Antibacterial and Antiviral Drugs

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Antibacterial and Antiviral Drugs

• Larry J. Scheffler
• Lincoln High School

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Antibacterials

• Bacteria
• Definition
• Replication
• Shapes
• Diseases

• Antibacterials
• Penicillin
• Discovery of
• Synthesis
• Structure
• Ways it functions
• General Antibacterials
• Problems
• Possible solutions

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Characteristics of Bacteria

• Single celled or non- cellular
• Spherical,spiral or rodshaped organisms
• Lack chlorophyll
• Reproduce by fission
• Important as pathogens and for biochemical
  properties.

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Infectious Bacteria

• Cocci Sphericial
• Often cause sore throats and pneumonia
• Bacilli Rod shaped
• Mycolbacterium cause
• tuberculosis
• Spirochete Spiral shaped
• Syphilis, gum infections

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Structure of a Bacterium

• 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 used in reproduction.

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Structure a Bacterium

• Bacteria can be either aerobic or anaerobic
• Aerobic-- require oxygen for metabolism. They
  are more likely to infect surface areas such as
  the skin and the respiratory tract.
• Anaerobic multiply in oxygen free and in low
  oxygen surroundings such as the intestines.

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Replication by Binary Fission

• One cell is split into two separate cells.

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Bacterial Caused Diseases

• Anthrax
• Cholera
• Plague
• Q-Fever
• Strep Throat
• Staph Infections
• Tuberculosis

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The Discovery of Penicillin

• 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

• Several years later Howard Florey and E.B. Chain
  stumbled across Flemings research papers and
  were intrigued by his findings.
• They were convinced that Flemmings 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?

• 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 Penicillins 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 beta lactam 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

• Antibiotic Resistance Mutated bacteria which
  are immune to antibiotics are more likely to
  survive when excessive antibacterials are used.
• Bacteria develop enzymes known as penicillinases
  that destroy or render 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, known as
  beta-lactam. It is comprised of two amino-acids
  (valine and cyteine) through a tripeptide
  intermediate. The third amino acid (the R group)
  is replaced by another group, which gives
  different characteristics to differing
  penicillins.

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Narrow Range and Broad Range Antibiotics

• Narrow range antibiotics target specific
• kinds of bacteria. They are usually more
  potent.
• Broad range antibiotics are effective against a
  wide range of bacteria.
• When doctors diagnose patients suspected of
  having bacterial infections, they must first take
  samples of body fluids, and try to determine the
  precise type of infection.
• A broad range antibiotic 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

• Leads to greater immunity of bacteria to
  penicillin, since the strongest and most
  resistant strains 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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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

• 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
• Definition
• Replication

• AIDS
• AIDS Definition
• History of AIDS
• Ways it can spread
• Treatment

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Virus Characteristics

• 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.
• They do not feed, excrete, or grow
• They cannot reproduce outside of a living cell.

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Virus Structure

• 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

• The replication of viruses can only occur if the
  virus has attached and penetrated the living host
  cell.
• It injects its DNA or RNA into the host cells
  cytoplasm.
• It takes over the replication mechanism of the
  host cell.
• This causes the cell to die or to be altered,
  which results in the symptoms of a 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

• A 10-year study completed in 2005 found a strain
  of Simian Immunodeficiency Virus (SIV) in a
  number of chimpanzee colonies in south-eastern
  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

• 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

• Wide spread in Africa.
• Lack of access to education.
• Reticence 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

• 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
• Sexual intercourse with an infected person,
• Contact with contaminated blood,
• Transmission from an infected mother to her child
  before or during birth or through breastfeeding.

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AIDS Diagnosis and Treatment

• While no medical treatment cures AIDS, there are
  many drugs that have recently been developed to
  eradicate the HIV virus.
• 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

• 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

• Common viral infections such as the influenza,
  mumps, or chicken pox are usually overcome by the
  bodys immune system.
• Vaccines are often used to build up immunity
  before a viral inflection occurs.
• Medications for viral diseases are used to
• 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

• Only a few effective antiviral drugs have been
  developed.
• Antiviral drugs work by
• Altering the cells genetic material so that the
  virus cannot use it to multiply, i.e. acyclovir
• Preventing new virus formed from leaving the
  cell, i.e. amatadine
• 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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