antimicrobials Flashcards
Deep sternal wound infections:
~Significantly worse long-term survival
*Costs between
$200 and $250k to treat!!!
MIC =
Minimum INHIBITORY
Concentration”
MBC =
Minimum BACTERIOCIDAL
Concentration”
problem with VAD besides thrombosis
Infection/sepsis
cidal
min. conc. at which you are killing bacteria
static
min conc at which you stop bacteria growth
1) Gram Positive Bacteria
thick cell wall take up blue dye
gram negative bacteria
thin cell wall no blue dye . peptidoglycan is protected
fungi
valley fever depressed immune system
Penicillins & Cephalosporins
β-Lactam antibiotics
• *Prevent bacterial cell wall peptidoglycan cross-linking so newly produced bacterial cell walls are “weak” and the bacteria “fall apart” (think bacterial Marfan’s Disease)
• Theseantibioticsare“cidal”
Penicillins & Cephalosporins
*Classified by their
pectrum of activity” and resistance to β-lactamases (as well as potency, methods of administration, toxicities, expense, and pharmacokinetics and –dynamics)
• “R group” attachment differentiates the penicillins
penicilli derived from
Penicillium mold
First Generation” Penicillins
are effective against
gram-positive organisms (particularly Strep), gram negative cocci (what’s that?) and a few others, but resistance levels are high and growing!
Penicillin-G
(benzylpenicillin) 1st gen
Anti-staphylococcal Penicillins
• Developedinresponse
to
growing resistance among Staph. *These antibiotics have a much
narrower “spectrum” and are used specifically for Methicillin resistant Staphylococcus aureus…
…AND SHOULD BE USED SPARINGLY (why?)
Dicloxacillin
(Dynapen) Anti-staphylococcal Penicillins
Nafcillin
(Nallpe) Anti-staphylococcal Penicillins
-Oxacillin
Anti-staphylococcal Penicillins
Broad-Spectrum Penicillins
• Spectrum similar to Pen-G against
ram negatives (such as?) • Resistance to broad-spectrum pens has increased dramatically (especially MRSA)
-Ampicillin
Broad-Spectrum Penicillins
-Amoxicillin
Broad-Spectrum Penicillins DRUG OF CHOICE
for pre-cardiac surgery dental prophyllaxis
Antipseudomonal Penicillins
Pseudomonas aeruginosa is a very problematic, very pathogenic gram negative that readily develops resistance to antibiotics. Also effective against other gram-negative bacilli.
-Pseudomonas aeruginosa is notorious for causing
blue/green pus!
Carbenicillin
(Geocillin) Antipseudomonal Penicillins
Piperacillin
(Piperacil) Antipseudomonal Penicillins
Ticarcillin
(Ticar) Antipseudomonal Penicillins
Clavulanic acid (CA) also has
β-lactam ring like the penicillins but no antimicrobial activity.
Clavulanic acid (CA) is a
suicide inhibitor of bacterial β-lactamase that
attaches to and permanently deactivates the enzyme.
Clavulanic acid (CA)
with amoxicillin (Augmentin) and ticarcillin (Timentin) (why?
penicillins are not excreted or metabolized by the kidneys so…
x
penicillins Don’t cross the blood/brain barrier except.
when meninges are inflamed
β-lactams essentially just like penicillins
*Classified as
1st, 2nd, 3rd, & 4th generation based on their resistance to β-lactamases and their antimicrobial spectrums
*Very commonly used in open heart surgery and as part of the “prime”
1st Generation Cephalosporins
The “Pen-G’s” of Cephs. • Less expensive then 2nd, 3rd, 4th generations. • Since the main open-heart infection culprits
are Staph. (mostly) and Strep. sp., no advantage found using more expensive later-generation cephalosporins for ECC prophyllaxis!
Cefazolin
Kefzol) -The only parenteral 1st generation -Typically dosed at a fixed
amount (1 gram/circuit, e.g.) or by weight (50mg/kg, e.g.)
*Cleared by the kidneys
*Cross sensitivity with penicillins is high (so check the charts!!!)
2nd Generation Cephalosporins
Again, no proven advantage over 1st gens when used in the pump prime!
• May provide the theoretical advantage of a greater V.O.D. and slightly broader spectrum of activity.
-Cefoxitin
2nd Generation Cephalosporins(Mefoxin)
Cefotetan
2nd Generation Cephalosporins Cefotan)
Cefuroxime
2nd Generation Cephalosporins (Ceftin)
Vancomycin
A glycopeptide • Similar action to pens/cephs
- Prevents peptidoglycan polymerization in the bacterial cell wall so they “fall apart.”
- Spectrum of activity limited to gram positives
vancomycin *Reserved for use in
MRSA, Methicillin Resistant Staph epidermidis (MRSE) and enterococcal infections.
Vancomycin
• Excreted
renally (like pens and cephs)
• Side effects much more common than pens and cephs:
sides of vancomycin
fever chills flushing phlebitis
Aminoglycosides
• Derived
from fungi (like penicillins)
-If they end in “…mycin
they’re from
Streptomyces sp.
If they end in “…micin
they’re from Micromonospora sp.`
Aminoglycosides
• Interfere with bacterial
protein synthesis by binding to bacterial ribosomal 30S subunit..*This action is “cidal
Aminoglycosides
• Spectrum of activity
limited to gram negative bacteria, such as E. coli, Proteus mirabilis, and Pseudomonas aeruginosa
Aminoglycosides Exhibit a synergistic effect when used with
pens, cephs, and vancomycin (why?) for resistant bacteria.
Aminoglycosides
• Exhibit
oncentration-dependentkilling:
- Increasing concentrations of aminoglycosides kill increasing proportions of bacteria at increasing rates.
- **All aminoglycosides are given parenterally or used topically!
Aminoglycosides
• Unlike other drugs discussed,
aminoglycosides exhibit poor CNS penetration even in the presence of meningitis.
Resistance to aminoglycosides is complicated.
Multiple methods of resistance, but cross- resistance doesn’t necessarily occur (bugs can be resistant to gentamycin and not amikacin)
-Streptomycin (little used, lots of resistance)
Tobramycin
(Nebcin) Streptomyces sp.
gentamicin
Micromonospora sp.`
Amikacin
Micromonospora sp.`(Amikin) = LEAST bacterial resistance
Aminoglycosides
• All are excreted
renally and readily become “more toxic” in the presence of renal failure (a self-fulfilling prophecy since one of their major side-effects is renal toxicity!)
Aminoglycosides
• Adequate hydration/urine output
minimizes side effects (what’s that mean for us?)
All aminoglycosides cross the
blood/placenta barrier and concentrate in fetal tissue!
Aminoglycoside Toxicity
*This reflects a “classic triad” of
#1) Ototoxicity: vestibular &/or cochlear #2) Neuromuscular Paralysis PARTICULARLY with myasthenia gravis patients. #3) Nephrotoxocity ranging from mild to total renal destruction
Neomycin:
used only topically (too nephrotoxic)
Streptomycin
first produced. LOTS of microbial resistance has developed
Gentamicin and Tobramycin
mid-level microbial resistance
Amikacin
least microbial resistance (also most expensive!)
