Antibacterial Antibiotics – Core Vocabulary

Vocabulary flashcards covering key terms, drug classes, mechanisms, and structural features from the Chapter 7 lecture on antibacterial antibiotics.

Beta-Lactam Antibiotics

Drug family with a four-membered β-lactam ring that blocks peptidoglycan cross-linking; includes penicillins, cephalosporins, carbapenems, and monobactams.

Glycopeptide Antibiotics

Large peptides (e.g., vancomycin) that inhibit cell-wall synthesis by binding the D-Ala-D-Ala terminus of peptidoglycan precursors.

Penicillin G

Natural narrow-spectrum penicillin given IV/IM; best activity against streptococci and other Gram-positive cocci.

Penicillin V

Oral formulation of natural penicillin; same spectrum as Pen G but acid stable for oral use.

Penicillinase-Resistant Penicillins

Oxacillin, nafcillin, dicloxacillin, etc.; bulky side chains protect the β-lactam from staphylococcal penicillinase.

Aminopenicillins

Ampicillin and amoxicillin; added polar groups broaden spectrum to some Gram-negatives (H. influenzae, Enterococcus).

Antipseudomonal Penicillins

Ticarcillin, piperacillin, etc.; extended-spectrum agents active against Pseudomonas and other Gram-negative rods.

β-Lactamase

Enzyme produced by bacteria that hydrolyzes the β-lactam ring, inactivating β-lactam antibiotics.

Peptidoglycan Synthesis

Multistep enzymatic process that builds the rigid bacterial cell wall; target of β-lactams, vancomycin, and bacitracin.

Cephalosporins

β-Lactam subgroup with a dihydrothiazine ring; classified into five generations with progressively broader Gram-negative activity.

Carbapenems

Imipenem, meropenem, ertapenem, doripenem; broadest β-lactam spectrum, resistant to most β-lactamases.

Monobactams

Aztreonam and analogues; monocyclic β-lactam active only against aerobic Gram-negative rods, including Pseudomonas.

6-Aminopenicillanic Acid (6-APA)

Core bicyclic nucleus (β-lactam + thiazolidine) common to all penicillins; site for side-chain modification.

First-Generation Cephalosporins

Agents such as cefazolin and cephalexin; active mainly against Gram-positive cocci ('FA/PHA' mnemonic).

Oxime Moiety

C=N-OH functional group on some cephalosporins that confers β-lactamase resistance.

Thiadiazole Ring

Heterocycle added to certain cephalosporins to enhance Gram-negative penetration and PBP affinity.

Imipenem + Cilastatin

Carbapenem combined with a renal dehydropeptidase inhibitor to prevent drug degradation in the kidney.

Aztreonam

Prototype monobactam; binds PBP-3 of Gram-negative aerobes, safe in penicillin-allergic patients.

Aminoglycosides

Polycationic antibiotics (e.g., gentamicin) that bind 30S ribosome, causing misreading and bactericidal protein synthesis inhibition.

Streptomycin

First aminoglycoside; used for tuberculosis and zoonotic infections; notable ototoxicity and nephrotoxicity.

Gentamicin

Widely used aminoglycoside from Micromonospora; strong activity versus Pseudomonas and Gram-negative enterics.

Amikacin

Semisynthetic kanamycin derivative with resistance to many aminoglycoside-inactivating enzymes; less ototoxic.

30S Ribosomal Subunit

Small bacterial ribosomal unit targeted by aminoglycosides and tetracyclines.

50S Ribosomal Subunit

Large bacterial ribosomal unit targeted by macrolides, lincosamides, chloramphenicol, oxazolidinones, and streptogramins.

Tetracyclines

Four-ring antibiotics that chelate metal ions and inhibit tRNA binding to 30S; broad spectrum and bacteriostatic.

Doxycycline

Long-acting tetracycline that does not accumulate in renal failure; preferred for uremic patients.

Minocycline

Most potent tetracycline; excellent activity against Gram-positive cocci, including some MRSA strains.

Tigecycline

First glycylcycline; IV agent that overcomes tetracycline resistance and is used for complicated skin and abdominal infections.

Macrolides

Lactone-ring antibiotics (erythromycin, azithromycin) that prevent 50S translocation; bacteriostatic.

