Germs frequently form a slimy colony on the wound surface called “biofilm”. Biofilm is a fascinating microscopic eco system that functions almost like a human society. Germs produce different chemicals and operate cooperatively. They protect each other by sharing antibiotic resistant genes. Our neutrophils, the soldier white blood cells, cannot kill the germs in the biofilm because they cannot penetrate it to reach the germs. Antibiotics cannot kill the germs in the biofilm either for the same reason.
Another reason that antibiotics are ineffective in killing the germs in biofilm is the low oxygen level in the biofilms. Oxygen in the tissue comes from blood vessels. But the distance from the blood vessels to the biofilm causes low oxygen level. This low oxygen level slows down the germs’ metabolism and turns them into a dormant state. Even when antibiotics can reach the germs in the biofilm, the germs will not die because they will not absorb the antibiotics to be killed. It is as though one has put rat poison around a colony of rats when they are sleeping and so not eating. Unless the rats eat the poison, they will not be killed.
As we have mentioned, to decrease the number of germs, removal of the dead tissue (debridement) is the most important step. As long as dead tissue is on the surface of the wound, no antibiotic can eliminate the germs. After dead tissue is removed, one can control the germs by changing the dressing frequently and by washing the wound with soap and water (or any wound cleaning solution). Anti-septic solutions and products containing silver ion may prevent over population of germs. Be aware, however, that while killing germs, anti-septic materials may also kill the growing human tissue. Hydrogen peroxide, Betadine solution, rubbing alcohol, Dakin’s solution (any concentration higher than 0.125%), are all notorious for delaying wound healing by damaging the human tissue. If you use any of the above products for more than a few days, stop using them and try just regular soap and water to clean the wound. In many cases, just stopping the prolonged use of an antiseptic solution may start the wound healing process.
Topical antibiotics (bacitracin, triple antibiotics, neomycin, mupirocin) do not kill the germs that live deeper than the surface of the wound. Topical antibiotics may be needed when the growth of germs is not controlled. But when using topical antibiotics, be aware of its side effects: over-the-counter topical antibiotics are notorious for causing allergies and yeast infections. Normally, no antibiotic is necessary to heal a wound, even when the wound culture reveals scary kinds of germs. But when germs penetrate and spread into the tissue, antibiotics either oral or IV will be necessary.