Lecture 19: Antibiotics, Phage Therapy and Vaccines

Penicillin

The first antibiotic and discovered by Alexander Fleming

What kind of cells do antibiotics kill?

Only growing cells

3 main classes of drugs

Beta-lactam antibiotics, fluoroquinolone and macrolides

Purpose of beta-lactam antibiotics

Inhibit cell wall synthesis: Bind to and inhibit activity of transpeptidases that are essential for cross linking glycan linked peptide chains in the bacterial cell wall.

Examples of beta-lactam antibiotics

Penicillin and ampicillin

What is the cell wall assembled by?

Transpeptidases and glyosyltransferases

What distinguishes beta-lactam antibiotics?

Beta-lactam ring

How does the beta-lactam ring interact with transpeptidases?

Antibiotic ring mimics acyl-D-Ala-D-Ala and binds to active transpeptidases which permanently inactivates them.

Cephalexin unique trait

Targets specific transpeptidase PBP3 which is required for cell division in E. coli

Augmentin

Combination of beta-lactam antibiotic and beta-lactamase inhibitor

Fluoroquinolones purpose

Synthetic compounds that interfere with gyrase and prevent packaging ion bacterial DNA

What are fluroquinolones used to treat?

Non-complicated infections such as UTIs and traveler’s diarrhea.

How do macrolide antibiotics work?

Serve as protein synthesis inhibitors by acting as 50S ribosomal subunit.

Example of macrolide antibiotic

Azithromycin

Selection for antibiotic resistant bacteria

Antibiotics kill bacteria causing illness along with some good bacteria so the resistant bacteria (survives) gives this trait to other bacteria to continue the spread of illness.

How do bacteria share antibiotic resistance?

Plasmids, transposons or phages in transduction, conjugation and transformation.

Features of immune response

Specificity and memory

Artificial Active Immunity

Injection of antigen to generate antibodies

Types of vaccines

Killed or inactivated, attenuated, toxoid and surface molecules

Killed or inactivated vaccine description

Made from whole organisms

Attenuated vaccine

Organism cultured to reduce pathogenicity but still have ability to infect and induce immune system.

Toxoid vaccine description

Uses denatured toxin and antibodies inactivate the toxin upon infection.

Surface molecules vaccines

Present purified and harmless fragments of pathogen’s exterior to stimulate antibody production.

What is mumps?

Negative stranded RNA virus, replicates in salivary glands and spread by aerosols.