Infectious Diseases

A 42-year-old man is brought to the emergency department by his friends due to unresponsiveness. They report that he consumed a large amount of alcohol at a party before becoming stuporous and vomiting profusely. On initial arrival, the patient is difficult to arouse but is protecting his airway. His vital signs are stable, and he is placed in a lateral decubitus position for observation. Two hours later, he develops sudden respiratory distress. Temperature is $37.9^\circ\text{C}$ ($100.2^\circ\text{F}$), blood pressure is $130/80\text{ mmHg}$, pulse is $110\text{/min}$, and respirations are $26\text{/min}$. Pulse oximetry shows an oxygen saturation of $88\%$ on room air. Physical examination reveals diminished breath sounds and crackles in the right lower lung field. Leukocyte count is $14,500/\mu\text{L}$. A chest radiograph demonstrates patchy alveolar opacities in the right lower lobe. Which of the following is the most appropriate next step in management?

A 34-year-old man comes to the urgent care clinic in early June because he found a tick attached to his left groin. He recently returned from a 3-day camping trip in the woods of Connecticut. The tick is still firmly attached to his skin and appears visibly engorged. He has no rash, fever, or joint pain. The patient asks the physician to safely manage the tick and prevent any potential diseases.

Arrange the following management steps in the most appropriate chronological order.

A 32-year-old woman comes to the urgent care clinic 8 hours after sustaining a bite to her right hand from a neighbor's cat. The incident occurred while she was attempting to feed the animal. Immediately after the bite, she washed the hand with soap and warm water. Her past medical history is unremarkable, and she takes no daily medications. She received a tetanus, diphtheria, and pertussis (Tdap) booster vaccination 2 years ago. Her temperature is 37.1°C (98.8°F), blood pressure is 118/76 mm Hg, and pulse is 74/min. Physical examination of the right hand reveals three deep puncture wounds on the dorsal surface. There is surrounding erythema extending approximately 1 cm from the wounds, accompanied by mild localized edema and tenderness to palpation. There is no active bleeding or purulent discharge. Sensation and active range of motion are intact, although movement exacerbates the pain. The wounds are copiously irrigated. Which of the following is the most appropriate pharmacotherapy for this patient?

A 62-year-old man is hospitalized for severe, unremitting lower back pain and fever. His temperature is 38.8°C (101.8°F), blood pressure is 130/80 mm Hg, and pulse is 98/min. Physical examination reveals focal tenderness to palpation over the L4 and L5 spinous processes. Magnetic resonance imaging of the lumbar spine confirms L4-L5 vertebral osteomyelitis. Blood cultures are drawn, and the patient is empirically started on intravenous vancomycin and ceftriaxone. On day 3 of hospitalization, he is clinically stable and afebrile. Final blood culture results return positive for Staphylococcus aureus. Susceptibility testing shows resistance to penicillin, and susceptibility to oxacillin, cefazolin, vancomycin, and daptomycin. Which of the following is the most appropriate next step in antibiotic therapy?

During morning rounds, the internal medicine team evaluates a male patient in his late fifties who was admitted three days prior for community-acquired pneumonia. On presentation to the emergency department, his temperature was $39.2^\circ\text{C}$ ($102.6^\circ\text{F}$) and chest imaging revealed a right lower lobe consolidation. Initial empiric therapy with intravenous ceftriaxone and oral azithromycin was instituted.

Currently, the patient reports significant symptomatic improvement, noting decreased cough and resolution of shortness of breath. He is comfortably eating a regular diet. His vital signs show a temperature of $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure of $124/82\text{ mm Hg}$, heart rate of $78/\text{min}$, and respiratory rate of $16/\text{min}$.

A high-quality sputum specimen collected prior to antibiotic administration has grown heavy *Streptococcus pneumoniae*. Antimicrobial susceptibility testing indicates that the organism is sensitive to penicillin, amoxicillin, ceftriaxone, and levofloxacin, but demonstrates resistance to macrolides.

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

A 45-year-old man presents to the emergency department complaining of a 4-week history of productive cough, intermittent hemoptysis, drenching night sweats, and an unintentional 5-kg (11-lb) weight loss. He recently emigrated from a country with a high prevalence of tuberculosis. His temperature is 38.2°C (100.8°F), blood pressure is 120/78 mm Hg, pulse is 92/min, and respiratory rate is 18/min. A portable chest radiograph performed in the triage area reveals a cavitary lesion in the right upper lobe. The patient is currently sitting in a standard shared emergency department waiting area. Arrange the following steps in the most appropriate sequential order for the management of this patient.

