Comprehensive Anti-Infective Pharmacology: Antibacterials, Antifungals, Antimycobacterials, and Antivirals

Comprehensive vocabulary flashcards covering the biological, chemical, pharmacological, and clinical principles of antimicrobial agents across antibacterials, antimycobacterials, antifungals, and antivirals.

Anti-Infective Agents

Drugs used to treat infections caused by pathogenic microorganisms including bacteria, viruses, fungi, and parasites.

Emerging Disease

A newly appearing or newly spreading infectious disease in a population.

Re-Emerging Disease

A previously known infectious disease that increases in incidence or geographic range after a period of decline.

Infectious Disease

An illness caused by a specific pathogen or its toxic product, transmitted from an infected person, an animal, or a contaminated inanimate object to a susceptible host.

Germ Theory

The scientific principle advanced by Louis Pasteur and Robert Koch stating that specific microscopic organisms are the direct cause of infectious diseases.

Chain of Infection

The epidemiological model of transmission consisting of four required links: a pathogen, a reservoir, a method of transmission, and a susceptible host.

Infectivity

The capacity of an infectious agent to invade and establish an infection in a host.

Pathogenicity

The inherent ability of an infectious agent to cause disease in a susceptible host.

Virulence

The quantitative measure of the severity of disease caused by an infectious pathogen.

Normal Flora

The community of approximately $50\text{ trillion}$ non-pathogenic bacteria, viruses, and fungi that normally colonize the mucosal and cutaneous surfaces of a healthy human body.

Asymptomatic Carrier

An infected individual who harbors and transmits an infectious pathogen without exhibiting clinical signs or symptoms of the disease.

Empiric Therapy

The initial administration of antimicrobial treatment based on clinical experience and presumptive diagnosis before specific microbiological pathogens and susceptibilities are confirmed.

Definitive Therapy

Targeted antimicrobial therapy chosen after microbiological identification of the causative organism and its specific antibiotic susceptibility profile.

Bacteriostatic

The property of an antimicrobial drug that arrests bacterial replication without directly killing cells, requiring an active host immune response to clear the infection.

Bactericidal

The property of an antimicrobial drug that actively kills bacteria, defined in vitro by a minimum bactericidal concentration to minimum inhibitory concentration ratio of $\frac{\text{MBC}}{\text{MIC}} \le 4$.

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial agent that inhibits visible bacterial growth after $24\,\text{hours}$ of incubation under standardized conditions.

Minimum Bactericidal Concentration (MBC)

The lowest concentration of an antimicrobial agent that produces a $1000\text{-fold}$ ($99.9\%$) reduction in viable bacterial density after $24\,\text{hours}$.

Time-Dependent Killing

A pattern of antimicrobial activity where clinical efficacy depends on the cumulative duration of time that drug concentrations remain above the minimum inhibitory concentration ($T > \text{MIC}$).

Concentration-Dependent Killing

A pattern of antimicrobial activity where bacterial killing increases in proportion to peak drug concentrations, indexed primarily by the $\frac{C_{\max}}{\text{MIC}}$ ratio.

Post-Antibiotic Effect (PAE)

The prolonged suppression of bacterial growth that persists after drug concentrations drop below the minimum inhibitory concentration.

Kirby-Bauer Disk Diffusion Assay

A standardized microbiological susceptibility test in which antibiotic-impregnated paper disks are placed on an agar plate inoculated with a bacterial lawn to evaluate susceptibility based on the diameter of the zone of inhibition.

Zone of Inhibition

The clear circular halo around an antibiotic disc on an agar plate where bacterial growth is completely prevented, inversely related to the minimum inhibitory concentration.

Gram Staining

A differential laboratory staining procedure that classifies bacteria into Gram-positive (purple) or Gram-negative (pink) based on peptidoglycan thickness and presence of an outer membrane.

Peptidoglycan

A mesh-like cross-linked polymer composed of repeating alternating units of $N$-acetylglucosamine (NAG) and $N$-acetylmuramic acid (NAM) that provides structural integrity to the bacterial cell wall.

