Introduction | Antibiotics in Human Medicine | The Antibiotic Arsenal | Antimicrobial Use in Food Animals | Solutions to the Resistance Problem
In 1928, Alexander Fleming ( left), a Scottish bacteriologist, discovered a mold with bacteria-killing powers so incredible it was effective even when diluted 800 times. Courtesy of the USDA. Right, a strain of P. notatum was used for some of the first tests of pencillin. Courtesy of the FDA’s Center for Drug Evaluation and Research.
Before the discovery of the first antibiotic, penicillin, in 1928, infections that are easily treated today killed millions of people around the world. More people (an estimated 30 million) died from the influenza epidemic of 1918–1919 than were killed during World War I.
The discovery of penicillin was followed by the discovery and development of other antibiotics, leading physicians, health officials, and the public alike to believe that these “magic bullets” would protect us from all manner of infectious diseases.
Bacteria have been around a long time — scientists estimate more than 3.5 billion years. A key to their success is their ability to adapt to changes in the environment. When you reproduce within a matter of minutes or hours, those changes come quickly.
When mass-produced penicillin made its debut in the 1940s, virtually all strains of Staphylococcus aureus were susceptible. Today, more than 90% of S. aureus strains are resistant to penicillin and other beta-lactam antibiotics that once vanquished this common bacterial cause of diseases such as abscesses, bronchitis, osteomyelitis, and pneumonia.
Another antibiotic, vancomycin, was called into use as a last line of defense against the potentially deadly S. aureus. Then the first vancomycin-resistant strains of S. aureus appeared in Japan in 1997, followed quickly by the first U.S. case.
Vancomycin resistance among the intestinal bacteria enterococci (a leading cause of hospital-acquired infections) increased 20 times in only four years (January 1989 to March 1993.)
Streptococcus pneumoniae (the most common cause of bacterial pneumonia, meningitis and ear infections) used to be effectively treated with penicillin, but resistant strains began to emerge in the U.S. in the mid 1980s. Scientists first noted the appearance of antibiotic-resistant strains of S. pneumoniae in New Guinea in 1967, but erroneously predicted that it was not likely to spread. Drug-resistant pneumococcal infections made their way through South Africa in the 1970s and on to Europe in the 1980s before arriving on U.S. shores.
The very young and the elderly are among those most vulnerable to antibiotic-resistant microbes.
This increased resistance can be especially devastating for the very young, the elderly, and people with weak immune systems.
Antimicrobial resistance is becoming a major concern in treating fungal infections, such as Candida, which can cause serious illness and even death in people with weakened immune systems. For example, a study of 157 orthotopic liver transplant patients found 23% had disseminated fungal infections, and that these infections contributed to the deaths of 13% of the 157 (more than half of those who were infected.) Up to 33% of AIDS patients carry a strain of Candida albicans in their mouths that is resistant to the standard antifungal drug fluconazole.
Antibiotic resistance is increasing worldwide. And in this era of globalization, antibiotic-resistant bacteria are proving to be adept travelers ready and willing to make their home wherever they land.
In some parts of the world, treatment of gonorrhea and some bacterial intestinal infections is now limited to a single effective antibiotic. In Thailand, ciprofloxacin resistance among the diarrhea-causing Campylobacter jumped from 0% before 1991 to 84% in 1995. Several hospitals in the Netherlands saw an increase in resistance to metronidazole by the ulcer-causing Helicobacter pylori from 7% in 1993 to 32% in 1996.
In many countries, no prescription is needed for common antibiotics. This lack of regulation can lead to resistance when antibiotics are taken for viral or other illnesses for which they do not work, or in the wrong doses for too long or too short time periods.
Here in the U.S., we take an estimated 133 million antibiotic prescriptions a year, according to the Government Accounting Office. About half of these are inappropriate or not needed.
The increased use and misuse of antibiotics to treat illnesses in people is the single largest factor in the spread of drug resistance.
A 1998 patient poll found that 52% of individuals said they believe antibiotics are the best medicine for viral infections. Physicians, who know that antibiotics are not effective against viruses, often go along with their patients’ desires. Surveys of pediatricians reveal that they prescribe antibiotics to 44% of patients with viral infections such as common colds, 46% with upper respiratory tract infections, and 75% with bronchitis.
