The term "prophylaxis" refers to the use of a preventative measure before it is strictly needed. Antimicrobial prophylaxis, which is a technique in medicine to prevent infections in certain situations, is primarily restricted to patients undergoing some surgeries, and people who may contract diseases on vacation. Although antibiotics are commonly used in antimicrobial prophylaxis, which target only bacteria, drugs which focus on other microbes like fungi or parasites also fall under the definition of antimicrobial prophylaxis.
Malaria is one disease that may be prevented through antimicrobial prophylaxis for people traveling in affected areas. Typically, this involves the traveler taking anti-malarial pills during the vacation as directed by a doctor. The traveler does not know if he or she may be infected with the malarial parasite, but taking the drug anyway prevents any infection from a mosquito bite from spreading. This type of defense against infection is different from vaccines, as vaccines contain portions of the infectious organism itself so the immune system can recognize its presence and defeat its attempt at infection.
Situations where a person's natural defenses against infection are damaged, such as open surgery, increase the risk of serious infections. To counter this, surgeons may put a patient on an antimicrobial prophylaxis regime before, during and after a planned surgery. People who suffer injuries and receive treatment when the wound appears to be clean and uninfected, may also receive prophylactic drugs to prevent an infectious organism from colonizing the wound.
A major disadvantage to antimicrobial prophylaxis in all situations is that all medicines carry a risk of side effects. Doctors balance the risk to health from the side effects against the risk to health of a potential infection when assessing whether antimicrobial prophylaxis is necessary. In addition, if the antimicrobial used affects bacteria, it can alter the natural bacterial population present in the digestive system of the patient, which can put the patient at risk of other infections later.
Generally, only situations where the patient is at high risk of developing a serious infection warrant antimicrobial prophylaxis. Operations such as open heart surgery, insertion of an artificial prostheses like a hip, and surgery on blood vessels, are some of the situations where the prophylactic medication can be helpful. Injuries such as animal bites or tick bites may also put a person at risk of serious infection, and prophylaxis may be used in these cases. As bacterial infections are the most significant cause of wound infections, the commonest form of prophylaxis is an antibiotic that can kill a wide variety of species.