Efficacy of an intravenous colistin regimen in ventilator-associated pneumonia and bacteraemia due to multiresistant Gram-negative bacteria: preliminary results

Introduction

Colistin has been recently reintroduced in clinical practice, because of the increasing prevalence of multiresistant Gram-negative strains in ICUs. There is controversy on the efficacy of the drug provided either as monotherapy or in combination with β-lactams in critically ill patients with ventilator-associated pneumonia (VAP). We compared prospectively the efficacy and safety of administration of colistin alone and incombination with β-lactams in patients with VAP and bacteremia caused by multiresistant Gram-negative bacteria.

Patients and methods

Twelve patients (mean age: 57 ± 17 years) with VAP (quantitative cultures of tracheal aspirates of bronchoalveolar lavage [BAL]) and bacteraemia (at least one positive blood culture), caused by Pseudomonas aeruginosa (33%), Acinetobacter baumanii (58%) and/or Klebsiella pneumonia (25%), resistant to all antibiotics except colistin, were treated with intravenous colistin. Four of them (group A) received monotherapy with colistin (3 × 10⁶ ssIU three times daily, adjusted for creatinine clearance) and eight of them received combination of colistin with cefepime, or piperacilline-tazobactam (group B). Follow-up cultures and clinical evaluation of all patients were performed 4 days after the initiation of therapy. Clinical success was defined by a lessening of the signs and symptoms of VAP, while microbiologic success was defined as eradication of the pathogen in blood culture.

Results

Follow-up blood cultures revealed microbiologic success in one patient from group A (25%) and four patients from group B (50%), but the difference was not statistically significant (P = 0.4). Eradication of the pathogen from tracheal aspirates or BAL was confirmed in the same patients. Clinical success followed microbiologic success in one patient from group A (25%) and five patients from group B (62.5%), difference not statistically significant (P = 0.3). One patient from group B developed acute renal failure and was treated with continuous venovenous hemofiltration (8%). No differences concerning mortality were observed between the two groups (group A: 100%, group B: 62.5%, P = 0.5).

Conclusion

Preliminary results demonstrate that combination therapy (colistin plus β-lactam) acts more effectively than monotherapy in VAP and bacteraemia from multiresistant Gram-negative strains. Colistin therapy in both groups was safe.