Chapter 20 – Antimicrobial Drugs (Microbiology: An Introduction)

Vocabulary flashcards covering key antimicrobial drug terms, mechanisms, drug classes, resistance strategies, and representative antibiotics from Chapter 20 of Microbiology: An Introduction.

Selective toxicity

The ability of a drug to destroy or inhibit pathogens without damaging the host.

Chemotherapy (microbiology)

The use of chemical agents to treat disease, especially infections.

Antibiotic

A substance produced by a microbe that, in small amounts, inhibits another microorganism.

Antimicrobial drug

Any synthetic or natural substance that interferes with the growth of microorganisms.

Narrow-spectrum antibiotic

A drug effective against a limited range of microbial types.

Broad-spectrum antibiotic

A drug effective against a wide range of gram-positive or gram-negative bacteria.

Superinfection

Overgrowth of normal microbiota that are resistant to antibiotics after treatment suppresses competitors.

Bactericidal

An antimicrobial agent that kills microbes outright.

Bacteriostatic

An antimicrobial agent that inhibits microbial growth without killing the organisms.

Inhibition of cell wall synthesis

Antimicrobial mode of action employed by penicillins, cephalosporins, bacitracin, and vancomycin.

Inhibition of protein synthesis

Antimicrobial mode targeting 70S ribosomes; exemplified by chloramphenicol, erythromycin, tetracyclines, and streptomycin.

Inhibition of nucleic acid replication and transcription

Mode of action of drugs such as quinolones and rifampin.

Plasma-membrane injury

Antimicrobial mechanism that disrupts membrane integrity; seen with polymyxin B and some antifungals.

Inhibition of essential metabolite synthesis

Competitive inhibition of key metabolic pathways; sulfanilamide and trimethoprim are classic examples.

Penicillin G

Natural penicillin administered by injection; narrow spectrum and penicillinase sensitive.

Penicillin V

Natural penicillin taken orally; narrow spectrum and penicillinase sensitive.

Penicillinase (β-lactamase)

Bacterial enzyme that inactivates penicillin by breaking its β-lactam ring.

Isoniazid (INH)

Antimycobacterial drug that inhibits mycolic-acid synthesis in Mycobacterium species.

Ethambutol

Antimycobacterial drug that blocks incorporation of mycolic acid into the cell wall.

Bacitracin

Polypeptide antibiotic from Bacillus subtilis that inhibits cell wall synthesis; used topically.

Polymyxin B

Polypeptide antibiotic from Paenibacillus polymyxa that disrupts bacterial plasma membranes; topical, effective against gram-negatives.

Polymyxin E (Colistin)

A polymyxin that damages gram-negative membranes; used for multidrug-resistant infections.

Daptomycin

Lipopeptide antibiotic that attacks bacterial cell membranes of gram-positive organisms.

Chloramphenicol

Broad-spectrum antibiotic from Streptomyces venezuelae that inhibits protein synthesis by binding the 50S ribosomal subunit.

Tetracycline

Broad-spectrum antibiotic (e.g., chlortetracycline) that inhibits protein synthesis by blocking tRNA attachment to the 30S subunit.

Erythromycin

Macrolide antibiotic from Saccharopolyspora erythraea that inhibits protein synthesis; alternative to penicillin.

Streptomycin

Aminoglycoside antibiotic from Streptomyces griseus that interferes with protein synthesis at the 30S subunit.

Gentamicin

Aminoglycoside from Micromonospora purpurea used against gram-negative infections; inhibits protein synthesis.

Neomycin

Topical aminoglycoside from Streptomyces fradiae that inhibits protein synthesis.

Amphotericin B

Polyene antifungal from Streptomyces nodosus that binds ergosterol and disrupts fungal cell membranes.

Cephalothin

First-generation cephalosporin from Cephalosporium species; inhibits bacterial cell wall synthesis.

Griseofulvin

Antifungal from Penicillium griseofulvum that interferes with microtubule function; treats dermatophyte infections.

Nitrofurantoin

Synthetic drug converted inside cells to intermediates that damage bacterial ribosomal proteins; used for UTIs.

Rifampin

Rifamycin antibiotic that inhibits bacterial RNA polymerase and mRNA synthesis; induces hepatic enzymes.

Nalidixic acid

Synthetic quinolone that inhibits DNA gyrase, blocking DNA replication.

Fluoroquinolone

Class of quinolone derivatives (e.g., ciprofloxacin) that inhibit DNA gyrase and topoisomerase IV.

Sulfanilamide

Sulfonamide that competes with PABA, blocking folic-acid synthesis in bacteria.

Trimethoprim

Antimetabolite that inhibits conversion of dihydrofolic acid to tetrahydrofolic acid; combined with sulfamethoxazole for synergy.

Drug synergism

Enhanced antimicrobial effect when two drugs are used together, e.g., TMP-SMZ combination.

Polyene

Class of antifungal drugs (e.g., amphotericin B) that bind membrane sterols, causing leakage.

Azole

Antifungal class that inhibits ergosterol synthesis; includes imidazoles (topical) and triazoles (systemic).

Echinocandin

Antifungal class that inhibits β-glucan synthesis in fungal cell walls.

Acyclovir

Guanine nucleoside analog antiviral that, after phosphorylation in infected cells, blocks viral DNA polymerase.

Quinine

Antiprotozoan drug historically used to treat malaria by interfering with Plasmodium heme detoxification.

Chloroquine

Synthetic antimalarial that inhibits heme polymerase in Plasmodium species.

Metronidazole

Antiprotozoan/antibacterial drug effective against anaerobes; causes DNA damage when reduced inside cells.

Persister cell

Microbe with genetic traits that allow survival after antibiotic exposure without acquiring resistance genes.

Superbug

Bacterium resistant to multiple or nearly all available antibiotics.

Efflux pump

Bacterial mechanism that rapidly expels antibiotics, contributing to multidrug resistance.

Enzymatic drug inactivation

Resistance mechanism in which bacterial enzymes destroy or modify an antibiotic (e.g., β-lactamase).

Altered target site

Resistance mechanism where the drug’s binding site in the microbe mutates, reducing drug affinity.

Prevention of drug penetration

Resistance strategy whereby microbes restrict antibiotic entry, often via changes in porin proteins.