Infectious Disease I: Background Flashcards
What color do gram-positive and gram-negative organisms stain on a gram stain? How do atypicals stain?
Gram pos: stain purple due to thick cell wall
Gram neg: stain pink due to thin cell wall
Atypicals do not gram-stain well
What bacteria is a gram negative cocci? What are 2 gram positive rods?
gram negative cocci: Neisseria spp.
gram positive rods:
- listeria monocytogenes
- corynebacterium spp.
What are the common mechanisms of resistance? (4)
- Intrinsic - natural resistance. For example, E. coli is resistant to vancomycin because the antibiotic is too large to enter the cell wall of the E. coli.
- Selection pressure - resistance occurs when the antibiotic kills the susceptible bacteria, but it leaves the more resistant strains to multiply. (ex. VRE)
- Enzyme inactivation - (ex. beta lactamases) the enzymes break down the antibiotics so they no longer are effective.
- Acquired - bacterial DNA containing resistant genes can be transferred between species or picked up from dead bacterial fragments in the environment
What are the common resistant pathogens?
Kill
Each
And
Every
Strong
Pathogen
Klebsiella pneumoniae (ESBL, CRE)
Escherichia coli (ESBL, CRE)
Acinetobacter baumannii
Enterococcus faecalis, Enterococcis faecium (VRE)
Staphylococcus aureus (MRSA)
Pseudomonas aeruginosa
What overarching drug classes are cell wall inhibitors? (2)
Beta lactams
- penicillins
- cephalosporins
- carbapenems
- monobactams
Glycopeptides
- vancomycin
- dalbavancin, telavancin, oritavancin
What drugs/classes are folic acid synthesis inhibitors (3)
- sulfonamides
- trimethoprim
- dapsone
What drugs/classes are DNA/RNA inhibitors? (3)
- quinolones (DNA gyrase, topoisomerase)
- metronidazole, tinidazole
- rifampin
What drugs/classes are cell membrane inhibitors? (3)
- polymyxin
- daptomycin
- telavancin, oritavancin
What drugs/classes are protein synthesis inhibitors? (6)
- aminoglycosides
- macrolides
- tetracyclines
- clindamycin
- linezolid, tedizolid
- quinupristin/dalfopristin
What are some differences between hydrophilic and lipophilic agents?
Hydrophilic: beta-lactams, aminoglycosides, glycopeptides, daptomycin, polymyxins
- small Vd (not really in extravascular space)
- renal elimination
- low intracellular (tissue) concentrations -> not active against atypical (intracellular) pathogens
- increased clearance in sepsis
- poor-moderate bioavailability
Lipophilic: quinolones, macrolides, rifampin, linezolid, tetracycline, chloramphenicol
- large Vd
- hepatic metabolism
- achieve intracellular concentrations
- clearance changed minimally in sepsis
- excellent bioavailability (often have 1:1 IV to PO ratio)
What do the natural penicillins cover?
Penicillin G, Penicillin VK
Coverage:
- gram positive cocci (strep, enterococci)
- gram positive rods (bacillus anthracis, corynebacterium, clostridium)
- gram positive anaerobes (peptostreptococci)
- gram negative cocci (neisseria, pasturella)
- other: treponema pallidum (syphillus)
Which natural penicillins are PO, IV, and IM?
PO: penicillin V potassium
IV: penicillin G aqueous
IM: penicillin G benzathine (Bicillin L-A)
What are the class effects of penicillins?
What type of infection are these meds commonly used for: penicillin VK, penicillin G benzathine, amoxicillin, amox/clav
Class effects:
- beta lactam allergy
- risk of seizures
Pen VK: strep throat, mild skin infection
Pen G Benzathine: syphilis (NEVER use IV, only IM)
Amoxicillin: acute otitis media, infective endocarditis phrophylaxis, H. pylori
*90mg/kg/day for AOM
Amox/Clav: acute otitis media
*use lowest dose of clavulanate
*90mg/kg/day for AOM
Which beta lactams do NOT need to be renally adjusted?
