Infectious Diseases

An 81-year-old man residing in a skilled nursing facility is evaluated during a routine clinic visit. The patient has advanced Alzheimer dementia and is completely bedbound. He has an indwelling urethral catheter that was placed 8 months ago for chronic urinary retention. The facility staff report that for the past 4 days, the urine in his collection bag has appeared persistently cloudy and malodorous. The patient has not exhibited any behavioral changes, increased agitation, or signs of physical discomfort. His temperature is $36.9^\circ\text{C}$ ($98.4^\circ\text{F}$), blood pressure is $132/82 \text{ mm Hg}$, pulse is $74\text{ /min}$, and respiratory rate is $16\text{ /min}$. Physical examination reveals a soft, non-tender abdomen with no suprapubic or costovertebral angle tenderness.

Laboratory studies show:
Leukocyte count: $6,800/\text{mm}^3$

Urinalysis:
- Appearance: Cloudy
- Leukocyte esterase: Positive
- Nitrites: Positive
- WBCs: $45/\text{hpf}$

Urine culture: $>100,000 \text{ CFU/mL}$ of *Klebsiella pneumoniae*

Antimicrobial susceptibilities for the isolate are as follows:

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

Select the most appropriate first-line antimicrobial therapy for each of the following patient scenarios.

A 52-year-old woman is evaluated in the hospital for a new-onset fever. She was admitted $12$ days ago for induction chemotherapy for acute myeloid leukemia. Her temperature is $38.8^\circ\text{C}$ ($101.8^\circ\text{F}$), blood pressure is $114/72$ mm Hg, pulse is $98$/min, and respirations are $16$/min. Oxygen saturation is $98\%$ on room air. Physical examination reveals a right internal jugular central venous catheter; the insertion site is clean, dry, and without erythema or tenderness. There is no oral thrush or mucositis. Lung fields are clear to auscultation. The abdomen is soft and non-tender. Skin examination shows no rashes or induration.

Laboratory studies show:
Leukocyte count: $800/\text{mm}^3$
Absolute neutrophil count: $120/\text{mm}^3$
Hemoglobin: $8.4$ g/dL
Platelet count: $45,000/\text{mm}^3$

Urinalysis is negative for leukocyte esterase and nitrites. Chest radiography reveals no infiltrates. Blood and urine cultures are obtained. Which of the following is the most appropriate empiric pharmacotherapy for this patient?

A $42$-year-old man presents to a busy urgent care clinic with a $5$-week history of worsening cough producing blood-tinged sputum, drenching night sweats, and an $8$-kg ($17.6$-lb) weight loss. He immigrated to the United States from a highly endemic region $3$ years ago. His temperature is $38.3^\circ\text{C}$ ($100.9^\circ\text{F}$), blood pressure is $118/76\text{ mm Hg}$, pulse is $88\text{/min}$, and respiratory rate is $18\text{/min}$. He is currently seated in the crowded main waiting room.

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

A $29$-year-old man comes to the outpatient clinic due to a painful swelling on his right thigh. He first noticed a "pimple" in the area $4$ days ago, which has progressively enlarged and become increasingly tender. He has no significant past medical history and takes no medications. Vital signs show a temperature of $37.0^\circ\text{C}$ ($98.6^\circ\text{F}$), blood pressure of $122/78$ mm Hg, and heart rate of $76$/min. Physical examination of the anterior right thigh reveals a $4$-cm, erythematous, exquisitely tender, and fluctuant mass. There is a $0.5$-cm rim of surrounding erythema. No induration extending beyond the erythema is noted, and there is no inguinal lymphadenopathy. Which of the following is the most appropriate next step in management?

Match each patient's clinical exposure scenario with the most appropriate post-exposure prophylaxis or management strategy.

