Making Peace with Microbes
Public sanitation and antibiotic drugs have brought about historic increases in the human life span; they have also unintentionally produced new health crises by disrupting the intimate, age-old balance between humans and the microorganisms that inhabit our bodies and our environment. As a result, antibiotic resistance now ranks among the gravest medical problems of modern times. Good Germs, Bad Germs addresses not only this issue but also what has become known as the "hygiene hypothesis"— an argument that links the over-sanitation of modern life to now-epidemic increases in immune and other disorders. In telling the story of what went terribly wrong in our war on germs, Jessica Snyder Sachs explores our emerging understanding of the symbiotic relationship between the human body and its resident microbes—which outnumber its human cells by a factor of nine to one! The book also offers a hopeful look into a future in which antibiotics will be designed and used more wisely, and beyond that, to a day when we may replace antibacterial drugs and cleansers with bacterial ones—each custom-designed for maximum health benefits.
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About the Author
Jessica Snyder Sachs is a freelance science writer. Her first book, Corpse: Nature, Forensics, and the Struggle to Pinpoint Time of Death, was published in 2001. She lives in New Jersey.
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Good Germs, Bad Germs
Health and Survival in a Bacterial World
By Jessica Snyder Sachs
Farrar, Straus and GirouxCopyright © 2007 Jessica Snyder Sachs
All rights reserved.
FROM MIASMAS TO MICROBES
As scientific geniuses go, Girolamo Fracastoro of Verona was an accommodating sort. If a medical theory didn't suit his politics or his patrons, the famed Renaissance physician could not only rationalize it away but do so in Latin hexameter. A clinician by necessity, a poet and scholar by inclination, he was justly proud of his poetical treatise, Syphilis sive morbus gallicus, or "Syphilis, the French Disease," published to great acclaim in 1530. Though most of Europe blamed Columbus and his Spanish sailors for bringing the "Great Pox" back from the New World, the title of Fracastoro's epic poem conveniently shifted the blame to the current enemies of Verona's Hapsburg occupiers (the Hapsburgs having aligned with Spain through marriage). Even Fracastoro's coining of the disease's name sprang from political gymnastics. For into his poem he wove the tale of Syphilis the shepherd, a resident of Atlantis who is instantly cured with a sip of guaiacum, the supposedly medicinal resin of a New World tree whose bark the Hapsburgs were importing en masse.
More profoundly, the poem's disease terminology marked a turning point in Western medicine, one that set it on a course toward direct warfare on the microbial world. Fracastoro was the first to set down in words the idea that germs — invisible contagious elements — exist in some kind of physical form. He wrote,
And such as Nature must with pangs bring forth, Were violent and various Seeds united, Break slowly from the Bosom of the Night Long in the Womb of Fate the Embryo's worn Whole Ages pass before the Monster's born.
Fracastoro's use of the word "seed" reflected the emerging beliefs of a small number of his contemporaries. These enlightened men and women had begun challenging the Hippocratic mindset of the previous millennium, which held that all disease derived from imbalances in the body's three "humors"— blood, phlegm, and bile.
Admittedly, the prototypic germs portrayed in Fracastoro's poetry were far from the microorganisms we know today. He used the terms "seeds" and "germs" to refer to elements more akin to atoms than to living organisms such as the spiral-shaped syphilis bacterium, Treponema pallidum, which was then wriggling its way into European genitalia from the Papal Court to the Scottish Highlands. Fracastoro also attributed an alignment of the planets as the "powerful cause" that drove these invisible seeds out of the "Sea and Earth and into the Aire," where they simultaneously infected the entire planet — conveniently explaining why Columbus and his sailors became infected in the New World around the same time as the disease erupted in the Old.
Certainly the idea of contagion — that is, the person-to-person transmission of disease — was not new to Renaissance Europe. Towns had begun quarantining plague victims, to little advantage, a century earlier. And the physicians of Egypt, India, and China had been grappling with the undeniable infectiousness of smallpox, a viral disease, since at least 3700 B.C. Indeed, all the world's early civilizations knew contagion, for it was the crowding of civilization that fueled it.
Over the millions of years that humans and their ancestors lived as hunter-gatherers, their populations remained too small to allow a deadly infection to last long, or to travel far before either killing everyone off or engendering population-wide immunity in the survivors — in either case, bringing extinction to the infectious organism. Exceptions included microbes that used humans as secondary homes while residing primarily in animals such as insects (which they did not harm). Of these, the mosquito-borne malaria parasite, a protozoan microbe, may be the oldest and deadliest.
