Prevalence and risk factors for colonisation with Gram-negative bacteria in an intensive care unit

Objective: To investigate prevalence and determine risk factors for colonis ation with Cram-negative bacteria in ICU patients. Design: Prospective, surveillance study. Setting: 26-bed surgical and paedi atric ICU. Patients: 159 patients - whereof 22 infants - admitted to the su rgical/paediatric ICU over a two-month period. Intervention: In all patients routine microbiological monitoring was perfor med by thrice weekly oral swabs, urine sampling and, additionally, tracheal aspirates in patients on mechanical ventilation (MV) and by anal swabs onc e weekly. Results: Population characteristics: Mean age of the adult population was 5 1.1+/-17.6 year. Mean age of the paediatric population was 6.3+/-5.3 year. The mean APACHE II-score was 18+/-9.1. The mean PRISM-score was 9.7+/-5.4. The mean ICU stay was 7.5+/-11.4 days. 43.4 percent of patients received me chanical ventilation (MV). The mean number of mechanical ventilation days w as 11.1+/-14.7 days. 32.1% of patients experienced colonisation with Gramnegative bacteria. Prev alence of colonisation increased with length of ICU stay. The probability o f colonisation was 24% after an ICU stay of 3 days (=median ICU stay). Time to colonisation was not different between the controlled sites (p>0.05). 4 7% of colonisations were due to multiresistant strains. Higher APACHE II-sc ores and MV were associated with a higher prevalence of colonisation (p<0.0 1). The ICU mortality was 8%among adult and 4% among paediatric patients. Conclusion: Patients with high APACHE II-scores, on mechanical ventilation and with an ICU stay of more than 3 days are most at risk for colonisation with Gramnegative bacteria. These patients should be cared with the optimal precautions in the prevention of colonisation and infection.