Transcript Set 7 Antibiotics - IUP Personal Websites

Emerging Diseases
Lecture 7:
Antibiotics
7.1 Overview
7.2 Dr. Ehrlich’s Magic Bullet
7.3 Sulfa drugs
7.4 Antibiotics
7.5 Disambiguation
7.1: Overview: Disease Prevention
Strategies Based on the Germ
Theory
• Clean streets
• Sewers and plumbing
• An emphasis on hygiene for everyone
(socialism of the microbe)
• Antiseptic surgical procedures
• Vaccines (later in 20th Century)
Another approach is to use
chemicals as medicines to kill
germs after they attack.
A “cure” not a preventative
Very useful when prevention
methods fail.
Disease Cures???
• According to the Germ Theory-killing the
germs ought to work well
• How do you kill living germ cells without
harming the patient?
Antiseptics such as Lister’s carbolic
acid killed germs on surfaces but
were too powerful to administer to
a sick patient.
By the start of the 20th Century the
search was on for a chemical that
could kills germs inside a living
person without harm.
7.2: Paul Ehrlich and the “Magic
Bullet”
Salvarsan-Compound 606
Early antimicrobial chemical
Introduced in 1910s
Not 100% effective
Long treatment: 1-2 years
Salvarsan was the first effective
antimicrobial drug in Western medicineso famous there was a movie about it.
Salvarsan was used to fight
Syphilis Infections
Infectious agent is Treponema
pallidum a “spirochaete”
Sexual transmission, may also
be transmitted through cuts and
scrapes
Can cause skin infection called
“yaws”
Salvarsan was much better than earlier
“cures”
High fevers?
Syphilis was anAn Emerging Disease
in the 1500s
• First European outbreak in
1494
• Origins-a new version of an
old disease?
• Or an entirely new disease?
• Highly fatal in 1500s
The “Great Pox”
The “French Disease”
A New World disease brought back to the Old
World by Columbus’ sailors???????
Syphilis has a variety of symptoms
and forms
• Primary-large sore or chancre
• Secondary-many possible symptoms
including skin rash
• Latent-no symptoms but still
infectious
• Teriary-disease invades entire body
including bones and brain
Syphilis is called the Great Imitator
because its symptoms resemble
those of other diseases
Some symptoms and stages
A serious problem for society
A serious problem because...
An STD so very widely transmitted
In the latent stage people thought they were
cured and continued to be sexually active
Can be transmitted from infected mother to
baby at birth
“Congenital” syphilis accounted for many
institutionalized patients in 19th Century
7.3: Sulfa Drugs
• Later class of antimicrobial compounds
• Discovered in Germany
1935
• Very effective but some
side effects
• The “First Wonder
Drug”
• Used against many
microbes
Sulfa drugs were the second
successful group of antimicrobial
drugs.
Saved many lives in World War II
7.4: Antibiotics- a new class of
antimicrobial in the 1940s
• Penicillin-produced by a fungus
• “Discovered” in 1928 and
investigated by Alexander Fleming
• Difficult to purify in quantity
• Not effective against all microbes
• Mass production an Allied effort in
World War II
• Antibiotics are produced by a
living organism to fight microbes
Antibiotics such as penicillin are
different from Salvarsan and sulfa
drugs.
Antibiotics come from a living
organism not a chemical factory.
Salvarsan and sulfa drugs are
artificial but antibiotics are natural
in the sense that they are used in
nature by one organism against
another.
Streptomycin
• Second important
antibiotic
• Effective against
microbes that are not
harmed by penicillin
• Waksman usually
credited-1943
• Used to treat tuberculosis
Antibiotics today
• Second or thirdgeneration compounds:
ampicillin, carbenicillin,
methicillin, etc.
• Resistance is the
problem today
• The widespread use of
antibiotics selects
resistant strains.
Most natural microbes are
susceptible to and can be killed by
antibiotics.
But microbial populations are large
And they always contain some preexisting mutants that are resistant
to antibiotics.
When antibiotics kill off the
susceptible cells-only the resistant
ones remain.
This is an example of artificial
selection.
Thus, hospitals, clinics, etc, (any
place where antibiotics are used a
lot) are great places to find
resistant microorganisms.
Once a resistance gene is selected,
microbes have many ways to share
it among themselves by sharing
pieces of DNA.
This is called horizontal gene
transfer.
It allows the rapid spread of
antibiotic resistance.
Sometimes the genes for many
different types of antibiotic
resistance travel on the same piece
of DNA and get shared widely.
Can lead to multi-drug resistant
microorganisms.
7.5: Disambiguation
• Antibiotics work against living organisms such
as bacteria.
• They are useless against non-living pathogens.
(viruses and subviral pathogens)
• Antiviral compounds are used against viruses.
• Antimycotics are used against fungi.