PK/PD-guided ceftazidime-avibactam dosing for multidrug-resistant

Background: Multidrug-resistant Methods: We report a 33-week preterm infant with congenital chylothorax/ascites complicated by MDR-PA infection. Antimicrobial susceptibility testing revealed resistance to meropenem (MIC > 16 μg/mL) and ceftazidime (MIC > 32 μg/mL) but sensitivity to CAZ-AVI (MIC = 4 μg/mL). A PK/PD-guided regimen of CAZ-AVI 40-50 mg/kg (based on the ceftazidime component, every 8 h, prolonged infusion ≥2 h) was administered to achieve a %fT > MIC target of ≥ 70%, considering the preterm infant's immature renal function and increased volume of distribution. Results: After initiation of CAZ-AVI, high-sensitivity C-reactive protein (hs-CRP) decreased from 30.00 mg/L to 7.21 mg/L within 5 days and normalized by day 7. Thoracic and abdominal drainage volumes declined significantly. The infant was successfully weaned from mechanical ventilation and discharged with clinical recovery. No drug-related adverse events were observed. Conclusion: PK/PD-based individualized CAZ-AVI therapy achieved a favorable clinical outcome in this preterm infant with MDR-PA infection. A dosing strategy targeting %fT> MIC ≥ 70% appears feasible and safe in neonates. This case provides quantitative PK/PD support for CAZ-AVI dosing in preterm infants, a population with limited existing evidence.