Transcript Antibacterials and Antivirals

Antibacterial and
Antiviral Drugs
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Antibacterials
Bacteria
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Definition
Replication
Shapes
Diseases
Antibacterials
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3.
4.
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2.
Penicillin
Discovery of
Synthesis
Structure
Ways it functions
General
Antibacterials
Problems
Possible solutions
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Characteristics of
Bacteria
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Single celled or
non- cellular
Spherical,spiral or
rod–shaped
organisms
Lack chlorophyll
Reproduce by
fission
Important as
pathogens and for
biochemical
properties.
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Infectious Bacteria
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Cocci – Sphericial
Often cause sore throats
and pneumonia
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Bacilli – Rod shaped
Mycolbacterium cause
tuberculosis
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Spirochete – Spiral
shaped
Syphilis, gum infections
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Structure of a Bacterium
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Capsule – Protective layer of
bacteria. made of proteins, sugars,
and lipids
Cell wall – Provides the bacteria
with its shape and structure.
Cell membrane – permeable
membrane that transfers nutrients
and chemicals in and out of the cell.
Cytoplasm – Liquid within the cell
which serves to protect cell parts as
well as move materials throughout
the cell. Contains glycogen, lipids
and other nutrients
Ribosomes – synthesizes proteins.
DNA – Single chromosome controls
the functions of the cell.
Flagella – A tail-like appendage
used for movement.
Pilus – Small hairs whose purpose
is to stick to surfaces. Can also be
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used in reproduction.
Structure a Bacterium
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Bacteria can be either
aerobic or anaerobic
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Aerobic:-- require
oxygen for metabolism.
Morel likely to infect
surface areas such as
the skin and the
respiratory tract
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Anaerobic – multiply in
oxygen free and in low
oxygen surroundings
such intestines
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Replication by Binary Fission
One cell is split into two separate cells.
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Bacterial Caused Diseases
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Anthrax
Cholera
Plague
Q-Fever
Strep Throat
Staph Infections
Tuberculosis
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The Discovery of Penicillin
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Penicillin was discovered in 1929 by
scientist Alexander Fleming.
He left for vacation with an agar
plate covered with the bacteria
Staphylococcus aureus.
When he returned he noticed that
the fungus, Penicillium, had grown
on the plate
The bacteria colony
surrounding the fungus had
become transparent because
the bacterial cells had
undergone lysis.
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Development of Penicillin
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Several years later Howard Florey and
E.B. Chain stumbled across Fleming’s
research papers and were intrigued by
his findings.
They were convinced that Fleming’s
discovery could save a lot of lives,
prevent pain, and make it much easier
to fight infectious diseases and prevent
other infections.
They developed a way to mass produce
penicillin making it available to soldiers
wounded in world war II
Florey and Chain were awarded the
Nobel Prize in 1945 for their work on
penicillin
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Penicillin Structure
Penicillins have a special structure that allows
them to interfere with the formation of the cell
wall when bacteria reproduce
The general structure of penicillin
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How Does it Function?
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Penicillin prevents the cross linking of small
peptide chains in peptidoglycan, which is
the main polymer in bacterial cell walls.
They do not affect bacteria which already
exist, rather Penicillin’s affect the synthesis
of new bacteria.
The new bacteria grow without the ability to
maintain cell rigidity, making them
susceptible to osmotic lysis.
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The Action of Penicillins
The
amide group in the
ring is more reactive
due to the strained ring.
The structure of the
beta lactam is similar to
the structures of
cysteine and valine.
The beta lactam binds
to the enzyme that
synthesizes the cell wall
in bacteria blocking its
action.
As a result the bacteria
rupture and break and
cannot reproduce.
Note the similarities in structure
to the beta lactam.
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Bacterial Immunity to
Penicillin
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Antibacterial Resistance –
mutated bacteria which are
immune to antibacterials are
more likely to survive when
excessive antibacterials are
used.
Bacteria develop penicillinase
enzymes rendering penicillin
ineffective.
New antibiotics are developed
by changing the R group side
chain.
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Structure of Penicillin
Penicillin is a group of compounds which all contain the
same basic ring structure, called a beta-lactam. It is
comprised of two amino-acids (valine and cyteine) through
a tripeptide intermediate. The third amino acid is replaced
by an acyl group, which gives different characteristics to
differing penicillins.
