Microbio Ch 20 Antimicrobial Drugs

Penicillin

Cell Wall Synthesis Inhibitor

Inhibits peptidoglycan synthesis
Bactericidal
Only affects growing cells
Destroyed by penicillinase

Penicillinase‑Resistant Penicillins (e.g., Methicillin)

Cell Wall Synthesis Inhibitor

Resistant to penicillinase

MRSA developed resistance

Methicillin discontinued in U.S.

Bacitracin

Cell Wall Synthesis Inhibitor

Polypeptide antibiotic

G+ (staph, strep)

Topical only

Blocks early steps of peptidoglycan synthesis

Vancomycin

Cell Wall Synthesis Inhibitor

Last‑line for MRSA

Inhibits cell wall synthesis

VRE emerging (hospital‑associated)

Carbapenems

Broad spectrum

Inhibit cell wall synthesis

Cephalosporins

Inhibit cell wall synthesis

Alternative to penicillins

Chloramphenicol

Protein Synthesis Inhibitor

Binds 50S

Blocks peptide bond formation

Broad spectrum

Can suppress bone marrow

Tetracyclines

Protein Synthesis Inhibitor

Block tRNA attachment

Broad spectrum (G+, G−, rickettsia, chlamydia)

Produced by Streptomyces

Streptomycin

Protein Synthesis Inhibitor

Changes 30S shape

Causes mRNA misreading

Rifamycin

Nucleic Acid Synthesis Inhibitor

Inhibits mRNA synthesis

Used for tuberculosis

Quinolones / Fluoroquinolones

Nucleic Acid Synthesis Inhibitor

Inhibit DNA gyrase

Used for UTIs

Polymyxin B

Plasma membrane injury

G−

Topical

Bactericidal

Polymyxin E (Colistin)

Plasma Membrane Injury

Treats resistant G− infections

Used in ventilator‑associated pneumonia

Colistin‑resistant E. coli reported (2016)

Amphotericin B (antifungal)

Plasma Membrane Injury

Binds fungal sterols

Damages membrane

Azoles (antifungal)

Plasma Membrane Injury

Inhibit sterol synthesis

Treat cutaneous + systemic mycoses

Sulfanilamide (Sulfa drugs)

Essential Metabolite Inhibitor

Competitive inhibitor of PABA

Blocks folic acid synthesis

Bacteriostatic

Echinocandins (e.g., Caspofungin) Antifungal

Inhibit glucan synthesis

Weakens fungal cell wall

Used for Aspergillus, Candida

Flucytosine Antifungal

Cytosine analog

Converted to 5‑fluorouracil in fungi

Inhibits RNA synthesis

Works on Candida, Cryptococcus

Griseofulvin Antifungal

Binds keratin

Treats dermatophytes (tinea, ringworm)

Inhibits fungal mitosis

Acyclovir Antiviral

Inhibits viral DNA synthesis

Used for herpes viruses

Zidovudine (AZT) Antiviral

Inhibits HIV reverse transcriptase

Entry Inhibitors (HIV) Antiviral

Block viral attachment to host receptors

Fusion Inhibitors (HIV) Antiviral

Block viral envelope fusion with host membrane

Alpha Interferons

Inhibit spread of viruses to new cells

Used for hepatitis, viral infections

Mebendazole / Albendazole Antihelminthic

Broad spectrum

Block nutrient absorption in helminths

Few side effects

Ivermectin Antihelminthic

Causes paralysis + death of helminths

Safe for mammals

Used widely in livestock