Bacteria Bite Back
FIFTY YEARS AGO, MIRACLE DRUGS CALLED ANTIBIOTICS HELPED CONQUER GERMS. NOW, THE BUGS ARE FIGHTING BACK–AND THEY’RE WINNING!
A four-month-old Japanese boy shivers with chills and high fever hours after he emerges from high-risk heart surgery. An infection, or uncontrolled invasion of bacteria, has crept into the baby’s surgical wound. The culprit: a common bacteria, or single-celled organism, called staphylococcus aureus (sta-fuh-loh-KO-cus OR-ee-us) or “staph,” which can potentially poison blood. To stop the dangerous infection, the baby’s doctors prescribe an antibiotic, a drug that kills disease-causing bacteria. But the baby only gets worse.
Puzzled, his doctors try a more powerful antibiotic. This, too, fails. They finally pull out the “big gun”–a last-resort drug known as vancomycin (van-ko-MY-sin), the strongest antibiotic available. No bacteria can survive such a deadly weapon. Or can they?
KILLER ON THE LOOSE
Unknown to his doctors, the Japanese baby was infected with a new strain, or type, of staph. And not even vancomycin, the “silver bullet” of antibiotics, could kill it. The year was 1996, and the baby’s case marked the first time the world had ever seen a seemingly invincible staph. By using several potent antibiotics at the same time, the doctors were able to save the baby.
But a year later, super staph struck again: A man fell ill in Michigan and another was assaulted in New Jersey. Both also survived. The germ’s most recent victim, however, a retired New York City narcotics detective admitted to the hospital for kidney trouble, died last March. The 79-year-old man was too weak to fight off the lethal bacteria that invaded his body. Neither vancomycin nor a “cocktail” of antibiotics could help.
The medical community was in shock. How could doctors and health-care workers combat bacteria that are immune to even the best drugs available? With such resistant germs, would the state of medicine revert back to the days when people died from a simple sore throat?
THE WAR AGAINST GERMS
In the past decade, the number of “supergerms” has increased dramatically. Ironically, the very same arsenal of drugs used to conquer these microbes gave rise to the antibiotic-resistant strains, says infectious-disease scientist Kenneth Castro of the Centers for Disease Control and Prevention (CDC) in Atlanta. And staph is only one of several dangerous bugs. Equally drugproof and fatal bacteria include mycobacterium tuberculosis (causes tuberculosis), pseudomonas aeruginosa (pneumonia), and enterococcus faecalis (urinary tract and blood infections). Now, researchers are scrambling to develop new drugs to overcome these mighty microbes.
For most healthy people, these super strains of bacteria are not that threatening. The immune system, the body’s natural defense against microbes, usually fights off disease-causing invaders, even stealthy ones. But when resistant bacteria attack people with weak immune systems–like the sick, elderly, and very young–they can be deadly.
Humans have been winning the war against germs ever since antibiotics became widely available in the 1940s. Hailed as miracle drugs, antibiotics cured thousands of bacterial infections, from acne to strep throat to ear infections. In 1954, the U.S. produced about 907,200 kilograms (2 million pounds) of antibiotics. Today, that number exceeds 22.7 million kg (50 million lbs), with more than 100 types of antibiotics on the U.S. market.
Antibiotics squash bacteria in different ways. Penicillin, a drug commonly used to treat strep throat, busts the bacterial cell wall, a protective covering that surrounds the cell, causing the bug to spill its guts. Vancomycin works in a similar way. Other antibiotics, like tetracycline (te-truh-SY-kleen), which is used to treat acne, cripple the bacteria’s ability to reproduce.
For a long time, such drugs were undefeated champions over microbes. So, why are bacteria now beating the medical community’s best germ killers?
Think about the last time you took antibiotics for a sore throat. Your doctor probably (and should have) instructed you to finish the whole bottle of pills even after you started feeling better. That’s because antibiotics will kill off an infection only when taken in the right dose and for the full length of the prescription. Forget a pill, and the strongest bacteria could survive the attack (see below). These strong bacteria could then reproduce and pass on their “tough” genes to the next generation of bacteria. The next time you take antibiotics, the new bacteria will have an inborn survival trait that makes them resistant to the same drug you took before. Bacteria also mutate when doctors inappropriately prescribe antibiotics to treat viral illnesses, like the common cold. The CDC estimates that 20 to 50 percent of the 145 million prescriptions given each year to patients are unnecessary. Many doctors say their patients pressure them to prescribe antibiotics even when their infections are caused by viruses, which are known to be immune to antibiotics.