A 54-year-old man presents to the urgent care clinic with a 2-day history of a red, warm, and tender rash on his right lower leg. The area has been progressively enlarging. He has a history of type 2 diabetes mellitus and hypertension. His temperature is $37.9^\circ\text{C}$ ($100.2^\circ\text{F}$), blood pressure is $128/82\text{ mm Hg}$, pulse is $88/\text{min}$, and respirations are $16/\text{min}$. Physical examination of the right lower extremity reveals a poorly demarcated, erythematous, warm, and tender area of skin extending from the ankle to the mid-calf. There is no fluctuance, purulent drainage, or palpable crepitus. Sensation to light touch is intact. His leukocyte count is $10,500/\text{mm}^3$. Which of the following is the most appropriate next step in pharmacotherapy?

A 62-year-old woman is currently mechanically ventilated in the intensive care unit due to acute respiratory distress syndrome following a motor vehicle collision 6 days ago. Over the past 12 hours, her clinical status has deteriorated. She has developed a new fever of 38.9°C (102.0°F), her endotracheal secretions have become increasingly purulent, and her oxygen requirements have significantly increased. A portable chest radiograph demonstrates a new consolidation in the right lower lobe.

Arrange the following clinical steps in the most appropriate chronological order for the management of this patient's suspected infectious condition.

Match each clinical exposure scenario with the most appropriate guideline-directed post-exposure prophylaxis (PEP) or preventative management.

A 35-year-old woman is evaluated in the hospital on day 3 of admission for acute pyelonephritis. She originally presented to the emergency department with a 2-day history of fever, chills, right-sided flank pain, and intractable vomiting. At that time, she was febrile to 39.2°C (102.6°F) and hypotensive. After initial fluid resuscitation, she was empirically started on intravenous vancomycin and piperacillin-tazobactam. Today, her temperature is 37.1°C (98.8°F), blood pressure is 120/78 mm Hg, and pulse is 82/min. Her flank pain has significantly improved, but she continues to experience severe nausea and vomits immediately after attempting to drink any liquids. Blood and urine cultures from admission are now growing *Proteus mirabilis*. Susceptibility testing shows the isolate is intrinsically resistant to nitrofurantoin but susceptible to ampicillin, ceftriaxone, piperacillin-tazobactam, and ciprofloxacin. Which of the following is the most appropriate next step in pharmacotherapy?

A 58-year-old man is admitted to the medical ward due to a 2-day history of severe right knee pain, swelling, and subjective fevers. He has a history of type 2 diabetes mellitus and essential hypertension. His temperature is 38.8°C (101.8°F), blood pressure is 132/82 mmHg, and pulse is 108/min. Physical examination reveals a large, erythematous, and exquisitely tender right knee effusion with significantly limited range of motion. There are no overlying skin lacerations or prior joint surgeries. Diagnostic arthrocentesis yields turbid fluid with a leukocyte count of 92,000/mm³ (94% neutrophils). Gram stain of the synovial fluid demonstrates Gram-positive cocci in clusters. The patient is promptly started on empiric intravenous vancomycin and ceftriaxone, and he undergoes urgent arthroscopic irrigation and debridement. Forty-eight hours later, he reports decreased joint pain and his temperature has normalized. Blood and synovial fluid cultures both grow Staphylococcus aureus that is resistant to penicillin but susceptible to oxacillin, cefazolin, and vancomycin. Which of the following is the most appropriate next step in targeted pharmacotherapy?

An outpatient clinic evaluates a 24-year-old male who reports a 5-day history of fatigue, severe sore throat, and a newly developed diffuse maculopapular rash. He discloses having unprotected sexual intercourse with a new partner two weeks ago. Clinical suspicion for acute human immunodeficiency virus (HIV) infection is high. Assuming his initial screening test is reactive, but his antibody levels remain undetectable due to the recent exposure, arrange the following diagnostic and management steps in the appropriate chronological sequence according to the current testing algorithm.

Match each clinical presentation with the most appropriate, guideline-directed primary antimicrobial therapy.

