# Multiple drug resistance

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Measure of microorganism drug resistance

This article is about multiple drug resistance in microorganisms. For multiple drug resistance in tumor/cancer cells, see [antineoplastic resistance](/source/Antineoplastic_resistance).

Not to be confused with [Multidrug tolerance](/source/Multidrug_tolerance).

**Multiple drug resistance** (**MDR**), **multidrug resistance** or **multiresistance** is [antimicrobial resistance](/source/Antimicrobial_resistance) shown by a species of [microorganism](/source/Microorganism) to at least one [antimicrobial](/source/Antimicrobial) drug in three or more antimicrobial categories.[1] Antimicrobial categories are classifications of antimicrobial agents based on their mode of action and specific to target organisms.[1] The MDR types most threatening to [public health](/source/Public_health) are MDR [bacteria](/source/Bacteria) that resist multiple [antibiotics](/source/Antibiotics); other types include MDR [viruses](/source/Virus), [parasites](/source/Parasitism) (resistant to multiple [antifungal](/source/Antifungal), [antiviral](/source/Antiviral_drug), and [antiparasitic](/source/Antiparasitic) drugs of a wide chemical variety).[2]

## Terminology

Recognizing different degrees of MDR in bacteria, the terms **extensively drug-resistant** (**XDR**) and **pandrug-resistant** (**PDR**) have been introduced. Extensively drug-resistant is the non-susceptibility of one bacteria species to all antimicrobial agents except in two or less antimicrobial categories. Within XDR, pandrug-resistant is the non-susceptibility of bacteria to all antimicrobial agents in all antimicrobial categories. The definitions were introduced in 2011.[1]

## Common multidrug-resistant organisms (MDROs)

Common multidrug-resistant organisms, typically bacteria, include:[3]

- [Vancomycin-Resistant Enterococci](/source/Vancomycin-resistant_Enterococcus) (VRE)

- [Methicillin](/source/Methicillin)-resistant *[Staphylococcus aureus](/source/Staphylococcus_aureus)* ([MRSA](/source/Methicillin-resistant_Staphylococcus_aureus))

- [Extended-spectrum β-lactamase](/source/Beta-lactamase#Extended-spectrum_beta-lactamase_(ESBL)) (ESBLs) producing [Gram-negative bacteria](/source/Gram-negative_bacteria)

- [*Klebsiella pneumoniae* carbapenemase](/source/Beta-lactamase#KPC_(K._pneumoniae_carbapenemase)_(class_A)) (KPC) producing Gram-negatives

- Multidrug-resistant Gram negative rods (MDR GNR) [MDRGN bacteria](/source/MDRGN_bacteria) such as *[Enterobacter](/source/Enterobacter) species*, *[E.coli](/source/E.coli)*, *[Klebsiella pneumoniae](/source/Klebsiella_pneumoniae)*, *[Acinetobacter baumannii](/source/Acinetobacter_baumannii)*, *[Pseudomonas aeruginosa](/source/Pseudomonas_aeruginosa)*

- [Multi-drug-resistant tuberculosis](/source/Multi-drug-resistant_tuberculosis)

Overlapping with MDRGN, a group of [Gram-positive](/source/Gram-positive) and [Gram-negative](/source/Gram-negative) bacteria of particular recent importance have been dubbed as the ESKAPE group (*[Enterococcus faecium](/source/Enterococcus_faecium)*, *Staphylococcus aureus*, *Klebsiella pneumoniae*, *Acinetobacter baumannii*, *Pseudomonas aeruginosa* and *[Enterobacter](/source/Enterobacter)* species).[4]

## Bacterial resistance to antibiotics

Main article: [Antibiotic resistance](/source/Antibiotic_resistance)

Various microorganisms have survived for thousands of years by their ability to adapt to antimicrobial agents. They do so via [spontaneous mutation](/source/Spontaneous_mutation) or by [DNA transfer](/source/DNA_transfer). This process enables some bacteria to oppose the action of certain antibiotics, rendering the antibiotics ineffective.[5] These microorganisms employ several mechanisms in attaining multi-drug resistance:

- No longer relying on a [glycoprotein](/source/Glycoprotein) [cell wall](/source/Cell_wall)[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

- [Enzymatic deactivation of antibiotics](/source/Antibiotic_resistance#Mechanisms_and_organisms)[6]

- Decreased cell wall permeability to antibiotics[7]

- Altered target sites of antibiotic[8]

- [Efflux](/source/Efflux_(microbiology)) mechanisms to remove antibiotics[9]

- Increased [mutation rate](/source/Mutation_rate) as a stress response[10]