When tribes of Homo sapiens first hiked north out of Africa some thirty-five thousand years ago, they largely escaped their tropical parasites and enjoyed a prolonged era of robust health. The cave paintings of Europe's prehistoric wanderers show no hint of epidemics; nor do the legends of the New World's first nations. This is not to say that hunter-gatherers enjoyed an idyllic existence. Starvation and injury made for a short and brutal life span, but it was nonetheless a life span largely free of infectious disease.
Permanent settlements brought the stability of yearly harvests and domesticated livestock and the safety of fortress walls. The trade-off: crowding and water contamination. With civilization, well-behaved microbes abruptly lost their near-monopoly over the human body and a new microbial lifestyle arose — one in which virulence paid off, given that deadly bacteria could count on the coughing and flux of the dying to contaminate the air and water shared by thousands living in close quarters.
Epidemiologists calculate that it takes a population of around half a million to perpetuate an infectious disease: in other words, to allow a disease-causing microbe to continue jumping from host to host ahead of death or complete recovery. Not coincidentally, the first recorded mention of "pestilence" dates to the first civilization to reach that population benchmark: Sumeria, a string of a dozen merchant-trader cities on the delta of the Tigris and Euphrates rivers in what is now southeastern Iraq. The four-thousand-year-old Epic of Gilgamesh, Sumeria's version of the great flood story, references the ravages of Ura, the plague demon, as being preferable to the terrible flood, for at least Ura would have left a few survivors to repopulate.
Like people in most ancient cultures, the Sumerians attributed the advent of plagues to angry gods and demons. So cures consisted of attempts to appease the heavens. As early medical traditions developed, the focus shifted away from finding the cause to finding symptomatic relief. The Hippocratic tradition, for example, relied on assessing imbalances in a patient's inner energies (as evidenced by fever, pus, and other symptoms) and then bleeding, purging, or sweating the person back into "equilibrium." It mattered not what caused a particular imbalance (too much bile, not enough blood, etc.), for the cure would be the same.
Syphilis may have been the mighty slap that convinced Europeans to look for a physical, albeit invisible, cause for infection. The magnitude of the syphilitic scourge of the sixteenth century can be difficult to appreciate today, for the disease has become far less virulent as man and microbe have coevolved over the centuries. Today only one in nine people infected with the syphilis bacterium develops symptoms obvious enough to send him or her to the doctor. Contrast this to the gaping sores, unrelenting pain, blindness, madness, and death so commonly portrayed in Renaissance literature and art.
The tremendous renown of Fracastoro's Syphilis, still the world's most famous medical poem, brought him the kind of fame and enduring patronage that allowed him to retire both from politicking and from clinical practice. With this newfound freedom, he produced the less poetic but far more scientifically important treatise De contagione, published in 1546. It lays out the revolutionary elements of his more fully developed germ theory of disease:
that infectious disease always spreads via invisible contagious seeds — seminaria contagionis;
that it does so in three ways: contactu afficit (by direct contact), fomite afficit (by contact with contaminated objects), and distans fit ("at a distance," as in through the air);
that germs have distinct identities: fevers are not all alike, nor can the germ that causes syphilis one year turn around and cause leprosy the next; and
that different diseases will respond to different remedies, including various methods for directly attacking, or "burning out," the germs from the patient's body. In the case of syphilis, for example, Fracastoro mentions mercury, or quicksilver (a brutal remedy, it turns out, for it destroys not only the fragile syphilis spirochete but also massive numbers of human brain cells).
For nearly four centuries, Fracastoro's category of "contagion at a distance" would linger as the vague concept of miasmas, or "poisonous aires." Belief in miasmas had become fully entrenched by the time the Black Death, or bubonic plague, showed its face in London during the broiling summer of 1665. To prevent the escape of these deadly "aires," communities nailed shut the doors of those who were stricken, and passersby kept their noses in "rings," or small bouquets, of posies, whose strong fragrance they hoped would deflect the toxic fog.
The real carriers of the infectious organism — rats and their attendant fleas — had massively multiplied, thriving in the household waste that the working poor tossed from their windows for lack of a better option. By the end of the summer, more than thirty-one thousand people, or 15 percent of the city's population, were dead, and the king, his court, and most everyone with means had fled the city. Samuel Pepys, a naval secretary, described the desolation on the eve of his own departure, writing in his diary, "But now, how few people I see, and those walking like people that have taken leave of the world."
Despite these horrific conditions, the same year brought the publication of the first of many scholarly books written by the "natural philosophers" of London's Royal Society. Robert Hooke filled his Micrographia with drawings of the fantastical structures that he had glimpsed beneath his magnifying lenses: the facets of a fly's eye, a louse clinging to a human hair, the individual "cells" (a term of Hooke's coinage) in a slice of cork.
