Microbiology Chapter 14 - Antimicrobial Drugs

Alexander Fleming

Discovered the FIRST natural antibiotic penincillin in 1928

Penincillin

the FIRST natural antibiotic discovered; works by inhibiting staphyloccocus growth

Drug Interactions

Synergistic and Antagonistic

Synergistic

two drugs work together

Antagonistic

harmful if used together

Bacteriostatic vs. Bactericidal

Bacteriostatic INHIBITS bacterial growth vs. Bactericidal which KILLS bacteria

Bacteriostatic

Bacteriostatic INHIBITS bacterial growth, used for minor accidents | ex. Neosporin

Bactericidal

Antibiotics | Used to treat life-threatening/major infections (i.e. acute endocarditis)

Narrow-Spectrum

Drug type often preferred to avoid superinfection and the development of antimicrobial resistance 

β-lactams

characterized by the presence of a β-lactam ring found within the central structure of the drug

β-lactams Examples

Penicillins, cephalosporins, monobactams, and carbapenems

Antimicrobial vs. Eukarya

Since fungi, protozoans, and helminths are eukaryotic organisms like human cells, it is more challenging to develop antimicrobial drugs that specifically target them

Antimicrobial Drugs vs. Viruses

It is hard to target viruses because human viruses replicate inside of human cells

HIV…

can easily mutate to become drug resistant, and thus is typically treated with several antiretroviral drugs

Antiretroviral Drugs

Drugs that interfere with viral binding and fusion to initiate infection. (includes reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors)

(1 Q on test) Antimicrobial Resistance result of…

• selection of drug-resistant strains in clinical environments

• the overuse and misuse of antibacterials

• the use of subtherapeutic doses (EXPIRED) of antibacterial drugs

• poor patient compliance with antibacterial drug therapies

Common Modes of Antimicrobial Resistance

• drug modification or inactivation

• prevention of cellular uptake or efflux

• target modification

• target overproduction

• target mimicry

Drug Modification or Inactivation

modify or destroy an antimicrobial through hydrolysis (β-lactamases enzymatic hydrolysis of the β-lactam bond)

Prevention of Cellular Uptake or Efflux

Efflux pump that transport drug out of the cell

Target Modification

Structural changes to those targets can prevent drug binding

Multidrug-resistant Microbes (MDRs)

“superbugs” | Carry one or more resistance mechanism(s), making them resistant to multiple antimicrobials

ESKAPE pathogens (list of superbugs/pathogens)

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.

Antibiograms

Useful for monitoring local trends (ex. TX gonorrhea vs LA gonorrhea) in antimicrobial resistance/susceptibility and for directing appropriate selection of empiric antibacterial therapy

The Etest is…

…a combination of the Kirby-Bauer disk diffusion test and dilution methods

Etest

commercially available plastic strips that contain a gradient of an antibacterial are placed on the surface of the inoculated agar plate

β-lactamases vs β-lactam

-lactamases are the enzymes vs. -lactam is the chemical itself

(MIC) Minimum Inhibitory Concentration

Where the TIP/POINTY of the teardrop is, is the minimum dosage that should be administered (i.e. 1.5 μg/mL)