Intro to ABX - Block 1 Flashcards
What is prophylaxis?
ABX administered to prevent infection that hasn’t occurred (high risk patients)
What is empiric therapy?
ABX given to proven or suspected infection, but culprit has not been identified
What is definitive therapy?
Given after the cultur and sensitivity report
What are the approaches of ABX systemic approach therapy?
- Confirm presence of infection
- Identifying the pathogen
- Selection of empiric therapy
- Monitor therapeutic response
What is stage 1 of infection?
- Early, 1-3 days of illness
- Characterized by clinical instability, abnormal lab values
- Uncertainty surrounding the identity of culprit for suspected infection
What is stage 2 of infection?
- 4-6 days of suspected infection
- Appropriate therapy -> clinical stability begins
What is stage 3 of infection?
- 7 days of suspected infection
- Appropriate therapy -> resolution of abnormal vital sugns, WBC count, fever
How can body temp indicate infection?
> 38°C (100.4°F) or < 36°C (96.8°F) -> inflammation
Normal WBC range
4,000-10,000
What are results of an elevated WBC?
Bacterial infection:
1. Presence of band neutrophils (left shift) -> increased bone marrow response to infection
2. Leukocytosis is normal in infection
What is the most common granulocyte def?
Neutropenia
What are the local signs of infection?
- Swelling, erythema, tenderness, purulent discharge
- Neutrophils in CSF, lung secretion, urine -> infection
How do we identify pathogens by microbial studies?
- Blood cultures in acute, febrile patients (2 sites, 1 hr apart)
- Gram stain
* Premature use of ABX -> false-negative cultures
What are the characteristics of G+?
- Thick cell wall
- Dark purple due to crystal violet
What are the characterisitcs of G-?
- Thin cell wall
- Pink/red due to safranin counterstain
Characterisitcs of atypical organisms?
- No cell wall
- Doesn’t stain well
Factors you need to consider when selecting empiric therapies?
- Severity of ID
- Local epidemiology trends
- Patient Hx
- Host factors
- Drug factors
- Necessity of combo therapy
What is an antibiogram?
Annual summary of antibiotic susceptibilities for organisms cultured from patients at a specific institution
What is the rule of thumb in patients with penicillin allergy?
- Avoid cephalosporins for patients with immediate/accelerated rx
- Use cephalosporins under close supervision for patients with history of delayed reactions
Use for gram-negative infections in patients with PCN allergy due to no β-lactam cross-sensitivity.
Aztreonam
Non-allergy rx to penicillin?
N/D, yeast vaginitis
Mild non-IgE mediated rx to penicillin?
- Maculopapular eruption
- Recorded to have penicillin allergy, but no recall of rx
IgE rx to penicillin
- Anaphylaxis
- Angioedema
- Breathing issues
- Hypotension
ABX that should be avoided in pregnancy?
- Fluoroquinolones
- Tetracyclines
Nephrotoxic ABX?
Aminoglycosides
What are the similar properties that don’t require renal dosing?
Lipophilic requiring liver metabolism
What are the drugs that don’t require renal dosing?
Penicillin V and G
Anti staph: Naficillin, oxacillin, dicloxacillin
Ceph+BLI: Cetriaxone
Macrolides: Azithromycin, Erythromycin
Fluoroquinolones: Moxifloxacin
Tetracyclines: Doxycycline, Minocycline, Tigecycline, Erovacycline, Omadacyclin
Pleuromutilins: Lefamulin
Lipoglycopeptides: Oritavancin
Oxazolidinones: Linezolid, Tedizolid
Lincosamide: Clindamycin
Folate Antagonists: Daysone, Pyremethamine
Streptogramins: Synercid
Nitrofurantoin and Fosfomycin
Nitromidazole: Metrinidazole, TInidazole
Polymyxins B
Anti-C diff: Vanc, Fidaxomicin
Anti TB: Rifampin, Isoniazind
What drugs can interact with AG?
Monitor renal function (nephro/ototoxins):
* Amphotericin B
* Cisplatin
* Cyclosporine
* Furosemide
* NSAIDs
* Radiocontrast dye
* Vancomycin
What do you need to do when combining AG with b-lactams?
Separate administration and flush line thoroughly between doses
Drugs that interact with Amphotericicn B?
Nephrotoxins:
* AG
* Cyclosporine
* Foscarnet
What happens when you combine isoniazids with anticonvulsants?
Monitor for signs and symptoms of phenytoin & carbamazepine toxicity:
* Decreased metabolism of carbamazepine and phenytoin -> increases serum drug concnetration
What drug interacts with metrinidazole? Effect?
Ethanol causes a disulfiram like rx -> Avoid concomitant use with EtOH-containing products
What are the effects of Rifampin?
