SHC Antibiogram Data For Bacterial & Yeast Isolates
Jan 1 - Dec 31, 2015

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Interpretation of susceptibility results

Results are reported as minimum inhibitory concentrations (MICs), the minimum amount of drug needed to inhibit growth in vitro. Interpretive criteria are based on achievable serum levels. For certain antibiotics, the amount excreted into the urine via the kidneys is above the MIC, and the agent is effective clinically in this site even though reported as "resistant". Intermediate results (I), especially for beta-lactam agents, indicate that doses higher than standard recommendations may be effective. In other cases, "I" results indicate that the organism may be susceptible or resistant but the in vitro tests are not sensitive enough to determine specifically. For this antibiogram, Intermediate results are NOT included within the "%S" category.

Situations for which the use of vancomycin is appropriate and acceptable

  • For treatment of serious infections due to β-lactam-resistant gram- positive bacteria. Clinicians should be aware that vancomycin is usually less active and less rapidly bactericidal than β-lactam agents for organisms that are susceptible to the β-lactams. Clinicians should also be aware that vancomycin sensitive MIC 2mcg/ml is associated with increased treatment failures.
  • For treatment of infections due to gram-positive organisms in patients with serious allergy to β-lactam- antibiotics.
  • Prophylaxis, (infused 60-120 min before the first incision), in penicillin- allergic patients, as recommended by the Amer. Heart Assoc., for endocarditis following certain procedures in patients at high risk for endocarditis. Cephalosporins are still recommended for non-allergic patients.
  • Prophylaxis for major surgical procedures involving implantation of prosthetic materials or devices, e.g., cardiac and vascular procedures and total hip replacements, at institutions with a high rate of infections due to MRSA or MRCoNS. Currently MRSA and MRCoNS rates are 24% and 61% at SHC, respectively. A single dose administered 60-120 min before surgery is sufficient unless the procedure lasts more than 6 hours, in which case the dose should be repeated. Prophylaxis should be dc'd after 2 doses maximum.

Haemophilus influenzae

For infections with β-lactamase- producing H. influenzae: cefuroxime, cefotaxime, trimethoprim/ sulfamethoxazole, amoxicillin/clavulanate or azithromycin is recommended. Cefotaxime or ceftriaxone is drug of choice for CNS infections. At Stanford, 74% of H. influenzae are ampicillin susceptible.

Clinical Microbiology

  • Niaz Banaei, MD, Director
  • Nancy Watz, CLS, Reference Technologist, Antibiotic Testing
  • Diane Getsinger, CLS Reference Technologist, AFB/Mycology
  • Patricia Buchner, CLS, Reference Technologist, Anaerobes

Stanford Medicine

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