Lab 6: Antibiotic Resistance 2 Flashcards
What is the natural origin of antibiotics?
They are produced by soil dwelling bacteria and fungi to eliminate microbial competition
Hwo does antibiotic resistance naturally evolve?
Through adaptation by microbes to inactivate or evade antibiotics, often via horizontal gene transfer
What are the 5 major cellular targets of antibiotics?
- Cell wall synthesis
- Cell membrane function
- Protein synthesis
- Nucleic acid synthesis
- Metabolism
Name two examples of beta-Lac tam antibiotics and their function.
Penicillin and ampicillin, they inhibit peptidoglycan cross-linking in cell walls
Why is vancomycin ineffective against gram negative bacteria?
It cannot penetrate the outer membrane of gram negative cells
How do protein synthesis inhibitors work?
They bind to ribosomal subunits (30S or 50S) or tRNA and block translation
What antibiotic inhibits RNA polymerase?
Rifampin
What antibiotic class inhibits DNA gyrase?
Fluoroquinolones and ciprofloxacin
What pathway do sulfonamides and trimethoprim target?
Folic acid synthesis
What is the main issue with overuse of antibiotics?
It selects for antibiotic resistant bacteria, reducing treatment options
What enzyme breaks beta-Lactam rings, conferring resistance to penicillin?
Beta-lactamase
What mechanisms do bacteria use for antibiotic resistance?
Enzyme degradation, decreased uptake, efflux pumps, target modification, and bypass pathways
What is the Kirby-Bauer test used for?
To determine bacterial sensitivity to antibiotics via zone of inhibition
What medium is used in the Kirby-Bauer test?
Mueller-Hinton agar
What is the formula for calculating viable counts from plates?
Viable count = (number of colonies/volume plated) x (1/dilution factor)
What does tetracycline do?
It inhibits protein synthesis by binding to the 30S ribosomal subunit
What percentage of oxytet-resistant cells is calculated from 5.2x10^4 / 1.6x10^6
3.25%
What are enteric bacteria?
Gram negative rods typically found in the intestines, including E. Coli and salmonella
What is the common virulence factor of enteric bacteria?
Endotoxin (lipopolysaccharide)
What diseases can salmonella cause?
Typhoid fever, paratyphoid fever, and food poisoning
