Infectious Diseases

A $61$-year-old male landscape architect presents to the emergency department in coastal Connecticut during early September. His wife reports that he has had $4$ days of high-grade fever, drenching sweats, profound fatigue, and progressive confusion. His medical history is significant for a splenectomy at age $25$ following blunt abdominal trauma, and essential hypertension. Vital signs show a temperature of $39.8^\circ\text{C}$ ($103.6^\circ\text{F}$), blood pressure of $88/54 \text{ mm Hg}$, heart rate of $126/\text{min}$, and respiratory rate of $28/\text{min}$. Oxygen saturation is $88\%$ on room air. Physical examination reveals marked scleral icterus and pale conjunctivae. Auscultation of the lungs reveals bibasilar crackles.

Laboratory evaluation shows the following:

A peripheral blood smear demonstrates numerous intraerythrocytic pleomorphic ring forms and occasional tetrad structures. Quantitative analysis reveals a parasitemia level of $16\%$.

Which of the following is the most appropriate management for this patient?

A 42-year-old woman is evaluated on the medical floor for ongoing management of a bloodstream infection. She was admitted three days ago with a high fever and localized erythema surrounding a peripheral intravenous catheter site. Blood cultures were drawn, the catheter was removed, and she was started on empiric intravenous vancomycin and intravenous cefepime. The patient is currently afebrile and her localized erythema has resolved. Today, the initial blood cultures are finalized, showing growth of Staphylococcus aureus. Susceptibility testing reveals the organism is resistant to penicillin but susceptible to oxacillin, cefazolin, and vancomycin. Repeat blood cultures drawn 48 hours after admission show no growth. Which of the following is the most appropriate next step in the antibiotic management of this patient?

A 62-year-old man is evaluated in the intensive care unit for antimicrobial management. He was admitted 8 days ago after a severe motor vehicle collision resulting in multiple rib fractures and a pulmonary contusion. He has required mechanical ventilation since admission. On hospital day 6, he developed a new fever, increased purulent endotracheal secretions, and a right lower lobe consolidation on chest radiography. He was empirically started on intravenous vancomycin and piperacillin-tazobactam for suspected ventilator-associated pneumonia.

Today (hospital day 8), his temperature is 37.6°C (99.7°F), blood pressure is 122/78 mmHg, and heart rate is 84/min. Endotracheal aspirate cultures obtained on day 6 now show $>10^5$ CFU/mL of *Enterobacter cloacae*. Blood cultures remain sterile. Antimicrobial susceptibility testing for the *E. cloacae* isolate is reported below:

Which of the following is the most appropriate modification to this patient's pharmacotherapy?

Match each clinical presentation of an immunocompromised patient with advanced HIV infection to the most appropriate initial targeted pharmacologic therapy.

A $68$-year-old woman is brought to the emergency department by her family due to a $24$-hour history of severe generalized headache, high fever, and progressive confusion. Her temperature is $39.2^\circ\text{C}$ ($102.6^\circ\text{F}$), blood pressure is $110/70 \text{ mmHg}$, pulse is $115/\text{min}$, and respirations are $18/\text{min}$. On physical examination, the patient is lethargic and oriented only to her name. She exhibits nuchal rigidity. There are no focal neurologic deficits, and funduscopic examination reveals no papilledema. Which of the following represents the most appropriate sequence of steps in the management of this patient?

Match the following clinical exposure scenarios with their most appropriate post-exposure prophylaxis or empiric treatment regimen.

Match each patient's clinical presentation and peripheral blood smear findings with the most appropriate definitive antimalarial treatment regimen.

A 24-year-old man comes to the clinic due to a sore on his penis that he noticed 5 days ago. He reports no pain, itching, or penile discharge. He is sexually active with a new male partner and does not use condoms consistently. Vital signs are within normal limits. Physical examination reveals a single, 1.5-cm, sharply circumscribed, indurated, and painless ulcer on the penile shaft. Bilateral, non-tender inguinal lymphadenopathy is present. Which of the following is the most appropriate pharmacotherapy for this patient?