Many different bacteria now exhibit multi-drug resistance, including [staphylococci](/source/Staphylococci), [enterococci](/source/Enterococci), [gonococci](/source/Gonococci), [streptococci](/source/Streptococci), [salmonella](/source/Salmonella), as well as numerous other Gram-negative bacteria and *[Mycobacterium tuberculosis](/source/Mycobacterium_tuberculosis)*. Antibiotic resistant bacteria are able to transfer copies of [DNA](/source/DNA) that code for a mechanism of resistance to other bacteria even distantly related to them, which then are also able to pass on the resistance genes, resulting in generations of antibiotics resistant bacteria.[11] This initial transfer of DNA is called [horizontal gene transfer](/source/Horizontal_gene_transfer).[12]

## Bacterial resistance to bacteriophages

Phage-resistant bacteria variants have been observed in human studies. As for antibiotics, horizontal transfer of [phage](/source/Bacteriophage) resistance can be acquired by [plasmid](/source/Plasmid) acquisition.[13]

## Antifungal resistance

Yeasts such as *Candida species* can become resistant under long-term treatment with [azole](/source/Azole) preparations, requiring treatment with a different drug class. *[Lomentospora prolificans](/source/Lomentospora_prolificans)* infections are often fatal because of their resistance to multiple antifungal agents.[14]

## Antiviral resistance

[HIV](/source/HIV) is the prime example of MDR against antivirals, as it mutates rapidly under monotherapy. [Influenza virus](/source/Influenza_virus) has become increasingly MDR; first to amantadines, then to [neuraminidase inhibitors](/source/Neuraminidase_inhibitors) such as [oseltamivir](/source/Oseltamivir), (2008-2009: 98.5% of Influenza A tested resistant), also more commonly in people with weak immune systems. [Cytomegalovirus](/source/Cytomegalovirus) can become resistant to [ganciclovir](/source/Ganciclovir) and [foscarnet](/source/Foscarnet) under treatment, especially in [immunosuppressed](/source/Immunosuppression) patients. [Herpes simplex virus](/source/Herpes_simplex_virus) rarely becomes resistant to [acyclovir](/source/Acyclovir) preparations, mostly in the form of cross-resistance to [famciclovir](/source/Famciclovir) and [valacyclovir](/source/Valacyclovir), usually in immunosuppressed patients.[15]

## Antiparasitic resistance

The prime example for MDR against antiparasitic drugs is [malaria](/source/Malaria). *[Plasmodium vivax](/source/Plasmodium_vivax)* has become [chloroquine](/source/Chloroquine) and [sulfadoxine-pyrimethamine](/source/Sulfadoxine-pyrimethamine) resistant a few decades ago, and as of 2012 [artemisinin](/source/Artemisinin)-resistant *[Plasmodium falciparum](/source/Plasmodium_falciparum)* has emerged in western Cambodia and western Thailand.[16] *[Toxoplasma gondii](/source/Toxoplasma_gondii)* can also become resistant to [artemisinin](/source/Artemisinin), as well as [atovaquone](/source/Atovaquone) and [sulfadiazine](/source/Sulfadiazine), but is not usually MDR[17] [Antihelminthic](/source/Antihelminthic) resistance is mainly reported in the veterinary literature, for example in connection with the practice of livestock drenching[18] and has been recent focus of [FDA](/source/Food_and_Drug_Administration) regulation.

## Preventing the emergence of antimicrobial resistance

To limit the development of antimicrobial resistance, it has been suggested to:[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

- Use the appropriate antimicrobial for an infection; e.g. no antibiotics for viral infections

- Identify the causative organism whenever possible

- Select an antimicrobial which targets the specific organism, rather than relying on a broad-spectrum antimicrobial

- Complete an appropriate duration of antimicrobial treatment (not too short and not too long)

- Use the correct dose for eradication; subtherapeutic dosing is associated with resistance, as demonstrated in food animals.

- More thorough education of and by prescribers on their actions' implications globally.

- Vaccination to prevent drug resistance for instance pneumococcus vaccine or flu vaccine

The medical community relies on education of its prescribers, and self-regulation in the form of appeals to voluntary [antimicrobial stewardship](/source/Antimicrobial_stewardship), which at hospitals may take the form of an antimicrobial stewardship program. It has been argued that depending on the cultural context government can aid in educating the public on the importance of restrictive use of antibiotics for human clinical use, but unlike [narcotics](/source/Narcotic), there is no regulation of its use anywhere in the world at this time. Antibiotic use has been restricted or regulated for treating animals raised for human consumption with success, in Denmark for example.[19]

[Infection prevention](/source/Infection_prevention) is the most efficient strategy of prevention of an infection with a MDR organism within a hospital, because there are few alternatives to antibiotics in the case of an extensively resistant or panresistant infection; if an infection is localized, removal or [excision](/source/Surgery) can be attempted (with MDR-TB the lung for example), but in the case of a systemic infection only generic measures like [boosting the immune system with immunoglobulins](/source/Immunoglobulin_therapy) may be possible. The [use of bacteriophages](/source/Phage_therapy) (viruses which kill bacteria) is a developing area of possible therapeutic treatments.[20]

It is necessary to develop new antibiotics over time since the [selection](/source/Natural_selection) of resistant bacteria cannot be prevented completely. This means with every application of a specific antibiotic, the survival of a few bacteria which already have a resistance gene against the substance is promoted, and the concerning bacterial population amplifies. Therefore, the resistance gene is farther distributed in the organism and the environment, and a higher percentage of bacteria means they no longer respond to a therapy with this specific antibiotic. In addition to developing new antibiotics, new strategies entirely must be implemented in order to keep the public safe from the event of total resistance. New strategies are being tested such as [UV light](/source/Ultraviolet) treatments and bacteriophage utilization, however more resources must be dedicated to this cause.

