Antimicrobial Chemotherapy and Resistance – Vocabulary Review

A comprehensive set of vocabulary flashcards summarising key terms, antibiotic classes, mechanisms, and resistance concepts from the lecture on antimicrobial chemotherapy and resistance.

Antimicrobial Chemotherapy

Use of drugs (antibacterial, antifungal, antiparasitic, antiviral) to combat infectious agents inside the body.

Differential Toxicity

Property whereby a drug 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; may be natural or synthetic.

Penicillin

First antibiotic, discovered in 1928 from the fungus Penicillium notatum; a β-lactam that inhibits cell-wall synthesis.

Alexander Fleming

Scientist who discovered penicillin by chance in 1928.

Bacillus subtilis

Gram-positive rod that produces the antibiotic bacitracin.

Bacitracin

Polypeptide antibiotic from Bacillus subtilis that interferes with cell-wall synthesis.

Streptomyces griseus

Actinomycete that produces the aminoglycoside streptomycin.

Streptomycin

First aminoglycoside; binds 30S ribosomal subunit to inhibit protein synthesis.

Ideal Antibiotic

Selective toxicity, broad enough spectrum, no resistance, good pharmacokinetics, non-allergenic, inexpensive.

Narrow-spectrum Antibiotic

Drug effective against a limited range of species (e.g., penicillin, isoniazid).

Broad-spectrum Antibiotic

Drug effective against a wide variety of Gram-positive and Gram-negative species (e.g., tetracycline).

Minimum Inhibitory Concentration (MIC)

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

Minimum Bactericidal Concentration (MBC)

Lowest concentration of an antibiotic that kills a test organism.

Bacteriostatic

Drug that inhibits growth without directly killing bacteria.

Bactericidal

Drug that kills bacteria outright.

Time-dependent Killing

Antibacterial activity correlates with the duration that drug levels exceed MIC (e.g., β-lactams).

Concentration-dependent Killing

Antibacterial activity increases with higher drug concentrations (e.g., aminoglycosides, fluoroquinolones).

Prophylaxis (antimicrobial)

Administration of agents to prevent infection.

Treatment (antimicrobial)

Use of agents to cure existing or suspected infection.

Peptidoglycan

Sugar-peptide mesh in bacterial cell walls composed of N-acetylglucosamine and N-acetylmuramic acid.

Penicillin-Binding Proteins (PBPs)

Enzymes that catalyse peptidoglycan cross-linking; targets of β-lactam antibiotics.

β-lactam Antibiotics

Class (penicillins, cephalosporins, carbapenems, monobactams) that inhibit PBPs and cell-wall synthesis.

Glycopeptide Antibiotics

Class (vancomycin, teicoplanin) that bind D-Ala-D-Ala termini and block peptidoglycan cross-linking.

Cell-membrane Active Agents

Polymyxin B, colistin; cationic peptides that disrupt bacterial membranes causing lysis.

DNA Gyrase

Type II topoisomerase in Gram-negatives targeted by fluoroquinolones.

Topoisomerase IV

Enzyme essential for decatenation in Gram-positives; inhibited by fluoroquinolones.

Fluoroquinolones

Broad-spectrum bactericidal drugs (e.g., ciprofloxacin) that inhibit gyrase/topoisomerase IV, blocking DNA replication.

Rifamycins

Drugs (rifampicin, rifabutin) that bind bacterial RNA polymerase and block DNA-dependent RNA synthesis.

70S Ribosome

Prokaryotic ribosome composed of 30S and 50S subunits; major target for protein-synthesis inhibitors.

Macrolides

50S binders (erythromycin, azithromycin) that block peptide-chain exit; usually bacteriostatic.

Aminoglycosides

30S binders (gentamicin) causing misreading of mRNA; bactericidal, concentration-dependent.

Chloramphenicol

Broad-spectrum drug that inhibits peptidyl transferase on 50S subunit.

Tetracyclines

30S binders that prevent tRNA attachment; broad spectrum, bacteriostatic.

Lincosamides

50S inhibitors (clindamycin) active against Gram-positives and anaerobes.