An 82-year-old woman is evaluated in the hospital on the day of her planned discharge. She was admitted 4 days ago for an acute exacerbation of heart failure, which has now resolved with intravenous diuresis. An indwelling urinary catheter was placed on admission to closely monitor her urine output. Today, the nursing staff reports that her urine appears cloudy and has a strong malodorous scent. The patient feels well, has no new complaints, and is eager to return home. Her temperature is 37.1 C (98.8 F), blood pressure is 126/78 mm Hg, and pulse is 76/min. Physical examination reveals clear lungs, normal heart sounds, and no suprapubic or costovertebral angle tenderness. A urinalysis shows 15-20 white blood cells/hpf and positive nitrites. Urine culture from a sample taken from the catheter port grows >100,000 CFU/mL of Escherichia coli. Which of the following is the most appropriate next step in management?

An internal medicine team evaluates a patient ready for transfer out of the acute care unit. The patient, a resident of an assisted living facility, presented 72 hours ago with profound chills, vomiting, and right-sided back pain. She was hemodynamically stable but highly symptomatic, prompting the initiation of empiric intravenous piperacillin-tazobactam. Currently, she has been afebrile for 24 hours, her vital signs are within normal limits, and she is comfortably eating a regular diet. Microbiological analysis of both blood and urine samples collected on admission reveals heavy growth ($>10^5 \text{ CFU/mL}$) of *Enterococcus faecalis*. Susceptibility testing confirms the isolate is susceptible to ampicillin, amoxicillin, vancomycin, and nitrofurantoin. Which of the following is the most appropriate next step in pharmacotherapy?

A 64-year-old man is evaluated on hospital day 4 for ongoing management of vertebral osteomyelitis. He initially presented with severe mid-back pain, fever, and focal spinal tenderness. Magnetic resonance imaging of the thoracic spine at admission demonstrated T8-T9 discitis and adjacent vertebral body osteomyelitis without an epidural abscess. Blood cultures drawn prior to antibiotic administration have now finalized, showing heavy growth of *Streptococcus agalactiae*. Susceptibility testing indicates the organism is sensitive to penicillin, ceftriaxone, cefepime, and vancomycin. He was empirically started on intravenous vancomycin and piperacillin-tazobactam. Currently, his temperature is 37.1°C (98.8°F), blood pressure is 128/82 mmHg, and pulse is 78/min. His back pain has improved, and his neurologic examination remains unremarkable. Which of the following is the most appropriate next step in pharmacotherapy?

A physician is reviewing several cases of suspected infective endocarditis. The causative microorganisms often have distinct clinical associations based on patient demographics and antecedent procedures. For each patient presentation described below, identify the most probable responsible pathogen.

A 31-year-old male is admitted to the general medical ward for evaluation of severe right arm pain and persistent fevers. He reports a history of injection drug use. His vital signs on admission include a temperature of 39.1°C (102.4°F), blood pressure of 112/70 mm Hg, and a heart rate of 115/min. Physical examination of the right upper extremity reveals a 4-cm area of fluctuance with overlying warmth and marked erythema. Initial blood cultures are obtained, and he is empirically commenced on intravenous vancomycin and piperacillin-tazobactam. An echocardiogram shows structurally normal valves with no vegetations. Over the subsequent two days, the patient defervesces and the localized arm erythema improves. The laboratory reports that the admission blood cultures are positive in all bottles for Staphylococcus aureus. Antimicrobial susceptibility testing demonstrates resistance to penicillin but susceptibility to oxacillin, cefazolin, daptomycin, and vancomycin. Which of the following is the most appropriate modification to his antimicrobial therapy?

Match the following clinical vignettes of central nervous system infections with their most appropriate targeted or empiric antimicrobial therapy.

A 47-year-old man presents to the emergency department with a 4-day history of high fever, severe headache, profound myalgias, and chills. He recently returned from a week-long hiking trip in the Ozark Mountains of Arkansas, where he reports sustaining multiple tick bites. His temperature is $39.4^\circ\text{C}$ ($102.9^\circ\text{F}$), blood pressure is $118/76\text{ mmHg}$, and pulse is $105/\text{min}$. Physical examination reveals a non-toxic appearing man with no focal neurological deficits, no lymphadenopathy, and no skin rash. Laboratory studies show:

Hemoglobin: $13.8\text{ g/dL}$
Leukocyte count: $2,400/\text{mm}^3$
Platelet count: $82,000/\text{mm}^3$
Aspartate aminotransferase (AST): $145\text{ U/L}$
Alanine aminotransferase (ALT): $152\text{ U/L}$

Which of the following is the most appropriate empiric pharmacotherapy for this patient?