15 Selecting Antimicrobial Regimens W-B

Question 1

What is the systemic approach to picking the proper antimicrobial?

Answer 1

Confirming the presence of infection. Identification of the pathogen. Selection of antimicrobial agents. Monitor therapeutic response

Question 2

What do you look for when confirming the presence of infection?

Answer 2

Fever. WBC with differential. Pain/inflammation. Cough/sputum production

Question 3

What is a Fever?

Answer 3

Elevation of body temperature above nl range (36-37.8). Hypothalamus - thermal regulatory center. Enhanced leukocyte migration, lymphocyte function and reduced microbial replication. Fever pattern - high spiking vs. sustained fevers

Question 4

What can cause a “False-Negative” fever?

Answer 4

Overwhelming sepsis (may be hypothermic < 36). Ingestion of antipyretics or corticosteroids (these mask the bodies ability to cause a fever). Partially effective therapy. Localized infections (cystitis, chronic abscesses). Body unable to cause fever usually has worse prognosis

Question 5

What can cause a “False-Positive” fever?

Answer 5

Autoimmune disease, malignancy. Acute MI, PE, postop 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 DC

Question 6

What is the general information on WBCs?

Answer 6

Normal: 5-10,000. Mildly elevated - elderly, less serious infections. Sepsis: > 50,000. Could be elevated d/t: RA, corticosteroids, lithium, post-major surgery, acute MI. Could be low d/t: leukemia

Question 7

What is a Differential Count?

Answer 7

Increased neutrophil (PMNs, segs): bacterial infections, nl = 50-70%. Increased bands “left shift”: immature cells released in acute infection (normally ~5%). Increased lymphocytes: viral infections (nl: 20-40%). Eosinophilia: parasitic infections (nl = 0-5%), drug allergies. Neutropenia (< 1,000). Lymphopenia (CD4-T helper)

Question 8

What is Elevated ESR?

Answer 8

Erythrocyte sedimentation rate. Chronic or acute infections: endocarditis, osteomyelitis, intra-abdominal infections. Non-ID: collagen vascular disease. Normal does NOT rule out infection

Question 9

What is “Colonization”?

Answer 9

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

Question 10

What is “Infection”?

Answer 10

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

Question 11

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

Answer 11

Drug and allergy history - PCN: rash vs. hives. Concomitant disease states and drugs. Age - increased risk of hepatotoxicity to INH. Pregnancy. Site of infection: CSF vs. bone vs. blood vs. urine

Question 12

What antibiotics are Pregnancy Category B?

Answer 12

B-lactams, Macrolides, Clindamycin, Nitrofurantoin, Quinupristin/dalfopristin, Daptomycin

Question 13

Which antibiotics are Pregnancy Category D?

Answer 13

Aminoglycosides, Tetracyclines (Tigecycline)

Question 14

What are some pharmacologic factors for antimicrobial failure?

Answer 14

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

Question 15

What are some host factors for antimicrobial failure?

Answer 15

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

Question 16

What are some microbial factors for antimicrobial failure?

Answer 16

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