The increasing use of antibiotics in the treatment of infection has led to resistance in certain types of bacteria to the effects of particular antibiotics. This resistance to the drug usually occurs when bacteria develop mechanisms of growth and reproduction that are not disrupted by the effects of the antibiotics. In other cases, bacteria produce enzymes that neutralize the antibiotics.

Antibiotic resistance may develop in a person during prolonged treatment when a drug has failed to eliminate the infection quickly. The resistant strain of bacteria is able to multiply, thereby prolonging the illness. It may also infect other people and result in the spread of resistant infection. One particularly important example is Methicillin resistant Staphylococus aureus, which resists most antibiotics but can be treated with other drugs such as Teicoplanin and Vancomycin.

Doctors try to prevent the development of resistance to antibiotics by selecting the drug most likely to eliminate the bacteria present in each individual case as quickly and as thoroughly as possible. Failure to complete a course of antibiotics that has been prescribed by your doctor increases the likelihood that the infection will recur in a resistant form.



Risks and Special Precautions

Most antibiotics used for short periods outside a hospital setting are safe for most people. The most common risk, especially with Cephalosporins and Penicillins, is a severe allergic reaction to the drug that can cause a rash and sometimes swelling of the face and throat. If this happens, you should stop the drug and seek immediate medical advice. If you have had a previous allergic reaction to an antibiotic, all other drugs in that class and related classes should be avoided. It is, therefore, important to inform your doctor if you have previously suffered an adverse reaction to treatment with an antibiotic (with the exception of minor bowel disturbances).

Another risk of antibiotic treatment, especially if it is prolonged, is that the balance among micro-organisms normally inhibiting the body may be disturbed. In particular, antibiotics may destroy the bacteria that normally limit the growth of Candida, a yeast that is often present in small amounts in the body. This can lead to overgrowth of Candida (thrush) in the mouth, vagina or bowel and an anti-fungal drug may be needed.
A rarer, but more serious result of disruption of normal bacterial activity in the body is a disorder known as Pseudo-membranous colitis, in which bacteria that are resistant to the antibiotic multiply in the bowel, causing violent, bloody diarrhoea. This potentially fatal disorder can occur with any antibiotic, but is most common with the Lincosamides.

Common Drugs

Aminoglycosides: Amikacin, Gentamicin, Neomycin, Netilmicin, Streptomycin, Tobramycin.
Cephalosporins: Cefadroxil, Cefaclor, Cefalexin, Cefamandole, Cefazolin, Cefixime, Cefodizime, Cefoxitin, Cefodoxime, Cefradine, Ceftazidime.
Lincosamides: Clindamycin.