Intro to Antibiotics Flashcards
3 general ways to use antibiotics
Empiric
Definitive
Prophylaxis
Source control
When all the infection that can be removed is removed
By drainage or surgically
Antibiogram
A summary of all the bacterial isolates over a given period of time and what % of them are susceptible to which antibiotics
Every hospital has one
4 routes of delivery
PO (by mouth)
IV
IM
PR (by rectum)
3 times we should use IV antibiotics
When patients cannot take oral antibiotics
When there is no oral option
When rapid peak serum antibiotic levels are critical
6 reasons why patients fail antibiotic therapy
Wrong bug Wrong drug Drug is not getting to bug Wrong diagnosis Inadequate source control Too much/too little immune system
Bacteriostatic
Drugs slow or stop replication so immune system can eliminate bacteria
Bactericidal
Drugs can kill bacteria directly
Synergy (and classic example)
2 drugs together have higher bactericidal activity than either alone
Ex: Beta lactam and aminoglycoside
Minimal inhibitory concentration
Minimal concentration of the antibiotic needed to inhibit the growth in vitro
Time-dependent antibiotic
Activity depends on the duration of time the concentration is over the MIC
Higher dose will not enhance activity
Need to be frequently dosed
Concentration-dependent antibiotic
Activity depends on the absolute concentration greater than MIC
A higher dose = higher activity
3 general targets of antibiotics
Cell wall synthesis
Nucleic acid synthesis
Protein synthesis
Where do 1. Beta Lactams 2. Tetracyclines 3. Macrolides 4. Quinolones target?
- cell wall
- 30S ribosomal subunit
- 50S ribosomal subunit
- DNA gyrase
4 general types of beta lactams
Penicillins
Cephalosporins
Carbapenems
Monobactams
General info about beta lactams
Most common antibiotics
Core beta lactam ring with unique side chain
Time-dependent killing (so need to be frequently doses)
Bactericidal
Safe in pregnancy and for children
What is the major mechanism of resistance in gram positive organisms?
Alteration of PBP
Efflux pumps
Major resistance mechanism in all bacteria
Active transmembrane pump that expels antibiotics
Can be chromosomal or acquired
What is the major mechanism of resistance in gram negative organisms?
B-lactamase
2 B-lactamase inhibitors
Tazobactam
Clavulanate
What do you use to treat Pseudomonas
Pip-Tazo
Can penicillin be used on gram positive or gram negative bacteria?
Gram positive
3 main bacteria treated with penicillin
Group A strep (strep pyogenes)
Strep pneumoniae (when sensitive)
Syphillis (treponema pallidum)
Main resistance mechanism to penicillin
Penicillinase
How do you get MRSA
mecA gene causes alteration of a PBP (PBP2a)
Cloxacillin can be used to treat…
Methicillin susceptible Staph aureus
Drugs for MRSA
- PO (4)
- IV (3)
- TMP-SMX, Linezolid, Doxycycline, +/- Clindamycin
2. Vanco, Daptomycin, Ceftaroline
The amino penicillins (amoxicillin and ampicillin) can be used to treat which 3 bacteria
Streptococci
Enterococcus faecalis
Listeria
Cephalosporins do NOT treat which 2 types of bacteria
Enterococcus
Anaerobes
As you go down the generations of cephalosporins… (3)
More resistant to beta lactamases
Better activity against gram negative organisms
Better ability to cross into tissue spaces
What are 1. first gen 2. second gen 3. third gen 4. fourth gen 5. fifth gen cephalosporins main clinical uses?
- Skin and soft tissue infections, surgical prophylaxis
- Better H, influenzae activity, mild CAP
- Gonorrhea, serious infections requiring hospitalization, CAP, meningitis, pylonephritis, pseudomonas
- Empiric for nosocomial infections and neutropenic gever
- Serious MRSA and ESBL infections
Which generation of cephalosporin is best for pseudomonas?
And which carbapenems?
Third gen
Meropenem and Imipenem
Carbapenems are used for…
Severe life threatending infections in which ESBL infections are likely
(Nosocomial pneumonia, sepsis)
4 adverse events from B-lactams
Hypersensitivity
Gastrointestinal
Renal (rare)
Hematologic (rare)
Fluoroquinolones
- Mechanism
- 3 bacteria it covers
- Resistance mechanisms
- Inhibits DNA gyrase and topoisomerase 4
- Mycoplasma, Chlamydophila, Leigonella
- Efflux pumps, alteration of target DNA enzyme and membrane porins
4 adverse events from Fluoroquinolones
Tendonitis Prolonged QTc Gastrointestinal CNS (dizziness, insomnia, delirium)
Macrolides
- Mechanism
- Resistance
- 2 examples
- Binds and prevents translocation of peptide chain
- Efflux pumps, alteration of ribosomal target
- Clarithromycin, azithromycin
Tetracyclines
- Mechanism
- 3 examples
- Works on…
- Binds and prevents translocation of peptide chain
- Doxycycline, tetracycline, minocycline
- Gram positive (including MRSA), gram negative, plasmodium, intracellular bacteria and bacteria without walls
2 adverse events from macrolides
GI
Prolonged QTc
3 adverse events from tetracyclines
Tooth discolouration
Erosive esophagitis
Photosensitivity
4 main resistance mechanisms
Efflux pumps
Porin membrane mutations
Alterations in PBPs
Beta lactamases
Drugs for pseudomonas
PO: ciprofloxacin
IV: pip-tazo, ceftazidime, cefepime, meropenem, imipenem
Drug for ESBL
Carbapenems
