6 High-Yield Infectious Disease Pearls for Clinical Practice and the ABIM Exam

In keeping with the popularity of the high-yield pearls posts from nephrology, I decided to write a post giving you my 5 high-yield infectious disease (ID) pearls, beneficial for your clinical practice and ABIM exam preparation. The purpose of these posts is to give you some concise, practical teaching points that are supported by the medical literature.


Pearl #1: Staphylococcus aureus bacteremia can be more complicated than getting 2 weeks of intravenous antibiotics

  • Patients treated for at least 2 weeks of antibiotics are more likely to be cured of bacteremia and less likely to have recurrence of bacteremia3
  • Recurrence of bacteremia may be due to bone, joint, and cardiac involvement due to inadequate initial antimicrobial course3
  • Patients with cardiac, bone, and joint involvement need at least 4 – 6 weeks of antimicrobial coverage
  • Remove intravascular catheters if patient has Staphylococcus aureus bacteremia (20 – 26% of cases are complicated by infective endocarditis or metastatic infection) 8
  • Patients with hematuria during Staphylococcus aureus bacteremia should have further evaluation for infective endocarditis8
  • Oral linezolid can be used to complete a 2-week course in some cases12


Pearl #2: Candida in the blood is not a contaminant, but could be in the sputum or urine

  • Candida in the blood is NEVER a contaminant 11
  • Removal of an intravenous catheter alone is never an absolute treatment; highest mortality rates are seen in patients without antifungal therapy9
  • All patients with candidemia should undergo ophthalmologic examination10
  • Micafungin is the treatment of choice for candidemia, and preferred over azoles8
  • Asymptomatic candiduria does not require further workups or antifungal therapy in most cases; Symptomatic funguria always requires treatment 6


Pearl #3: Clostridium difficile toxin should not be re-checked for cure and has a poor sensitivity

  • Clostridium difficile associated diarrhea (CDAD) should be suspected after recent antibiotic use and/or if in the hospital for more than 2 days
  • Consider infection with C. difficile in the differential diagnosis when a leukocytosis in hospitalized patients develops
  • Diarrhea does not have to be present to have a diagnosis of C. difficile colitis
  • C. Diff stool assay produces a false negative test 10 – 20% of the time2
  • C. Diff stool toxin assays remain positive during and after successful treatment, therefore follow up assays for cure are not helpful, follow clinical course 7


Pearl #4: Blood cultures should always be obtained before parenteral antibiotics are given

  • Both the Infectious Disease Society of America (IDSA) and American Thoracic Society (ATS) advocate obtaining two sets of blood cultures prior to initiating antibiotic therapy
  • Coagulase-negative staphylococci is a contaminant in blood cultures about 82% of the time11
  • The difference between blood cultures before the initiation of antibiotics and after the initiation of antibiotics in identifying a pathogen is 40% versus 18.7%4
  • Appropriate blood cultures, allows for prompt identification of the offending organisms which influences diagnosis, therapy, and prognosis when positive


Pearl #5: Empiric antibiotics for acute uncomplicated cystitis have changed5

  • Nitrofurantoin monohydrate/macrocrystals 100mg BID for 5 days is the appropriate choice for empiric therapy of urinary tract infection
  • Trimethoprim-sulfamethoxzaole 160/800mg BID for 3 days is an appropriate empiric choice if local resistance rates of uropathogens do not exceed 20% (expert opinion)
  • Fosfomycin trometamol 3g in a single dose is an appropriate empiric choice for urinary tract infection, but may be inferior efficacy compared to standard short-course regimens
  • Pivmecillinam 400mg BID for 3 – 7 days is also an appropriate empiric antimicrobial agent where available
  • Fluoroquinolones (ofloxacin, ciprofloxacin, and levofloxacin) should be considered alternative antimicrobials for acute uncomplicated cystitis
  • Amoxicillin or ampicillin should not be used for empirical treatment due to resistance to these agents


Pearl #6: The loading dose of vancomycin is 25 – 30mg/kg based on actual body weight in critically ill patients

  • Best predictor of efficacy of vancomycin is time above the antimicrobial MIC1


There are so many more high-yield pearls for infectious disease, but these in my humble opinion are practice changing, cost saving, and also affect patient outcomes. If there are other high-yield topics in infectious disease or other specialties you would like to read about in the future, please leave your comments or message me @srrezaie.



