Flashpoint! Electronic Magazine

        Common Questions About Infectious Disease

        What are antibiotics and where do they come from?

        Literally meaning "anti-life," antibiotics are substances derived from microbes, primarily found in soil, that kill other bacteria, although the term has been extended to include synthetic compounds that inhibit microbes.

        What is drug resistance?

        As the name implies, drug resistance is a condition in which microbes acquire the ability to resist drugs that once destroyed or controlled them. In the case of antibiotics, overuse and misuse is contributing to the growth of resistant strains of everything from pneumonia and strep to meningitis and tuberculosis. Indeed, some strains of TB are resistant to as many as 11 different drugs.

        How does drug resistance develop?

        Mutations, often given a bad reputation when they relate to the development of diseases such as cancer, are, in fact, nature's way of ensuring the survival of an organism by creating diversity. Most of these natural experiments fail because they fail to give the organism a survival advantage. But when conditions suddenly change, as happens when a colony of bacteria or a cluster of parasites is attacked by antibiotics, some mutants invariably survive.

        The survivor, now free of competition, becomes the progenitor of a new breed that incorporates this resistance into its genes. As more drugs are introduced, the chances of the process repeating itself increase, leading to multiple drug resistant strains. Casual and indiscriminate use of antibiotics similarly kills harmless strains and allows resistant strains to flourish.

        Moreover, bacteria exchange genetic material easily, allowing a resistant strain to pass along its trait to one responsible for a completely different disease, sometimes before the drug has ever been used against it.

        How common is drug resistance now?

        It is easy to become an alarmist when most evidence suggests that almost every bacterial disease organism now known is resistant to at least one of the current 155 antibiotics. (The actual number of antibiotics is closer to 2,000 if you count the slight variations of each one used to counteract bacterial resistance.

        There are now, for example hundreds of varieties of penicillin.) The fact remains, however, that prudent use of antibiotics is still an effective method for treating most bacterial diseases and that most common strains retain at least some susceptibility for the time being.

        Are people protected from drug-resistant strains of disease if they have never or seldom taken antibiotics?

        No. It is the strain of disease, not one's personal use of antibiotics that matters. And if a person is unfortunate enough to acquire a resistant strain, other more expensive combinations will have to be used. One clear example is the growth of resistant Streptococcus pneumonias, the cause of childhood ear infections, of which there are already seven million cases per year.

        Testing at sites around the country has revealed that as many as 25 percent of children in some areas carry the resistant strain. Although most children are not at risk for complications such as meningitis, the odds that minor problems could become catastrophes increase as more and more drugs become ineffective.

        Do antibiotics given to animals affect humans?

        There is disagreement on this point. Some 25 million pounds of antibiotics are fed to pigs, turkeys, chickens and other animals in the U.S. each year. Trade and industry groups contend that such use keeps meat, poultry, milk and egg supplies cheap and plentiful.

        Others argue that plying animals with antibiotics can lead to drug-resistant animal strains of disease, such as psittacosis_a bacterial disease that dwells in birds_or salmonellosis, a diarrheal disease that can be transmitted to humans. No such cases of transmission of psittacosis have yet been recorded, although drug-resistant strains of salmonella can be traced to animal sources.

        Is there a cost to antibiotic resistance?

        Yes, a staggering one. Although the figures are far from exact, the best estimates are that the need to use more expensive antibiotics, and the increased length of hospital stays because of more resistant infections add $30 billion annually to the nation's health care bill. The CDC also estimates that treating a case of drug-resistant tuberculosis costs $180,000, compared to the average $12,000 price tag for a normal sixmonth course of antibiotic treatment.

        Do antibiotics kill viruses?

        No. Although antiviral compounds, such as AZT and acyclovir, exist they are not antibiotics in the true sense. Viruses need to hijack a cell's machinery to reproduce; otherwise they are just lifeless particles, presenting no molecular targets for antibiotics to attack. Unfortunately, physicians sometimes prescribe antibiotics to fulfill the patient's psychological need for therapy, even though the drugs are useless for viral infections.

        In fact, some studies have suggested that of the 150 million antibiotic prescriptions filled each year in the U.S., half are unnecessary or unwarranted. Antibiotics also are widely available over the counter in many countries, contributing to their inappropriate and indiscriminate use.

        What are the risks of getting infected inside a hospital?

        They vary depending upon your condition. Transplant, surgery, cancer, burn, AIDS and other immunocompromised patients, as well as those over 65, are at increased risk. Others are less so. But acute care hospitals, where these patients tend to concentrate, remain stubborn sources of infection. Indeed,2.1 million, or nearly six percent of all acute-care hospital patients develop hospital-based infections each year.

