An 81-year-old woman is transferred to you from another hospital with a history of methicillin-resistant Staphylococcus aureus bacteremia that led to prosthetic hardware infection of a recent total hip arthroplasty. Her bacteremia cleared, and rifampin was initiated on the day of transfer, while also continuing vancomycin. She remains intubated and sedated on a ventilator for respiratory failure due to comorbid chronic obstructive pulmonary disease. You consider starting corticosteroids for her exacerbation of her chronic obstructive pulmonary disease. Before starting any new medications for this patient, what should you do?
Correct Answer: A
Rifamycins are often used in the management of infections associated with implanted prosthetic materials, and for tuberculosis. Because rifamycins are potent inducers of the cytochrome P450 system (CYP 3A4), it is important to be check for drug-drug interactions and changes in drug metabolism for patients taking these medications. Corticosteroids are metabolized by the cytochrome P450 system, and steroid doses might need to be increased to counteract this increase in metabolism. It is best to work closely with a pharmacist when caring for a patient receiving medications that dramatically alter drug metabolism. Rifampin levels are not useful in indicating the extent to which the cytochrome P450 system has been induced.
References:
You are caring for an 18-year-old woman undergoing CAR T-cell therapy for relapsed acute lymphoblastic leukemia. She was admitted to the ICU with hypotension and altered mental status. Blood cultures are positive for S. aureus in all four bottles collected on the day of admission.
Which of the following has been associated with a mortality benefit in S. aureus bacteremia?
Correct Answer: D
Patients with indwelling central venous catheters (CVCs) are at increased risk of invasive bloodstream infections. S. aureus is one of the most common bloodstream infections and is associated with considerable morbidity and mortality. Because of the complexities in management of S. aureus bacteremia, infectious diseases consultation is recommended and was shown to provide a mortality benefit in a 2016 systematic review and meta-analysis. Although removal of CVCs early in the course of treatment for S. aureus bacteremia is generally recommended, removal on the day of diagnosis is not necessary in most cases and has not been associated with a mortality benefit. Intravenous antibiotic therapy is the mainstay of treatment for S. aureus bacteremia, but the duration of therapy is generally 2 to 6 weeks unless there is associated endocarditis or infection of prosthetic material. Adding rifampin is not recommended early in the course of therapy when bacterial burden is high, as there is a low barrier to developing resistance to rifampin.
A 56-year-old man is admitted to the ICU for sepsis and meningismus. Eleven days before admission, he had started a corticosteroid burst for severe atopic dermatitis. He is found to have Streptococcus bovis meningitis, and polymicrobial bacteremia with Escherichia coli, Enterococcus faecalis, and S. bovis. Of note, he immigrated to the United States from South America 2 years ago. In addition to abdominal imaging with computed tomography and serologic testing, which of the following should you consider treating the patient with?
This patient likely has Strongyloides stercoralis hyperinfection syndrome leading to polymicrobial bacteremia and meningitis. When gastrointestinal organisms are cultured from the cerebrospinal fluid, clinicians should suspect an intestinal source of bacteremia. Common sources include gastrointestinal malignancy, perforation, or intra-abdominal disaster. At least 10% to 40% of people living in tropical and subtropical regions are exposed to the soil helminth S. stercoralis, and most infections are asymptomatic, though affected persons may have peripheral eosinophilia. After infection, S. stercoralis is normally contained within the gastrointestinal tract by the host immune system, but parasite larvae can escape from the gastrointestinal tract in the setting of high-dose steroid administration or other systemic immune suppression, carrying gastrointestinal bacteria along with the escaped parasite. The larvae can then penetrate multiple sites including the central nervous system, leading to bacterial meningitis with gastrointestinal flora, which is sometimes polymicrobial. The treatment of choice for S. stercoralis hyperinfection syndrome is ivermectin. The other antiparasitic medications are not wellestablished treatments for strongylodiasis.
You are treating a patient for Klebsiella pneumoniae bacteremia. Your microbiology laboratory provides you with the following antimicrobial susceptibility data:
Which of the following medications is the BEST choice for treatment?
For most bacteremias caused by gram-negative organisms, the antibiotic with the narrowest spectrum and fewest toxicities is generally the best choice for treatment. Both ciprofloxacin and ceftriaxone would be reasonable choices for this patient; however, the minimum inhibitory concentration to ciprofloxacin for this isolate is too high to be considered susceptible. As ciprofloxacin and levofloxacin are the only oral antibiotics commonly used in the United States to treat gram-negative bacteremias, aminoglycosides are associated with greater toxicity, and the other antibiotic choices have a broad spectrum; ceftriaxone is therefore the best of the remaining options.
Reference:
You are treating a patient with acute renal failure for Enterobacter aerogenes bacteremia. Your microbiology laboratory provides you with the following antimicrobial susceptibility data:
Of the following medications, which is the BEST choice for treatment?
Correct Answer: B
E. aerogenes is also one of the so-called SPICE or SPACE organisms that exhibit inducible beta-lactamases or stable depression of the chromosomal beta-lactamase. These organisms include bacteria of the genera Serratia, Pseudomonas, indole-positive Proteus, Acinetobacter, Citrobacter, and Enterobacter. These bacteria can develop resistance to third- and fourthgeneration cephalosporins (such as Ceftriaxone and Cefepime) during, or shortly after, a course of treatment. The risk of developing resistance is highest in the setting of bacteremia and is estimated at 5% to 20%. The carbapenem antimicrobial class (meropenem, imipenem, or ertapenem) has a low failure rate in this setting, and medications from this class can be safely used in patients with renal failure.
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