Infectious Diseases

A 68-year-old man comes to the emergency department due to a 3-day history of worsening shortness of breath, increased cough, and a change in sputum color from clear to yellow-green. He has a history of severe chronic obstructive pulmonary disease (COPD) and ischemic cardiomyopathy with a left ventricular ejection fraction of 35%. His home medications include an albuterol inhaler, tiotropium, lisinopril, and carvedilol.

On presentation, his temperature is $38.0^\circ C$ ($100.4^\circ F$), blood pressure is 138/86 mm Hg, pulse is 98/min, and respirations are 24/min. Pulse oximetry is 92% on room air. Physical examination reveals a barrel chest, prolonged expiratory phase, and diffuse bilateral expiratory wheezes without crackles. Jugular venous pressure is 7 cm $H_2O$. There is trace bilateral lower extremity edema, which the patient states is his baseline.

Laboratory results show:
Leukocyte count: $11,500/mm^3$
B-type natriuretic peptide: 150 pg/mL

Arterial blood gas (room air):
pH: 7.36
$PaCO_2$: 52 mm Hg
$PaO_2$: 64 mm Hg
Calculated $HCO_3^-$: 28 mEq/L

A chest radiograph shows hyperinflated lungs with flattened diaphragms and no focal consolidations or pleural effusions. He is started on supplemental oxygen, nebulized albuterol and ipratropium, and systemic glucocorticoids.

Which of the following is the most appropriate additional step in management?

A 52-year-old woman is evaluated in the emergency department for a fever of 38.8°C (101.8°F) and severe chills that began 2 hours ago. She was diagnosed with acute myeloid leukemia 3 weeks ago and is currently undergoing induction chemotherapy. She has an indwelling central venous catheter. Her blood pressure is 105/65 mm Hg, pulse is 110/min, and respirations are 18/min. Physical examination reveals a well-healed catheter site with no erythema or purulent drainage, and the remainder of the examination shows no obvious source of infection. A complete blood count reveals an absolute neutrophil count of 150/mm³. Arrange the following management steps in the most appropriate chronological order for this patient.

A 55-year-old man with a 15-year history of poorly controlled type 2 diabetes mellitus presents to the clinic with a deep, non-healing ulcer on the plantar surface of his right foot. Examination reveals a 2-cm wide ulcer with surrounding erythema, edema, and purulent exudate. The patient is afebrile, but underlying osteomyelitis is highly suspected. Arrange the following steps in the correct sequential order for the diagnostic evaluation of this patient, starting with the most appropriate initial step and concluding with the definitive diagnostic procedure.

A $78$-year-old man is brought to the clinic by his son for a routine follow-up. The patient has a history of advanced Parkinson disease and neurogenic bladder, which is managed with a chronic indwelling urethral catheter. The son reports that over the past week, the urine in the collection bag has become notably turbid and foul-smelling. The patient is otherwise acting at his baseline; he has had no fevers, chills, abdominal pain, or changes in oral intake. Vital signs are temperature $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$), blood pressure $132/82\text{ mm Hg}$, pulse $74\text{/min}$, and respirations $14\text{/min}$. Physical examination demonstrates a soft, non-tender abdomen and no costovertebral angle tenderness. There is no leakage or erythema around the urethral meatus.

A urine culture grows $>100,000\text{ CFU/mL}$ of *Klebsiella pneumoniae*. Which of the following is the most appropriate next step in management?

A patient is hospitalized for the management of an acute, swollen, and exquisitely tender left knee. Diagnostic arthrocentesis performed at admission yielded opaque, purulent synovial fluid, prompting the immediate initiation of empiric antimicrobial therapy with intravenous vancomycin and intravenous ceftriaxone. Over the past 48 hours, the patient has demonstrated marked clinical improvement, with complete resolution of fever and a significant decrease in joint effusion. The microbiology laboratory subsequently contacts the team to report that the admission synovial fluid culture is growing *Streptococcus pyogenes* (Group A Streptococcus). The isolate demonstrates standard susceptibility patterns to all tested beta-lactams, macrolides, and fluoroquinolones. In accordance with the principles of antimicrobial stewardship, which of the following is the most appropriate next step in the pharmacologic management of this patient?

