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.

• 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

• 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

• 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

• 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

• 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

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

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.