Medical Microbiology Antimicrobial Drugs

Vocabulary flashcards covering antimicrobial drugs, classifications, sources, mechanisms of action, and enzymatic targets based on the Medical Microbiology lecture notes.

Amoxicillin

A semi-synthetic penicillin antibiotic derived from a natural 6-aminopenicillanic acid (6-APA) core produced by Penicillium chrysogenum and a modified D-(-)-4-Hydroxyphenylglycine side chain.

Amoxicillin Mechanism of Action

Binds to penicillin-binding proteins (PBPs) in bacteria and blocks transpeptidation, preventing proper peptidoglycan cell-wall formation and causing cell lysis.

Amoxicillin Structural Features

A structural diagram displaying the para-hydroxy phenylglycine side chain and the four-membered cyclic amide $\beta$-lactam ring required for its antimicrobial activity.

Azidothymidine (AZT)

A synthetic Nucleoside Reverse Transcriptase Inhibitor (NRTI), also known as Zidovudine (ZDV), used to treat HIV-1 and HIV-2 retroviruses.

Azidothymidine Mechanism of Action

Converted inside host cells to AZT-triphosphate, which is incorporated into viral DNA by HIV reverse transcriptase; lacking a $\text{3'-OH}$ group due to substitution with an azido ($\text{-N}_3$) group, it terminates DNA chain elongation.

Azithromycin

A semi-synthetic macrolide antibiotic belonging to the azalide group (chemical formula $\text{C}_{38}\text{H}_{72}\text{N}_2\text{O}_{12}$) chemically modified from erythromycin, produced by Saccharopolyspora erythraea.

Azithromycin Mechanism of Action

Selectively attaches to the 50S subunit of the bacterial ribosome, blocking peptide chain formation and preventing bacterial growth.

Bacitracin

A cyclic polypeptide antibiotic naturally produced by Bacillus subtilis (Tracy strain / licheniformis group), used primarily as a topical antibacterial.

Bacitracin Mechanism of Action

Binds to C55-isoprenyl pyrophosphate (bactoprenol pyrophosphate), preventing dephosphorylation and regeneration of the lipid carrier that transports peptidoglycan precursors across the bacterial membrane.

Bactrim (TMP-SMX)

A synthetic antifolate combination drug composed of Sulfamethoxazole (SMX) and Trimethoprim (TMP).

Bactrim Mechanism of Action

Executes a sequential blockade of bacterial folate synthesis by inhibiting dihydrofolic acid formation and the enzyme dihydrofolate reductase, preventing conversion to tetrahydrofolate.

Cephalexin

A semi-synthetic first-generation cephalosporin antibiotic in the $\beta$-lactam family (chemical formula $\text{C}_{16}\text{H}_{17}\text{N}_3\text{O}_4\text{S}$), derived from cephalosporin C produced by Acremonium.

Cephalexin Mechanism of Action

Binds to penicillin-binding proteins (PBPs) to block peptidoglycan cross-linking in the bacterial cell wall, weakening the structure and leading to cell lysis.

Ciprofloxacin

A synthetic broad-spectrum fluoroquinolone antibacterial drug active against many Gram-negative and Gram-positive bacteria.

Ciprofloxacin Mechanism of Action

Inhibits bacterial DNA gyrase (topoisomerase II) and topoisomerase IV by trapping enzyme-DNA complexes, inducing lethal double-stranded chromosome breaks.

Clindamycin

A semi-synthetic lincosamide antibiotic derived from lincomycin (isolated from Streptomyces lincolnensis), targeting anaerobic and Gram-positive bacteria.

Clindamycin Mechanism of Action

Inhibits bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome, preventing translation.

Doxycycline

A broad-spectrum semi-synthetic tetracycline antibiotic synthetically derived from oxytetracycline (produced by Streptomyces rimosus).

Doxycycline Mechanism of Action

Reversibly binds to the 30S bacterial ribosomal subunit, blocking aminoacyl-tRNA from entering the ribosomal A-site and exerting a bacteriostatic effect.

Gentamicin

An aminoglycoside antibiotic naturally produced by the soil bacterium Micromonospora purpurea.

