also possess some tolerance.
• Types of disinfectants
• Disinfection liquid attached to hospital bed
• Alcohols
• Alcohols, usually ethanol or isopropanol, are wiped over benches and skin
and allowed to evaporate for quick disinfection. They have wide
microbiocidal activity, are non corrosive, but can be a fire hazard. They also
have limited residual activity due to evaporation, which results in brief
contact times, and have a limited activity in the presence of organic
material. Alcohol is not effective against fungal or bacterial spores.
• Aldehydes
• Aldehydes, such as Glutaraldehyde, have a wide microbiocidal activity and
are sporocidal and fungicidal. They are partly inactivated by organic matter
and have slight residual activity.
• Halogens
• Chloramine is used in drinking water treatment instead of chlorine
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because it produces fewer disinfection byproducts.
Chlorine is used to disinfect swimming pools, and is added in small
quantities to drinking water to reduce waterborne diseases.
Iodine is usually dissolved in an organic solvent or as Lugol's iodine
solution. It is used in the poultry industry. It is added to the birds' drinking
water. Although no longer recommended because it increases scar tissue
formation and increases healing time, tincture of iodine has also been used
as an antiseptic for skin cuts and scrapes.
Disinfection liquid attached
to hospital bed
• Relative effectiveness of disinfectants
One way to compare disinfectants is to compare
how well they do against a known disinfectant
and rate them accordingly. Phenol is the
standard, and the corresponding rating system is
called the "Phenol coefficient". The disinfectant
to be tested is compared with phenol on a
standard microbe (usually Salmonella typhi or
Staphylococcus aureus). Disinfectants that are
more effective than phenol have a coefficient >
1.
Examples of UV sensors for water disinfection monitoring
• Materials:
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8 nutrient agar plates
1 thumb forceps
1 bent glass rod
2 sterile 1mLpipettes
Alcohol for sterilization
Metric ruler
Antibiotic sensitivity disks
Sterile paper disks
Assorted antiseptics
Ultraviolet lamps
Nutrient both cultures of E.Coli and Bacillus cereus
• We have two methods:
• 1-Disk diffusion
• R=range
• I = intermediate
• S= senisivity
Antibiotic
Gentamycin
R
I
S
Less 15 16-19 more 20
• 2- Tube dilution
• MIC (minimium inhibition con.)
http://en.wikipedia.org/wiki/Disinfectant
1.http://mic.sgmjournals.org/cgi/content/full/152/4/989
1.^ EPA's Registered Sterilizers, Tuberculocides, and
Antimicrobial Products Against HIV-1, and Hepatitis B and
Hepatitis C Viruses. (Obtained January 4, 2006)