《制药工程专业英语》Unit9,P96-98

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原稿

Throughout recorded history ，bacterial infections have periodically exacted heavy tolls on the human population .During “Black Death”bubonic plague episode of 1347-1351.Yersinia pestis killed an estimated 25 million in Asia and Europe .US Public

Heath Service statistics for 1910 and 1920 show that early in this century tuberculosis killed one in every 1000 US residents . Even today ,mainly in developing countries ,Mycobacterium tuberculosis remains the leading cause of death attributable to a single infectious agent, killing over three million people worldwide every year.

Within just a few decades, the availability of an anti-infective pharmacopoeia suddenly provided humans with the potential to circumvent Nature's time-tested, live-or-die evolutionary paradigm for enhancing their survival prospects under constant microbial barrage. Those members that previously would have succumbed could now survive longer with the help of vaccines and antibiotics - auxiliary agents which work alongside the immune system to fight infection. In effect, humans' employment of these auxiliaries can be looked upon as exemplifying a self-contrived evolution in their immunological defense system.

Once the usefulness of Sir Alexander Fleming's penicillin discovery had been demonstrated, a flurry of other antibiotics unearthed from natural sources followed. Some of these proved suitable for treating disease, usually after chemical modification to improve the natural compound's potency, safety or pharmacokinetic profiles.

For most of the past 50 years, it seemed that medical science had gained a strong upper hand over bacterial disease. Some pharmaceutical houses and funding agencies decided to cut back on antibiotic discovery efforts, as it appeared that the physician's antibacterial arsenal was well stocked. But the nature of the diseases has proved otherwise.

The rapid escalation in the incidence of multiple-antibiotic-resistant pathogens is now raising very serious concerns worldwide.This development underscores the powerful evolutionary capabilities of bacterial populations under the selective pressure imposed by antibiotic therapy .

Antibiotic resistance Resistance problems are seen with both Gram-negative(for example Escherichia coli) and Gram-positive bacteria (such as Staphylococcus aureus), but most of the concerns are with the latter group of pathogens.Streptococcus is a respiratory Gram-positive pathogen responsible for 40,000 deaths a year in the US alone. A rapidly rising prevalence of penicillin-resistant S. pneumoniae infections is now problematic in many countries. One of the worst situations is in Hungary, where 70%of the S. from children tested in 1988-1989 were resistant to penicillin.

Bacteria have evolved numerous ploys for defeatng antibiotic action——they inactivate the antibiotic by hydrolysis, acylation , phosphorylation or nucleotidylation reactions; aitre the