Airway colonization in patients with prolonged and difficult weaning from mechanical ventilation

Purpose: It is well known that airway colonization enhances the risk of developing ventilator associated pneumonia in Intensive Care Unite (ICU) patients. Aim of the study was to acquire more data on the incidence of colonizing pathogens in tracheostomized and/or intubated patients with difficult/prolonged weaning. Methods: From January to-December 1995 a total of 124 bacterial strains were isolated from bronchial tracheoaspirates, routinely performed in 44 consecutive, tracheostomized (32) and/or intubated (12) patients, (29 M, mean age: 66±9 years) admitted to a Respiratory Intermediate Intensive Care Unit (RIICU), to be weaned from prolonged mechanical ventilation. Mean duration of stay in RIICU was 14±2.7 days, whereas mean weaning time was 4.8±2.7 days. Pneumonia (defined as new infitrates on chest radiograph, raised white blood cell count, pirexia and the production of purulent secretions) was diagnosed in 16 patients (32%). Tracheoaspirates were performed by sterile methods. A cut-off point of 104 CFU/ml was established as an indicator of pulmonary infection. Antibiotic susceptibility was assessed using an agar disk diffusion method according to Kirby-Bauer. Results: S. aureus was the most frequently isolated pathogen among gram positive bacteria (46/48, 96%), while Ps. aeruginosa (30 isolates, 40%), Ps. putida (13 isolates, 17%) and Enterobacteriaceae (25 isolates, 32.8%) among gram negative ones (76 isolates). Concerning antibiotic susceptibility pattern, S. aureus strains were mostly (42/46, 91%) methicillin resistant, whereas among Pseudomonas spp. multiresistant strains were frequently isolated. Conclusions: Bacterial epidemiology and antibiotic susceptibility in RIICU patients may be considered similar to those staying in a classic ICU. Clinical implications: Ps.aeruginosa, Enteroactericeae and Methicillin Resistant S. aureus should always be considered as potential colonizing and infecting agents, when prescribing empiric antibiotic treatment in such critically ill patients.