A $64$-year-old woman is evaluated in the primary care clinic due to a $4$-week history of progressive fatigue, generalized weakness, and low-grade fevers. She reports an unintentional weight loss of $3\text{ kg}$ ($6.6\text{ lbs}$) over this period. Her medical history is significant for mitral valve prolapse with regurgitation. Five weeks ago, she underwent a complex root canal procedure. Her temperature is $37.8^\circ\text{C}$ ($100.0^\circ\text{F}$), blood pressure is $132/84\text{ mmHg}$, pulse is $82\text{/min}$, and respiratory rate is $14\text{/min}$. Physical examination reveals a well-appearing, comfortable patient. Cardiac auscultation demonstrates a grade $3/6$ holosystolic murmur heard best at the apex and radiating to the axilla. Small, dark red, linear lesions are noted under the nail beds of her right index and middle fingers. The patient is hemodynamically stable without signs of acute heart failure. Three sets of peripheral blood cultures are obtained, and a transesophageal echocardiogram is scheduled. Which of the following is the most appropriate next step in the antimicrobial management of this patient?

A $54$-year-old man is brought to the emergency department by his partner due to a severe headache, subjective fever, and progressive lethargy over the past $24$ hours. His temperature is $39.4^\circ\text{C}$ ($102.9^\circ\text{F}$), blood pressure is $142/88$ mmHg, pulse is $112$/min, and respirations are $20$/min. Physical examination demonstrates marked resistance to passive neck flexion. Neurologic examination reveals somnolence, disorientation to place and time, and a pronounced right-sided pronator drift with right lower extremity weakness. Arrange the following interventions in the most appropriate sequential order for this patient's management.

During morning rounds in the intensive care unit, the medical team discusses the care of a patient who was recently treated for a severe asthma exacerbation. The patient had a central venous catheter placed $5$ days ago, which was removed yesterday when he developed rigors and a temperature of $39.2^\circ\text{C}$. Empiric intravenous vancomycin and piperacillin-tazobactam were started at that time. Today, the microbiology laboratory reports that two sets of blood cultures are positive for methicillin-susceptible *Staphylococcus aureus* (MSSA). The isolate is susceptible to oxacillin, cefazolin, and vancomycin. The patient's vital signs are now stable and he is afebrile. Which of the following is the most appropriate next step in pharmacotherapy?

For each of the following patients presenting with a suspected zoonotic or tick-borne illness, identify the most appropriate targeted antimicrobial therapy.

An $82$-year-old male is admitted to the inpatient ward after developing a high fever, severe global headache, and worsening lethargy over the past $24$ hours. His medical history includes hypertension, type 2 diabetes mellitus, and benign prostatic hyperplasia. Upon arrival, his temperature is $39.1^\circ\text{C}$ ($102.4^\circ\text{F}$), blood pressure is $112/68\text{ mmHg}$, and pulse is $108\text{/min}$. Physical examination demonstrates marked nuchal rigidity and disorientation to time and place. A lumbar puncture is promptly performed, and cerebrospinal fluid (CSF) analysis reveals a leukocyte count of $1,200/\mu\text{L}$ with $85\%$ neutrophils, a glucose level of $35\text{ mg/dL}$, and a protein level of $140\text{ mg/dL}$. He is empirically started on intravenous ceftriaxone, vancomycin, ampicillin, and dexamethasone. Two days later, the CSF culture confirms the growth of *Listeria monocytogenes*. Which of the following is the most appropriate next step in the antimicrobial management of this patient?

A 34-year-old man with a recent history of emigration from a tuberculosis-endemic region presents to the emergency department complaining of a 4-week history of productive cough, intermittent hemoptysis, drenching night sweats, and a $5$-kg ($11$-lb) weight loss. His vital signs show a temperature of $38.2^\circ\text{C}$ ($100.8^\circ\text{F}$), blood pressure of $120/78\text{ mmHg}$, and oxygen saturation of $96\%$ on room air. Chest auscultation reveals bronchial breath sounds and crackles over the right upper lung field. A subsequent chest radiograph demonstrates a prominent cavitary infiltrate in the apical segment of the right upper lobe. Arrange the following management steps in the most appropriate chronological order to optimize both patient outcomes and infection control.

