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!!
What is unique about tetracycline coverage (4)?
Covers Rickettsiae, CA-MRSA, VRE, and H. pylori
What patient populations should we avoid use of tetracyclines in?
DO NOT USE in pregnancy, breastfeeding, or children < 8 years old
What is the IV: PO ratio for doxy and minocycline?
IV:PO 1:1
What adverse drug reaction can minocycline cause?
drug induced lupus erythematosus
What does SMX/TMP not cover? (4)
- pseudomonas
- enterococci
- atypicals
- anaerobes
What patient populations should we avoid Bactrim use in? What are 2 warnings for Bactrim? What are some side effects (4)?
Avoid in:
- sulfa allergy
- pregnant
- breastfeeding
Warnings:
- skin reactions (including SJS/TEN)
- G6PD deficiency
Side effects:
- photosensitivity
- increased potassium
- hemolytic anemia (pos. Coombs test)
- crystalluria
What strengths of SMX and TMP are in the SS vs. DS tab? What is the Bactrim dosing for uncomplicated UTI and PCP ppx/tx?
SS: 400mg SMX/80mg TMP
DS: 800mg SMX/160mg TMP
dosed based on TMP
Uncomplicated UTI:
- 1 DS tablet PO BID x3 days
Pneumocystis pneumia (PCP) ppx:
- 1 DS or SS tablet daily
PCP tx:
- 15-20mg TMP/kg/day divided q5h
What is the starting mg/kg dosing for IV vancomycin? What weight do you use?
What is the PO vanc dosing for C. diff?
At what MIC should we use another agent instead of vanc?
IV: 15-20mg/kg q8-12h
- use TBW
- if CrCl 20-49mL/min -> Q24h interval
- target trough for severe infections is 15-20mcg/mL
C. diff: 125mg QID for 10 days
If MIC for MRSA is ≥2, do not use!!
Which lipoglycopeptides are single-dose regimens? What type of infection can these treat?
Single-dose: oritavancin, dalbavancin
All approved for skin infections
Telavancin also approved for HAP/VAP
What are the boxed warnings for telavancin (3)? What are the contraindications for telavancin (1) and oritavancin (1)? What are the warnings associated with telavancin and oritavancin (1)?
Boxed warnings (telavancin)
- fetal risk
- nephrotoxicity
- increased mortality in patients w/ CrCl ≤ 50mL/min
Contraindications
- telavancin: concurrent use of IV UFH
- oritavancin: use of IV UFH for 5 days after
Warnings
- telavancin: falsely elevated aPTT/PT/INR
- oritavancin: elevated PT/INR and aPTT
What should we NOT use daptomycin for? What are 2 warnings associated with dapto? What fluids is dapto compatible with?
Do not use for pneumonia
Warnings:
- myopathy/rhabdomyolysis (monitor CPK weekly)
- falsely elevate PT/INR
Compatability:
- compatible with NS or LR
- NOT compatible with dextrose
What is the IV: PO ratio for linezolid? What contraindication (1) does linezolid have? What warnings is it associated with (3)?
IV: PO ratio is 1:1
- no renal dose adjustments required
Contraindication
- do not use within 2 weeks of MAO inhibitors (serotonin syndrome)
Warnings
- duration related myelosuppression (thrombocytopenia)
- optic neuropathy
- serotonin syndrome (caution with tyramine-containing foods as well)
What does tigecycline cover? What does it NOT cover? What is the boxed warning for tigecycline? What disease should we NOT use tigecycline for? What color should the solution be?
Covers: broad-spectrum against gram-pos bacteria including MRSA, VRE, also gram-neg, anaerobes, and atypicals
- no activity against the 3 P’s: Pseudomonas, Proteus, Providencia
Boxed warning: increased risk of death
Do not use for blood stream infections!!!
- approved for SSTIs, intra-abdominal infections, CAP
Solution should be yellow-orange in color
What type of infections are the polymyxins (polymyxin B,, colistimethate, colistin) used for? What toxicities should we be aware of (2)?
used for MDR gram-negative infections
toxicities
- nephrotoxicity
- neurotoxicity
What are the 2 adverse effects of chloramphenicol?
- blood dyscrasias
- Gray syndrome
What does clindamycin cover? Does it need a renal dose adjustment? When would we use an induction D-test?
Coverage:
- staph
- strep
- anaerobes
No dose adjustment in renal impairment
D-test should be performed of S. aureus that is susceptible to clinda but resistant to erythromycin (flattened zone = inducible clinda resistance, so DONT USE)
What does metronidazole cover? What is the IV: PO ratio? What are 2 contraindications? Side effects (1)?
Coverage:
- anaerobes
- protozoal infections
IV: PO ratio is 1:1
Contraindications
- pregnancy
- alcohol (disulfiram)
Side effect
- metallic taste
What are common uses of rifaximin? (3)
(E. coli)
Uses (hardly absorbed systemically, PO only)
- Traveler’s diarrhea
- prevention of hepatic encephalopathy
- IBS with diarrhea
(used off label for C diff)
When should we avoid use for nitrofurantoin?
Do Not Use
- CrCl < 60mL/min
- G6PD deficiency
what medication is used as a nasal ointment for MRSA decolonization?
mupirocin nasal
What liquid oral antibiotics need to be refrigerated after reconstitution? What does NOT need to be refrigerated?
Refrigeration required:
- penicillin VK
- amox/clav
- lots of beta lactams can be or should be refrigerated
Do NOT refrigerate:
- cefdinir
Which 3 IV abx do not need to be refrigerated?
Do NOT refrigerate:
- metronidazole
- moxifloxacin
- sulfamethoxazole/trimethoprim
Which antibiotics do NOT need renal dose adjustments? (9 groups/drugs)
Antistaph penicillins (dicloxacillin, nafcillin)
Azithromycin
Erythromycin
Ceftriaxone
Clindamycin
Doxycycline
Metronidazole
Moxifloxacin
Linezolid
What three antibiotics may cause DILE?
Isoniazid
Minocycline
Terbinafine
What are 7 drugs that have a 1:1 IV:PO ratio?
azithromycin
levofloxacin
moxifloxacin
doxycycline
minocycline
linezolid
metronidazole
What are 2 abx that need to be protected from light during administration?
doxycyline
micafungin
What 2 abx are compatible with dextrose only? What 3 are compatible with saline only? What 2 are compatible with NS/LR only?
Dextrose only
- sulfamethoxazole/trimethoprim
- amphotericin B
Saline only
- ampicillin
- amp/sulbactam
- ertapenem
NS/LR only
- caspofungin
- daptomycin