1. Ackerman BH et al. Necessity of a Loading Dose When Using Vancomycin in Critically Ill Patients. Journal of Antibicrobial Chemotherapy. 1992; 29 (4): 460 – 1. PMID: 1607335

2. Bartlett JG et al. Antibiotic-Associated Diarrhea. NEJM 2002 346: 334 – 339. PMID: 11821511

3. Fowler VG et al. Outcome of Staphylococcus Aureus Bacteremia According to Compliance With Recommendations of Infectious Diseases Specialists: Experience With 244 Patients. Clin Infect Dis 1998 Sep; 27 (3): 478 – 86. PMID: 9770144

4. Grace CJ et al. Usefulness of Blood Culture for Hospitalized Patients who are Receiving Antibiotic Therapy. Clin Infect Dis 2001 Jun; 32 (11): 1651 – 5. PMID: 11340541

5. Gupta et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis 2011 Mar; 52 (5): e103 – 20. PMID: 21292654

6. Hollenbach E. To Treat or Not to Treat – Critically Ill Patients with Candiduria. Mycoses 2008 Sep. 51; (2) 12 – 24. PMID: 18721329

7. Kelly CP et al. Clostridium difficile – More Difficult than Ever. NEJM 2008 Oct; 359 (18): 1932 -40. PMID: 18971494

8. Kim AI et al. Staphylococcus Aureus Bacteremia: Using Echocardiography to Guide Length of Therapy. Cleve Clin J Med 2003 Jun; 70 (6): 517, 520 -1, 525 -6. PMID: 12828223

9. Nguyen MH et al. Therapeutic Approaches in Patients with Candidemia. Evaluation in a Multicenter, Prospective, Observational Study. Arch Inern Med 1995; 155 (22): 24 – 29. PMID: 7503601

10. Pappas PG et al. Clinical Practice Guidelines for the Management of Candidiasis: 2009 Update by the Infectious Diseases Society of America. Clin Infect Dis 2009 Mar; 48 (5) 503 – 35. PMID: 19191635.

11. Pien BC et al. The Clinical and Prognostic Importance of Positive Blood Cultures in Adults. Am J Med 2010 Sep; 123 (9): 819 – 28. PMID: 20800151

12. Sharpe JN et al. Clinical And Economic Outcomes of Oral Linezolid Versus Intravenous Vancomycin in the Treatment of MRSA-complicated, Lower-Extremity Skin and Soft-Tissue Infections caused by Methicillin-Resistant Staphylococcus Aureus. Am J Surg 2005 Apr; 189 (4): 425 – 8. PMID: 15820454



Dr. Salim R. Rezaie is a physician at the University of Texas Health Science Center at San Antonio. He is double board-certified in Emergency Medicine and Internal Medicine.

_______________________________________________________________________________ You can find other posts by Dr. Rezaie on the Knowmedge Blog. You can also find additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.

About Salim Rezaie

Dr. Rezaie completed his medical school training at Texas A&M Health Science Center, and followed that up with a combined Emergency Medicine/Internal Medicine residency at East Carolina University in Greenville, NC. Currently, he is an attending on the faculty of UTHSCSA in San Antonio, TX, where he focuses on medical education, social media as a tool for education (FOAMed), and building the bridges between internal medicine, critical care, and emergency medicine. Feel free to contact him on Twitter (@srrezaie) (@UTHSCSAPearls) about anything EM/IM! Salim Rezaie
August 2, 2013

Of course, it is my pleasure and passion to teach and I am humbled that you are getting good use out of the information. I only hope that others are also finding this series of “High Yield Pearls” useful. I will continue to work on some of the other subspecialties as well. It appears, that several folks are getting some useful info from them, plus I enjoy writing them. Consider your request done, and I will start working on some more pearls.


August 2, 2013

Dr Rezaie, you are awesome….. Thank you for these pearls in ID and previously in Nephrology. Only if I can thank you enough for all this work and dedication. please keep them coming. We also need ABIM pearls Endocrine, Hematology, Cardio, Rheumatology…among others.

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