Microbes and the mechanisms of infection As
early as the 16th century some scientists postu-
lated the existence of unseen organisms as
accountable for disease. The development of the
microscope gave proof to the existence of such
organisms; proving their connection to disease
was more difficult. The first to succeed did so in a
major way. German physician Robert Koch
(1843–1910) isolated and cultivated Mycobacterium
tuberculosis, the MICROBEresponsible for the West-
ern world’s most pervasive and devastating dis-
ease. By the 19th century, tuberculosis infected so
many people that it was more common than not.
What puzzled doctors was why some people
became ill and others did not.
Koch solved this mystery in 1882 when he
demonstrated the ability of M. tuberculosisto cause
tuberculosis infection. The methods of vaccination
successful in preventing smallpox, anthrax, and
other infectious diseases did not work with tuber-
culosis, however. Not until biochemist Selman
Waksman (1888–1973) discovered streptomycin, a
powerful antibiotic, in 1943 were doctors finally
able to gain the upper hand against tuberculosis.
Waksman received the Nobel Prize in Physiology
or Medicine in 1952 for his work.
Through their work to understand a disease
prevalent among livestock in the 19th century,
foot-and-mouth disease, German researchers
Friedrich Loeffler (1852–1915) and Paul Frosch
(1860–1928) expanded the spectrum of pathogens.
The pair postulated the existence of a particle
smaller than bacteria caused the infectious disease.
However, they lacked the technology to visualize
such a particle. The development of the electron
microscope in 1939 gave scientists the ability to see
these smallest of infective agents, viruses.
Breakthrough Research and Treatment Advances
Molecular medicine advances in the late 20th cen-
tury gave another enormous boost to the fight
against infectious diseases. In 1995 the bacterium
Haemophilus influenzae, an insidious microbe
responsible for numerous pulmonary and gas-
trointestinal diseases, became the first pathogen
for which researchers unraveled the genetic code.
The advance led to improvements in vaccines and
treatments for H. influenzaeinfections as well as
other bacterial diseases.
Molecular medicine also has provided tremen-
dous breakthroughs in understanding the modus
operandi of viruses such as HIV (human immun-
odeficiency virus), a Machiavellian retrovirus that
subverts the immune system itself to perpetuate
its own survival. These breakthroughs have paved
the way for new antiviral medications that target
specific molecular mechanisms of HIV, slowing its
progress, and show promise for the development
of a vaccine that can prevent HIV infection and
AIDS.
As researchers gain insight into the adaptive
mechanisms of pathogens such as bacteria and
viruses, they are able to develop new drugs—and
drugs that work in new ways—to treat the infec-
tions these pathogens cause. This is particularly
important in light of the alarming rise in DRUG-
resistant infections in diseases such as tuberculo-
sis, GONORRHEA, and staphylococcal pneumonia.
New viruses also threaten public health, placing
renewed emphasis on vaccines and infection con-
trol measures to stop their spread. Though the
control and eradication of many infectious dis-
eases represent many of medicine’s greatest tri-
umphs, many of medicine’s greatest challenges
remain these same factors.Infectious Diseases 305