Match each clinical presentation of infective endocarditis with the most likely causative microorganism.

A 64-year-old man is evaluated in the intensive care unit on hospital day 3. He was admitted with septic shock secondary to an obstructing right ureteral calculus. A percutaneous nephrostomy tube was placed shortly after admission. Empiric therapy with intravenous vancomycin and meropenem was initiated. Today, his temperature is $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure is $118/74\text{ mmHg}$, and pulse is $82/\text{min}$. Vasopressors were weaned off yesterday. Blood and urine cultures obtained at admission both grow *Enterobacter cloacae*. Susceptibility testing results for both isolates are as follows:

Based on these results and the patient's clinical improvement, which of the following is the most appropriate next step in pharmacotherapy?

A 45-year-old man is evaluated during hospital rounds. He was admitted 3 days ago for fever, productive cough, and pleuritic chest pain. A chest radiograph on admission showed a right lower lobe consolidation, and he was diagnosed with community-acquired pneumonia. Empiric therapy with intravenous ceftriaxone and oral azithromycin was initiated. He has no significant past medical history and takes no daily medications. He has no known drug allergies. Today, the patient reports feeling significantly better. His temperature is 37.1°C (98.8°F), blood pressure is 120/80 mmHg, pulse is 78/min, and respiratory rate is 16/min. Oxygen saturation is 98% on room air. Blood cultures obtained on admission are now growing *Streptococcus pneumoniae*. Susceptibility testing indicates the isolate is highly susceptible to penicillin, ceftriaxone, and levofloxacin, but resistant to macrolides. The patient is tolerating a regular diet without difficulty. Which of the following is the most appropriate next step in pharmacotherapy?

A 58-year-old woman is brought to the emergency department by her husband due to a 24-hour history of severe headache, confusion, and high fever. Her temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, pulse is 115/min, and respirations are 18/min. Physical examination reveals marked nuchal rigidity. Funduscopic examination shows bilateral optic disc swelling (papilledema). She is somnolent but localizes to painful stimuli. There are no focal motor deficits. The physician suspects acute bacterial meningitis. Arrange the following interventions in the most appropriate chronological order of execution.

A 71-year-old female presents to the orthopedic clinic for a final preoperative evaluation. She is scheduled to undergo an elective right total knee arthroplasty in one week for severe osteoarthritis. Her medical history includes hypertension and diet-controlled type 2 diabetes mellitus. The patient feels well and reports no dysuria, urinary frequency, urgency, or suprapubic discomfort. Vital signs are within normal limits. Physical examination reveals crepitus and decreased range of motion in the right knee but is otherwise unremarkable. Routine preoperative laboratory testing is notable for a urinalysis demonstrating positive leukocyte esterase and 15 leukocytes/hpf. A reflex urine culture grows $>10^{5}$ CFU/mL of *Escherichia coli* that is susceptible to cephalexin, nitrofurantoin, ciprofloxacin, and trimethoprim-sulfamethoxazole. Which of the following is the most appropriate management regarding her urinary findings?

A 54-year-old male is evaluated on the medical ward on hospital day 6. He was initially admitted for severe acute pancreatitis complicated by a prolonged ileus, for which he is receiving total parenteral nutrition through a right internal jugular central venous catheter. Two days ago, the patient had a single temperature spike to 38.2°C (100.8°F). At that time, a complete blood count and two sets of blood cultures (one drawn from the central venous catheter and one from a peripheral vein) were obtained. Since then, the patient has remained afebrile and his abdominal pain has significantly improved. He currently reports feeling well. Vital signs today show a temperature of 37.0°C (98.6°F), blood pressure of 122/78 mm Hg, and heart rate of 78/min. Physical examination reveals a clean, non-erythematous central line exit site without tenderness or exudate. The white blood cell count has decreased from 14,500/mm³ on admission to 8,200/mm³ today. The microbiology laboratory calls to report that the aerobic bottle from the peripheral blood draw has signaled positive for coagulase-negative staphylococci at 42 hours of incubation. The other three culture bottles (anaerobic peripheral, aerobic central, anaerobic central) have shown no growth. Which of the following is the most appropriate next step in management?