Penicillin-Binding Proteins (PBPs)

Bacterial enzymes embedded in the cytoplasmic membrane that catalyze the elongation, cross-linking, and remodeling of peptidoglycan during bacterial cell wall synthesis.

Transpeptidase

A specific penicillin-binding protein that forms peptide cross-links between adjacent glycan chains by cleaving terminal D-Ala-D-Ala residues, conferring mechanical rigidity to the cell wall.

Fosfomycin

A bactericidal phosphonic acid antibiotic that enters bacteria via nutrient transporters and acts as a suicide inhibitor by forming an irreversible covalent bond with Cys115 in the active site of MurA.

MurA (Pyruvyl Transferase)

The cytoplasmic bacterial enzyme that catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to UDP-NAG during the initial stage of peptidoglycan precursor synthesis.

$\beta$-Lactam Ring

A strained four-membered cyclic amide ring that structurally mimics the D-Ala-D-Ala dipeptide substrate of bacterial transpeptidases.

Suicide Inhibitor

A substrate analog that undergoes normal catalytic conversion by an enzyme to form a reactive intermediate that irreversibly and covalently inactivates the enzyme.

Autolysins

Bacterial endopeptidases and muramidases that normally cleave cell wall bonds to permit cell expansion and division, leading to osmotic lysis when peptidoglycan synthesis is blocked by $\beta$-lactams.

Penicillin G

A natural benzylpenicillin administered intravenously due to degradation by gastric hydrochloric acid, indicated for endocarditis, meningitis, syphilis, and clostridial infections.

Penicillin V

A natural phenoxymethylpenicillin containing an ether oxygen side chain that imparts acid stability, enabling oral administration for mild streptococcal pharyngitis and dental infections.

Cephalosporins

A major class of $\beta$-lactam antibiotics discovered from Cephalosporium acremonium composed of a $\beta$-lactam ring fused to a six-membered dihydrothiazine ring.

7-Aminocephalosporanic Acid (7-ACA)

The semisynthetic bicyclic core structure derived from cephalosporin C that contains R1 and R2 substitution positions that determine antibacterial spectrum and pharmacokinetic parameters.

Methylthiotetrazole (MTT) Group

A sulfur-containing heterocyclic side chain found on certain cephalosporins (e.g., cefamandole, cefotetan) associated with hypoprothrombinemia, bleeding risk, and disulfiram-like ethanol intolerance.

Ceftaroline

A fifth-generation cephalosporin featuring a 1,3-thiazole ring conferring binding affinity to altered PBP2a in MRSA, alongside an oxime group for $\beta$-lactamase resistance and a phosphono prodrug moiety.

Drug-Induced Immune Hemolytic Anemia (DIIHA)

An immune-mediated adverse reaction where an antibiotic binds to red blood cell surface antigens, provoking Coombs-positive IgG autoantibodies and subsequent hemolysis.

Carbapenems

Broad-spectrum $\beta$-lactam antibiotics characterized by the replacement of sulfur with carbon at position 1 and the incorporation of an endocyclic double bond in the five-membered ring.

Cilastatin

A reversible inhibitor of renal brush-border dehydropeptidase I (DHP-I) co-formulated with imipenem to prevent renal metabolic degradation and avert the formation of nephrotoxic metabolites.

Aztreonam

A synthetic monocyclic monobactam antibiotic resistant to many $\beta$-lactamases that selectively binds PBP3 of aerobic Gram-negative bacilli with negligible allergic cross-reactivity in penicillin-allergic patients.

$\beta$-Lactamase

A bacterial enzyme that hydrolytically cleaves the amide bond of the four-membered $\beta$-lactam ring, eliminating the antibiotic's capacity to inhibit transpeptidases.

Metallo-$\beta$-Lactamases (Class B MBLs)

A class of $\beta$-lactamases that use one or two catalytically essential $\text{Zn}^{2+}$ ions to activate water for nucleophilic attack on the $\beta$-lactam carbonyl, hydrolyzing carbapenems but sparing aztreonam.

New Delhi Metallo-$\beta$-Lactamase 1 (NDM-1)

A plasmid-borne Class B metallo-$\beta$-lactamase requiring zinc that hydrolyzes penicillins, cephalosporins, and carbapenems, conferring widespread multidrug resistance.

