What are antibiotics?
Antibiotics are medicines that combat bacterial infections.
Why are there so many different types of antibiotics?
Because there are so many different types of bacteria. For example, some bacteria need oxygen to survive; others don't like oxygen. Some bacteria live in your intestines; others live on your skin. There is a tremendous amount of variability in these organisms, so we need antibiotics tailored to each different family of organisms.
How do antibiotics work?
Most antibiotics work by disrupting the cell wall of the invading bacteria. But others target the function inside the invading bacterial cell.
You mention bacteria, but not viruses. Don't antibiotics work on viral infections, too?
No. Antibiotics don't work on viral infections.
Bacterial infections are single-celled organisms that invade your body and multiply into more and more single-celled organisms. Bacteria are relatively easy for drugs to affect because their cell wall is different and they often have different biochemistry going on inside their cells. Hence, it's relatively easy to design drugs to exploit this difference, thereby killing the bacteria, without harming ourselves.
Viruses are basically tiny strands of genetic material that is injected inside an infected cell. That genetic material then alters the cell so that it works for the purposes of the virus. Because infected cells look like normal cells, and because their biochemistry looks like normal cells, it's hard to find ways to design drugs to kill only the infected cells.
Warts are the most common viral infection of the feet, but the vast majority of infections of the feet are bacterial.
But getting an antibiotic for a viral infection doesn't do any harm, right? Isn't it better just to give out an antibiotic to be sure the infection isn't viral?
Actually, giving out antibiotics when you have a viral infection--or giving out inappropriate antibiotics even when the infection is bacterial--does cause problems. It sensitizes bacteria to the drug, creating stronger, more resilient bugs. This makes future infections difficult to treat. You've probably heard of the recent increase in infections that can't be treated by antibiotics--so called superbugs. These are a result of the overuse and inappropriate use of antibiotics.
What antibiotics are you most likely to prescribe?
It depends upon the infection. Our goal is to prescribe the drug that has the narrowest spectrum (meaning it kills only those bugs we wish to kill), is safest to the patient, at the cheapest price.
As most infections in the foot are staphylococcus or streptococcus, we use a lot of antibiotics in the penicillin category, (like Cloxacillin and Amoxicillin). We also use first generation cephalosporins (like Cephalexin and Ancef), a family of drugs related to penicillin. These antibiotics which pretty much kill the same family of organisms as penicillin. In patients with allergies to penicillins, we'd likely prescribe clindamycin and vancomycin. Both are unrelated to penicillin, but kill the same spectrum of bacteria.
For diabetics, the types of bacteria found in wounds becomes more complicated. Sometimes there are harder-to-kill bugs found in the wound, or combinations of bugs. For this reason, the types of antibiotics prescribed will often change, either to a different family of antibiotics, or to a combination of antibiotics.
There are many, many different types of bacteria, and many, many different types of antibiotics. The field can get quite complicated, and it is ever-changing, as bacteria evolve defence mechanisms to antibiotics, and new antibiotics are developed.
What do I need to remember about antibiotics?