Physicians treating adults with viral infections prescribed antibiotics for 51% of patients with colds, 52% with urinary tract infections, and 66% diagnosed with bronchitis.
Well, any time you take an antibiotic, needed or not, it kills the friendly bacteria called microflora that normally reside on your skin and in your intestines, making you more susceptible to infection from unfriendly microbes that can cause disease (pathogens).
And you help create bacteria that are resistant to antibiotics. Especially if you do not take your full prescription. A lot of people stop taking their antibiotics when they feel better, hoarding their remaining supply in case they become sick again. More than a third (37%) of patients polled admitted they stop taking their antibiotics before finishing all their pills, and 25% conceded that they save pills for future illnesses.
Taking only part of a prescription doesn’t kill the bacteria, but simply gives them a chance to meet the antibiotic and learn how to outsmart it next time around.
Even appropriate use of antibiotics contributes to resistance through sheer exposure. Laboratory tests to determine exactly what organism is causing your illness may take several days, so doctors try to predict the likely cause of the disease and the best antibiotic to use.
As resistance to first-line antibiotics like penicillin rises, the use of newer, more expensive, broader-spectrum cephalosporins and combination agents has increased.
Otitis media (middle ear infection) in children is the leading cause of emergency room visits and is the second leading cause of office visits to physicians. Although studies show that only one third to one half of the 24.5 million otitis media cases that occur each year actually benefit from antibiotics, most physicians prescribe antibiotics.
The Centers for Disease Control and Prevention (CDC) estimates that 6 to 8 million unnecessary courses of antibiotics are prescribed each year for the treatment of ear infections.
More than 80% of children with acute otitis media will get better without antibiotics. Many ear infections are caused by viruses, and even those caused by bacteria may go away on their own without antibiotic treatment.
Because antibiotics increase the likelihood that a child will harbor resistant bacteria in their noses and throats, more and more physicians are going along with the CDC’s recommendation that parents watch their child for two or three days before giving them antibiotics.
While that is common practice in Europe, many American parents and physicians still opt for antibiotics. A middle-ground approach is being increasingly tried here, in which parents are advised to give their children the appropriate pain medication and a prescription for antibiotics to be filled only if their children’s symptoms increase or do not resolve. One U.S. study found that only 47 of 153 such antibiotic prescriptions were filled after a 48-hour waiting period.
Infections caused by antibiotic-resistant pathogens lead to more serious illnesses and a greater likelihood of death. They also cost a lot to treat, more than $4 billion a year according to an estimate by the CDC in the early 1990s.
There’s a lot of confusion stemming from loose usage of the various terms describing microbe-inhibiting products. People and news stories sometimes use the terms ‘antibiotic,’ ‘antibacterial’ and 'antimicrobial' interchangeably and sometimes as distinct terms. This confusion over what kinds of infectious agents these products work against can lead to their misuse.
Disinfectants are being increasingly used in everything from cutting boards to soap, gym clothes, baby toys, and toothpaste. That sends the message that every attempt should be made to eliminate as many bacteria in our personal environment as possible.
While there is evidence that using antibacterial soap may reduce the risk of infection from Salmonella when handling raw poultry, other studies suggest that the use of antibacterial products may reduce the number of harmless bacteria and increase antimicrobial resistance among harmful organisms. For example, some kinds of Escherichia coli have been found to resist triclosan, an antiseptic used in products such as soaps and toothpaste.
Unfortunately, few studies have been conducted in this area. Until data can be provided that antimicrobial agents do harm to beneficial bacteria, these products will continue to be heavily advertised, and consumers will believe they are helping raise the level of hygiene in the home.
In spite of the many advances in microbiology, biochemistry, and drug discovery and development in recent years, we are not keeping pace with the ability of microbes to adapt to and resist antibacterials.
We have developed only one new class of antibiotics in the last 40 years. So we need to more carefully use the antibacterials we have, better identify and diagnose the cause of an infection, and work to develop new vaccines to prevent infection.
Introduction | Antibiotics in Human Medicine | The Antibiotic Arsenal | Antimicrobial Use in Food Animals | Solutions to the Resistance Problem
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