Neither plague nor war with England could keep copies of Micrographia out of the Netherlands, where the doe-eyed fabric merchant Antoni van Leeuwenhoek (pronounced Lay-wen-hook) fell under its spell. So inspired, Leeuwenhoek taught himself lens grinding and constructed the first of hundreds of microscopes with which he would eventually discover the world of microscopic organisms. Leeuwenhoek's earliest discoveries included the giants of the microbial world: the one-celled algae and protozoas that floated in swamps near his home. Yet for pure shock value, nothing came close to Leeuwenhoek's findings of 1683, when he turned his increasingly powerful microscopes on himself. In a letter dated September 17, 1683, he describes the hyperactive zoo that he found inside a mixture of his own tooth scum and spittle, enclosing a drawing that now ranks as an icon of microbiology:
I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort had the shape of Figure A. The biggest sort had a very strong and swift motion, and shot through the water (or spittle) like a pike does through water. These were most always few in number ... The second sort had the shape of Fig. B. These oft-times spun round like a top, and every now and then took a course like that shown between C and D: and these were far more in number. To the third sort I could assign no figure, for at times they seemed to be oblong, while anon they looked perfectly round. These were so small that I could see them no bigger than Fig. E: yet there wit hall they went ahead so nimbly, and hovered so together that you might imagine them to be a big swarm of gnats or flies, flying in and out among one another. These last seemed to me e'en as if there were several thousand of 'em in an amount of water or spittle no bigger than a sand-grain.
Neither Leeuwenhoek nor his esteemed London correspondents viewed the fantastical "animalcules" he had discovered as anything but harmless, and for the most part they were. The middle-aged Dutchman's own remarkable health and vigor seemed testament enough to that. He even had all his own teeth. What's more, the idea that such fragile creatures could injure someone would have seemed laughable. As Leeuwenhoek himself observed, a mere sip of hot coffee or wine vinegar could make the animalcules on the surface of his teeth to "fall dead forthwith." For the next century microbiology would remain a fringe science — one of interest only to the naturalists who had to describe and name the inhabitants of this lush new kingdom of life.CHAPTER 2
GERM THEORY REBORN
The late 1700s brought the opening of Europe's first maternity wards, or lying-in hospitals — a great development in public health designed to benefit the wealthy and poor alike. But the time proved to be especially deadly as well, with puerperal, or childbed, fever racing through the newly popular maternity wards and killing thousands. And no wonder, for doctors and midwives were constantly moving between the sick and the merely birthing, thrusting contaminated hands and instruments high into raw and torn birth canals and wombs. But the idea that medical workers might be spreading infection was shared by few and shunned by many. In fact, the controversial concept would destroy many careers.
The first was that of the Scottish surgeon Alexander Gordon. In his 1795 Treatise on the Epidemic Puerperal Fever of Aberdeen, Gordon wrote,
That the cause of this disease was a specific contagion, or infection, I have unquestionable proof ... [for] this disease seized such women only, as were visited, or delivered, by a practitioner, or taken care of by a nurse, who had previously attended patients affected by the disease.
Gordon also noted the resemblance between the milky substance seen in the wombs of women dead of puerperal fever and the pussy discharge of erysipelas, or wound infections. He pointed out that "if in a dissection of a putrid [pus-containing] body, a surgeon scratches his finger, the part festers." Gordon's proposed cure for puerperal fever was all but medieval: bleeding off a pint and a half of blood from the woman, who in many cases had already bled copiously through childbirth. But his recipe for preventing its spread was spot-on:
The patient's apparel and bedcloths ought either be burnt or thoroughly purified; and the nurses and physicians who have attended patients affected with the puerperal fever ought carefully to wash themselves and get their apparel properly fumigated [with smoking sulfur] before it be put on again.
Similar measures were already in use for stopping outbreaks of measles and smallpox, which were thought to arise from miasmas and then propagate from person to person.
Gordon would be the first of a string of physicians who offended far more people than they convinced with their polemics on hand-washing and sterilization. A half century later, a young Oliver Wendell Holmes tried unsuccessfully to hector doctors on the left side of the Atlantic into recognizing the infectious nature of puerperal fever. Dismissed as another crazy "contagionist" physician, he left medical practice four years later, in 1847, to teach at Harvard and earn international fame for his literary wit, even as the world forgot his medical insight.