Avoid concomitant use: Increased metabolism of interacting agent by CYP induction -> decrease serum concentrations
Interacting agents with fluoroquinolones?
QTc prolonging agents
Multivalent cations -> decreased absorption -> separate for at least 2 hrs
Interacting agent of sulfonamides?
Warfarin
* Decrease metabolism -> increase serum drug concnetration
* Monitor INR
Interacting agents of doxycycline?
Multivalent cations -> decreased absorption -> separate by 2 hrs
What is the difference between bactericidal and static?
Cidal: eliminates bacterial growth
Static: inhibits bacterial growth
What are the hydrophilic meds?
B-lactams, AG, Glycopeptides, Daptamycin, Polymyxins
What are the characterisitcs of hydrophillic meds?
- Poor tissue penetration
- Renal elimination
- No activity vs atypicals
- Consider LD and higher doses
- Low F -> IV:PO ration is NOT 1:1
Examples of lipophilic meds?
Fluroquinolones, macrolides, linezolid, rifampin, tetracyclines
Characterisitcs of lipophillic drugs?
- GOod tissue penetration
- Hepatic metabolism (DDI and hepatotoxicity)
- GOod activity vs atypicals
- No dose adjustment for sepsis
- Good F -> IV:PO ratio is 1:1
What are the bactericidal agents?
- Aminoglycosides
- β-lactams
- Colistin
- Daptomycin
- Fluoroquinolones
- Metronidazole
- Vancomycin
What are the bacteriostatic agents?
Clindamycin
Linezolid
Macrolides
Sulfonamides
Tetracyclines
Tigecycline
Trimethoprim
Time dependnet agents?
β-lactams
Vancomycin
Tigecycline
Linezolid
Macrolides
Clindamycin
Concentration dependent agents?
- AG
- Fluoroquinolines
- Daptomycin
- Metrinidazole
- Colistin
- Bactrim
What ABX demonstrates postABX effects?
AMinoglycosides
PK/PD of AG?
Concentration dependent, bactericidal
* peak:MIC
PK/PD of fluroquines?
Concnetration-dependent, bactericidal
* AUC:MIC
PK/PD of beta-lactams?
Time dependent, bactericidal
Due to tissue penetration, which ABX is not good for the lungs?
Daptomycin is not good for MRSA pneumonia -> inactivated by lung surfactant
Why is nitrofurantoin not good for pyelonephritis?
Poor cocnetration in kidneys
Why is moxifloxacin not good for UTIs?
Poor concentration in urine/bladder
When do you use PO vs IV formulations?
PO: mild infection
IV: severe infection
What is MIC?
Lowest concnetration of an antimicrobial agent that inhibits visible in-vitro bacterial growth
What is MBC?
Lowest concnetration of antimicrobial that kills 99.9% of bacterial inoculum
ABX with lowest MIC is the best therapy choice?
False: different ABX have different concentrations in different areas
* DOn’t select ABX by comparing MICs
What is susceptible dose dependent?
Specific organisms are suspectible to higher doses
What is susceptible?
Specific cutoff MIC (breakpoint)
Drugs that target cell wall?
- Beta lactams (penicillins, cephalosporins, carbapenems, monobactams)
- Bacitracin
- Glycopeptids
ABX that are 30S inhibitors?
- AG
- Tetras
- Tigecycline
ABX that are 50S inhibitors?
- Chloramphenicol
- Clindamycin
- Linezolid
- Macrolides
- Streptogramins
ABX that disrupt membrane integrity?
- Polymyxin B
- Daptomycin
ABX that disrupt nucleic acid synthesis?
- Fluoroquinolones
- Metronidazole
- Rifamycins
ABX that disrupt the folate metbolic pathway?
- Sulfonamides
- Trimethoprim
What are the reasons to consider combo?
- Broaden spectrum of coverage
- Achieve synergistic activity against infection
- Reduce the emergece of antimicrobial resistance
Origins of ABX resistance?
- Active eddlux
- Decreased permeability
- Enzymatic mods
- Target site changes
What are the ESKAPE pathogens?
§Enterococcus faecium
§Staphylococcus aureus
§Klebsiella pneumoniae
§Acinetobacter baumannii
§Pseudomonas aeruginosa
§Enterobacter species
How do we prevent resistance?
- Treatment guidelines
- Avoid antibiotics to treat colonization or contamination
- Utilize the most narrow-spectrum agent appropriate to treat the infection -> definitive therapy
- Utilize appropriate dosing & shortest effective duration of therapy
ABX that require serum monitoring?
Vanc and aminoglycosides
What type of ABX do you use for de escalation?
Narrowest SOA