Trimethoprim

Inhibits dihydrofolate reductase in folate pathway; often combined with sulfamethoxazole.

Sulfonamides

PABA analogues that inhibit dihydropteroate synthase in folate synthesis.

Antimetabolite

Drug that blocks a metabolic pathway by mimicking a substrate (e.g., TMP-SMX on folate synthesis).

Antiviral Drug

Agent that inhibits viral replication processes inside host cells.

HAART

Highly Active Antiretroviral Therapy; combination of ≥3 drugs to reduce HIV viral load.

Reverse Transcriptase Inhibitors (RTIs)

NRTIs/NNRTIs that block HIV reverse transcriptase and prevent viral DNA synthesis.

Protease Inhibitors (PIs)

Antivirals that inhibit HIV protease, blocking virion maturation.

Fusion Inhibitors

Antivirals (e.g., enfuvirtide) that block fusion of HIV envelope with host cell membrane.

Antimicrobial Resistance (AMR)

Ability of microorganisms to withstand effects of antimicrobials that once killed or inhibited them.

Inherent (Intrinsic) Resistance

Natural insensitivity due to lack of target, outer-membrane barrier, or absent uptake system.

Acquired Resistance

Resistance gained via mutation or horizontal gene transfer of new genetic material.

Multi-resistance

Resistance to multiple unrelated antibiotic classes (e.g., Pseudomonas aeruginosa).

Cross-resistance

Resistance to all members of the same antibiotic class (e.g., β-lactams).

β-lactamase

Enzyme that hydrolyses β-lactam ring, inactivating β-lactam antibiotics.

Extended-Spectrum β-lactamase (ESBL)

β-lactamase variant that degrades penicillins and cephalosporins; plasmid-borne in Enterobacteriaceae.

Methicillin-Resistant Staphylococcus aureus (MRSA)

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

Vancomycin-Resistant Staphylococcus aureus (VRSA)

S. aureus with modified peptidoglycan (D-Ala→D-Lac) that reduces vancomycin binding.

Efflux Pump

Membrane protein that exports antibiotics out of bacterial cells, lowering intracellular drug concentration.

Alternative Antibiotic Target

Novel essential bacterial process identified for future drug development.

Teixobactin

New antibiotic in development that binds lipid II & III precursors, showing no detectable resistance so far.

Priority 1 Critical Pathogens

WHO list: carbapenem-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, ESBL-producing Enterobacteriaceae.

Stewardship (Responsible Prescribing)

Strategies promoting appropriate antimicrobial use to slow resistance development.

Folate Synthesis Inhibitors

Drug pair trimethoprim-sulfamethoxazole blocking sequential steps of folic acid pathway.

Polymyxin B

Cationic peptide antibiotic that binds LPS and disrupts Gram-negative membranes.

Colistin

Polymyxin E; last-resort drug for multidrug-resistant Gram-negative infections.

Vancomycin Mechanism

Binds D-Ala-D-Ala termini, blocking transglycosylation and transpeptidation in Gram-positive cell walls.

Carbapenems

Broad-spectrum β-lactams (e.g., meropenem) resistant to most β-lactamases.

Cephalosporins

β-lactam subclass with generations of expanding Gram-negative coverage.

Macrolide Mechanism

Reversibly binds 50S exit tunnel, preventing polypeptide elongation.

Aminoglycoside Mechanism

Irreversibly binds 30S, causing mRNA misreading and bactericidal effect.

Chloramphenicol Mechanism

Blocks peptidyl transferase activity on 50S subunit, inhibiting peptide bond formation.

Tetracycline Mechanism

Prevents aminoacyl-tRNA docking to 30S-mRNA complex.

Fluoroquinolone Mechanism

Traps gyrase/topoisomerase-DNA complexes, blocking supercoiling relaxation and DNA replication.

Protease Inhibitors Mechanism

Bind active site of viral protease, preventing cleavage of polyproteins required for assembly of mature virions.

Reverse Transcriptase Inhibitors Mechanism

Act as nucleotide analogues or allosteric blockers to halt conversion of viral RNA into DNA.