        One reason for the relatively high number is the increase in extensive, complicated surgeries over the last 30 years. There were no hip replacement surgeries before 1966, for example. Now there are approximately 125,000 each year in North America alone.

        The growth in coronary artery bypass operations is even more dramatic_ from none in 1966 to 390,000 now in the U.S. each year. Other factors contributing to infection include the rising use of artificial heart valves, cardiac pacemaker leads, nervous system ventricular shunts and catheters of all types. Carelessness in carrying out routine infection control guidelines, such as frequent hand washing and removal of gloves once a procedure or task has been completed, is to blame as well.

        What happens if we run out of drugs that work

        In the most extreme cases, we will be back where we were before the advent of penicillin in 1942. Bacterial diseases such as pneumonia, which now kills 25,000 to 50,000 out of an estimated 600,000 cases annually, will be left to run their course, causing death rates for this and many other infections to soar. Should American soldiers be involved in a war, many more also will die from battlefield injuries. The main weapons against viral diseases, vaccines, should remain effective, however.

        Is there anything individuals can do to help counter drug resistance?

        Yes. Since physicians often feel pressured to write prescriptions to keep patients happy - and patient satisfaction ratings high - individuals can help by not demanding antibiotics when doctors explain they are not warranted; colds, sore throats and bronchitis are the best examples.

        Parents can help, too, by ensuring that the course of antibiotics prescribed for a child's ear infection (or for their own condition) - 10 days is the usual period - is followed religiously. Parents also should be especially alert if the child's symptoms do not improve soon after the medication begins. This could be a sign that the antibiotic is not working properly.

        Is it possible to get TB during a bus ride, from a public telephone or on an airplane?

        This question has several answers, which differ depending on the condition of one's immune system. In general, healthy people who happen to become infected will contain the bacteria and be unaffected, at least while they remain well. However, those who are immunocompromised, such as cancer or AIDS patients, are at greater risk for developing the disease.

        Because sunlight kills the bacteria that causes TB, and because these bacteria cannot live outside the human body indefinitely, it is impossible to become infected by using a public telephone. The risk increases slightly on a bus or subway train or similar enclosed environment, but the infectious person would have to have an active case of TB and be coughing in another's face with the windows closed for many hours before transmission would even be remotely possible.

        As for airplane travel, a Massachusetts Medical Society Report (March 3,1995) investigated six instances in which passengers or flight crew traveled on commercial aircraft while infectious with TB. In two examples, affecting eight people, transmission did occur. The factors most responsible were the sick person's stage of infection, the length of the flight (more than eight hours) and proximity to the person coughing.

        Where does the flud come from?

        The three major strains of the influenza virus_A, B and C_live and change inside animals, primarily horses, pigs and ducks. Each year the strains mutate slightly, resulting in different surface proteins (antigenic drift) that interact with the human immune system. This causes different degrees of severity. Type A is usually the most severe, Type B milder and Type C so mild that it may barely register as an illness.

        It is this ability to change constantly that ensures the survival of the virus. It also demands international cooperation among the agencies responsible for monitoring flu activity, namely the World Health Organization, the Centers for Disease Control and the National Institute for Medical Research (England and Australia). Together they analyze the dominant strains occurring in the fall and winter months in different hemispheres in order to predict which vaccine will be most effective as the seasons change.

        What makes a regular flu turn into a "killer" flu?

        When two different influenza strains exchange genetic material (antigenic shift), they may create an entirely novel virus against which humans have no immunity. That is what happened in the great flu pandemic of 1918 in which 560,000 Americans died in less than a year, part of an estimated 20 to 40 million deaths worldwide.

        Can a "killer" flu happen again?

        It already has. In 1957 and 1968, there were flu pandemics, with the death rate in the U.S. for the latter example_the Hong Kong pandemic_ estimated at 30,000. Another 51 million were reported ill at an economic cost of $4 billion. The conditions for creating the viral exchange continue as well, especially in China where ducks, which harbor the influenza virus, live in close proximity with pigs. This integrated pig-duck agricultural system serves as an ideal natural laboratory for creating potential new killer strains whose ability to spread through the air, according to infectious disease experts, makes them a far more significant threat than the highly publicized Ebola virus.

        Is it possible that HIV could mutate and become as easily transmissible through coughing as the flu?

        Nothing is impossible, but an HIV mutation of this kind is considered highly unlikely. The reason stems from the nature of the retrovirus itself, which has become so dependent on the cellular host for sanctuary and for the raw chemical material it needs to survive that existing independently in the air seems beyond its power.

        Originally published: October, 1995

        from UCSF Magazine
        U.C. San Francisco Medical Center