$\beta$-Lactamase Inhibitors (BLIs)

Molecules such as clavulanic acid, sulbactam, and tazobactam that act as suicide substrates to irreversibly inactivate bacterial serine $\beta$-lactamases and restore the potency of co-administered $\beta$-lactams.

Bacitracin

A topical macrocyclic peptide antibiotic derived from Bacillus licheniformis that complexes with divalent metal ions to inhibit undecaprenyl pyrophosphate ($\text{C}_{55}\text{-P-P}$) dephosphorylation, halting lipid carrier recycling.

Vancomycin

A glycopeptide antibiotic that binds specifically to the terminal D-Ala-D-Ala sequence of peptidoglycan precursors via five hydrogen bonds, blocking transglycosylase and transpeptidase access in Gram-positive bacteria.

Red-Man Syndrome

An infusion-related pseudoallergic reaction caused by histamine release following rapid intravenous administration of vancomycin, characterized by flushing, tingling, and an erythematous rash on the face and neck.

Vancomycin-Resistant Enterococci (VRE)

Strains of Enterococcus that evade vancomycin by replacing the terminal D-Ala-D-Ala cell wall precursor with D-Ala-D-Lactate or D-Ala-D-Serine, removing an essential hydrogen bond and causing electrostatic repulsion.

MIC Creep

The progressive, gradual increase in baseline minimum inhibitory concentrations of an antibiotic over time within the clinically designated susceptible range, leading to a narrowed therapeutic window.

Daptomycin

A cyclic lipopeptide antibiotic that complexes with $\text{Ca}^{2+}$ to insert its hydrophobic lipid tail into Gram-positive cytoplasmic membranes, causing rapid membrane depolarization and potassium efflux without lysis.

Polymyxins (Colistin)

Cationic amphiphilic polypeptide antibiotics whose diaminobutyric acid residues displace $\text{Ca}^{2+}$ and $\text{Mg}^{2+}$ from lipid A of Gram-negative outer-membrane lipopolysaccharide, disrupting outer and inner membrane permeability.

Sulfonamides

Bacteriostatic synthetic structural analogs of para-aminobenzoic acid (PABA) that competitively inhibit dihydropteroate synthase in the bacterial de novo folate synthesis pathway.

Dihydropteroate Synthase (DHPS)

A bacterial-specific enzyme absent in mammalian cells that condenses dihydropteridine pyrophosphate with para-aminobenzoic acid (PABA) to synthesize dihydropteroic acid.

Trimethoprim (TMP)

A synthetic pyrimidine analog that competitively inhibits bacterial dihydrofolate reductase (DHFR), preventing the reduction of dihydrofolic acid to active tetrahydrofolic acid (THF).

Co-Trimoxazole (TMP-SMX)

A fixed-dose antimicrobial combination formulated in a $1:5$ dose ratio ($1:20$ plasma concentration ratio) that exerts synergistic bactericidal activity through sequential enzymatic inhibition of bacterial folate biosynthesis.

Crystalluria

The precipitation of insoluble drug crystals within the renal collecting ducts and urinary tract, an adverse effect of sulfonamides mitigated by hydration and urine alkalinization.

Kernicterus

Bilirubin-induced brain damage in neonates caused by sulfonamides competitively displacing unconjugated bilirubin from plasma albumin-binding sites.

DNA Gyrase

A bacterial type II topoisomerase ($\text{GyrA}_2\text{GyrB}_2$ heterotetramer) that hydrolyzes ATP to introduce negative supercoils into DNA, relieving topological strain ahead of advancing replication forks.

Topoisomerase IV

A bacterial type II topoisomerase ($\text{ParC}_2\text{ParE}_2$ or $\text{GrlA}_2\text{GrlB}_2$) that resolves linked DNA molecules through decatenation, allowing newly replicated daughter chromosomes to segregate.

Decatenation

The enzymatic cleavage, passage, and religation process by which intertwined circular double-stranded DNA duplexes are physically separated after replication.