A 56-year-old woman is evaluated on the medical ward on hospital day 2. She was admitted the previous day for a rapidly spreading, painful, erythematous rash on her right lower leg. Her medical history is notable for type 2 diabetes mellitus and chronic venous insufficiency. On admission, her temperature was $39.1^\circ\text{C}$ ($102.4^\circ\text{F}$), heart rate was $110/\text{min}$, and blood pressure was $118/74\text{ mmHg}$. Physical examination revealed a well-demarcated, intensely red, warm, and tender plaque on the right anterior shin without any underlying fluctuance, purulent drainage, or overlying eschar. Due to the high fever and tachycardia, she was empirically started on intravenous vancomycin and piperacillin-tazobactam in the emergency department.

Today, the patient reports feeling much better. Her temperature is $37.4^\circ\text{C}$ ($99.3^\circ\text{F}$), heart rate is $82/\text{min}$, and blood pressure is $124/80\text{ mmHg}$. The margins of the erythema have not advanced. Blood cultures drawn on admission show no growth to date.

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

Match each clinical exposure scenario with the most appropriate post-exposure prophylaxis (PEP) regimen.

A 42-year-old man is evaluated in the hospital on day 3 of admission for community-acquired pneumonia. He initially presented with a productive cough, high fever, and shortness of breath. Chest radiography on admission showed a right lower lobe infiltrate. He was empirically started on intravenous ceftriaxone and azithromycin. Blood and sputum cultures obtained on admission have now grown Streptococcus pneumoniae. Susceptibility testing reveals the isolate is highly susceptible to penicillin (minimum inhibitory concentration < 0.06 mcg/mL), amoxicillin, ceftriaxone, and levofloxacin. Today, his temperature is 37.0 C (98.6 F), blood pressure is 120/78 mm Hg, pulse is 78/min, and respiratory rate is 14/min. His oxygen saturation is 97% on ambient air. He is tolerating a regular diet and reports feeling much better. Which of the following is the most appropriate next step in management?

A 68-year-old renal transplant recipient is brought to the emergency department by his family due to profound confusion and high fever for the past 24 hours. Vital signs show a temperature of 39.2°C (102.6°F), blood pressure of 110/70 mmHg, and heart rate of 115/min. Neurologic examination reveals marked nuchal rigidity, somnolence, and a new left-sided pronator drift. Arrange the following steps in the most appropriate sequential order for the initial management of this patient.

Match each clinical and neuroradiological presentation of central nervous system (CNS) disease in a patient with advanced HIV to the most likely etiologic pathogen.

A 65-year-old male is reevaluated during bedside rounds on his third day of hospitalization. He originally presented to the emergency department with high fever, left-sided costovertebral angle tenderness, and dysuria. Due to a history of recurrent urinary tract infections and a recent skilled nursing facility admission, he was empirically started on intravenous vancomycin and piperacillin-tazobactam. His clinical condition has markedly improved; he has been afebrile for 24 hours, and his flank pain has resolved. Blood and urine cultures drawn on admission now demonstrate growth of Enterococcus faecalis. The isolate is susceptible to ampicillin, vancomycin, linezolid, and daptomycin. Which of the following is the most appropriate next step in pharmacotherapy?

A $29$-year-old woman is evaluated on the medical ward on hospital day $3$ for acute pyelonephritis. On admission, she reported a $2$-day history of high fever, dysuria, and severe right-sided back pain. She works as a nurse and has a history of recurrent urinary tract infections. Due to local antibiogram data showing high rates of fluoroquinolone resistance and her recent healthcare exposure, she was started empirically on intravenous piperacillin-tazobactam. The patient has improved significantly; she has been afebrile for $24$ hours, her flank pain is minimal, and she is tolerating oral intake perfectly. Her temperature is $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure is $112/70\text{ mm Hg}$, and pulse is $76/\text{min}$. Final urine culture results from admission demonstrate $>100,000$ colony-forming units/mL of *Klebsiella pneumoniae*. Susceptibility testing shows the isolate is resistant to ampicillin, but sensitive to ceftriaxone, cefazolin, ciprofloxacin, and piperacillin-tazobactam. Which of the following is the most appropriate next step in management?

Match each patient presentation and history of infective endocarditis to the most likely causative organism.