A $58$-year-old man is evaluated in the intensive care unit for worsening respiratory status. Eight days ago, he was intubated following a severe motor vehicle collision. Over the past $24$ hours, his oxygen requirements have increased, and he has developed a fever of $38.9^\circ\text{C}$ ($102.0^\circ\text{F}$). Copious thick, purulent secretions are noted in the endotracheal tube. Physical examination reveals coarse rhonchi over the right lung field. Laboratory studies show a leukocyte count of $16,500/\text{mm}^3$ with $85\%$ neutrophils. A chest radiograph demonstrates a new dense consolidation in the right lower lobe. The patient was empirically started on intravenous vancomycin, piperacillin-tazobactam, and amikacin.

Today, the quantitative endotracheal aspirate culture returns positive for $>10^5\text{ CFU/mL}$ of *Pseudomonas aeruginosa*. The isolate is susceptible to piperacillin-tazobactam, cefepime, meropenem, and amikacin. Blood cultures show no growth. His serum creatinine has increased from $1.0\text{ mg/dL}$ on admission to $2.3\text{ mg/dL}$ today.

Which of the following is the most appropriate next step in pharmacotherapy?

A 65-year-old man is hospitalized for community-acquired pneumonia. Upon admission, he was empirically started on intravenous ceftriaxone and azithromycin. Two days later, his clinical condition has significantly improved. He is now afebrile, his oxygen saturation is 96% on room air, and his cough has decreased. He is eating well and tolerating oral intake. Sputum culture results return positive for Streptococcus pneumoniae. Susceptibility testing shows the organism is highly sensitive to penicillin, amoxicillin, ceftriaxone, and levofloxacin. Which of the following is the most appropriate next step in pharmacotherapy?

A 26-year-old woman presents to the clinic for sexually transmitted infection screening. She reports having condomless sexual intercourse with a new male partner three weeks ago. She recently learned that this partner is living with HIV and is not taking any medications. She currently feels well and has no symptoms of acute illness. Vital signs and physical examination are unremarkable. The physician decides to evaluate her for HIV. Assuming her initial screening test is reactive, but her subsequent confirmatory antibody test is indeterminate, arrange the following diagnostic and management steps in the correct chronological sequence according to the standard Centers for Disease Control and Prevention (CDC) HIV algorithm.

Match each patient's clinical and microbiological presentation with the most appropriate targeted antimicrobial therapy.

An oncology team is evaluating a 47-year-old male inpatient who has had persistent fever despite ongoing antimicrobial therapy. He has been hospitalized for the past $16$ days receiving induction chemotherapy for acute myeloid leukemia. Six days prior to the current evaluation, his absolute neutrophil count dropped to $90/\text{mm}^3$, coinciding with a new-onset fever of $39.2^\circ\text{C}$ ($102.6^\circ\text{F}$). At that time, comprehensive pan-culturing was performed, and empiric intravenous piperacillin-tazobactam was initiated.

Currently, the patient's temperature is $38.9^\circ\text{C}$ ($102.0^\circ\text{F}$), blood pressure is $122/78 \text{ mmHg}$, and pulse is $95/\text{min}$. He reports feeling exhausted but has no focal symptoms such as cough, dyspnea, sinus pain, or dysuria. Physical examination reveals a clean, non-tender central venous catheter insertion site. Cardiopulmonary and abdominal examinations are unremarkable. The absolute neutrophil count remains profoundly low at $40/\text{mm}^3$. All previous blood and urine cultures have remained sterile after six days of incubation. High-resolution computed tomography of the chest demonstrates no pulmonary nodules or infiltrates.

Which of the following is the most appropriate next step in pharmacotherapy?

A 28-year-old male graduate student presents to the university health center reporting a 3-day history of profound fatigue, a severe sore throat, and a widespread rash. He notes that 14 days ago, he engaged in unprotected receptive anal intercourse with a new male partner whose infectious status is unknown. His temperature is $38.4^\circ\text{C}$ ($101.1^\circ\text{F}$). Physical examination reveals tender cervical and axillary lymphadenopathy, pharyngeal erythema without exudate, and a diffuse maculopapular rash on the trunk and extremities. The physician suspects an acute viral illness and initiates the standard diagnostic algorithm for the most likely pathogen.