Erythromycin

Prototype macrolide from Streptomyces erythraeus; alternative to penicillin for Gram-positive infections.

Azithromycin

15-membered 'azalide' macrolide with improved acid stability and long half-life allowing 5-day regimens.

Clarithromycin

6-O-methyl erythromycin; active against atypical pathogens and inhibits CYP450.

Ketolide

Macrolide analogue lacking cladinose, possessing a 3-keto group (e.g., telithromycin) to reduce MLSB resistance.

MLSB Resistance

Cross-resistance to macrolide, lincosamide, and streptogramin-B antibiotics mediated by 23S rRNA methylation.

Linezolid

Oxazolidinone that blocks initiation complex formation on 30S/70S; active against MRSA and VRE.

Quinupristin/Dalfopristin

Synergistic streptogramin combination (30:70) that binds 50S, bactericidal against staphylococci and streptococci.

Vancomycin

IV glycopeptide inhibiting cell-wall transglycosylation; used for MRSA, C. difficile (oral), and serious Gram-positive infections.

Teicoplanin

Long-acting glycopeptide similar to vancomycin but less nephrotoxic; once-daily IM/IV dosing.

Bacitracin

Topical polypeptide that blocks bactoprenol dephosphorylation, preventing peptidoglycan transport; zinc enhances action.

Polymyxin B

Cationic polypeptide that disrupts Gram-negative bacterial membranes; mainly topical due to nephrotoxicity.

Colistin

Polymyxin E; last-line parenteral agent for multidrug-resistant Gram-negative infections and refractory UTIs.

Daptomycin

Cyclic lipopeptide that depolarizes Gram-positive membranes; inactive in pneumonia due to surfactant binding.

Chloramphenicol

Broad-spectrum 50S inhibitor; risk of aplastic anemia; reserved for serious infections or rickettsial disease.

Sulfonamides

PABA analogues that block dihydropteroate synthase in folate synthesis; often combined with trimethoprim.

Fluoroquinolones

Ciprofloxacin, levofloxacin, etc.; inhibit DNA gyrase and topoisomerase IV, bactericidal against many bacteria.

Rifampin

Rifamycin that blocks DNA-dependent RNA polymerase; cornerstone of tuberculosis therapy; induces CYP450.

Fosfomycin

Broad-spectrum cell-wall inhibitor that blocks enolpyruvyl transferase; single-dose oral treatment of uncomplicated UTI.

Platensimycin

Novel lipid-synthesis inhibitor from Streptomyces platensis with potent activity against Gram-positive bacteria.

Glycylcyclines

Tetracycline derivatives (e.g., tigecycline) with glycylamido substitutions that evade efflux and ribosomal protection.

β-Lactamase Inhibitors

Clavulanate, tazobactam, sulbactam; suicide substrates that protect β-lactam antibiotics from enzymatic hydrolysis.

Penicillin-Binding Proteins (PBPs)

Bacterial transpeptidases/transglycosylases that catalyze cell-wall cross-linking and are inhibited by β-lactams.

Electron-Withdrawing Side Chain

Substituent on penicillins that lowers carbonyl electron density and improves acid stability for oral use.

Penicillin Carboxylic Acid

Essential free COOH on thiazolidine ring; conversion to ester/alcohol reduces antibacterial activity.

3-Keto Function (Ketolide)

C-3 carbonyl in telithromycin that lowers MLSB induction and improves ribosomal binding.

Extended-Spectrum β-Lactamase (ESBL)

Plasmid-encoded enzymes that hydrolyze third-generation cephalosporins and aztreonam but not carbapenems.

Aminoglycoside Ototoxicity

Irreversible damage to auditory and vestibular hair cells caused by high serum aminoglycoside levels.

Broad-Spectrum Antibiotic

Agent effective against a wide range of Gram-positive, Gram-negative, and atypical organisms.

Narrow-Spectrum Antibiotic

Drug active against a limited group of bacteria, minimizing disruption of normal flora.

Bactericidal

Describes antibiotics that kill bacteria outright (e.g., β-lactams, aminoglycosides).

Bacteriostatic

Describes antibiotics that inhibit bacterial growth, relying on host immunity for clearance (e.g., tetracyclines).