Infectious Diseases

Match each clinical exposure scenario with the most appropriate post-exposure prophylaxis or initial preventive management strategy.

An 82-year-old male resident of a skilled nursing facility is brought to the outpatient clinic for a routine follow-up appointment. His medical history is significant for benign prostatic hyperplasia, type 2 diabetes mellitus, and vascular dementia. The patient relies on a chronic indwelling urinary catheter due to refractory urinary retention. His caregiver reports that he has been at his baseline mental and physical status, eating well, and participating in daily activities without issue. The patient denies any fever, chills, flank pain, or suprapubic discomfort. Vital signs are temperature 37.1°C (98.8°F), blood pressure 130/80 mmHg, pulse 78/min, and respiratory rate 14/min. Physical examination reveals a soft, non-tender abdomen and no costovertebral angle tenderness. As part of a recent facility protocol, a routine urinalysis was performed yesterday which showed 50 white blood cells per high-power field, positive leukocyte esterase, and positive nitrites. Today, the urine culture results return showing >10^5 CFU/mL of multidrug-resistant Pseudomonas aeruginosa. Which of the following is the most appropriate next step in management?

An 82-year-old woman is evaluated in her long-term care facility for a 1-day history of acute confusion and agitation. She has a history of advanced Alzheimer dementia, hypertension, and osteoarthritis. According to the nursing staff, she has been combative during morning care and is disoriented to place, which represents a significant change from her baseline behavior. She has not exhibited any cough, vomiting, or diarrhea. Vital signs are temperature 37.1°C (98.8°F), blood pressure 138/86 mm Hg, pulse 82/min, and respirations 14/min. Physical examination shows dry mucous membranes and decreased skin turgor. Cardiopulmonary examination is unremarkable. The abdomen is soft and non-tender; there is no suprapubic or costovertebral angle tenderness.

Laboratory results:
Serum sodium: 149 mEq/L
Blood urea nitrogen: 38 mg/dL
Serum creatinine: 1.3 mg/dL (baseline: 0.9 mg/dL)

Urinalysis:
Color: Cloudy yellow
Leukocyte esterase: Positive
Nitrites: Positive
White blood cells: 25/hpf
Bacteria: Numerous

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

Match each clinical presentation of an immunocompromised patient with HIV to the most appropriate initial targeted antimicrobial regimen.

A critical care physician is reviewing the microbiological data for a patient admitted with a severe burn injury. One week into the hospitalization, the patient developed a new-onset fever of $39.4^\circ\text{C}$ ($102.9^\circ\text{F}$) and hypotension requiring vasopressor support. Blood cultures were obtained from a central venous catheter and a peripheral vein, and empiric antimicrobial therapy with intravenous vancomycin, cefepime, and gentamicin was instituted.

Today, both sets of blood cultures are positive for *Klebsiella pneumoniae*. The microbiology laboratory reports that the isolate is susceptible to ceftriaxone, cefepime, piperacillin-tazobactam, and meropenem, but resistant to ampicillin. The patient's clinical status has stabilized significantly; the fever has resolved, and vasopressor support was discontinued yesterday. Based on the principles of antimicrobial stewardship, which of the following is the most appropriate modification to this patient's pharmacologic regimen?

A 72-year-old man is evaluated on hospital day 3 for discharge planning. He was initially admitted with fever, productive cough, and left-sided pleuritic chest pain. Chest radiography on admission demonstrated a dense left lower lobe consolidation. He was started on empiric intravenous ceftriaxone and azithromycin. Two sets of blood cultures drawn upon presentation have grown *Streptococcus pneumoniae*. Antimicrobial susceptibility testing is reported as follows:

The patient's clinical status has markedly improved. He has been afebrile for 24 hours, maintains an oxygen saturation of 96% on room air, and is tolerating an oral diet. His medical history includes hypertension and benign prostatic hyperplasia. He has no known drug allergies. The plan is to discharge the patient to complete a total 7-day course of antibiotics at home. Which of the following is the most appropriate oral antibiotic to prescribe for discharge?

A first-year internal medicine resident sustains a deep, bleeding needlestick injury to their index finger while drawing arterial blood from a patient with known, poorly controlled HIV infection. Arrange the following steps in the most appropriate chronological sequence for managing this occupational exposure.

Match each patient's clinical presentation and cerebrospinal fluid (CSF) analysis findings with the most appropriate targeted or empiric treatment regimen.