Arrange the following steps in the most appropriate chronological sequence for the diagnosis and initial management of this patient.

An infectious diseases consultation is requested for a 74-year-old woman admitted with subacute bacterial endocarditis. She has a history of osteoarthritis and underwent a screening colonoscopy with polypectomy one month ago. She presented to the hospital with three weeks of low-grade fever, severe fatigue, and a new holosystolic murmur heard loudest at the cardiac apex. Transesophageal echocardiography revealed a $14\text{ mm}$, highly mobile vegetation on the anterior mitral valve leaflet.

Four sets of blood cultures drawn upon admission are positive for *Enterococcus faecalis*. The microbiology laboratory provides the following antimicrobial susceptibility report:

Based on the susceptibility profile provided, which of the following is the most appropriate targeted pharmacotherapy to achieve bactericidal activity in this patient?

A 55-year-old man is evaluated in the hospital prior to discharge. Three days ago, he was admitted for a diabetic foot infection characterized by a 3-cm area of erythema, induration, and warmth surrounding a shallow, non-purulent ulcer on the plantar surface of his right foot. Upon admission, he was afebrile, and his vital signs were within normal limits. He was started on empiric intravenous vancomycin and piperacillin-tazobactam. Today, the erythema has decreased to 1 cm, and the patient is ambulating without difficulty. Deep tissue cultures obtained during initial debridement on admission have grown methicillin-susceptible Staphylococcus aureus (MSSA) and Streptococcus agalactiae. Susceptibility testing shows both isolates are sensitive to cefazolin, cephalexin, and amoxicillin-clavulanate. The patient is tolerating a regular diet. Which of the following is the most appropriate antibiotic regimen for this patient upon discharge?

A 48-year-old woman is brought to the emergency department by her husband due to a 24-hour history of severe generalized headache, high fever, and progressive confusion. She has a history of a deceased-donor renal transplant 3 years ago and takes tacrolimus, mycophenolate mofetil, and prednisone. Her temperature is 39.2°C (102.6°F), blood pressure is 112/68 mmHg, pulse is 115/min, and respirations are 18/min. On examination, the patient is lethargic but arousable to verbal stimuli. Marked nuchal rigidity is present. Neurologic examination reveals a new-onset right-sided pronator drift and a mild right lower facial droop. Arrange the following next steps in management in the most appropriate chronological order.

Match each patient's clinical scenario regarding malaria prevention or treatment with the most appropriate targeted pharmacotherapy.

A 68-year-old woman is brought to the emergency department by her family due to a severe headache, fever, and confusion that started earlier today. On examination, her temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, and heart rate is 115/min. She exhibits nuchal rigidity and a new-onset right-sided facial droop with right arm weakness. Arrange the following steps in the most appropriate chronological sequence for the immediate management of this patient.

During multidisciplinary rounds in the surgical intensive care unit, the team evaluates the antimicrobial regimen for a 54-year-old man. The patient underwent an exploratory laparotomy 8 days ago for a perforated viscus. On his fifth postoperative day, he developed a temperature of 38.9°C (102.0°F) and tachycardia. His right internal jugular central venous catheter, which had been placed preoperatively, was removed, and blood cultures were drawn from peripheral veins and the catheter before removal. Empiric therapy with intravenous vancomycin and cefepime was initiated. Today, the microbiology laboratory reports that two out of two blood culture sets are growing Staphylococcus aureus. The susceptibility panel indicates resistance to penicillin and ampicillin, but susceptibility to oxacillin, cefazolin, vancomycin, and daptomycin. The patient has no known drug allergies. His current temperature is 37.2°C (99.0°F), blood pressure is 128/82 mmHg, and pulse is 82/min. Which of the following is the most appropriate next step in the pharmacologic management of this patient?