Free practice quiz
ABIM Infectious Disease Prep Course (ID): free quiz
10 questions from the program. See your score right away, then unlock the explanation of every answer.
- Question 1 of 10
A 68-year-old man with severe COPD is hospitalized with fever, increased sputum production, and right lower-lobe infiltrate. He has not received antibiotics in the past 6 months. A high-quality expectorated sputum specimen shows many neutrophils, rare squamous epithelial cells, and numerous small pleomorphic gram-negative coccobacilli. Blood cultures are pending. Which organism is most consistent with this Gram stain morphology?
H. influenzae is a small, pleomorphic gram-negative coccobacillus and commonly causes COPD-associated bronchitis and pneumonia. A high-quality sputum smear with neutrophils supports infection but still requires culture and susceptibility confirmation. M. catarrhalis is tempting in COPD but appears as gram-negative diplococci. S. pneumoniae causes lobar pneumonia but is a lancet-shaped gram-positive diplococcus. K. pneumoniae can cause severe pneumonia in older adults but appears as plump gram-negative rods, often capsulated. Diagnose using smear quality plus morphology, order culture, treat empirically for community respiratory pathogens, and escalate if severe pneumonia or resistant-risk features emerge.
- Question 2 of 10
A 34-year-old healthcare worker develops fatigue, anorexia, dark urine, and jaundice approximately 10 weeks after an occupational needlestick injury. Laboratory studies reveal markedly elevated aminotransferases. Hepatitis serologic testing demonstrates positive hepatitis B surface antigen, positive IgM antibody to hepatitis B core antigen, and negative antibody to hepatitis B surface antigen. Which interpretation is most appropriate?
A. Incorrect. Successful hepatitis B vaccination produces antibody to hepatitis B surface antigen without antibody to hepatitis B core antigen. Positive surface antigen and IgM core antibody indicate infection rather than vaccine-induced immunity.
B. Incorrect. Resolved natural hepatitis B infection generally produces negative surface antigen with positive total core antibody and positive surface antibody. The current findings indicate ongoing infection.
C. Incorrect. Chronic hepatitis B infection is defined by persistence of hepatitis B surface antigen for at least 6 months. IgM core antibody can occasionally appear during severe chronic hepatitis B flares, but the recent exposure and typical acute presentation favor newly acquired infection.
D. Correct. Positive hepatitis B surface antigen indicates current infection, while IgM antibody to hepatitis B core antigen strongly supports acute infection in this clinical setting. The exposure history, compatible incubation period, and acute hepatitis syndrome further support acute hepatitis B.
- Question 3 of 10
9. A 61-year-old patient with fever has one blood culture set collected, consisting of two bottles. Both bottles become positive for the same bacterial organism, but no additional independently collected or subsequent blood cultures are available. The treating physician asks whether this finding proves sustained bacteremia. Which response best reflects the available microbiological evidence?
A. Correct. Positivity in both bottles strengthens concern for true bacteremia compared with an isolated positive bottle, although organism identity remains important. Sustained bacteremia specifically implies continued bloodstream infection, which cannot be determined from one collection alone.
B. Incorrect. Multiple positive bottles within a single collection do not demonstrate persistence across time.
C. Incorrect. A single blood culture set may still provide clinically meaningful evidence. Its significance depends on organism identity, positivity pattern, and clinical context.
D. Incorrect. Blood culture results can raise suspicion for an endovascular focus but do not independently establish the anatomical source.
- Question 4 of 10
A 68-year-old woman with a mechanical aortic valve presents with persistent fever and multiple blood cultures positive for a typical endocarditis-associated organism. Initial transthoracic echocardiography does not demonstrate a definite vegetation, but clinical suspicion for prosthetic valve endocarditis remains high. Which imaging study is most appropriate next?
A: Noncontrast chest CT does not adequately assess prosthetic valve vegetations or the relevant intracardiac structures.
B: Spinal MRI is appropriate for suspected vertebral or epidural infection, but no spinal syndrome is described.
C: Waiting until treatment completion risks overlooking an infection that could require an earlier change in management.
D: Correct. Transesophageal echocardiography provides improved visualization of prosthetic valves and nearby cardiac structures compared with transthoracic imaging. Persistent suspicion after an inconclusive transthoracic study warrants more sensitive cardiac imaging to identify vegetations or complications that may alter treatment and surgical planning.
- Question 5 of 10
A 57-year-old man is hospitalized with complicated pyelonephritis and bacteremia. Empiric ceftriaxone was initiated before susceptibility testing became available. On hospital day 2, concordant blood and urine cultures identify Escherichia coli resistant to ceftriaxone but susceptible to meropenem. His temperature has decreased modestly, although he remains intermittently febrile. Which antimicrobial decision is most appropriate?
A: Incorrect. Partial symptomatic improvement does not override definitive resistance findings in a patient with documented bacteremia. Targeted antimicrobial treatment should account for the organism's susceptibility profile.
B: Incorrect. A modest decline in temperature does not establish that documented pyelonephritis and bacteremia have been adequately treated. Clinical response must be interpreted with microbiology rather than in isolation.