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Narrow Range and Broad
Range Antibiotics
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Narrow range antibiotics target specific
kinds of bacteria. They are usually more potent
Broad range are effective against a wide range of
bacteria.
When a doctor diagnoses a patient suspected of having a
bacterial infection, the doctor must take samples of body
fluids to determine the precise type of infection.
A broad range epidemic might be prescribed initially. Once
a bacterial infection is properly diagnosed it may be
appropriate to switch to a narrow range antibiotic.
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Overuse of Penicillin
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Leads to greater immunity of bacteria
to penicillin, since the strongest and
most resistant survive.
Greater doses of penicillin are required
to be effective
Danger of developing super bacteria
Kill beneficial bacteria as well as
harmful bacteria
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Effects of over prescription of
Penicillins
1. Penicillins are usually safe except for a small percentage of
the population (about 10%) who experience allergic reactions
and suffer side effects ranging from fever and body rash to
occasionally shock and death. Repeated use can sometimes
lead to allergic reaction.
2. Antibiotics, if used repeatedly, may wipeout harmless
bacteria and helpful ones in the alimentary canal (this is the
food canal, or gut, including the esophagus stomach and
intestines). Also, the destroyed bacteria may be replaced by
more harmful bacteria.
3. Another serious problem is that of genetic resistance. As
antibiotics are used extensively, a few organisms survive and
pass on their resistance to succeeding generations. For
example typhoid, gonorrhea, TB and other diseases all have
strains that are now resistant to many antibiotics.
4. A microorganism may also become resistant as a result of
mutation. The mutated strain may be able to reproduce on a
large scale, with very serious consequences. A mutated strain
may develop an enzyme that changes an antibiotic into a
harmless substance.
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This is why antibiotics are considered miracle drugs in constant
need of renewal. The prime rule for the use of antibiotics is that
they should be used only when no other treatment can
significantly reduce suffering or save life.
We live in a world where antibiotics are often misused and
abused. Strict adherence to a recommended treatment
regime is necessary for the effective treatment of an
infection. For example, bacteria that cause tuberculosis
(TB) by destroying lung tissues require patient cooperation
in the use of several anti-TB drugs used in combination to
ovecome the infection.
The Use of Antibiotics in Animal
Feedstock
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Antibiotics are used as supplements in animal
feedstock for the control of animal diseases and to
increase the rate of growth of animals.
Feedstock can contain plant and animal pathogens
which can be a danger to animal and human
health.
Thus antibiotics are used in the production of meat
and poultry to control these bacteria and hence to
increase productivity.
Penicillin Synthesis
A sterilized growth
medium and an
inoculum of strongly
growing hyphae is
added to stainless
steel fermenters. The
fermenters stirred
continuously and
glucose, nitrate and
sterile air are
periodically added.
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Antibacterial Phages
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These can replace antibacterial drugs
such as penicillin by utilizing viruses
which infect bacterial cells which
causes them to lyse, releasing more of
the destructive phages.
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Antivirals
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Antivirals
Viruses
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Definition
Replication
AIDS
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AIDS Definition
History of AIDS
Ways it can spread
Treatment
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Virus Characteristics
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A virus is an infectious agent found in
virtually all life forms.
Viruses consist of genetic material, and have
a central core either DNA nor RNA
Although they are infectious agents, they
differ from bacteria in that they contain no
nucleus or cytoplasm
Do not feed, excrete, or grow
They cannot reproduce outside of a living
cell.
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Virus Structure
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There are many
types of virus with
varying shape and
structure.
All virus have a
central core of either
DNA or RNA
surrounded by a coat
of regularly packed
protein units.
No nucleus or
cytoplasm like
bacteria.
Diagram of an AIDS Virus
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Virus Replication
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The replication of viruses can only occur if the virus
has attached and penetrated the living host cell
It injects it’s DNA or RNA into the host cell’s
cytoplasm.
It takes over the host cells replication mechanism
This causes the cell to die or to be altered which
lead to symptoms of viral infection.
The host cell produces new viral DNA or RNA cells
which are then released to affect other healthy
cells.