The same year that Holmes abandoned medical practice, the Hungarian physician Ignaz Semmelweis supplied clear proof of Gordon's and Holmes's contagionist theories. At Vienna's world-famous teaching hospital, the Allgemeine Krankenhaus, Semmelweis reversed skyrocketing rates of childbed fever by insisting that doctors and medical students scrub their hands with chloridated lime (powdered bleach) between performing autopsies and assisting women in labor. But in the process, the scowling and socially maladept Hungarian so insulted his Viennese colleagues with his implications of their slovenliness that they turned against him. Stripped of his research privileges at the Vienna Medical School in 1850, Semmelweis abruptly resigned and returned to his native Hungary, where he suffered a mental breakdown. With their would-be savior locked in an asylum, the new mothers of Vienna once again began dying. In a cruel twist of fate, the institutionalized Semmelweis likewise died of an overwhelming blood infection, most likely contracted through a finger cut he sustained during one of his last medical school autopsies.
By this time, European and American doctors had largely split into two camps: the contagionists, who advocated germ theories, and the sanitarians, or hygienists, who clung to the idea of miasmas — with the added twist that these "poisonous aires" arose from filth and decay.
On the contagionists' side, a number of researchers had glimpsed the presence of microscopic organisms in diseased tissue. But many countered that if, in fact, bacteria existed in the blood and tissues of the sick, they did not cause the disease; rather they sprang — spontaneously — from the dead and dying tissue. Even the renowned Prussian zoologist Christian Ehrenberg, who in 1847 coined the word bacteria (from the Greek baktron, or "small stick"), maintained that he "view[ed] with disfavor the new-fangled idea that microbes can cause disease."
Excerpted from Good Germs, Bad Germs by Jessica Snyder Sachs. Copyright © 2007 Jessica Snyder Sachs. Excerpted by permission of Farrar, Straus and Giroux.
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Table of Contents
SEVEN KEY TERMS AND CONVENTIONS - A QUICK,
PROLOGUE - A GOOD WAR GONE BAD,
REVENGE OF THE MICROBES?,
PART I - THE WAR ON GERMS,
FROM MIASMAS TO MICROBES,
GERM THEORY REBORN,
THE SEARCH FOR MAGIC BULLETS,
PART II - LIFE ON MAN,
THE BODY AS ECOSYSTEM,
INTO THE MOUTHS OF BABES,
LIFE ON THE SURFACE,
LIFE ON THE INSIDE,
BUGS IN SPACE,
WHERE NO BIOLOGIST HAS GONE BEFORE,
THE INNER TUBE OF LIFE,
WHO'S THE BOSS?,
A NEW WINDOW OPENS,
STEALTH INFECTIONS OR INNOCENT BYSTANDERS?,
PART III - TOO CLEAN?,
FROM HIPPOCRATES TO THE HYGIENE HYPOTHESIS,
A HISTORY OF SELF-DESTRUCTION,
CHILDREN IN THE COWSHED,
THE DIRT VACCINE,
PART IV - BUGS ON DRUGS,
A KILLER IN THE NURSERY,
AN END TO BACTERIAL DISEASE?,
MICROSCOPIC MATING GAMES,
THE BACTERIAL SUPERORGANISM,
OLD HABITS, NEW INSIGHTS,
OUT OF THE HOSPITAL AND INTO OUR DAILY LIVES,
THE RESERVOIR WITHIN,
RESISTANCE BY THE SHOVEL,
DOWN ON THE FARM,
THE ANTIBIOTIC PARADOX,
PART V - FIGHTING SMARTER, NOT HARDER,
THE GOOD OLD DAYS?,
PRESERVING ANTIBIOTICS: LESS IS MORE,
HOMING IN ON THE ENEMY,
DRUGS WITH ON-OFF SWITCHES,
FARMING OUT RESISTANCE,
BEYOND ANTIBIOTICS: NEW WAYS TO KILL,
COCOONS AND FROG SLIME,
PART VI - BEYOND LETHAL FORCE — DEFANG, DEFLECT, AND DEPLOY,
DRUGS THAT DISARM,
VACCINES — FOREWARNED IS FOREARMED,
DOMESTICATE AND DEPLOY,
FIGHTING FIRE WITH FIRE,
A SUPERHERO FOR THE MOUTH,
PROBIOTICS FOR LIVESTOCK,
A SECOND NEOLITHIC REVOLUTION,
PART VII - FIXING THE PATIENT,
THE DRAGON WITHIN,
ENHANCING THE BIONIC HUMAN,
FROM SEPSIS TO CHRONIC INFLAMMATION,
TWEAKING THE BUG,
INTO THE FUTURE,
CODA - EMBRACING THE MICROBIOME,