A $19$-year-old male college student presents to the emergency department accompanied by his roommate after developing a severe headache, confusion, and high fever over the previous $12$ hours. His temperature is $39.6^\circ\text{C}$ ($103.3^\circ\text{F}$), blood pressure is $108/68\text{ mmHg}$, and heart rate is $118\text{ beats/min}$. Physical examination reveals marked nuchal rigidity and a non-blanching petechial rash on his lower extremities. A lumbar puncture is performed, and empiric therapy with intravenous ceftriaxone, vancomycin, and dexamethasone is promptly initiated. Cerebrospinal fluid (CSF) analysis shows a leukocyte count of $3,200\text{ cells/mm}^3$ ($92\%$ neutrophils), a glucose level of $22\text{ mg/dL}$, and a protein level of $165\text{ mg/dL}$. The following day, the patient's mental status improves. CSF culture grows *Neisseria meningitidis*. Antimicrobial susceptibility testing is pending. Which of the following is the most appropriate next step in this patient's antimicrobial management?

A 65-year-old man presents to the outpatient clinic with a 4-day history of a productive cough, fevers, and progressively worsening shortness of breath. His medical history is significant for hypertension and type 2 diabetes mellitus, for which he takes lisinopril and metformin. His temperature is 38.4°C (101.1°F), blood pressure is 132/82 mm Hg, pulse is 98/min, and respiratory rate is 22/min. Pulse oximetry shows an oxygen saturation of 94% on room air. Physical examination reveals bronchial breath sounds and crackles in the right lower lung field. A chest radiograph demonstrates a dense consolidation in the right lower lobe. The physician determines the patient is stable for outpatient management. Which of the following is the most appropriate empiric pharmacotherapy for this patient?

Primary care evaluation is requested for a 52-year-old male reporting four weeks of profound fatigue, night sweats, and unintentional weight loss. The patient underwent an uncomplicated cystoscopy for benign prostatic hyperplasia two months ago. Vital signs include a temperature of 38.2°C (100.8°F), blood pressure of 118/76 mmHg, and a heart rate of 94/min. Physical examination reveals splinter hemorrhages on the bilateral fingernails and a new grade III/VI holosystolic murmur loudest at the cardiac apex. Transesophageal echocardiography demonstrates a 1.4-cm oscillating mass on the anterior leaflet of the mitral valve. Four out of four blood culture bottles grow *Enterococcus faecalis*. Antimicrobial susceptibility testing reveals the following:

Based on the antimicrobial susceptibility results, which of the following is the most appropriate definitive intravenous antibiotic regimen?

A $62$-year-old man is evaluated in the hospital on hospital day $3$. He originally presented with a $2$-day history of fever, right flank pain, and dysuria. Medical history is significant for nephrolithiasis, for which he underwent a cystoscopy with stent placement $1$ week ago.

On admission, temperature was $38.9^\circ\text{C}$ ($102.0^\circ\text{F}$), blood pressure was $104/62\text{ mmHg}$, and pulse was $112/\text{min}$. Laboratory studies showed a leukocyte count of $16,500/\mu\text{L}$. He was empirically started on intravenous piperacillin-tazobactam.

Today (hospital day $3$), his temperature is $37.4^\circ\text{C}$ ($99.3^\circ\text{F}$), blood pressure is $122/78\text{ mmHg}$, and pulse is $84/\text{min}$. Blood and urine cultures obtained on admission both grow *Enterobacter cloacae*. Antimicrobial susceptibility testing reveals the following:

* Ampicillin: Resistant
* Cefazolin: Resistant
* Ceftriaxone: Susceptible
* Cefepime: Susceptible
* Piperacillin-tazobactam: Susceptible
* Meropenem: Susceptible

Based on these results, which of the following is the most appropriate next step in the patient's antimicrobial management?

A 68-year-old man is evaluated in the hospital on the third day of his admission for community-acquired pneumonia. He originally presented with a 3-day history of fever, productive cough, and shortness of breath. Chest radiography on admission showed a left lower lobe consolidation. He was empirically started on intravenous ceftriaxone and azithromycin. Today, he reports feeling much better and his cough has improved. He has been afebrile for the past 24 hours. His temperature is 37.1°C (98.8°F), blood pressure is 126/82 mm Hg, heart rate is 78/min, and respirations are 16/min. Pulse oximetry is 96% on ambient air. The patient is tolerating a regular diet. Blood cultures obtained on admission are sterile. Sputum culture has grown heavy *Streptococcus pneumoniae*. Susceptibility testing reveals the isolate is sensitive to penicillin, amoxicillin, ceftriaxone, levofloxacin, and vancomycin. Which of the following is the most appropriate next step in management?

A 52-year-old man is evaluated in the hospital for fever. He was admitted 12 days ago for induction chemotherapy to treat acute myeloid leukemia. Two days ago, he developed a fever of $38.8^{\circ}\text{C}$ ($101.8^{\circ}\text{F}$). At that time, his blood pressure was $108/68\text{ mm Hg}$ and pulse was $112/\text{min}$. Laboratory studies showed an absolute neutrophil count (ANC) of $80/\mu\text{L}$. Empiric intravenous cefepime and vancomycin were initiated after blood and urine cultures were obtained. Today, the patient reports feeling much better. He has been afebrile for the past 24 hours. His blood pressure is $122/78\text{ mm Hg}$ and pulse is $84/\text{min}$. The central venous catheter site appears clean with no erythema or induration. Today's laboratory results show an ANC of $110/\mu\text{L}$. Blood cultures drawn two days ago are positive for *Escherichia coli*. Susceptibility testing indicates the organism is susceptible to ceftriaxone, cefepime, piperacillin-tazobactam, and ciprofloxacin, and resistant to ampicillin. Which of the following is the most appropriate next step in the management of this patient's antibiotic therapy?

