Infectious Diseases

A 42-year-old woman is evaluated in the hospital on the fourth day of admission for acute severe pancreatitis. She has been receiving intravenous fluids via a right internal jugular central venous catheter placed on admission. Yesterday, her temperature briefly spiked to 38.3°C (100.9°F). One set of peripheral blood cultures and one set from the central venous catheter were obtained at that time. Today, she reports that her abdominal pain is improving. Her temperature is 37.1°C (98.8°F), blood pressure is 118/76 mm Hg, pulse is 82/min, and respirations are 14/min. Physical examination shows a clean central catheter insertion site with no surrounding erythema or induration. Laboratory studies show a leukocyte count of 9,200/mm³. The aerobic bottle of the peripheral blood culture set is growing coagulase-negative staphylococci after 24 hours of incubation. The anaerobic peripheral bottle and both bottles from the central catheter show no growth. Which of the following is the most appropriate next step in management?

A 32-year-old man who recently immigrated from a region with high tuberculosis endemicity presents to the emergency department with a 4-week history of low-grade fevers, night sweats, productive cough, and unintended weight loss. Temperature is 37.8°C (100.0°F), blood pressure is 110/70 mmHg, pulse is 88/min, and respiratory rate is 18/min. Physical examination reveals bronchial breath sounds and crackles over the right upper lung field. A chest radiograph demonstrates a cavitary opacity in the right upper lobe. Arrange the following steps in the most appropriate chronological order for the clinical management of this patient.

A first-year surgical resident is assisting in the repair of a complex lower extremity laceration in the emergency department. The patient is known to have untreated HIV with a recent viral load of $120,000$ copies/mL. During the procedure, the resident accidentally sustains a deep percutaneous puncture wound to their left index finger with a hollow-bore needle that is visibly contaminated with the patient's blood. The resident immediately stops assisting and removes their surgical gloves.

Arrange the following steps in the most appropriate chronological sequence for the management of this occupational exposure.

Match the following clinical presentations of patients with advanced HIV infection to the most appropriate initial targeted antimicrobial therapy.

An infectious diseases consultation is requested for a $59$-year-old male inpatient. He was admitted $4$ days ago with severe back pain and fever, leading to a diagnosis of $\text{T10}-\text{T11}$ vertebral osteomyelitis and an associated epidural abscess. Urgent surgical decompression and debridement were performed on the day of admission. Blood cultures obtained prior to antibiotic administration, as well as intraoperative tissue specimens, have both grown Staphylococcus aureus. Susceptibility testing confirms the isolate is susceptible to oxacillin, cefazolin, vancomycin, and daptomycin. The patient has been receiving empiric intravenous vancomycin therapy since presentation. His medical history includes type $2$ diabetes mellitus and hypertension. $3$ years ago, he experienced a severe allergic reaction following a dose of oral amoxicillin; he rapidly developed diffuse urticaria, wheezing, and facial angioedema, which necessitated emergency administration of intramuscular epinephrine. He has no prior exposure to cephalosporin antibiotics. Currently, his vital signs are stable, and his serum creatinine is $0.9 \text{ mg/dL}$. Based on current guidelines, which of the following is the most appropriate next step in the pharmacologic management of this infection?

Match the following classic infectious disease clinical presentations with the most appropriate first-line antimicrobial therapy.

A 72-year-old man with a history of a bioprosthetic aortic valve replacement three years ago is hospitalized due to a 4-week history of low-grade fever, progressive fatigue, and night sweats. On physical examination, his temperature is $38.2^\circ\text{C}$ ($100.8^\circ\text{F}$), blood pressure is $118/76\text{ mmHg}$, and heart rate is $92/\text{min}$. A new grade 2/6 diastolic decrescendo murmur is heard at the right upper sternal border. Laboratory evaluation shows a leukocyte count of $14,500/\text{mm}^3$ and a serum creatinine of $1.1\text{ mg/dL}$. Transesophageal echocardiography reveals a $1.4\text{ cm}$ vegetation on the prosthetic valve. Three sets of blood cultures obtained prior to antibiotic administration are all positive for *Enterococcus faecalis*. The patient is empirically started on intravenous vancomycin and gentamicin.

Antimicrobial susceptibility testing for the isolate demonstrates the following:
* Ampicillin: Susceptible
* Penicillin: Susceptible
* Vancomycin: Susceptible
* Gentamicin: High-level resistance

Which of the following is the most appropriate antimicrobial regimen for this patient?

