Antibiotics III Flashcards
What is the primary goal when treating skin and soft tissue infections with beta hemolytic streptococcal species?
Every effort must be made to sue an appropriate penicillin or cephalosporin
If failing to use a penicillin or cephalosporin w/i the first 24 hrs of infection, what is the outcome?
Patient at a significant risk of morbidity and has prompted a marked increase in hospitalization
Compared to their corresponding cephalosporins, are penicillins more or less effective?
Penicillins are MORE effective
What is a benefit of cephalosporins compared to their corresponding penecillins?
Cephalosporins have a broader spectrum of action
What is the bacterial spectrum of penicillins?
Strep species and oral anaerobes
What do penicillinase resistant penicillins and 1st gen cephalosporins treat?
Strep species and MSSA
What are aminopenicillins and 2nd generation cephalosporins used to treat?
Strep species, and H. flu (non-penicillinase-producing)
When clavulanic acid is added to aminopenicillins, what is the spectrum include?
Strep species, all anaerobes, all H. flu, and MSSA
What do the extended spectrum penicillins and 3rd generation cephalosporins treat?
Strep species and Gram negative rods
What is the coverage for extended spectrum penicilns +tazobactam and 4th generation cephalosporins?
Strep species, Gram negative rods, all anaerobes, MSSA
What are 30% of Strep pneumoniae resistant to and why?
Resistant to all penicillins and 1st generation cephalosporins because of alteration in PBP2b
What is the carbapenem that we’re responsible for?
Imipenem
What do carbapenems (imipenem) cover?
Broad Gram positive (except MRSA) and Gram negative coverage
What is the monobactam that we’re responsible for?
aztreonam
What are monobactams effective against?
Gram negatives
A patient with lobar pneumonia has Gram postive diplococci. What should be used?
Patient has streptococcus pneumoniae. 30% of S. pneumoniae are resistant to penicillins because of the mutation in PBP 2b and therefore it would be wise to use a drug that binds to PBP2x (Cephalosporin 2nd, 3rd, 4th gen)
What are the glycopeptides that inhibit cell wall synthesis?
Vancomycin (it’s the only one)
What is the MOA of Vancomycin?
Vancomycin binds to the two D-alanine residues at the end of a peptide chain and inhibits the proper interaction with the cell wall cross-linking enzyme
What is the MOR of Vancomycin?
The D-alanine AA at the end of the polypeptide is replaced with D-lactate. Vancomycin cannot bind and therefore the crosslinking enzyme can properly operate.
What is the drug of choice for MRSA?
Vancomycin
What are the adverse reactions for Vancomycin?
- Panoply of drug allergy
- REdman Syndrome - FLushing, tachycardia, hypotension,
What is the spectrum of activity for Vancomycin?
Give IV for serious Gram (+) infections such as:
- MRSA
- Staphylococcus epidermidis
- Ampicillin-Resistant Group D Strep faecalis
- pneumococcal meningitis
- metronidazole-resistant strains of C. difficile
What are the cell membrane toxins?
- Cyclin lipopeptide (Daptomycin)
- Polymixins (Colistin)
What is the MOA of daptomycin?
Cyclic lipopeptide in which the lipophilic tail goes thru the teichoic acid backbone of the cell membrane of Gram (+) organisms [Not effective against Gram (-) because of LPS]
Adverse reactions to Daptomycin
- Allergy
- Risk of drug-induced rhabdomyolysis especially after prolonged exposure >7 days
What is the AB spectrum of daptomycin?
Strictly for infections with Gram (+) organisms that are vanco and lactam resistant OR patient has severe vanco or lactam allergy
Two specific bugs where daptomycin should be used?
- Vancomycin-Resistant Enterococci
- Vancomycin-Resistant Staphylococcus aureus
What is the mechanism of action of Colisitin?
A polymixin that is essentially the Gram (-) counterpart of daptomycin
Binds to LPS causing the disruption of outer cell membrane in Gram (-) bacteria
What are the adverse reactions to colistin?
- Highly nephrotoxic
What situations are colistin used?
Reserved for Gram (-) bacteria (usually Pseudomonas species) resistant to all other ABs as frequently occur in patients with cystic fibrosis
