29 - Antibacterial chemotherapy

Vocabulary flashcards covering key concepts from the antibacterial chemotherapy lecture notes.

Antibacterial chemotherapy

Chemicals or substances produced by microorganisms to kill or prevent growth of other microorganisms.

Selective toxicity

Exploitable differences between the organism and host that allow selective killing of microbes.

Gram staining

A technique classifying bacteria into Gram-positive and Gram-negative based on cell wall properties.

Gram-positive cocci

Spherical bacteria that stain purple with Gram staining due to a thick peptidoglycan layer.

Gram-negative bacteria

Bacteria with an outer membrane containing lipopolysaccharide and a thinner peptidoglycan layer.

Peptidoglycan

Polymer in bacterial cell walls; a key target for many antibiotics.

Lipopolysaccharide (LPS)

A component of the outer membrane of Gram-negative bacteria; contributes to endotoxin activity.

Broad spectrum

Antibiotics active against a wide range of bacteria.

Narrow spectrum

Antibiotics active against a limited subset of bacteria.

Folate metabolism (bacteria)

Bacteria synthesize folate de novo; humans cannot, enabling selective inhibition.

PABA

Para-aminobenzoic acid; substrate in bacterial folate synthesis.

Dihydrofolate synthase

Enzyme in folate synthesis inhibited by sulphonamides.

Dihydrofolate reductase

Enzyme converting dihydrofolate to tetrahydrofolate; inhibited by trimethoprim.

Tetrahydrofolate

Active folate cofactor required for DNA synthesis.

Sulphonamides

PABA analogs that competitively inhibit dihydropteroate synthase; bacteriostatic.

Trimethoprim

Inhibits dihydrofolate reductase; often used with sulphonamides for synergy.

Folate antagonism

Excess PABA can antagonize sulphonamides; resistance can arise via plasmids.

Beta-lactamases

Enzymes that hydrolyze beta-lactam rings, causing penicillin resistance.

Clavulanic acid

Beta-lactamase inhibitor often combined with penicillins to prevent degradation.

Penicillin-binding proteins (PBPs)

Bacterial enzymes targeted by penicillins to inhibit cell wall synthesis.

MRSA

Methicillin-resistant Staphylococcus aureus; resistant to many beta-lactam antibiotics.

Permeability and efflux

Decreased drug entry and/or active pumping out of drug as resistance mechanisms.

Aminoglycosides

Inhibit initiation complex and cause misreading of mRNA; mainly against Gram-negative and some Gram-positive; not well absorbed orally; risk of ototoxicity.

Tetracyclines

Bind 30S ribosomal subunit; block tRNA entry; broad spectrum; adverse effects include dental staining and bone effects.

Macrolides (erythromycin)

Inhibit 50S ribosomal subunit, blocking translocation; alternative to penicillins in penicillin-sensitive patients.

Clindamycin

Inhibits 50S ribosomal subunit; broad spectrum; associated with pseudomembranous colitis (C. difficile).

Rifampicin

Inhibits bacterial RNA polymerase; used for TB; rapid resistance if used alone.

Quinolones

Inhibit DNA gyrase/topoisomerase IV; effective against Gram-negative infections.

Metronidazole

Active against anaerobes and protozoa; cytotoxic metabolites; can cause disulfiram-like reaction with alcohol.

Penicillins

Beta-lactam antibiotics that inhibit bacterial cell wall synthesis; include narrow and broad spectrum forms; susceptible to beta-lactamases.

Cephalosporins

Beta-lactam antibiotics inhibiting cell wall synthesis; generally more beta-lactamase resistant than penicillins.

Vancomycin

Glycopeptide that inhibits cell wall synthesis; used for serious Gram-positive infections.

Bacitracin

Inhibits dephosphorylation of bactoprenol; topical agent; bactericidal.

Antibiotic resistance mechanisms

Altered targets, decreased drug access, drug inactivation, and efflux; often plasmid- or chromosome-encoded.

Conjugation

Plasmid transfer between bacteria as a mechanism for spreading resistance.

Transduction

Bacteriophage-mediated transfer of resistance genes.

Transformation

Uptake of free DNA from the environment spreading resistance.

Prudent antibiotic use

Targeted therapy with correct dosage and duration to minimize resistance and adverse effects.

Combination therapy

Using two or more antibiotics to achieve additive or synergistic effects, or prevent resistance.

Additive vs synergistic vs antagonistic

Additive: effects sum; synergistic: greater than sum; antagonistic: reduced effectiveness.

Disulfiram-like reaction with alcohol

Metronidazole can cause a disulfiram-like reaction when taken with alcohol.

Penicillin resistance mechanisms

Beta-lactamase production and altered PBPs contribute to resistance in bacteria like Staphylococcus and Neisseria.