Emerging Diseases Lecture 7: Antibiotics

7.1 Overview7.2 Dr. Ehrlich’s Magic Bullet

7.3 Sulfa drugs7.4 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 606Early antimicrobial chemical Introduced in 1910sNot 100% effectiveLong treatment: 1-2 years

Salvarsan was the first effective antimicrobial drug in Western medicine-so 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 brainSyphilis 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 anti-

microbial 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 third-

generation 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 largeAnd they always contain some pre-existing 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.