Selecting Antimicrobial Regimens Flashcards
What can cause a “False-Negative” fever?
- Overwhelming sepsis (may be hypothermic < 36 - usually worse prognosis)
- Ingestion of antipyretics or corticosteroids (these mask the bodies ability to cause a fever)
- Partially effective therapy
- Localized infections (cystitis, chronic abscesses)
What can cause a “False-Positive” fever?
- Autoimmune disease, malignancy
- Acute MI, PE, post-op atelectasis
- Drug-induced: hypersensitivity reaction or antigen-antibody complex resulting in stimulation of macrophages and release of IL-1 (amphotericin B, B-lactams, anticonvulsants, allopurinol, nitrofurantoin). Drug-induced fever usually resolves 48 hrs after drug D/C
Normal WBC Count vs. Sepsis WBC Count
Normal: 5-10,000
Sepsis: > 50,000
Increased Neutrophils is a Sign of
80-95% = Bacterial Infection
Increased Bands is a Sign of
“Left shift”
Sign of acute infection
Increased Lymphocytes is a Sign of
Normal Level: 20-40%
Viral infection
Eosinophilia is a Sign of
Normal Level: 0-5%
Parasitic infection
Normal Procalcitonin Level vs. Sepsis Procalcitonin Level
Normal: <0.05 ng/mL
Sepsis: >/= 0.5 ng/mL
What is procalcitonin useful for?
- Differentiating between bacterial and viral infections
- Determining when to de-escalate antibiotic therapy
Should you obtain infected body materials for gram stain and cultures before or after starting abx?
Before
Factors to help determine likely pathogen - basis for empiric abx
- Site of Infection
- Age of pt
- Immune status of pt (AIDS, transplant)
- Prior use of abx
- Concomitant diseases (COPD, EtOH, IVDA)
- Nosocomial vs. community-acquired
What is “Colonization”?
Presence of an organism at a body site WITHOUT production of disease in a host, “normal flora”
What is “Infection”?
Presence of an organism within tissues with invasiveness that often results in a response by the host’s immune defenses
What do you need to confirm the presence of an infection?
- Signs and symptoms of infection
- Cultures
What are the host factors to think about when selecting an antimicrobial agent?
- Drug and allergy history
- Concomitant disease states and drugs (renal or hepatic dysfunction, seizure hx, DDI)
- Age
- Pregnancy
- Site of infection: CSF vs. bone vs. blood vs. urine
Antibiotics with Pregnancy Considerations
- Fluoroquinolones: C/I
- Tetracyclines: C/I
- Macrolides: only use if no alternative therapies
- Bactrim: avoid in 1st and 3rd trimester
- Nitrofurantoin: safe except at term (38-42 weeks)
- Metronidazole: avoid in 1st trimester if possible, but can be used in any trimester to treat bacterial vaginosis due to trichmonas
- Telavancin, Dalbavancin, Oritavancin are Pregnancy Category C
Pregnancy Trimesters by Weeks
- 1st Trimester: 1-12 weeks
- 2nd Trimester: 13-26 weeks
- 3rd Trimester: 27 weeks - end of pregnancy
What are some drug factors to think about when choosing an antimicrobial agent?
- PK
- Tissue penetration
- Cost effectiveness
- Route of administration
- Dosing
- Combination therapy
How long after starting antimicrobials should you start to see pt improvement?
48-72 hrs
What are some pharmacologic factors for antimicrobial failure?
- Subtherapeutic dosing
- Reduced oral absorption
- Inadequate duration of therapy
- Poor penetration: meningitis, prostatitis, endophthalmitis
What are some host factors for antimicrobial failure?
- Immune status: neutropenia, HIV infection
- Undrained abscesses, prosthetic materials not removed
- Structural abnormalities of various organs
- Poor circulation - peripheral vascular disease
What are some microbial factors for antimicrobial failure?
- Drug resistance
- Superinfection - isolation of a new pathogen resistant to the previous antibiotic regimen
