Antibiotics
The term
‘antibiotic’ was derived from ‘antibiosis’ which refers to the suppression of
microorganisms due to secretion of toxic or inhibitory compounds by other
microorganisms. Although antibiosis has been observed by many scientific
workers fairly frequently towards the end of the nineteenth century, it was not
until the discovery and development of Penicillin that a truly wide ranging
search for antibiotics was initiated.
Antibiotics are not effective against
viral infections such as the common cold.
The first
chemotherapeutic agent, discovered by Paul Ehrlich, was Salvarsan, used to
treat syphilis.
Alexander
Fleming discovered the first antibiotic, penicillin, in 1929; its first
clinical trails were done in 1940.
Antibiotics
are produced by species of Streptomyces, Bacillus, Penicillium and
Cephalosporium
Infobits
1904 Ehrlich found that the dye trypan red was active against
the trypanosome that causes African sleeping sickness and could be used
therapeutically
Drugs
such as the sulfonamides are sometimes called antibiotics although they are
synthetic chemotherapeutic agents which are not synthesized using microbes.
The
antibiotics are usually classified on the basis of:
• Target
group of microorganisms
• Antimicrobial
spectrum and
• Mode of
action
Based on
the target group, the antibiotics can be classified as antibacterial,
antifungal and antiviral.
Antimicrobial
spectrum or antibiotic spectrum refers to the range of effectiveness of
antibiotics on different kind of microorganisms, i.e. the range of different kind
of microorganisms that can be inhibited, killed, or lysed by a particular type
of antibiotic.
The
susceptibility of microorganisms to individual antibiotic varies significantly
and on account of this, the antibiotics can be classified in two groups as,
These
attack different kinds of microbial pathogens and therefore find wider medical
use. Antibacterial antibiotics of broad – spectrum are effective against both
Gram positive and Gram negative bacteria. They also attack pathogens belonging
to Mycobacteria, Rickettsia, and Chlamydia .
Similarly, broad – spectrum antifungal
antibiotics attack different type of fungal pathogens.
Narrow –
spectrum antibiotics are categorized as those that are effective only against a
limited variety of microbial pathogens. These antibiotics are quite valuable
for the control of microbial pathogens that fail to respond to other
antibiotics. For example, vancomycin is a narrow spectrum glycopeptide. It is
an effective bactericidal agent for gram – positive penicillin resistant
bacterial pathogens belonging to genera Staphylococcus,
Bacillus, and Clostridium.
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