Got A Cold?
(You're on your own)
by Robert Fusco, MD
When you think about it, it is amazing that we live as long as we do. Each of us is constantly at war with millions of viruses and bacteria that would like nothing better than to invade and consume our bodies. On average, there are over 500,000 such organisms on each square inch of our skin trying to get in. This is called colonization. As long as we are alive, we must continuously defend ourselves against these foreign invaders. Only in death do we give up the battle and allow these microorganisms to use our bodies as food and convert us back into dust.
What are bacteria?
At the most basic level, bacteria are one-celled living organisms. Compared to us, they are not very big. In fact, a typical bacterium is about 1/100th the size of a human cell. They can live in water, soil, or within other organisms. Each bacterium is like a little complicated machine with many internal working parts. It's a crude analogy, but each working part represents a different chemical process that has a specific job. Just as we rely on all our organs to function, so does a bacterium.
Most bacteria are harmless to humans. In fact, many are quite beneficial. We don't bother them, and fortunately, they usually don't bother us. Bacteria in our intestinal tract aid in digestion and produce Vitamin K that helps blood clotting. Bacteria in the stomach of cows and sheep are what enable them to digest grass. Bacteria are also essential in the production of yogurt from milk, sauerkraut from cabbage, and wine from grapes. Some bacteria, however, are capable of causing infections in humans. In fact, before antibiotics bacteria were one of the leading causes of death and still are a major cause of illness.
What are viruses?
Okay, so how do viruses differ from these complex one-celled bacteria? A virus is totally different. In fact, at their most basic level, viruses are not even alive and can't reproduce on their own. A viral particle simply consists of a viral protein jacket wrapped around a strand of DNA. The jacket and its short strand of DNA can be extremely small - a thousand times smaller than a bacterium. When they attack our bodies, you can visualize bacteria swimming around our big cells like many tiny motorboats trying to attack and board an ocean liner. A virus is more like a message in a bottle floating nearby.
Well, they may be too simple to multiply on their own, but over millions of years, viruses have survived. The outer protein jacket of a virus is equipped with chemical feelers that can bond to the outside of a host cell - like a magnetic mine in the ocean. Once docked, the viral DNA is injected into the host cell where it takes over the reproductive machinery within. This viral DNA injection turns the host cell (such as one in the lining of your throat) into an unwilling incubator where new viruses are born. Ungratefully, they eventually kill their host, releasing millions of new viruses into the bloodstream. This is the fundamental difference. While bacteria are complex self-sustaining living organisms with many internal parts, viruses are little simple packets of information that must actually hijack the host's own cells to replicate.
Our triple defense against infection
How do we defend ourselves against these foreign invaders? Our first line of defense is the physical barrier provided by our skin and the mucous membranes that line our lungs and digestive system. Together they make up the main interface between us and our environment. When a bacteria or virus lands on our skin, it usually does no harm unless it is allowed to penetrate the surface. However, if there is a break in the skin such as a small scratch or cut on our hand, bacteria and viruses immediately try to take advantage of this injury and invade the moist tissues beneath the skin. There, if allowed, they grow and multiply rapidly - sometimes with only minutes between generations. This is called an infection.
Immune system - our second line of defense
Once the outer barrier has been breached, our second line of defense quickly takes over - our immune system. The immune system is a complex system of organs and highly specialized white blood cells called lymphocytes. Lymphocytes are our internal police patrolling all the tissues of the body, acting as sentries on the lookout for foreign invaders. When they encounter a bacteria or virus, lymphocytes and proteins in the blood, called antibodies, mark the intruders as enemies and call for reinforcements to destroy them. When the number of invading organisms is small, our immune system prevails.
Antibiotics - our last line of defense
If, however, the infection is massive such as a ruptured appendix or pneumonia, our immune system is quickly overwhelmed and the bacteria multiply unchecked. In the past, this meant a death sentence. But over the past 70 years medical science has been able to create powerful antibiotics to help us wage this war.
Antibiotics have nothing to do with your immune system. An antibiotic is basically a poison that works to kill bacterial cells while leaving human cells unharmed. All antibiotics take advantage of the fact that there are many differences between a human cell and a bacterial cell. Discovered in 1928 by English scientist Sir Alexander Fleming, penicillin was one of the first antibiotics. Penicillin disrupts a bacteria's ability to build cell walls. Most bacterial cells have double layers on their outside. The outermost layer - the "cell wall" - is similar to the outer layer of plant cells, but is missing in human and animal cells. This wall must grow along with the cell, or the growing cell will eventually burst and die. Penicillin kills bacteria by interfering with the bacteria's wall-building system. Since we don't have cell walls, neither we nor animals, are harmed by the medicine. At first, supplies of penicillin were very limited, but by World War II it was being mass-produced by the American pharmaceutical industry, and supplies given to all soldiers before active service.
Other antibiotics, such as sulfa drugs, work by interfering with the production of DNA for new bacteria. Without this enzyme, the bacteria cannot reproduce. Sulfa drugs do not actually kill bacteria, but they can stop them from growing. Since the early days of Fleming, medical scientists have developed hundreds of new antibiotics - each of which take advantage of a particular difference between the internal workings of human cells and bacterial cells.