Fluoroquinolones

Synthetic bactericidal antibiotics containing a C6 fluorine substituent that stabilize cleavable DNA-enzyme complexes with DNA gyrase and topoisomerase IV, causing permanent double-stranded DNA breaks.

Gepotidacin (Blujepa)

A first-in-class novel bacterial topoisomerase inhibitor (NBTI) belonging to the triazaacenaphthylene class that interacts with non-overlapping sub-sites on GyrA and ParC without fluoroquinolone cross-resistance.

Nitrofurantoin

A synthetic urinary antiseptic reduced by bacterial flavoenzymes into electrophilic reactive intermediates that nonspecifically damage bacterial ribosomal proteins, DNA, and metabolic enzymes.

Metronidazole

A synthetic nitroimidazole prodrug that is selectively reduced by pyruvate:ferredoxin oxidoreductase (POR) and ferredoxin in anaerobic organisms to form reactive nitro radicals that induce DNA strand breakage.

Disulfiram-Like Reaction

An unpleasant adverse reaction characterized by nausea, vomiting, flushing, and diaphoresis resulting from drug-mediated inhibition of aldehyde dehydrogenase and acetaldehyde accumulation following ethanol consumption.

70S Bacterial Ribosome

The prokaryotic translation complex composed of a small 30S subunit ($16\text{S rRNA}$ and 21 proteins) and a large 50S subunit ($23\text{S}$ and $5\text{S rRNA}$ with 33 proteins).

A-Site (Aminoacyl Site)

The ribosomal cavity that binds an incoming aminoacyl-tRNA carrying an amino acid specified by the corresponding codon on the mRNA transcript.

P-Site (Peptidyl Site)

The ribosomal compartment that retains the tRNA attached to the growing nascent polypeptide chain.

E-Site (Exit Site)

The ribosomal chamber that temporarily binds and releases deacylated tRNA molecules following translocation.

Tetracyclines

Broad-spectrum bacteriostatic antibiotics containing a four-ring naphthacene carboxamide nucleus that reversibly bind $16\text{S rRNA}$ on the 30S ribosomal subunit, sterically blocking aminoacyl-tRNA attachment to the A-site.

Chelation (Tetracyclines)

The chemical formation of insoluble coordination complexes between tetracycline molecules and polyvalent metal ions ($\text{Ca}^{2+}$, $\text{Mg}^{2+}$, $\text{Al}^{3+}$, $\text{Fe}^{2+}$), severely reducing oral drug bioavailability.

Tigecycline

A broad-spectrum glycylcycline antibiotic bearing an $N$-alkylglycylamido modification at position C9 that overcomes tetracycline-specific efflux pumps and ribosomal protection mechanisms.

Aminoglycosides

Bactericidal polycationic antibiotics composed of amino sugars connected by glycosidic bonds that irreversibly bind $16\text{S rRNA}$ on the 30S ribosomal subunit, causing codon misreading and translational arrest.

Translational Misreading

The aminoglycoside-induced structural perturbation of the decoding region of $16\text{S rRNA}$ that promotes insertion of non-cognate amino acids into growing peptides, producing toxic mistranslated proteins.

Aminoglycoside Ototoxicity

Irreversible damage to cochlear auditory hair cells or reversible vestibular injury caused by drug accumulation in endolymph and generation of reactive oxygen species.

Chloramphenicol

A lipid-soluble bacteriostatic antibiotic that reversibly binds the peptidyl transferase center of $23\text{S rRNA}$ on the 50S subunit, inhibiting peptide bond formation during elongation.

Gray Baby Syndrome

A dangerous neonatal drug toxicity syndrome featuring abdominal distension, cyanosis, and vasomotor collapse caused by deficient hepatic UDP-glucuronyltransferase and chloramphenicol accumulation.

Macrolides

Bacteriostatic antibiotics characterized by a 14-, 15-, or 16-membered macrocyclic lactone ring that bind the 50S ribosomal subunit to obstruct the nascent peptide exit tunnel.

Nascent Peptide Exit Tunnel (NPET)

The structural conduit within the 50S ribosomal subunit through which elongating peptide chains transit to emerge into the cytoplasm, targeted and occluded by macrolide antibiotics.

