The Microbial World: Drugs and Drug Resistance

Flashcards covering key vocabulary and concepts related to drugs, drug resistance, and antimicrobial resistance.

Antimicrobials

Medicines used to prevent and treat infections in humans, animals, and plants; includes antibiotics, antivirals, antifungals, and antiparasitics.

Ideal antimicrobial

In vitro and in vivo activity. Lack of toxicity (target not conserved in human). Cost. Broad-spectrum.

Bactericidal

Killing the target bacterium or fungus.

Bacteriostatic

Inhibiting the growth of a bacterium or fungus.

Antimicrobial Resistance (AMR)

Occurs when bacteria, viruses, fungi, and parasites change over time and no longer respond to medicines.

Multi-Drugs Resistance

Microbes that carry one or more resistance mechanism(s), making them resistant to multiple antimicrobials

Cross Resistance

A single resistance mechanism confers resistance to multiple antimicrobial drugs (i.e. efflux pump).

MRSA

An example of multi-drug resistance. Staphylococcus aureus: Gram-positive coccus whose cells tend to occur either singly or if dividing cells do not separate, forming irregular “grape-like” structures.

β-lactamase

An enzyme produced by resistant strains that inactivated the drug Penicillin

Combination Therapy

Antibiotics are frequently used in combination: to treat a life-threatening infection; to prevent emergence of bacterial resistance; to treat mixed infections of aerobic and anaerobic bacteria; to enhance antibacterial activity (synergy); to use lower doses of a toxic drug

Mechanisms of Resistance

Target modification, Target overproduction, Drug modification, Prevention of Cellular Uptake or Efflux, Target Mimicry.

Target modification

The drug will not bind to the target (enzyme). The target still perform its function

Target overproduction

The microbe may overproduce the target enzyme such that there is a sufficient amount of antimicrobial-free enzyme to carry out the proper enzymatic reaction

Drug inactivation

Resistance genes may code for enzymes that chemically modify an antimicrobial, thereby inactivating it, or destroy an antimicrobial

Prevention of Cellular Uptake or Efflux

Inhibition the accumulation of an antimicrobial drug, which then prevents the drug from reaching its cellular target Overproduction of efflux pumps that actively transport an antimicrobial drug out of the cell and prevent the accumulation of drug

Target mimicry

Production of proteins that bind and sequester drugs, preventing the drugs from binding to their target. Mycobacterium tuberculosis produces a protein with regular pentapeptide repeats that appears to mimic the structure of DNA This protein binds fluoroquinolones, sequestering them and keeping them from binding to DNA