A virus that contains RNA rather than DNA is called
a retrovirus
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Virus Replication
The virus uses the cell mechanism to replicate itself
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AIDS - a Viral Transmitted
Disease
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A 10-year study completed in 2005 found a
strain of Simian Immunodeficiency Virus
(SIV) in a number of chimpanzee colonies in
south-east Cameroon that was a viral
ancestor of the HIV-1 that causes AIDS in
humans.
In 1981 AIDS was first identified within
homosexual men
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AIDS in the US
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940,000 cases of AIDS were reported
in the United States from 1981
through 2004.
In 2004, about 39,000 new cases of
HIV infection were reported.
Currently, there are approximately 1.1
million people in the United States
who are infected with the human
immunodeficiency virus.
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History of AIDS in Africa
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Wide spread in
Africa
Lack of access to
education
Reticence
(reluctance) of
some leaders to
recognize the
problem
Lack of access to
treatment
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AIDS Definition
AIDS ( Acquired
Immune Deficiency
Syndrome) is caused
by a retrovirus that
contains RNA rather
then DNA.
This specific virus
invades particular
cells, that are within
the immune system
making the body
unable to fight off
infections.
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AIDS Definition
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The human
immunodeficiency virus
(HIV), which causes
acquired immunodeficiency
syndrome (AIDS),
principally attacks T-4
lymphocytes, a vital part of
the human immune
system.
As a result, the ability of
the body to resist
opportunistic viral,
bacterial, fungal, protozoal,
and other infections is
greatly weakened.
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3 Ways AIDS can be spread
Scientists have identified three ways that
HIV infections spread:
1. Sexual intercourse with an infected
person,
2. Contact with contaminated blood,
3. Transmission from an infected mother
to her child before or during birth or
through breastfeeding.
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AIDS Diagnosis and
Treatment
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While no medical treatment cures AIDS,
there are many drugs that have recently
been developed to eradicate the HIV virus.
Although full blown symptoms of AIDS may
not appear for more then 10 years.
It usually takes 2-3 months after the initial
infection for a person to test positive for HIV
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AIDS Diagnosis and
Treatment
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While no medical treatment cures AIDS,
there are many drugs that have recently
been developed to eradicate the HIV virus.
Although full blown symptoms of AIDS may
not appear for more then 10 years.
It usually takes 2-3 months after the initial
infection for a person to test positive for HIV
During this time frame a person inflected
with HIV can easily spread the virus without
realizing it
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Antiviral Drugs
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Common viral infections such as the influenza,
mumps, or chicken pox are usually overcome
by the body’s immune system.
Vaccines are often used to build up immunity
before a viral inflection occurs.
Medications for viral diseases are used to:
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relieve associated pain,
reduce fever, or
counteract secondary inflections
Rapid replication of viruses makes it difficult to
develop effective antiviral drugs. The viruses
are often very high even before the first
symptoms appear.
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Antiviral Drugs
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Only a few effective antiviral drugs have
been developed.
Antiviral drugs work by
1. Altering the cell’s genetic material so that the
virus cannot use it to multiply, i.e. acyclovir
2. Preventing new virus formed from leaving the
cell, i.e. amatadine
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Viruses mutate frequently leaving the
antiviral drug ineffective
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Antiviral Drugs - Acyclovir
Acyclovir is
an antiviral
drug used to
treat Herpes
Simplex
Acyclovir has a structure similar to deoxyguanosine, one of
the building blocks of DNA. It tricks the viral enzyme DNA
polymerase into incorporating it into its DNA instead of
guanine making it impossible to replicate.
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Antiviral Drugs - AZT
AZT was the first antiviral
drug used to effectively
treat HIV-AIDS
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AZT combines with the enzyme that the HIV virus uses
to build DNA from RNA and clogs up its active site. It
acts as a reverse transcriptase inhibitor. Since only
Retro-Viruses such as HIV use this enzyme, AZT does
not affect normal cells. Unfortunately it causes anaemia
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Other HIV Antiviral Drugs
More recently
ddI and ddC
have been
developed for
HIV treatment.
While antiviral drugs show promise in preventing AIDS in
people who are HIV positive, these drugs are still very
expensive and not available to many people who are HIV
positive,
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Other Antiviral Drugs
Recently, a series of nucleoside have been developed that
appear to be effective against herpes virus
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