Chapter 14: Overview of Antimicrobials and Their Mechanisms

Selective Toxicity

Harms microbes without damaging the host.

Chemotherapeutic Agent

Chemical used in medical practice for treatment.

Antibiotic

Substance made by microorganisms to inhibit growth.

Antimicrobial Agent

Chemical similar to antibiotics, often synthetic.

Spectrum of Activity

Range of organisms affected by an antimicrobial.

Narrow Spectrum

Targets specific subsets of bacterial pathogens.

Broad Spectrum

Targets a wide variety of bacterial pathogens.

Minimal Inhibitory Concentration (MIC)

Lowest concentration preventing organism growth.

Minimum Bactericidal Concentration (MBC)

Lowest concentration killing the organism.

Kirby-Bauer Test

Measures antibiotic susceptibility using agar diffusion.

E-test

Determines MIC using a gradient strip method.

Dosage

Amount of medication given over time.

Half-life

Time for 50% of drug to be eliminated.

Empirical Therapy

Initial treatment before specific diagnosis is known.

Targeted Drug Therapy

Treatment based on specific pathogen identification.

Synergism

Combined effect of drugs greater than individual effects.

Antimicrobial Resistance

Microorganisms' ability to withstand drug effects.

Prontosil

First synthetic antimicrobial discovered in the 1930s.

Sulfanilamide

Active breakdown product of prontosil, first synthetic.

Penicillin

First natural antibiotic discovered by Alexander Fleming.

Chemotherapeutic Index

Maximum tolerable dose divided by minimum effective dose.

Ideal Antimicrobial Attributes

Soluble, selective, stable, non-allergenic, cost-effective.

Superinfections

Infections resulting from antibiotic treatment disrupting normal flora.

Chemotherapeutic Index

Ratio of toxic dose to therapeutic dose.

Synergism

Combined effect greater than additive effect.

Antagonism

Drugs interfere with each other's effectiveness.

Selective Toxicity

Targets unique structures in bacterial cells.

Penicillin-Binding Proteins (PBPs)

Enzymes crucial for bacterial cell wall synthesis.

Bactericidal Drug

Causes bacterial cell death.

Cephalosporins

Beta-lactam antibiotics with multiple generations.

Bacitracin

Topical antibiotic effective against gram-positive bacteria.

Vancomycin

Last-resort antibiotic against resistant S. aureus.

Isoniazid (INH)

Inhibits synthesis of mycolic acid in bacteria.

Ethambutol

Prevents incorporation of mycolic acid in bacteria.

Polymyxin

Disrupts bacterial membrane, highly toxic.

Gramicidin

Cyclic peptide that disrupts gram-positive membranes.

Metronidazole

Activated by anaerobic bacteria for DNA targeting.

Sulfonamides

Inhibit folic acid synthesis in bacteria.

Quinolones

Inhibit bacterial DNA gyrase, blocking replication.

Antimicrobial Resistance

Bacteria's ability to resist effects of antibiotics.

Antimicrobial Combinations

Using multiple antibiotics to enhance treatment efficacy.

Cell Wall Synthesis Inhibitors

Antibiotics that disrupt bacterial cell wall formation.

DNA Synthesis Inhibitors

Target bacterial DNA replication processes.

Protein Synthesis Inhibitors

Antibiotics that block bacterial protein production.

RNA Synthesis Inhibitors

Interfere with bacterial RNA transcription.

Metabolism Inhibitors

Disrupt bacterial metabolic pathways.

Rifampin

Antibiotic that inhibits bacterial RNA polymerase.

RNA polymerase

Enzyme that synthesizes RNA from DNA template.

Aminoglycosides

Class of antibiotics causing mRNA misreading.

Streptomycin

Aminoglycoside antibiotic used against tuberculosis.

Tetracyclines

Antibiotics that block tRNA entry to ribosome.

Doxycycline

A tetracycline antibiotic effective against various infections.

Glycylcyclines

Inhibit tRNA entry in tetracycline-resistant bacteria.

Chloramphenicol

Inhibits peptide bond formation in protein synthesis.

Macrolides

Antibiotics that inhibit tRNA translocation in ribosomes.

Erythromycin

A macrolide antibiotic used for respiratory infections.

Lincosamides

Prevent peptide bond formation in bacterial ribosomes.

Oxazolidinones

Block assembly of the 70S ribosome.

Streptogramins

Block tRNA entry and protein exit from ribosome.

Drug modification

Enzymatic alteration rendering antibiotics ineffective.

Efflux pumps

Transport proteins expelling antibiotics from cells.

Target overproduction

Microbe produces excess target enzyme to resist drugs.

Enzymatic bypass

Microbe circumvents need for functional target enzyme.

Target mimicry

Production of proteins that sequester antibiotics.

Clavulanic acid

Inactivates beta-lactamases from resistant bacteria.

Amantadine

Prevents influenza virus uncoating and exit.

Neuraminidase inhibitors

Prevent virus particles from leaving infected cells.

Nystatin

Antifungal that disrupts fungal membrane integrity.

Metronidazole

Antiprotozoan causing DNA breakage, treats giardiasis.

Ivermectin

Paralyzes intestinal roundworms in antiparasitic treatment.