Тематический сборник текстов для чтения (английский язык). Соснина Е.П - 46 стр.

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46
TOP IC 5. HEALTH AND MED ICIN E, ILLN ES S E, TREATMENT
Text 1. Antibiotic
An anti biotic is a drug that kills or slows the growth of bacteria. Antibiotics are one
class of "antimicrobials", a larger group which also includes anti-viral, anti-fungal, and anti-
parasitic drugs. They are relatively harmless to the host, and therefore can be used to treat
infection. The term originally described only those formulations derived from living
organisms, but is now applied also to synthetic antimicrobials, such as the sulfonamides.
Unlike previous treatments for infections , which included poisons such as s trychnine,
antibiotics were labelled "magic bullets": drugs which targeted disease without harming the
host. Antibiotics are not effective in viral, fungal and other nonbacterial infections, and
individual antibiotics vary widely in their effectiveness on various types of bacteria. Some
specific antibiotics target either gram-negative or gram-positive bacteria, and others are
mo re wide-spectrum antibiotics. The effectiveness of individual antibiotics varies with the
location of the infection and the ability of the antibiotic to reach this s ite. Oral antibiotics
are the simplest approach when effective, with intravenous antibiotics reserved for more
serious cases. Antibiotics may sometimes be administered topically, as with eyedrops or
ointments.
Following earlier experiments that had demonstrated interesting anti-bacterial effects
from various bacterial secretions, the German scientist E. de Freudenreich in 1888 isolated a
bacterial s ecretion and noted its antibacterial properties . Pyocyanase, s ecreted by Bacillus
pyocyaneus, retarded the growth of other bacteria in situ and was toxic to many disease-
causing bacteria. Unfortunately, pyocyanase's own toxicity and unstable character prevented
its use as an effective, safe antibiotic within the human body.
The first effective antibiotic discovered was penicillin. French physician Ernest
Duchesne noted in his 1896 thes is that certain Penicilliu m molds killed bacteria. Duchesne
died within a few years, and his research was forgotten for a generation, until an accident
intervened. Alexander Fleming had been culturing bacteria on agar plates, one of which was
ruined by an accidental fungal contamination. Rather than discarding the contaminated
plate, Fleming noticed a clear zone surrounding the colony of mold. Having previously
s tudied the ability of the enzyme lysozyme to kill bacteria, Fle ming realized that the mold
was secreting something that stopped bacterial growth. He knew that this substance might

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