A 74-year-old woman is evaluated on postoperative day 3 following a left total knee arthroplasty. Her temperature is 38.1°C (100.6°F), blood pressure is 128/76 mm Hg, pulse is 82/min, and respirations are 14/min. The patient is ambulating with physical therapy and reports that her surgical pain is well controlled. An indwelling urinary catheter, placed during the surgery, was removed yesterday. She denies dysuria, urinary urgency, frequency, and flank pain. Physical examination shows a clean surgical incision without erythema, induration, or purulent drainage. The lungs are clear to auscultation. The calves are soft, non-tender, and symmetric. A urinalysis reveals 25 white blood cells/hpf and is positive for leukocyte esterase and nitrites. Which of the following is the most appropriate next step in management?

A 65-year-old man is evaluated in the hospital for management of infective endocarditis. He was admitted three days ago after presenting with a one-week history of fevers, severe fatigue, and night sweats. His medical history is significant for hypertension and stage 3a chronic kidney disease with a baseline serum creatinine of 1.6 mg/dL.

Upon admission, multiple sets of blood cultures were obtained, and the patient was started on empiric intravenous vancomycin and piperacillin-tazobactam. Transthoracic echocardiography performed yesterday demonstrated a 1.2-cm mobile vegetation on the anterior leaflet of the native mitral valve.

Today, the microbiology laboratory finalizes the blood culture results, reporting that all four bottles are growing *Enterococcus faecalis*. The isolate is susceptible to ampicillin, vancomycin, gentamicin, and linezolid.

Based on current clinical guidelines, which of the following is the most appropriate definitive antimicrobial regimen for this patient?

A 45-year-old man with newly diagnosed acute myeloid leukemia is hospitalized for induction chemotherapy. On day 10 of his hospital stay, he develops a new-onset fever. He reports feeling mildly fatigued but denies cough, shortness of breath, dysuria, or abdominal pain. Temperature is 38.8°C (101.8°F), blood pressure is 122/78 mm Hg, heart rate is 98/min, and respiratory rate is 16/min. Physical examination reveals clear lungs, normal bowel sounds, and no skin rashes. His totally implantable venous access port in the right upper chest is clean, with no surrounding erythema, induration, or tenderness. Laboratory studies show a leukocyte count of 400/mm³ with an absolute neutrophil count of 100/mm³. Blood and urine cultures are obtained. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

An elderly male patient, aged 72, comes to the clinic reporting a four-week history of profound fatigue, night sweats, and unintentional weight loss. He notes that these symptoms began roughly two weeks after he underwent a transurethral resection of the prostate for benign prostatic hyperplasia. His temperature in the clinic is 38.2°C (100.8°F), blood pressure is 134/68 mm Hg, and pulse is 96/min. Cardiovascular auscultation reveals a new early diastolic decrescendo murmur best heard at the left third intercostal space. Physical examination also demonstrates nontender, erythematous macules on the palms and soles. Transesophageal echocardiography confirms a mobile, 1.1-cm vegetation on the right coronary cusp of the aortic valve. Two days later, all three sets of blood cultures are positive for *Enterococcus faecalis*. Antimicrobial susceptibility testing indicates that the isolate is susceptible to ampicillin and vancomycin. However, high-level resistance to both gentamicin and streptomycin is detected. Renal function is within normal limits. Which of the following is the most appropriate definitive intravenous antibiotic regimen for this patient?

A 64-year-old woman is brought to the emergency department by her husband due to rapidly progressive confusion and a severe headache over the past 14 hours. She has a history of a deceased-donor renal transplant performed three years ago and is currently maintained on a regimen of tacrolimus, mycophenolate mofetil, and low-dose prednisone. On arrival, her temperature is 39.4°C (102.9°F), blood pressure is 98/60 mmHg, heart rate is 118/min, and respiratory rate is 24/min. Physical examination demonstrates marked nuchal rigidity. She is lethargic, oriented only to person, and withdraws appropriately from painful stimuli. Pupils are equal and reactive to light.

Arrange the following diagnostic and therapeutic steps in the most appropriate sequential order for the immediate management of this patient.

An antimicrobial stewardship team is auditing the appropriateness of targeted therapies for various complex infections. Match each specific patient scenario and pathogen profile below with its single most appropriate targeted treatment strategy based on current clinical guidelines.