C: Correct. Cultures identify the causative organism and demonstrate resistance to the empiric drug but susceptibility to meropenem. Changing to confirmed active therapy applies culture-guided treatment selection, with subsequent reassessment according to clinical response.
D: Incorrect. Continuing or increasing exposure to an antibiotic reported as resistant does not meaningfully incorporate the definitive susceptibility data. The identified resistance requires a reassessment of treatment selection.
- Question 6 of 10
A 54-year-old lung transplant recipient receiving voriconazole for invasive pulmonary aspergillosis is diagnosed with active tuberculosis. A rifampin-containing regimen is proposed while the patient continues voriconazole. Which concern requires immediate clarification before starting treatment?
Option A: Correct. Rifampin is a potent inducer of hepatic drug-metabolizing enzymes and can profoundly reduce systemic voriconazole exposure. This interaction risks antifungal treatment failure, and the combination is contraindicated. An alternative tuberculosis or antifungal strategy should be selected before treatment proceeds.
Option B: Incorrect. Rifampin does not increase voriconazole exposure through gastric acid enhancement. The dominant interaction is metabolic induction rather than improved gastrointestinal absorption.
Option C: Incorrect. Direct gastrointestinal binding is characteristic of certain interactions involving polyvalent cations, not the rifampin-voriconazole interaction.
Option D: Incorrect. Rifampin induces rather than inhibits the major pathways responsible for voriconazole elimination. The expected result is markedly reduced voriconazole exposure, not increased exposure.
- Question 7 of 10
A 58-year-old man presents to the emergency department with 3 days of fever, productive cough, and progressive dyspnea. Chest imaging demonstrates a new right lower lobe infiltrate, and he has not recently been hospitalized or received mechanical ventilation. Which pneumonia classification is most appropriate for guiding his initial management?
A: Incorrect. HAP develops in the hospital after admission rather than presenting as an infection acquired in the community. The patient's pneumonia was already present when he sought hospital care.
B: Correct. CAP is the appropriate framework for pneumonia developing outside the hospital. Classification establishes the initial management pathway, although individual host factors and resistance risks must still guide empiric antibiotic selection.
C: Incorrect. VAP occurs in patients receiving invasive mechanical ventilation. This patient has not been mechanically ventilated.
D: Incorrect. Aspiration-associated pneumonia is considered when aspiration is an important contributing mechanism. The presentation does not identify an aspiration event or a relevant aspiration risk factor.
- Question 8 of 10
A 68-year-old man presents with increasing pain, warmth, swelling, and drainage around his right knee 18 days after total knee arthroplasty. He initially recovered well but developed worsening symptoms over the preceding 4 days. The infectious disease consultant suspects a prosthetic joint infection. Which clinical presentation category best describes this patient's condition?
A — Correct: Infection developing shortly after prosthetic joint implantation is characteristic of an early postoperative presentation. Recognizing the temporal relationship to surgery helps classify the infection and informs subsequent diagnostic and hardware-management decisions.
B — Incorrect: Delayed infection presents after a more prolonged interval following implantation, rather than within the initial postoperative period.
C — Incorrect: Hematogenous infection involves seeding of an implanted joint from an infection elsewhere. The presentation is closely associated with recent surgery, without a described distant infectious source.
D — Incorrect: Prosthetic joint infections may occur early after implantation. Recent surgery does not exclude infection when compatible local findings develop.
- Question 9 of 10
A 34-year-old woman presents with 2 days of dysuria, urinary frequency, and suprapubic discomfort. She is afebrile, has no flank pain or costovertebral angle tenderness, and has no history of urinary tract instrumentation. Which of the following is the most likely clinical syndrome?
A: Acute pyelonephritis is less likely because the presentation lacks fever, flank pain, or other findings suggesting upper urinary tract involvement.
B: Correct. Dysuria, frequency, and suprapubic discomfort without systemic illness or flank symptoms are most consistent with cystitis. Distinguishing lower from upper urinary tract infection guides subsequent evaluation and treatment.
C: Obstructive infection is not supported by the presented history or examination. No findings suggest impaired urinary drainage or an associated upper tract complication.
D: Catheter-associated infection requires an appropriate instrumentation context. This patient has no history of urinary catheterization.
- Question 10 of 10
A 67-year-old man is hospitalized with persistent fever and elevated inflammatory markers. He received broad-spectrum antibiotics for 4 days at an outside facility before blood cultures were obtained. All routine blood cultures subsequently show no growth, but his fever continues. Which interpretation of the negative cultures is most appropriate?
A: Incorrect. Negative routine cultures cannot definitively exclude infection, particularly when antibiotics were administered before specimen collection.
B: Correct. Prior antibiotic exposure is an important explanation for culture-negative infection. Persistent clinical suspicion should prompt continued evaluation, including consideration of fastidious organisms, deep infectious foci, and targeted diagnostic testing.
C: Incorrect. Noninfectious conditions remain part of the differential diagnosis, but negative cultures following antimicrobial exposure do not establish a noninfectious etiology.
D: Incorrect. Waiting for routine cultures to become positive risks missing infections that require alternative diagnostic methods, including serology, molecular testing, or tissue sampling.
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