Antimicrobial Chemotherapy & Resistance – Core Vocabulary

Vocabulary flashcards covering key terms, classes, mechanisms, and resistance concepts from the Antimicrobial Chemotherapy & Resistance lecture.

Antimicrobial Chemotherapy

Use of drugs to combat infectious agents such as bacteria, fungi, parasites and viruses.

Differential Toxicity

Principle that an antimicrobial is more toxic to the infecting organism than to the host.

Antibiotic

Substance produced by a microorganism that, in small amounts, inhibits or kills bacteria.

Penicillin

First discovered antibiotic (1928) produced by Penicillium species; β-lactam class cell-wall inhibitor.

Narrow-Spectrum Antibiotic

Drug effective against a limited range of species, e.g., only Gram-positive or only Gram-negative bacteria.

Broad-Spectrum Antibiotic

Drug effective against a wide variety of bacterial species, both Gram-positive and Gram-negative.

Minimum Inhibitory Concentration (MIC)

Lowest concentration of an antibiotic that prevents visible growth of a test organism.

Minimum Bactericidal Concentration (MBC)

Lowest concentration of an antibiotic that kills a test organism.

Bacteriostatic

Describes an antimicrobial that inhibits bacterial growth without killing the cells outright.

Bactericidal

Describes an antimicrobial that kills bacteria rather than merely inhibiting growth.

Time-Dependent Killing

Antimicrobial activity determined by the length of time drug levels stay above the MIC.

Concentration-Dependent Killing

Antimicrobial activity determined by achieving high peak drug concentrations relative to MIC.

Prophylaxis

Administration of antimicrobials to prevent potential infection.

Treatment (Therapy)

Administration of antimicrobials to cure an existing or suspected infection.

Peptidoglycan

Mesh-like polymer of NAM and NAG sugars cross-linked by peptides; forms bacterial cell wall.

β-Lactam Antibiotics

Class that includes penicillins, cephalosporins, carbapenems; inhibit cell-wall synthesis by binding PBPs.

Penicillin-Binding Proteins (PBPs)

Essential enzymes involved in peptidoglycan synthesis; targets of β-lactam antibiotics.

Glycopeptide Antibiotics

Class (e.g., vancomycin) that binds D-Ala-D-Ala termini of peptidoglycan precursors, blocking cross-linking.

Polymyxins

Cationic polypeptide antibiotics (e.g., colistin) that disrupt Gram-negative bacterial membranes.

Quinolones / Fluoroquinolones

Synthetic antibiotics that inhibit DNA gyrase and topoisomerase IV, blocking DNA replication.

DNA Gyrase

Bacterial enzyme that introduces negative supercoils into DNA; target of quinolones in Gram-negatives.

Topoisomerase IV

Bacterial enzyme that decatenates replicated DNA; quinolone target in Gram-positives.

Rifamycins

Antibiotic class (e.g., rifampicin) that inhibits bacterial RNA polymerase and transcription.

70S Ribosome

Prokaryotic ribosome consisting of 50S and 30S subunits; site of protein synthesis and antibiotic action.

Macrolides

Protein-synthesis inhibitors (e.g., erythromycin) that bind 50S subunit; usually bacteriostatic.

Aminoglycosides

Protein-synthesis inhibitors (e.g., gentamicin) that bind 30S subunit; bactericidal, concentration dependent.

Tetracyclines

Broad-spectrum antibiotics that block tRNA attachment to the 30S ribosomal subunit.

Chloramphenicol

Broad-spectrum drug that inhibits peptide-bond formation on the 50S ribosomal subunit.

Trimethoprim

Antimetabolite that blocks dihydrofolate reductase in folic-acid synthesis pathway.

Sulfonamides

Antimetabolites that inhibit dihydropteroate synthase, an early step in folic-acid synthesis.

Antimetabolite

Drug that inhibits a metabolic pathway by mimicking a natural substrate (e.g., folate pathway blockers).

Outer Membrane

Additional lipid bilayer in Gram-negative bacteria containing lipopolysaccharide and porins.

Gram-Positive Bacteria

Bacteria with thick peptidoglycan and no outer membrane; retain crystal-violet stain.

Gram-Negative Bacteria

Bacteria with thin peptidoglycan and outer membrane; lose crystal violet and stain red with safranin.

β-Lactamase

Enzyme that hydrolyses the β-lactam ring, rendering β-lactam antibiotics inactive.

Extended-Spectrum β-Lactamase (ESBL)

Plasmid-encoded β-lactamase able to inactivate a wide range of penicillins and cephalosporins.

Methicillin-Resistant Staphylococcus aureus (MRSA)

S. aureus strain carrying mecA gene encoding PBP2a with low β-lactam affinity.

Vancomycin-Resistant Enterococcus (VRE)

Enterococcal strains that replace D-Ala-D-Ala with D-Ala-D-Lac, preventing vancomycin binding.

Inherent (Intrinsic) Resistance

Natural lack of susceptibility due to structural or functional characteristics of the organism.

Acquired Resistance

Resistance developed via mutation or acquisition of new genes through horizontal or vertical transfer.

Horizontal Gene Transfer

Movement of genetic material between bacteria via conjugation, transduction or transformation.

Cross-Resistance

Resistance to multiple drugs in the same class due to a shared mechanism (e.g., all β-lactams).

Multi-Resistance

Resistance to several unrelated antimicrobial classes within the same organism.

Efflux Pump

Transport protein that expels antimicrobial agents out of the bacterial cell, lowering intracellular levels.

Target Modification

Resistance mechanism whereby bacteria alter antibiotic binding sites (e.g., PBP2a, mutated gyrase).

Antiviral Drug

Agent that interferes with specific stages of viral replication while sparing host functions.

Highly Active Antiretroviral Therapy (HAART)

Combination regimen of at least three antiretroviral drugs used to control HIV infection.

Reverse Transcriptase Inhibitor (RTI)

Antiviral that blocks HIV reverse transcriptase, preventing viral DNA synthesis.

Protease Inhibitor (PI)

Antiviral that blocks viral protease activity, stopping maturation of infectious particles.

Fusion Inhibitor

Antiviral that prevents fusion of viral envelope with host cell membrane (e.g., enfuvirtide).

Consequence of AMR

Increased morbidity, mortality, healthcare costs, and threat of untreatable infections.

Responsible Prescribing

Strategy promoting appropriate antimicrobial use to slow resistance development.

Alternative Therapy

Non-traditional approaches to infection control such as phage therapy, probiotics or immunotherapy.

Teixobactin

Novel antibiotic in development that targets lipid II and lipid III in cell-wall synthesis, with low resistance potential.

Selective Toxicity

Ability of a drug to harm the pathogen without significant damage to the host.

Plasmid

Extrachromosomal circular DNA in bacteria often carrying antibiotic-resistance genes.

Porin

Protein channel in Gram-negative outer membrane that permits small molecule passage, including some drugs.

Cell-Wall Active Agent

Antimicrobial whose primary mode of action is inhibition of peptidoglycan synthesis leading to lysis.

Carbapenemase

β-lactamase capable of hydrolysing carbapenems, often conferring resistance to last-line drugs.