Fidaxomicin

A narrow-spectrum, non-systemic macrocyclic antibiotic that inhibits bacterial RNA polymerase transcription, used exclusively as a bactericidal therapy for Clostridioides difficile enterocolitis.

Clindamycin

A lincosamide antibiotic that binds $23\text{S rRNA}$ on the 50S ribosomal subunit to inhibit peptidyl transferase and peptide chain elongation in anaerobic and Gram-positive infections.

Linezolid

A synthetic oxazolidinone antibiotic that binds the peptidyl transferase center on the 50S subunit to prevent formation of the functional 70S initiation complex, active against MRSA and VRE.

Acid-Fast Bacilli (AFB)

Bacteria of the genus Mycobacterium that retain basic arylmethane dyes despite acid-alcohol decolorization due to the high concentration of waxy mycolic acids in their cell wall.

Isoniazid (INH)

A frontline antitubercular prodrug activated by mycobacterial KatG into a nicotinoyl-NAD adduct that inhibits InhA and KasA, arresting mycolic acid biosynthesis.

KatG (Catalase-Peroxidase)

The endogenous mycobacterial enzyme required to oxidatively activate the prodrug isoniazid into its bactericidal nicotinoyl-NAD complex.

Rifampin

A bactericidal rifamycin antibiotic that binds the $\beta$-subunit of mycobacterial DNA-dependent RNA polymerase, sterically blocking RNA chain elongation after $2\text{ to }3\,\text{nucleotides}$.

Ethambutol

A synthetic bacteriostatic antitubercular agent that inhibits arabinosyl transferase III, blocking the synthesis of the arabinogalactan layer of the mycobacterial cell wall.

Pyrazinamide

A frontline antitubercular prodrug converted by mycobacterial pyrazinamidase into pyrazinoic acid, which accumulates in acidic phagolysosomes to disrupt bacterial membrane potentials and transport.

Bedaquiline

A diarylquinoline antibiotic used in multidrug-resistant tuberculosis (MDR-TB) that selectively inhibits the proton pump of mycobacterial ATP synthase, depleting energy reserves.

RIPE Regimen

The standard four-drug initial treatment protocol for drug-susceptible active tuberculosis consisting of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol, co-prescribed with pyridoxine (vitamin B6).

Ergosterol

The principal sterol found in fungal cell membranes that regulates membrane fluidity and integrity, serving as the biochemical target for polyenes, allylamines, and azoles.

Dimorphic Fungi

Fungi such as Histoplasma capsulatum that alternate between an environmental hyphal or mould form at room temperature and a parasitic unicellular yeast form at host body temperature.

Amphotericin B

A polyene macrolide antifungal that selectively binds fungal ergosterol to form transmembrane channels that leak intracellular ions ($\text{K}^+$, $\text{Mg}^{2+}$), causing fungal cell death.

Shake and Bake Phenomenon

An acute infusion-related reaction to amphotericin B characterized by rigors, severe shaking chills, and high fever within $1\text{ to }3\,\text{hours}$, mediated by prostaglandin release and complement activation.

AmBisome

A liposomal pharmaceutical formulation of amphotericin B enclosed within unilamellar lipid bilayers, designed to reduce drug distribution to renal tubules and minimize nephrotoxicity.

Terbinafine

An allylamine antifungal that inhibits squalene epoxidase, accumulating toxic squalene intermediates and depleting downstream ergosterol synthesis in dermatophyte nail infections.

Azole Antifungals

Antifungals (imidazoles and triazoles) that bind the heme iron of lanosterol $14\alpha$-demethylase (CYP51/ERG11), halting ergosterol synthesis and generating toxic methylated sterols.

Fluconazole

A water-soluble bistriazole antifungal with high oral bioavailability ($>90\%$) and excellent cerebrospinal fluid penetration, indicated for oropharyngeal, esophageal, and cryptococcal candidiasis.

Voriconazole

A broad-spectrum second-generation triazole that exhibits nonlinear pharmacokinetics, indicated as first-line therapy for invasive aspergillosis but associated with transient visual photopsia and hallucinations.