Lecture 13: Antibiotics Part 2 Flashcards
What is intrinsic resistance vs. acquired resistance?
- Intrinsic = bacteria are normally resistant to an antibiotic without any changes in their genetic composition
- Acquired = bacteria gain resistance through mutations or through mobile genetic elements (plasmids)
What are some mechansisms of antibiotic resistance in bacteria?
What is driving the emergence of antibiotic resistance?
- Healthcare: overprescription of antibiotics
- Agriculture: giving animals antibiotics
It is estimated that antibiotic resistance can become widespread in how long after the introduction of a new antibiotic?
2-3 years
What is the reservoir of mobile antibiotic resistant genes?
Natural environment, especially soil
What percent of antibiotic prescriptions are not needed?
Estimated 28%
What are some medically important organisms (Gram-negative and Gram-positive)?
- Gram-negatives
- Extended-spectrum β-lactamase (ESBL) GN
- Carbapenem-resistant (CR) GN - Gram-positives
- Methicillin-resistant Staphylococcus aureus (MRSA)
- Vancomycin-resistance Enterococcus faecium/faecalis (VRE)
What are the β-lactamase classifications?
- Serine β-lactamases (contain serine at their active site)
- Metallo-β-lactamases (contain zinc at their active site)
- Ambler classification (stuctural homology)
What is the last resort for β-lactam resistant organisms?
Polymixins
What are the β-lactamase genes called?
bla
What antibiotics do ESBLs hydrolyze? When are these effective?
- 1st-3rd gen cephalosporins
- Penicillins
- Monobactam
- Effective when combined with clavulanic acid (inhibitor)
What organisms are ESBL producers?
- Klebsiella pneumoniae
- K. oxytoca
- Escherichia coli
- Proteus mirabilis
What are the most common ESBLs (extended-spectrum B-lactamases)?
The CTX-M enzymes which emerged in the 1990s
What antibiotics do carbapenemases hydrolyze?
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenems
What is the most common carbapenemase?
KPC-1