So while the body may be free of disease-causing bacteria, antibiotics are attacking the millions of helpful bacteria that also live in your body. Again, the strongest bacteria could survive an incomplete onslaught of antibiotics and then pass their strong traits on to future microbial generations. In turn, these super bacteria can “donate” their antibiotic-resistant genes to other disease-causing bacteria in the body (see right).
IT’S NOT OVER!
To stop this vicious cycle, medical researchers now are developing different and smarter ways of killing microbes. A new antibiotic called linezolid (lih-NAY-zo-lid) is currently being tested on humans to treat skin infections. The drug disables a bacteria’s RNA (ribonucleic acid), the part of a cell that makes the proteins necessary for cell life. As a result, the cell starves to death. Linezolid targets several genes, making it difficult for bacteria to develop resistance to the new antibiotic, explains researcher Robert Moellering of Harvard Medical School in Boston.
In the meantime, the CDC is launching a massive educational campaign to teach the world about the dangers of misusing antibiotics. “We’re trying to get doctors to stop prescribing drugs for every sniffle and sneeze,” says Dr. Castro.
Stricter regulations also try to curb the spread of superbugs in hospitals, where most outbreaks of resistant bacteria occur. (The high concentration of sick people, plus a large supply of drugs to treat patients, make hospitals excellent breeding grounds for superbugs.) “If a patient develops an infection caused by a super germ, we immediately isolate them from other patients,” says Ginny McMath, infectious-disease controller at the United Hospital Medical Center in Port Chester, New York. “This will help stop the germ from spreading.”
For now, the super staph that killed the New York detective is still on the loose. Nobody knows when or where it will strike again. Only one thing is certain–the war against germs is far from over.
Pseydomonas aeruginosa (magnified 21,450 times) causes infections in wounds and burns, and respiratory diseases and severe diarrhea in small children. These bacteria are highly resistant to chemical disinfectants and respond only to specilized antibiotics.
Myobacterium tubercolosis (magnified 11,408 times) causes tubercolosis (TB) in humans. TB is the world’s leading cause of death from an infectious disease. New strains of bacteria that are resistant to all current antitubercular drugs have recently emerged, killing about 50 to 80 percent of their victims.
Enterococcus faecalis (magnified 39,000 times) can cause urinary tract, bile duct, and wound infections. Some strains are resistant to multiple antibiotics and are untreatable.
Staphylococcus aureus (magnified 9,499 times) are the most common infection-causing bacteria in hospitals, creating wound infections, blood poisoning, and pneumonia. About 60 percent of staph strains in some hospitals are resistant to methicillin, the second-most powerful antibiotic.
RELATED ARTICLE: SUPER SOAPS: DO THEY WORK?
Bacteria are everywhere–on your skin, in your food, in the air you breathe. And now so are the chemicals that kill them. Many soaps, hand lotions, and cleansers commonly found in the home contain bacteria-busting compounds to help kill unwanted germs. But do you really need them?
According to many germ specialists, the answer is no. Scrubbing your hands with soap and warm water for 10 seconds and rinsing thoroughly works just as well. In fact, soap rinses away 99 percent of all unwanted germs. Regular soap works by suspending the germs in water so they can be washed away.
In hospitals and other places where people with weaker immune systems are at higher risk for infection, people should wash with antibacterial soaps. These work by killing germs on contact, and stay on your skin to keep new germs from reproducing.
But, if you’re healthy, the super suds are duds–good old soap and water will do the trick.
RELATED ARTICLE: HOW ANTIBIOTICS BREED RESISTANT GERMS
Antibiotics are designed to kill infection-causing bacteria. But if the amount of antibiotics taken is too low, stronger bacteria can survive the treatment. The semi-resistant bacteria can reproduce and breed equally resistant offspring. It’s the microbial version of “survival of the fittest.” Continued weak treatment could breed even more resistant bacteria until a population of nearly invincible microbes, immune to all antibiotics, take over the body.
RELATED ARTICLE: GENE EXCHANGE
In the microscopic world, bacteria freely exchange genes with each other–an effective way of passing antibiotic-resistant traits to weaker germs. Here are three ways an ordinary bacteria can get antibiotic-resistant genes from her germs and turn into a superbug:
(1) Antibiotic-resistant genes are often found on plasmids (circular DNA). Plasmids can transfer from one type of bacteria, say a staph, to a different kind, like streptococcus, as long as the germs are in contact.
(2) When a bacteria dies, it could release its insides into the immediate environment. A nearby bacteria can absorb a drug-resistant gene from the dead bacteria.
(3) Some can extract a gene viruses that infect bacteria from one bacteria and inject it into another.
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