For each of the following individuals presenting after a potential infectious exposure, select the most appropriate guideline-concordant prophylactic regimen.

Match the following clinical vignettes describing zoonotic and environmental infections with their most appropriate targeted antimicrobial therapy.

Match each clinical and neuroimaging presentation of a central nervous system disorder in patients with advanced HIV infection to its most appropriate definitive or empiric management.

A 62-year-old woman is receiving care on the inpatient ward for a catheter-associated bloodstream infection. She was admitted 3 days ago with high fever, chills, and localized erythema around a peripheral intravenous catheter site. The catheter was promptly removed, and she was started on empiric intravenous vancomycin and piperacillin-tazobactam. Today, she reports feeling much better. Her temperature is 37.1°C (98.8°F), blood pressure is 128/82 mmHg, pulse is 76/min, and respirations are 14/min. The erythema at the prior catheter site has significantly improved. Blood cultures obtained on admission are now finalized and grow *Staphylococcus aureus*. Susceptibility testing demonstrates resistance to penicillin G and susceptibility to oxacillin, cefazolin, vancomycin, and daptomycin. Which of the following is the most appropriate next step in pharmacotherapy?

A 32-year-old man who recently emigrated from Southeast Asia presents to the emergency department with a 4-week history of productive cough, night sweats, unintentional weight loss, and low-grade fever. A chest radiograph reveals a cavitary lesion in the right upper lobe. You highly suspect active pulmonary tuberculosis. Arrange the following steps in the most appropriate chronological sequence for the management of this patient.

During morning rounds, the care team reviews the progress of a 34-year-old female patient admitted two days ago with complicated urinary tract infection.

Vital signs at admission were:
- Temperature: 39.4°C (102.9°F)
- Blood pressure: 92/58 mm Hg
- Pulse: 115/min

She received intravenous fluid resuscitation and empiric therapy with intravenous piperacillin-tazobactam. Today, the patient reports feeling much better, noting her flank pain has nearly resolved and she is eating a regular diet. Current vital signs show a temperature of 37.0°C (98.6°F), blood pressure of 116/74 mm Hg, and a pulse of 78/min.

The microbiology laboratory updates the results from the admission urine and blood cultures. Both are positive for *Escherichia coli*. The isolate demonstrates the following susceptibility profile:

Based on these findings, which of the following is the most appropriate next step in the management of this patient's infection?

An infectious diseases consultation is requested for a 48-year-old female who was admitted to the hospital three days ago with subacute onset of fever, fatigue, and dyspnea. Initial evaluation revealed a new holosystolic murmur radiating to the axilla. A transesophageal echocardiogram confirmed a $1.4\text{ cm}$ oscillating vegetation on the posterior mitral leaflet. Upon admission, three sets of blood cultures were drawn, and she was started on empiric intravenous vancomycin and ceftriaxone. Today, the patient is clinically stable, and her temperature is $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$). The microbiology laboratory reports that all three blood culture sets are growing *Streptococcus mutans*. The isolate has a penicillin minimum inhibitory concentration (MIC) of $0.06 \text{ mcg/mL}$ (highly susceptible) and is also susceptible to ceftriaxone. Based on the culture and susceptibility data, which of the following is the most appropriate modification to her pharmacotherapy?

Match each clinical exposure scenario with the most appropriate first-line oral antimicrobial regimen.

An emergency department physician evaluates a patient presenting with severe, unrelenting mid-back pain that has progressively worsened over the past week. The patient, who has a history of type 2 diabetes mellitus and injection drug use, now reports new-onset bilateral leg weakness and an inability to urinate for the past $6 \text{ hours}$. Vital signs show a temperature of $38.9^\circ\text{C}$ ($102.0^\circ\text{F}$), heart rate of $110/\text{min}$, and blood pressure of $130/80\text{ mmHg}$. Physical examination demonstrates tenderness to percussion over the thoracic spine, $3/5$ motor strength in both lower extremities, and absent deep tendon reflexes at the knees and ankles. A bedside bladder ultrasound reveals a post-void residual volume of $600\text{ mL}$.

Arrange the following management steps in the most appropriate chronological sequence for this patient.