drug resistance, condition in which infecting bacteria bacteria [pl. of bacterium], microscopic unicellular prokaryotic organisms characterized by the lack of a membrane-bound nucleus and membrane-bound organelles. Once considered a part of the plant kingdom, bacteria were eventually placed in a separate kingdom, Monera .
..... Click the link for more information. can resist the destructive effects of drugs such as antibiotics antibiotic, any of a variety of substances, usually obtained from microorganisms, that inhibit the growth of or destroy certain other microorganisms.

Types of Antibiotics

..... Click the link for more information. and sulfa drugs sulfa drug, any of a class of synthetic chemical substances derived from sulfanilamide, or para-aminobenzenesulfonamide. Sulfa drugs are used to treat bacterial infections, although they have largely been replaced for this purpose by antibiotics ; some are also used
..... Click the link for more information. . Drug resistance has become a serious public health problem, since many disease-causing bacteria are no longer susceptible to previously effective drug therapies. For nearly 50 years after the first antibiotic, penicillin, became available in the 1940s, people took antibiotics' effectiveness against bacterial infections for granted. By the 1960s some doctors were predicting the end of infectious diseases. By the 1990s, however, a "post-antibiotic era," characterized by the proliferation of untreatable bacterial strains, was considered inevitable, and the rate at which bacteria were becoming resistant to antibiotics was catching up with the rate at which new antibiotics were being produced.

The number of drug-resistant bacterial strains has increased in part because of the indiscriminate use of antibiotics, which have sometimes been overprescribed. Such misuse speeds the process by destroying bacteria that would compete with resistant strains. In addition, patients sometimes stop treatment when they start to feel better, leaving a residual population of bacteria that is likely to be more resistant to drug treatment. Another source of resistance is the routine use of antibiotics in animal feed to enhance growth, a practice that has led to resistant strains of Escherichia coli and Salmonella that have been passed on to consumers. The presence of drugs in the water supply, due at least in part to human and animal excretion and the disposal of unused drugs, is also believed to contribute to drug resistance in bacteria.

Resistance is due to random genetic mutations mutation, in biology, a sudden, random change in a gene , or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any change in the delicate balance of an organism having a high level of adaptation to its
..... Click the link for more information. in the bacterial cell that alter its sensitivity to a single drug or to chemically similar drugs through a variety of mechanisms. Many bacteria can transfer their resistance to other bacteria of the same or different species. Resistance has occurred in common infectious bacteria such as pneumococcus (a cause of pneumonia, meningitis, and childhood ear infections) and enterococcus (a cause of wound infections). It has also occurred in such diseases as malaria malaria, infectious parasitic disease that can be either acute or chronic and is frequently recurrent. Malaria is common in Africa, Central and South America, the Mediterranean countries, Asia, and many of the Pacific islands.
..... Click the link for more information. and tuberculosis tuberculosis (TB), contagious, wasting disease caused by any of several mycobacteria. The most common form of the disease is tuberculosis of the lungs (pulmonary consumption, or phthisis), but the intestines, bones and joints, the skin, and the genitourinary,
..... Click the link for more information. . Concerns are increasing as strains develop resistance to multiple drugs, including even the most powerful antibiotics (e.g., vancomycin). Although drug companies are again concentrating on antibiotic research, no new products are expected until the turn of the century, and many infectious-disease experts are urging that doctors consider the public health risk before prescribing antibiotics and that the government regulate the use of antibiotics in agriculture.

Bibliography

See S. Levy, The Antibiotic Paradox (1992).

drug resistance

Property of a disease-causing organism that allows it to withstand drug therapy. In any population of infectious agents, some have a mutation that helps them resist the action of a drug. The drug then kills more of the nonresistant microbes, leaving the mutants without competition to multiply into a resistant strain. This situation is more likely if the drug is not taken properly (e.g., a course of antibiotics not completed, anti-HIV drug doses missed) or not prescribed properly (e.g., an antibiotic given for a viral disease). Resistance factors can also be transferred between species that infect the same body. The overprescription of antibiotics in humans and the addition of antibiotics to animal feed have accelerated the evolution of resistant strains of bacteria, making it increasingly difficult to fight off certain disease-causing organisms.