Selecting Antimicrobial Regimens

Question 1

What can cause a “False-Negative” fever?

Answer 1

• 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)

Question 2

What can cause a “False-Positive” fever?

Answer 2

• 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

Question 3

Normal WBC Count vs. Sepsis WBC Count

Answer 3

Normal: 5-10,000
Sepsis: > 50,000

Question 4

Increased Neutrophils is a Sign of

Answer 4

80-95% = Bacterial Infection

Question 5

Increased Bands is a Sign of

Answer 5

“Left shift”

Sign of acute infection

Question 6

Increased Lymphocytes is a Sign of

Answer 6

Normal Level: 20-40%

Viral infection

Question 7

Eosinophilia is a Sign of

Answer 7

Normal Level: 0-5%

Parasitic infection

Question 8

Normal Procalcitonin Level vs. Sepsis Procalcitonin Level

Answer 8

Normal: <0.05 ng/mL

Sepsis: >/= 0.5 ng/mL

Question 9

What is procalcitonin useful for?

Answer 9

• Differentiating between bacterial and viral infections
• Determining when to de-escalate antibiotic therapy

Question 10

Should you obtain infected body materials for gram stain and cultures before or after starting abx?

Answer 10

Before

Question 11

Factors to help determine likely pathogen - basis for empiric abx

Answer 11

• 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

Question 12

What is “Colonization”?

Answer 12

Presence of an organism at a body site WITHOUT production of disease in a host, “normal flora”

Question 13

What is “Infection”?

Answer 13

Presence of an organism within tissues with invasiveness that often results in a response by the host’s immune defenses

Question 14

What do you need to confirm the presence of an infection?

Answer 14

• Signs and symptoms of infection
• Cultures

Question 15

What are the host factors to think about when selecting an antimicrobial agent?

Answer 15

• 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

Question 16

Antibiotics with Pregnancy Considerations

Answer 16

• 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

Question 17

Pregnancy Trimesters by Weeks

Answer 17

• 1st Trimester: 1-12 weeks
• 2nd Trimester: 13-26 weeks
• 3rd Trimester: 27 weeks - end of pregnancy

Question 18

What are some drug factors to think about when choosing an antimicrobial agent?

Answer 18

• PK
• Tissue penetration
• Cost effectiveness
• Route of administration
• Dosing
• Combination therapy

Question 19

How long after starting antimicrobials should you start to see pt improvement?

Answer 19

48-72 hrs

Question 20

What are some pharmacologic factors for antimicrobial failure?

Answer 20

• Subtherapeutic dosing
• Reduced oral absorption
• Inadequate duration of therapy
• Poor penetration: meningitis, prostatitis, endophthalmitis

Question 21

What are some host factors for antimicrobial failure?

Answer 21

• Immune status: neutropenia, HIV infection
• Undrained abscesses, prosthetic materials not removed
• Structural abnormalities of various organs
• Poor circulation - peripheral vascular disease

Question 22

What are some microbial factors for antimicrobial failure?

Answer 22

• Drug resistance
• Superinfection - isolation of a new pathogen resistant to the previous antibiotic regimen