A 65-year-old male (weight 70 kg) has been intubated and mechanically ventilated in the ICU for 10 days. He completed a 7-day course of ceftriaxone for a urinary tract infection 2 weeks ago. Overnight, he develops a fever of 39 °C, purulent endotracheal secretions, and his oxygen saturation falls to 88% on an FiO₂ of 0.8. Chest radiography shows a new left lower lobe infiltrate. His WBC count is 18,500/mm³ with 90% neutrophils. Given his risk factors for multidrug-resistant organisms, which empiric antimicrobial regimen is most appropriate?

A 62-year-old man in the surgical ICU is on assist-control ventilation and receiving norepinephrine (0.1 µg/kg/min via central line) for septic shock from severe pancreatitis admitted 10 days ago. His medical history includes type 2 diabetes and hypertension. Vital signs: temperature 39.1 °C, heart rate 110 beats/min, blood pressure 90/55 mm Hg (on norepinephrine), respiratory rate 20 breaths/min, SpO₂ 94% on FiO₂ 0.6. Serum creatinine is 1.2 mg/dL. Over the past 24 hours, he developed new fever, purulent tracheal secretions, and leukocytosis (WBC from 9,500 to 18,000/mm³). Chest X-ray shows new right lower lobe infiltrates. Gram stain of tracheal aspirate reveals numerous Gram-negative rods and Gram-positive cocci in clusters. The hospital antibiogram for late-onset VAP shows Pseudomonas aeruginosa resistance rates: cefepime 25%, meropenem 15%, piperacillin-tazobactam 30%, and MRSA incidence 40%. Three weeks ago, he completed a 5-day course of ceftriaxone for a urinary tract infection. Given his risk factors and local resistance data, which empiric antimicrobial regimen is most appropriate?

A 65-year-old man, three days after abdominal surgery, is mechanically ventilated in the ICU and receiving norepinephrine for blood pressure support. He develops a fever (39.2 °C), purulent sputum, and increased oxygen requirements. Chest radiography shows a new right lower lobe infiltrate consistent with ventilator-associated pneumonia. Empiric therapy with piperacillin-tazobactam 4.5 g IV every 6 hours has been initiated. Considering the time-dependent pharmacodynamics of piperacillin-tazobactam and altered pharmacokinetics in critical illness, which administration strategy is most appropriate to optimize its efficacy against potential multidrug-resistant pathogens?

A 62-year-old man with septic shock is on assist-control mechanical ventilation and a continuous norepinephrine infusion via a right subclavian central line. He has no drug allergies, no antibiotic exposure in the prior 90 days, and his unit’s MRSA prevalence is <10%. On hospital day 5 he develops a new fever (38.9°C), purulent tracheal secretions, and worsening oxygenation (PaO₂/FiO₂ 180). A chest X-ray shows new bilateral infiltrates. Empiric therapy was started 72 hours ago with meropenem 1 g IV q8h, levofloxacin 750 mg IV daily, and vancomycin 15 mg/kg IV q12h, planned for a 7-day course. A semi-quantitative endotracheal aspirate culture obtained immediately before antibiotics returns with no growth (<10⁴ CFU/mL). His fever has resolved, oxygenation has improved (PaO₂/FiO₂ 250), and secretions are less purulent. Which of the following is the MOST appropriate next step in antimicrobial management?

A 65-year-old male (weight 80 kg; serum creatinine 1.1 mg/dL, estimated CrCl ≈ 70 mL/min by Cockcroft–Gault), intubated and mechanically ventilated for 8 days due to severe sepsis, is receiving a continuous norepinephrine infusion via a central line. He was transferred from an outside hospital where he received a 5-day course of ceftriaxone for community-acquired pneumonia 10 days ago. Over the past 24 hours, he has developed a new fever (38.9 °C), increased purulent sputum production, and worsening oxygenation (SpO₂ 88% on FiO₂ 0.8). Chest X-ray shows new bilateral lower lobe infiltrates. WBC is 18,500/mm³ with 85% neutrophils. Given his risk factors for multidrug-resistant pathogens, which empiric antimicrobial regimen is most appropriate to initiate?

A 62-year-old male has been intubated and mechanically ventilated for 10 days for severe sepsis. He remains on low-dose norepinephrine for vasopressor support. Five days ago, he was diagnosed with late-onset ventilator-associated pneumonia and started on IV meropenem 1 g every 8 hours and IV linezolid 600 mg every 12 hours. Over the past 48 hours, his fever has resolved, white blood cell count has normalized, and oxygen requirements have decreased. Cultures grew Pseudomonas aeruginosa susceptible to meropenem and ciprofloxacin; MRSA was not isolated. His renal function is stable (CrCl > 80 mL/min), and he has enteral access. Which of the following represents the most appropriate next step in antimicrobial management?

A 68-year-old man on assist-control ventilation and a norepinephrine infusion for septic shock develops a new fever (39.2°C), increased purulent tracheal secretions, and new bilateral infiltrates on chest X-ray 48 hours ago. His white blood cell count is 18,500/mm³. He was admitted 10 days ago for aspiration pneumonia, treated initially with ceftriaxone and azithromycin, and completed a 7-day course of piperacillin–tazobactam 5 days ago for a suspected intra-abdominal infection. The local antibiogram shows high rates of multidrug-resistant Pseudomonas aeruginosa and MRSA in ventilator-associated pneumonia. Which empiric antibiotic regimen is most appropriate for this patient?

A 65-year-old man is managed in the intensive care unit for septic shock secondary to a suspected ventilator-associated pneumonia (VAP). He is mechanically ventilated, requires a norepinephrine infusion via a central line, and has new bilateral infiltrates on chest imaging. The local hospital antibiogram indicates a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in VAP cases, and some ESBL-producing Klebsiella pneumoniae. Given this patient’s clinical presentation and risk factors, which of the following empiric antimicrobial regimens is MOST appropriate?

A 62-year-old man with acute respiratory distress syndrome on assist-control ventilation develops ventilator-associated pneumonia. He was started empirically on meropenem 1 g IV every 8 hours and tobramycin 7 mg/kg IV daily (tobramycin trough 0.8 µg/mL). Sputum cultures return Pseudomonas aeruginosa (meropenem MIC ≤0.5 µg/mL) and Legionella pneumophila. His creatinine clearance is 90 mL/min. Which of the following is the most appropriate modification to his antimicrobial regimen?

A 65-year-old man is in the intensive care unit for septic shock secondary to a suspected ventilator-associated pneumonia (VAP). He is mechanically ventilated, requires a norepinephrine infusion via a central line, and has new bilateral infiltrates on chest imaging. The local hospital antibiogram indicates a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA). Empiric therapy including vancomycin is initiated. For this critically ill patient, which pharmacokinetic/pharmacodynamic parameter is recommended for therapeutic drug monitoring of vancomycin to optimize efficacy and minimize toxicity?