Gentamicin Mechanism of Action

Binds to the 30S subunit of the bacterial ribosome, causing mistranslation/misreading of mRNA and producing nonfunctional proteins that disrupt the cell membrane.

Isoniazid

A synthetic antimycobacterial agent (isonicotinic acid hydrazide) used to treat active or latent tuberculosis caused by Mycobacterium tuberculosis.

Isoniazid Mechanism of Action

Activated by the bacterial enzyme KatG inside M. tuberculosis to form an adduct with NAD that inhibits InhA, blocking the synthesis of essential mycolic acids for the cell wall.

Ivermectin

A semi-synthetic broad-spectrum antiparasitic avermectin ($22,23\text{-dihydroavermectin B}_{1}$) sourced from Streptomyces avermitilis fermentation products.

Ivermectin Mechanism of Action

Binds selectively to glutamate-gated chloride channels in invertebrate nerve and muscle cells, causing increased chloride ion permeability, hyperpolarization, paralysis, and death.

Metronidazole

A synthetic nitroimidazole antimicrobial prodrug active against anaerobic bacteria and specific protozoa.

Metronidazole Mechanism of Action

Activated by microbial reduction pathways in anaerobic organisms to form toxic free radicals that break DNA strands and inhibit DNA synthesis.

Micafungin

A semi-synthetic echinocandin antifungal agent (formula $\text{C}_{56}\text{H}_{71}\text{N}_9\text{NaO}_{23}\text{S}$) derived from a natural peptide produced by Coleophoma empetri.

Micafungin Mechanism of Action

Non-competitively inhibits $1,3\text{-}\beta\text{-D-glucan}$ synthase, disrupting fungal cell wall structural integrity and inducing osmotic lysis in Candida species.

Miconazole

A synthetic imidazole class antifungal drug used to treat fungal skin and mucosal infections.

Miconazole Mechanism of Action

Inhibits fungal cytochrome P450 $14\times\text{-demethylase}$, stopping ergosterol synthesis and disrupting fungal cell membrane structure and function.

Mupirocin

A natural topical antibiotic (pseudomonic acid A) isolated from the fermentation of Pseudomonas fluorescens.

Mupirocin Mechanism of Action

Reversibly binds to bacterial isoleucyl-tRNA synthetase, preventing isoleucine attachment to tRNA and halting protein synthesis.

Oseltamivir

A synthetic neuraminidase inhibitor antiviral drug (Tamiflu) synthesized using shikimic acid, active against Influenza A and B.

Oseltamivir Mechanism of Action

Inhibits influenza viral neuraminidase, blocking the release of progeny virions from infected host cell surfaces.

Rifampin

A semi-synthetic rifamycin derivative (ansamycin antibiotic) derived from rifamycin B produced by Amycolatopsis mediterranei.

Rifampin Mechanism of Action

Binds to bacterial RNA polymerase to inhibit RNA synthesis, preventing transcription and protein production.

Valacyclovir

A synthetic purine nucleoside analogue prodrug of acyclovir used to treat herpes virus infections.

Valacyclovir Mechanism of Action

Rapidly converted to acyclovir, which is phosphorylated by viral thymidine kinase and cellular kinases to acyclovir triphosphate; this inhibits viral DNA polymerase and terminates viral DNA elongation.

Vancomycin

A natural glycopeptide antibiotic isolated from Amycolatopsis orientalis active against Gram-positive bacteria.

Vancomycin Mechanism of Action

Binds to D-alanyl-D-alanine amino acid sequences on cell wall precursors, preventing peptidoglycan cross-linking and leading to osmotic cell lysis.

6-Aminopenicillanic Acid (6-APA)

The core bicyclic structure of penicillin antibiotics naturally produced by Penicillium chrysogenum fungi.

KatG Enzyme

A catalase-peroxidase enzyme in Mycobacterium tuberculosis responsible for converting the prodrug isoniazid into its active form.

InhA Enzyme

An enoyl-ACP reductase enzyme in Mycobacterium tuberculosis that is inhibited by activated isoniazid, preventing mycolic acid cell-wall synthesis.