Antibiotic resistance
The unfortunate problem with any antibiotic is that it becomes ineffective over time. When they were first used, penicillin and sulfa worked against many kinds of bacteria. Unfortunately, the more we used them, the more bacteria became resistant to them. This is also true for all the many antibiotics that medical science has since developed. Bacteria (and viruses) aren't particularly intelligent. However, it is possible - and unfortunately all too common - for them to "learn" how to survive even with antibiotics around. Again their strength lies in numbers. Bacteria reproduce so quickly that the probability for random mutation is high. There may be millions of bacteria in your body that the antibiotic kills, but if just one of them has a mutation that makes it immune to the antibiotic, that one cell can reproduce quickly and then spread to other people. Most bacterial diseases have become immune to some or all of the antibiotics used against them through this process.
Another problem that exists is when people do not take their antibiotics to their prescribed completion. If you think about survival of the fittest, you will realize that if an antibiotic is not taken to completion, only the strongest of the bacteria will survive. This usually results in an even worse infection and the possibility that a bacterium will become resistant to an antibiotic that previously would have worked. In some cases, these mutations have led to the development of so-called "superbugs," a group of dangerous bacteria that have become more and more resistant to antibiotics.
Why don't antibiotics kill viruses?
While your doctor has access to many different antibiotics that help kill bacteria, agents to fight viruses are very rare and in most cases are much less effective. Why is this? Why do viruses seem so much harder to treat?
The problem is two-fold. First, antibiotics kill bacteria by disrupting one of their internal mechanisms. Viruses are so simple that they have few internal mechanisms against which antibiotics can be directed. In fact, they are not even technically alive to begin with, so it's hard to kill them. Secondly, unlike bacteria, viruses covertly do all their reproducing inside a human cell, so it's hard to attack them without killing the host cell. All we can do is let our immune system do its work, and in very rare cases (perhaps a half-dozen viruses at most) give drugs that slow down the infection, so that the body can clear it out more easily.
Vaccination - giving our immune system a head start
Currently, the best way to combat viruses seems to be vaccination. Since we can't depend on antibiotics to eradicate viral infections, we must rely on our immune system even more. Our immune system can find and kill many of the viruses that attack us, but sometimes a virus can multiply and overwhelm the immune system before it "comes up to full speed." Each viral strain is different and requires a unique vaccine. Vaccinations allow our immune system to learn how to defeat a particular virus so that when the real thing comes along, it's prepared.
For example, we now routinely "immunize" or vaccinate people against mumps, measles, chickenpox, polio, hepatitis, and influenza. By exposing our bodies to a deactivated form of these viruses, vaccination teaches us what the invaders look like. When the real viruses attack, our immune system is ready and there is no delay in the counterattack. That seems to be the most successful way to prevent infection. An example is smallpox, which has been eradicated due mainly to the use of vaccines against it -- without which the virus killed thousands, if not millions, in epidemics.
Got a cold? You're on your own
An upper respiratory infection, or so-called "cold," is a viral infection of the mucous membranes that line your nose and throat. Antibacterial antibiotics will do nothing to help get rid of the virus. And since over 200 different viruses are known to cause the symptoms of the common cold, it has been impossible to develop a single effective vaccine.
So, if you "catch a cold," you are on your own. The only way to get over a cold is to wait for your immune system to eliminate the virus, and for your body to produce a new virus-free mucous membrane surface. Medical science can't do anything to speed up this process. Resurfacing the mucus membranes takes 3-4 days, but getting rid of the virus takes a week or two, and until the virus is gone, the new membranes will keep getting infected. Since we have no medicines that will eliminate or even slow down the cold viruses, most doctors do not give antibiotics to someone who has only a cold, unless there seems to be a very good chance that they may develop a bacterial infection on top of the cold. Giving antibiotics when there is a viral infection will likely do nothing except help the bacteria in the nose and throat become resistant -- which makes the next bacterial infection much harder to treat.
Reducing your risk of infection
First of all, it is impossible to completely avoid exposure to viruses and bacteria. They are all around us. All surfaces have some bacteria as do our friends and family. At work, the most contaminated surfaces are found on computer keyboards and mice, desktops, and telephones. In hotels, the remote control has more bacteria than the toilet seat. In the home, the kitchen counter, cutting boards, and moist sponges are breeding grounds for bacteria. Seventy per-cent of people with colds have infectious levels of viruses on their hands. So much, for the friendly handshake. We are literally picking up these germs all day and bringing them to where they want to be - our nose, mouth, and eyes.
How can you protect yourself? Germs may be clever, but there are ways to reduce your risk of infection. Frequent careful handwashing with soap and hot water is one of the most critical defenses in preventing illness. When this is not possible, alcohol-based disinfectant hand lotions such as Purell Hand Sanitizer are very effective. Using disinfectant wipes on desktops, phones, computers, and remote controls may be helpful - especially in cold and flu season. In the kitchen, use separate cutting boards for vegetable and meats. Disinfect them with a weak bleach solution (3/4th cup Clorox Bleach per gallon of water) or run them through the dishwasher after each use. If you use a kitchen sponge, microwave it on high for 30 seconds daily to eliminate any harmful bacteria.
It's a war out there...
So at the most basic level, bacteria are complex self-sustaining organisms while viruses are actually just simple messengers that must take over the host's own cells to survive. Viruses are so simple that they are hard to treat, and the vast majority of antibiotics are bacteria fighters. Unfortunately, antibiotic resistance is a looming threat. To search for new antibiotics, scientists must carefully examine the internal machinery of these organisms. The trick is to create drugs that disrupt the internal function of bacteria (and viruses), but do not kill the human host cells. Many bacteria look at us as their next meal. Much research is being dedicated to keeping us ahead of our attackers. The good news is that so far humans are winning!
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September 5, 2006
