Antimicrobials are drugs used to treat microbial infections. The way that antimicrobials target and inhibit or kill microbes differs greatly and, in part, determines which microbes they are effective against. The types of chemicals used as antimicrobials vary, and the composition of these chemicals affects the type of microbe they inhibit and side effects in patients. Standardized biochemical tests are used to determine which microbes are susceptible to which antimicrobials and the most effective drug concentration. Many microbes have evolved resistance to antimicrobials, and this presents challenges to the development of new antimicrobials.

At A Glance

  • Antimicrobial chemicals differ widely in their strength, the pathogens they are effective against, and their modes of action, so each must be evaluated based on selective toxicity, spectrum of activity, mode of action, side effects, and potential for resistance.
  • Antimicrobial chemicals work to disrupt the cell membrane and cell wall synthesis, inhibit protein synthesis, and inhibit of nucleic acid synthesis.
  • The class of antibiotics characterized by the presence of beta-lactam, a specialized ring in the molecular structure, inhibits bacterial cell wall synthesis and is the most popular class of antibiotics in the world.
  • Bacitracin and isoniazid target enzymes on the pathogen cell membrane to prevent the building of the cell wall.
  • Quinolones disrupt the unwinding of bacterial DNA during replication, preventing its duplication.
  • Four major groups of drugs are used to treat fungal infections: polyenes, azoles, echinocandins, and cytosine nucleotide analogs.
  • Antiprotozoan drugs include those that affect protein synthesis, are metabolites, and inhibit DNA synthesis in the organism.
  • Antimicrobials against helminths work by inhibiting glucose uptake, preventing oxidative phosphorylation of ATP, and inhibiting nucleic synthesis.
  • Antiviral drugs include those that inhibit nucleic acid synthesis, prevent attachment to the host cell, and prevent the uncoating of the viral coat.
  • Antimicrobial drug toxicity can affect the liver, kidneys, GI tract, cardiovascular system, nervous system, respiratory system, skin, bones, teeth, and blood-forming tissue, and allergic reactions are not uncommon.
  • The disk diffusion method, ETEST, dilution method, serum killing power, and new automated methods can be used to determine a microbe's sensitivity to particular antimicrobials.
  • The ideal antimicrobial must be soluble in body fluids, be toxic to microbe but not host, not be allergenic, be stable under host body conditions, and have a toxicity that is not easily altered.
  • Antimicrobial resistance is a condition where a microbial species or strain gains the ability to survive in the presence of a drug that would normally inhibit its growth or kill it outright.
  • Antibiotic stewardship is the unified effort to improve the use of antimicrobial medicines to increase human health and reduce resistance.