An evaluation is requested for a 67-year-old male patient who reports a persistent sore on the bottom of his right foot for the past two months. He has a 15-year history of type 2 diabetes mellitus complicated by peripheral neuropathy. His vital signs include a blood pressure of 135/85 mm Hg, a heart rate of 76/min, and a temperature of 37.0°C (98.6°F). On physical examination, there is a 2.5-cm, painless ulcer on the plantar aspect of the right first metatarsal head. There is no significant surrounding erythema, warmth, or fluctuance. During exploration of the wound, a sterile metallic probe easily contacts hard, gritty tissue at the base of the ulcer. Laboratory testing reveals a leukocyte count of 8,200/mm³ and an erythrocyte sedimentation rate of 95 mm/h. Radiography of the right foot demonstrates focal periosteal elevation and frank cortical erosion of the underlying metatarsal head. Which of the following is the most appropriate next step in the management of this patient?

A $35$-year-old man presents to the clinic with an $8$-day history of a persistent cough. He states that the cough is productive of yellowish sputum and is occasionally accompanied by mild retrosternal chest soreness. He reports having a runny nose and a low-grade fever that resolved $3$ days ago. He has no significant past medical history and does not smoke. Vital signs are temperature $37.2^\circ \text{C}$ ($99.0^\circ \text{F}$), blood pressure $122/78 \, \text{mmHg}$, pulse $78/\text{min}$, and respiratory rate $16/\text{min}$. Pulse oximetry is $98\%$ on room air. Physical examination reveals normal tympanic membranes, mild pharyngeal erythema without exudate, and clear lung fields bilaterally without wheezes, rhonchi, or crackles. Which of the following is the most appropriate next step in management?

Match the following complex clinical scenarios and isolated pathogens with the most appropriate, definitive targeted antimicrobial therapy.

A 68-year-old man with a history of benign prostatic hyperplasia is admitted to the hospital with fever, severe left flank pain, and dysuria. His temperature is $39.4^\circ\text{C}$ ($102.9^\circ\text{F}$), blood pressure is $100/60\text{ mmHg}$, and heart rate is $110\text{/min}$. Laboratory studies show a leukocyte count of $18,000\text{/mm}^3$. He is empirically started on intravenous piperacillin-tazobactam and intravenous fluids.

On hospital day 3, the patient is clinically improved and afebrile. Blood and urine cultures drawn at admission both grow *Enterobacter cloacae*.

Antimicrobial susceptibility testing of the isolate reveals the following:
- Ampicillin: Resistant
- Cefazolin: Resistant
- Ceftriaxone: Sensitive (MIC $\leq 1\text{ }\mu\text{g/mL}$)
- Cefepime: Sensitive (MIC $\leq 1\text{ }\mu\text{g/mL}$)
- Piperacillin-tazobactam: Sensitive (MIC $4\text{ }\mu\text{g/mL}$)
- Meropenem: Sensitive (MIC $\leq 0.25\text{ }\mu\text{g/mL}$)

Which of the following is the most appropriate next step in the antimicrobial management of this patient?

A 76-year-old woman is evaluated in the hospital on day 5 of her admission due to an episode of hypotension and altered mental status. She was initially admitted for a severe COPD exacerbation and has been receiving systemic glucocorticoids, nebulized bronchodilators, and prophylactic enoxaparin. An indwelling Foley catheter was placed on admission due to urinary retention and has remained in place.

Today (Day 5), her temperature is $38.3^\circ\text{C}$ ($100.9^\circ\text{F}$), blood pressure is $88/56\text{ mmHg}$, heart rate is $112\text{/min}$, and respiratory rate is $22\text{/min}$. Physical examination reveals a lethargic patient. The abdomen is soft and non-tender, and there is no costovertebral angle tenderness. Laboratory findings show a leukocyte count of $16,500\text{/mm}^3$. A urinalysis obtained from the Foley catheter port shows $25\text{ WBCs/hpf}$ and positive leukocyte esterase, but negative nitrites.

Blood and urine cultures are drawn. The patient receives intravenous fluid resuscitation, and empiric intravenous vancomycin and cefepime are initiated.

Two days later (Day 7), the patient is clinically improved, her mental status has returned to baseline, she is hemodynamically stable off fluids, and she is afebrile. Blood cultures show no growth at 48 hours. The urine culture grows $>10^5\text{ CFU/mL}$ of *Enterococcus faecalis*.

Antimicrobial susceptibility testing for the *E. faecalis* isolate demonstrates the following:
- Ampicillin: Susceptible
- Cefepime: Resistant
- Ciprofloxacin: Resistant
- Linezolid: Susceptible
- Vancomycin: Susceptible

Which of the following is the most appropriate next step in the antimicrobial management of this patient?

An 82-year-old woman who resides in a skilled nursing facility is brought to the clinic for a routine wellness visit. She has a history of mild vascular dementia and type 2 diabetes mellitus. The patient is at her baseline cognitive function and reports no fever, chills, dysuria, increased urinary urgency, or abdominal pain. Vital signs are temperature 37.0°C (98.6°F), blood pressure 138/82 mmHg, and pulse 78/min. The abdomen is non-tender and there is no costovertebral angle tenderness. As part of a general protocol by the nursing facility, a urinalysis and urine culture were obtained prior to the visit. The urinalysis shows moderate leukocyte esterase and positive nitrites. The urine culture grows >100,000 CFU/mL of Escherichia coli. Which of the following is the most appropriate next step in management?