## See also

- [Drug resistance](/source/Drug_resistance)

- [MDRGN bacteria](/source/MDRGN_bacteria)

- [Xenobiotic metabolism](/source/Xenobiotic_metabolism)

- [NDM1 enzymatic resistance](/source/New_Delhi_metallo-beta-lactamase_1)

- [Herbicide resistance](/source/Herbicide_resistance)

- [P-glycoprotein](/source/P-glycoprotein)

## References

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## Further reading

- Greene HL, Noble JH (2001). *Textbook of primary care medicine*. St. Louis: Mosby. [ISBN](/source/ISBN_(identifier)) [978-0-323-00828-0](https://en.wikipedia.org/wiki/Special:BookSources/978-0-323-00828-0).

## External links

- [BURDEN of Resistance and Disease in European Nations - An EU project to estimate the financial burden of antibiotic resistance in European Hospitals](https://web.archive.org/web/20070701212012/http://www.eu-burden.info/burden/pages/home.php)

- European Centre of Disease Prevention and Control and (ECDC): Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: An international expert proposal for interim standard definitions for acquired resistance [Disease Programmes Unit](http://www.ecdc.europa.eu/en/activities/diseaseprogrammes/ARHAI/Pages/public_consultation_clinical_microbiology_infection_article.aspx)

- State of Connecticut Department of Public Health MDRO information [MultidrugResistant Organisms MDROs What Are They](https://portal.ct.gov/DPH/HAI/MultidrugResistant-Organisms-MDROs-What-Are-They)

v t e Use of antimicrobials Types Antibacterial Antifungal Antiviral Antiparasitic Concepts Antibiotic sensitivity Antimicrobial resistance multidrug Antibiotic prophylaxis Empiric therapy Directed therapy Social issues Antimicrobial stewardship Antibiotic misuse Pharmacology Antimicrobial pharmacodynamics List of antibiotics Production of antibiotics Agriculture Antibiotic use in livestock Antibiotics in poultry farming in America Subtherapeutic antibiotic use in swine Pesticide resistance

v t e Pharmacology Ligand (biochemistry) Excitatory Agonist Endogenous agonist Irreversible agonist Partial agonist Superagonist Physiological agonist Inhibitory Antagonist Competitive antagonist Irreversible antagonist Physiological antagonist Inverse agonist Enzyme inhibitor Drug Neurotransmitter Agonist-antagonist Pharmacophore Pharmacodynamics Activity at receptor Mechanism of action Mode of action Binding Receptor (biochemistry) Desensitization (medicine) Other effects of ligand Selectivity (Binding, Functional) Pleiotropy (drugs) Non-specific effect of vaccines Adverse effect Toxicity (Neurotoxicity) Analysis Dose–response relationship Hill equation (biochemistry) Schild plot Del Castillo Katz model Cheng-Prussoff Equation Methods (Organ bath, Ligand binding assay, Patch clamp) Metrics Efficacy Intrinsic activity Potency (EC50, IC50, ED50, LD50, TD50) Therapeutic index Affinity Pharmacokinetics Metrics Loading dose Volume of distribution (Initial) Rate of infusion Onset of action Biological half-life Plasma protein binding Bioavailability LADME (L)ADME: (Liberation) Absorption Distribution Metabolism Excretion (Clearance) Compartment Bioequivalence Related fields Neuroscience and psychology Neuropsychopharmacology Neuropharmacology Psychopharmacology Electrophysiology Medicine Clinical pharmacology Pharmacy Medicinal chemistry Pharmacoepidemiology Biochemistry and genetics Pharmacoinformatics Pharmacogenetics Pharmacogenomics Toxicology Pharmacotoxicology Neurotoxicology Drug discovery Classical pharmacology Reverse pharmacology Photopharmacology Immunopharmacology Cell biology Physiology Other Coinduction (anesthetics) Combination therapy Functional analog (chemistry) Polypharmacology Chemotherapy Lists of drugs WHO list of essential medicines Tolerance and resistance Drug tolerance Tachyphylaxis Drug resistance Antibiotic resistance Multiple drug resistance Antimicrobial pharmacology Antimicrobial pharmacodynamics Minimum inhibitory concentration Bacteriostatic Minimum bactericidal concentration Bactericide

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Adapted from the Wikipedia article [Multiple drug resistance](https://en.wikipedia.org/wiki/Multiple_drug_resistance) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Multiple_drug_resistance?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.