Effect of aerosolized colistin as adjunctive treatment on the outcomes of microbiologically documented ventilator-associated pneumonia caused by colistin-only susceptible Gram-negative bacteria

ABSTRACT BACKGROUND: The increasing frequency of ventilator-associated pneumonia (VAP) caused colistin-only susceptible (COS) Gram-negative bacteria (GNB) is of great concern. Adjunctive aerosolized (AS) colistin can reportedly increase alveolar levels of the drug without increasing systemic toxicity. Good clinical results have been obtained in patients with cystic fibrosis, but conflicting data have been reported in patients with VAP. METHODS: We conducted a retrospective, 1:1 matched case-control study to evaluate the efficacy and safety of AS plus IV colistin, versus IV colistin alone, in 208 ICU patients with VAP caused by COS Acinetobacter baumannii, Pseudomonas aeruginosa, or Klebsiella pneumoniae. RESULTS: Compared with the IV colistin cohort, the AS+IV cohort had a higher clinical cure rate (69.2% vs. 54.8%, P=0.03) and required fewer days of mechanical ventilation after VAP onset (8 vs. 12, P = 0.001). In the 166 patients with post-treatment cultures, eradication of the causative organism was also more common in the AS-IV colistin group (63.4% vs. 50%, P=0.08). No between-cohort differences were observed in all-cause ICU mortality, length of ICU stay after VAP onset, or rates of acute kidney injury (AKI) during colistin therapy. Independent predictors of clinical cure were trauma-related ICU admission (P=0.01) and combined AS+IV colistin therapy (P=0.009). Higher mean SAPS II (P=0.002) and SOFA (P=0.05) scores, septic shock (P<0.001), and AKI onset during colistin treatment (P=0.04) were independently associated with clinical failure. CONCLUSIONS: Our results suggest that AS colistin might be a beneficial adjunct to IV colistin in the management of VAP caused by COS GNB.