Antibiotics

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Microbes: Can't live with them, can't live without them.
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We focus more on the first of these truths, as shown by the huge sums spent every year on preventing, treating, and researching infectious diseases.
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But the second is equally valid:
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Each human body contains at least 10 times as many microbes as human cells.
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The human gut alone contains about 1 kilogram of bacteria indispensable to digestion.
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But sometimes microbes get out of hand, triggering everything from athlete's foot to influenza pandemics that kill tens of millions, and for millennia humans have sought ways to control them.
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People have tried everything from prayer, to natural biocides (Ötzi, the 5,300-year-old hunter found frozen in an Alpine glacier in 1991, carried fungal oils to treat intestinal parasites), to cautery (scorching wounds with a hot iron).
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The results were mixed at best. Then, in 1929, Alexander Fleming noticed a clear zone on an agar plate of staphylococci bacteria "contaminated" with Penicillium mold.
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Ten years later, Ernst Chain and Howard Florey found a way to isolate the active ingredient.
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Penicillin was used to treat infections in World War II and was commercialized immediately afterward. From this accidental beginning, the global anti-infective market has grown to nearly US$70 billion a year; antibiotics account for about half.
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Producing mass quantities of antibiotics requires a bioindustrial fermentation technique.
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The source microorganisms, usually genetically modified strains of naturally occurring microbes, are grown in enormous vats of liquid growth mediums under carefully controlled conditions.
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The antibiotic compounds are actually metabolites of the microbes; these compounds are isolated, often using various organic solvents, then extracted, purified, and refined into one of several drug forms.
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The chief downstream impacts of antibiotic use involve antibiotic resistance.
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Resistance is natural; microbes that produce antibiotics do so to stave off competition from other microbes, which in turn evolve to escape harm.
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This co-evolutionary dance is expanded and accelerated by the immense scale of human antibiotic use - and misuse.
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Antibiotic resistance developed almost immediately after commercial production of antibiotics began in 1946.
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It has since become a major threat to the control of pathogens, nearly all of which are resistant to one or more standard antibiotics.
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Resistant pathogens have become common in institutional settings such as hospitals and nursing homes; according to the U.S. Centers for Disease Control, about 70 percent of common hospital infections are resistant to at least one antibiotic.
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One of the most common institutional microbes, methicillin-resistant Staphylococcus aureus, kills more people in the United States each year than AIDS.
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Microbes' inherent tendency to develop antibiotic resistance is aggravated by human actions.
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For example, microbe resistance genes are sometimes used as markers in genetically modified crops and wind up in the products made from them.
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Antibiotics are often misused in medical settings, as when patients demand antibiotics for viral infections, against which they are useless.
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Even when the prescribed antibiotics are appropriate, patients often fail to use them properly. Both practices increase antibiotic resistance.
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Perhaps most important, nearly 70 percent of U.S.-produced antibiotics and related drugs are fed to livestock to promote growth and prevent sickness.
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These uses help create resistant pathogens that can reach people directly via the meat and byproducts or indirectly via feedlot runoff that contaminates streams and groundwater.
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Antibiotics are also sprayed on fruit and vegetable crops, and the plants can absorb antibiotics from manure used as fertilizer.
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These problems and others-there is some evidence, for instance, that the misuse of antibiotics has contributed to the increase in childhood asthma and allergies-have led the European Union to ban the nontherapeutic use of antimicrobial drugs in livestock.
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To date the U.S. Food and Drug Administration has declined to do so.
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Tom Prugh is the editor of World Watch