- nafcillin, oxacillin, dicloxacillin
- ceftriaxone
What formulations does cefuroxime (Ceftin) come in? What is the only cephalosporin that has MRSA coverage?
Cefuroxime comes in IV, IM, and PO
Ceftaroline (Teflaro) covers MRSA. Other than that it has similar coverage to ceftriaxone
What are the class effects of cephalosporins?
What type of infection are these meds commonly used for: cephalexin, cefazolin, cefuroxime, cefotetan/cefoxitin, cefdinir, ceftriaxone/cefotaxime, ceftazidime/cefepime, ceftaroline
What reaction is associated with cefotetan
Class effects:
- beta-lactam allergy
- risk of seizures
cephalexin - strep throat, MSSA skin infections
cefazolin - surgical prophylaxis
cefuroxime - AOM, CAP, sinus infections
cefotetan/cefoxitin - surgical prophylaxis for GI procedures
*cefotetan associated with disulfiram-like reaction
cefdinir - CAP, sinus infection
ceftriaxone/cefotaxime - CAP, meningitis, SBP, pyelonephritis
*ceftriaxone doesn’t need renal adjustment, do not use in neonates
ceftazidime/cefepime - pseudomonas
ceftaroline - MRSA
What 3 pathogens does ertapenem not cover? What fluid does ertrapenem need? What 3 pathogens do the carbapenems NOT cover?
- Ertapenem doesnt cover PEA (pseudomonas, entercoccus, acinetobacter)
- Ertapenem needs NS only
All do not cover: atypicals, VRE, MRSA
What drug is similar to beta lactams and can be used in a patient with a beta lactam allergy? What does it cover?
aztreonam
- only covers gram negative
- HAS pseudomonas coverage
*IV only
What is the typical dosing
(mg/kg) for aminoglycosides (gent/tobra) when doing traditional and extended-interval dosing?
traditional - 1-2.5mg/kg IV q8h (if CrCL ≥ 60mL/min)
extended-interval - 4-7mg/kg IV q24h (dosing interval determined by nomogram)
- If weight is less than IBW, use ABW. If obese, use AdjBW
monitor renal function - will need to adjust frequency based on function
If doing traditional dosing with aminoglycosides, when do you draw a trough and peak? What is the goal concentration of peak and trough?
Trough: draw 30 mins before 4th dose
- goal trough: <2mcg/mL
Peak: draw 30 mins after end of 4th dose infusion
- goal peak: 5-10mcg/mL
What are the boxed warnings (3) for quinolones? What are some additional warnings (6) for them? What drug interaction do they have?
Boxed warnings
- tendon rupture
- peripheral neuropathy
- CNS effects (including seizures)
Warnings
- QT prolongation (caution if pt has low K/Mg)
- hypo and hyperglycemia
- psychiatric disturbances
- photosensitivity
- avoid use in children (risk vs. benefit)
- caution if cardiovascular disease
Interaction
- chelation with divalent cations
Which quinolone cannot be used for UTIs? Which quinolone is active against MRSA? Which quinolone does not require a renal dose adjustment?
Moxifloxacin cannot be used to treat UTI
- Moxi also doesn’t need a renal dose adjustment
Delafloxacin is active against MRSA
What is the IV to PO ratio for levofloxacin and moxifloxacin?
IV to PO ratio is 1:1
What are the common uses for all macrolides, azithromycin, clarithromycin, and erythromycin? What is the Z-Pak dosing? What drug interactions do we need to worry about?
All: CAP, alternative to beta lactam for pharyngitis
Azithromycin: COPD exacerbations, pertussis, chlamydia (if pregnant), ppx for mycobacterium avium complex, severe travelers’ diarrhea
- Z-Pak: 2 250mg PO tabs x1, then 250mg PO daily x4 days
Clarithromycin: H. Pylori
Erythromycin: gastroparesis becuase it increases gastric motility
- but not used as common as the other macrolides due to side effects
Drug interactions:
- QT prolonging drugs
- Clarithromycin and erythromycin are CYP3A4 inhibitors, so lovastatin and simvastatin are contraindicated!!