A 68-year-old man is evaluated in the hospital on day 3 of admission for community-acquired pneumonia. His medical history is significant for hypertension and osteoarthritis. On admission, he presented with a temperature of 38.9°C (102.0°F), a productive cough, and a right lower lobe consolidation on chest radiography. He was started on empiric therapy with intravenous ceftriaxone and oral azithromycin.

Sputum and blood cultures obtained on admission have now finalized, both growing *Streptococcus pneumoniae*. Susceptibility testing of the isolate demonstrates the following:

Today, the patient reports feeling much better. He has been afebrile for the past 28 hours. His heart rate is 78/min, blood pressure is 128/82 mmHg, and respiratory rate is 16/min. Oxygen saturation is 96% on room air. He is tolerating a regular diet without difficulty. Which of the following is the most appropriate next step in his antimicrobial management?

Match each patient's clinical presentation with the most appropriate first-line pharmacotherapy.

A 54-year-old man comes to the office due to worsening redness and swelling of his left lower leg over the past 48 hours. He reports no fever, chills, or systemic symptoms. His medical history includes hypertension and diet-controlled type 2 diabetes mellitus. Vital signs show a temperature of 37.2°C (99.0°F), blood pressure of 130/80 mm Hg, and heart rate of 78/min. Physical examination of the left lower extremity reveals a 10-cm area of poorly demarcated erythema, warmth, and tenderness over the anterior shin. There is no fluctuance, purulent drainage, or palpable fluid collection. Which of the following is the most appropriate antibiotic therapy?

A 34-year-old unhoused man is brought to the emergency department by paramedics after being found in severe distress in an alleyway. He sustained a deep puncture wound to his right sole from a rusty metal fence approximately 8 days ago. He has no known medical history, and his childhood vaccination status is unknown. On arrival, he is diaphoretic, tachycardic to 122/min, and tachypneic to 26/min. Physical examination reveals profound trismus, a sustained grimace of the facial muscles, and episodic, painful spasms of the paraspinal musculature that are immediately triggered by the noise of a dropping tray in the trauma bay. The right foot shows a 3-cm deep, purulent puncture wound surrounded by necrotic tissue.

Arrange the following therapeutic interventions in the most appropriate chronological sequence for the management of this patient's condition.

A 32-year-old man presents to the emergency department triage desk with a 4-week history of severe cough, low-grade fevers, and drenching night sweats. He recently returned from a prolonged trip to a region where tuberculosis is highly endemic. He is currently sitting in the crowded main waiting room. Arrange the following steps in the correct chronological order for managing this patient's suspected infection.

A 64-year-old man with a 15-year history of poorly controlled type 2 diabetes mellitus is evaluated in the outpatient clinic for a chronic ulcer on the plantar surface of his right foot. He first noticed the ulcer 8 weeks ago. He has established peripheral neuropathy and reports no pain at the site. His temperature is 37.1°C (98.8°F), blood pressure is 135/82 mmHg, and pulse is 78/min. Physical examination reveals a 2.5-cm, full-thickness ulcer under the first metatarsal head. The ulcer base is composed of pale granulation tissue. There is no surrounding erythema, warmth, fluctuance, or purulent discharge. A sterile, blunt stainless-steel probe easily reaches the underlying bone. Pedal pulses are palpable bilaterally. Laboratory studies show a leukocyte count of $7,500/\mu L$ and an erythrocyte sedimentation rate of $65 \text{ mm/h}$. A plain radiograph of the right foot demonstrates cortical erosion and periosteal elevation at the first metatarsal head. Which of the following is the most appropriate next step in management?

A 54-year-old man is reviewed by the medical team during his inpatient hospitalization. He was admitted 72 hours ago after presenting to the emergency department with an acutely painful, erythematous, and swollen right knee accompanied by shaking chills. Initial arthrocentesis yielded turbid synovial fluid containing $85,000 \text{ leukocytes}/\mu L$ with $92\%$ neutrophils. Following the procedure, he was empirically started on intravenous vancomycin and piperacillin-tazobactam. Today, his temperature has improved to $37.4^\circ\text{C}$ ($99.3^\circ\text{F}$), blood pressure is $128/82 \text{ mmHg}$, and pulse is $84/\text{min}$. The right knee shows decreased swelling and erythema. Blood cultures and synovial fluid cultures obtained on admission are both positive for *Staphylococcus aureus*. Antimicrobial susceptibility testing reveals the following:

Which of the following is the most appropriate next step in antibiotic management?