ITE Infectious Disease Management Questions and Answers — Questions and Answers
Question 1: A 58-year-old male with acute myeloid leukemia is undergoing induction chemotherapy. He develops a fever of 39.2°C (102.6°F) and his absolute neutrophil count is 150 cells/mm³. He is hemodynamically stable with no clear source of infection on initial examination. According to IDSA guidelines, which of the following is the most appropriate initial empiric antibiotic regimen?
- Ceftriaxone
- Vancomycin plus Cefepime
- Piperacillin-tazobactam (Correct answer)
- Metronidazole plus Ciprofloxacin
Correct answer: Piperacillin-tazobactam
In high-risk febrile neutropenia, empiric monotherapy with an anti-pseudomonal beta-lactam is the standard of care. Piperacillin-tazobactam, cefepime, meropenem, or imipenem-cilastatin are all appropriate first-line choices. Ceftriaxone lacks reliable Pseudomonas aeruginosa coverage. Vancomycin is not recommended for routine initial empiric therapy unless specific indications are present, such as suspected catheter-related infection, pneumonia, hemodynamic instability, or known MRSA colonization. Metronidazole would only be added if an anaerobic source, like an intra-abdominal infection, is suspected.
Question 2: According to the 2021 IDSA and SHEA focused update, which of the following is the preferred first-line agent for an initial episode of non-severe *Clostridioides difficile* infection?
- Oral Fidaxomicin (Correct answer)
- Oral Metronidazole
- Oral Vancomycin
- Fecal Microbiota Transplantation
Correct answer: Oral Fidaxomicin
The 2021 IDSA/SHEA guidelines conditionally recommend oral fidaxomicin as the preferred agent over oral vancomycin for an initial episode of C. difficile infection (CDI). This preference is based on evidence showing fidaxomicin has a lower rate of CDI recurrence compared to vancomycin. Oral metronidazole is no longer recommended as a first-line agent for even mild-to-moderate disease. Fecal microbiota transplantation is reserved for patients with multiple recurrent episodes.
Question 3: A 72-year-old man with a history of alcoholism is brought to the emergency department with a 24-hour history of high fever, severe headache, nuchal rigidity, and confusion. A lumbar puncture is planned but will be delayed for a CT scan of the head. Which of the following empiric antimicrobial regimens should be administered immediately?
- Vancomycin plus ceftriaxone
- Ceftriaxone plus ampicillin
- Meropenem monotherapy
- Vancomycin, ceftriaxone, and ampicillin (Correct answer)
Correct answer: Vancomycin, ceftriaxone, and ampicillin
For adults over the age of 50 with suspected bacterial meningitis, empiric therapy must cover the most common pathogens, including *Streptococcus pneumoniae*, *Neisseria meningitidis*, and *Listeria monocytogenes*. The combination of vancomycin (for resistant pneumococcus), a third-generation cephalosporin like ceftriaxone (for pneumococcus and meningococcus), and ampicillin (for *Listeria*) is the recommended regimen. Omitting ampicillin would leave the patient vulnerable to *Listeria*, which has increased incidence in older adults, pregnant women, and the immunocompromised.
Question 4: A 42-year-old individual with HIV is found to have a CD4+ T-cell count of 85 cells/µL and is seropositive for *Toxoplasma gondii*. According to the CDC and NIH guidelines, which of the following prophylactic medications is indicated?
- Azithromycin
- Trimethoprim-sulfamethoxazole (Correct answer)
- Valganciclovir
- Itraconazole
Correct answer: Trimethoprim-sulfamethoxazole
Trimethoprim-sulfamethoxazole is indicated for primary prophylaxis against both *Pneumocystis jirovecii* pneumonia (PJP) and toxoplasmosis in this patient. Prophylaxis for PJP should be initiated when the CD4 count is <200 cells/µL, and prophylaxis for toxoplasmosis should be initiated in seropositive patients when the CD4 count is <100 cells/µL. Trimethoprim-sulfamethoxazole is the preferred agent for both conditions. Azithromycin is used for *Mycobacterium avium* complex (MAC) prophylaxis when the CD4 count is <50 cells/µL. Valganciclovir and Itraconazole are not indicated for primary prophylaxis in this scenario.
Question 5: A 35-year-old person who injects drugs presents with a fever of 38.8°C (101.8°F) and a new holosystolic murmur. Blood cultures are drawn, and an echocardiogram is ordered. According to the modified Duke criteria, which of the following findings constitutes a major criterion for the diagnosis of infective endocarditis?
- Echocardiogram showing an oscillating intracardiac mass on a valve (Correct answer)
- Fever >38.0°C
- Presence of Janeway lesions
- Positive blood culture for *Staphylococcus epidermidis* from a single sample
Correct answer: Echocardiogram showing an oscillating intracardiac mass on a valve
The modified Duke criteria classify findings into major and minor categories. The major criteria include: (1) positive blood cultures typical for infective endocarditis and (2) evidence of endocardial involvement. Evidence of endocardial involvement on an echocardiogram includes an oscillating intracardiac mass (vegetation), abscess, or new partial dehiscence of a prosthetic valve. Fever, vascular phenomena (like Janeway lesions), and immunologic phenomena are all minor criteria. A single positive blood culture with a common skin contaminant like *S. epidermidis* does not meet the major criterion for blood cultures.
Question 6: A 29-year-old nurse undergoes routine employee health screening and is found to have a positive tuberculin skin test (15 mm induration). She is asymptomatic and her chest X-ray is negative for active disease. According to current CDC guidelines, which of the following is a preferred short-course regimen for treating latent tuberculosis infection (LTBI)?
- Isoniazid daily for 9 months
- Ethambutol daily for 12 months
- Isoniazid and rifapentine once weekly for 3 months (Correct answer)
- Levofloxacin daily for 6 months
Correct answer: Isoniazid and rifapentine once weekly for 3 months
The CDC preferentially recommends short-course, rifamycin-based regimens for the treatment of LTBI due to higher completion rates and similar efficacy compared to the older 9-month isoniazid regimen. The preferred regimens include once-weekly isoniazid plus rifapentine for 3 months (3HP), daily rifampin for 4 months (4R), or daily isoniazid plus rifampin for 3 months (3HR). While 9 months of daily isoniazid is still an acceptable alternative, it is no longer the sole preferred regimen. Ethambutol and levofloxacin are not first-line agents for treating LTBI.
ITE Infectious Disease Management Questions and Answers
A 58-year-old male with acute myeloid leukemia is undergoing induction chemotherapy.
He develops a fever of 39.2°C (102.6°F) and his absolute neutrophil count is 150 cells/mm³.
He is hemodynamically stable with no clear source of infection on initial examination.
According to IDSA guidelines, which of the following is the most appropriate initial empiric antibiotic regimen?