Antibiotics

The word "antibiotic" means something that kills living organisms. Typically we use the word to mean a drug that kills bacteria. There are other types of microorganisms, such as viruses, fungi and parasites, but we use different words to describe the drugs we use to fight them. Antibiotics are also sometimes used to fight these other types of organisms.

Different types of antibiotics work in different ways. Some actually attack bacteria and chew up their cell walls. Some block the production of certain necessary ingredients for bacterial growth. Some do their best work in the blood while others may be concentrated in the urine or bone or other body tissues. Because of their different modes of action, some antibiotics work better than others in a given situation. For instance, one that destroys cell walls will not work well on bacteria that don't produce cell walls. Different antibiotics will also have different side effects and allergy profiles depending on their structure and mode of action. An allergy to one member of a group will likely result in an allergy to other similar antibiotics.

An antibiotic that is concentrated in bone is also most apt to cause side effects in the bone.

Because of the way they work, however, antibiotics are not the cure for everything. Many if not most of the infections travelers get are caused by either viruses or parasites. Using an antibiotic in this case is sort of like using a machine gun to kill a mosquito. It's not that the weapon isn't powerful enough. It's just not likely to hit the target and at the same time is apt to do a lot of collateral damage.

Another problem with the overuse of antibiotics is the development of resistance. It's a complex issue but to simplify, let's just say that no antibiotic, even when given in the right dose and for the right organism, kills all of the germs in its path. The best we can hope for is to sufficiently reduce the numbers and weaken the rest so that the body's immune system can finish the job. But this doesn't always happen. A few bacteria survive. Those most likely to survive are ones that have "accidentally" developed some mechanism to render the drug harmless to them. These then go on to multiply and presto, you have a "resistant strain." That antibiotic then becomes useless to fight that particular disease. The more times a given drug is used the more chances there are for this to happen. That's why drugs we used to use for traveler’s diarrhea, for instance, are no longer effective. (See article on traveler’s diarrhea)

It is important, therefore, to use antibiotics only when necessary and to fit the right drug to the right bug.

The tetracyclines, for instance, are a class of antibiotics that work by inhibiting protein synthesis. Because during an infection it is the microbes that are producing proteins the fastest, they are hampered by these medicines more than normal body cells are. That is why tetracyclines can be used against a wide range of organisms, including malaria, where other antibiotics have no effect. But normal, developing body cells can also be affected by them, which is why they are not given to pregnant women or small children. Doxycycline is the one most often chosen because it can be taken once or twice a day rather than four times. But it also has the effect of sensitizing the skin to ultraviolet rays so can result in a bad sunburn.

Other antibiotics that affect growing tissue and thus are best avoided in pregnancy and childhood are the quinolones, such as Ciproâ and Floxinâ. Sulfa drugs may be concentrated in the fetal liver and cause liver damage. Some, like gentamycin, can similarly affect a baby's kidneys. Antibiotics which are generally safe to take in pregnancy include penicillin-like drugs {e.g. ampicillin) and erythromycin-like ones including Zithromaxâ.

The side effects of some antibiotics are more of an annoyance than a real danger. For instance, just about any antibiotic may result in a vaginal yeast infection or can reduce the effectiveness of birth control pills and result in unintentional pregnancy.

Even the "dangerous" drugs may be used in pregnancy if the situation warrants. But whether pregnant or not it is best to let the body use other means of fighting infection if at all possible.