Drug resistance is the reduction in effectiveness of a drug such as an antimicrobial or an antineoplastic in curing a disease or condition. When the drug is not intended to kill or inhibit a pathogen, then the term is equivalent to dosage failure or drug tolerance. More commonly, the term is used in the context of resistance that pathogens have "acquired", that is, resistance has evolved. When an organism is resistant to more than one drug, it is said to be multidrug-resistant. In a broad sense the immune system of an organism is such a drug delivery system, albeit autonomous, and faces the same arms race problems as external drug delivery.
The development of antibiotic resistance in particular stems from the drugs targeting only specific bacterial proteins. Because the drug is so specific, any mutation in these proteins will interfere with or negate its destructive effect, resulting in antibiotic resistance.
Bacteria are capable of not only altering the enzyme targeted by antibiotics, but also by the use of enzymes to modify the antibiotic itself and thus neutralise it. Examples of target-altering pathogens are Staphylococcus aureus, vancomycin-resistant enterococci and macrolide-resistant Streptococcus, while examples of antibiotic-modifying microbes are Pseudomonas aeruginosa and aminoglycoside-resistant Acinetobacter baumannii.
Resistance to chemicals is only one aspect of the problem, another being resistance to physical factors such as temperature, pressure, sound, radiation and magnetism, and not discussed in this article, but found at Physical factors affecting microbial life.
Read more about Drug Resistance: Introduction, Mechanisms, Metabolic Price, Treatment
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