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

Objective: To investigate prevalence and determine risk factors for colonisation with Cram-negative bacteria in ICU patients. Design: Prospective, surveillance study. Setting: 26-bed surgical and paediatric ICU. Patients: 159 patients - whereof 22 infants - admitted to the surgical/paediatric ICU over a two-month period. Intervention: In all patients routine microbiological monitoring was performed by thrice weekly oral swabs, urine sampling and, additionally, tracheal aspirates in patients on mechanical ventilation (MV) and by anal swabs once weekly. Results: Population characteristics: Mean age of the adult population was 51.1+/-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 mechanical ventilation (MV). The mean number of mechanical ventilation days was 11.1+/-14.7 days. 32.1% of patients experienced colonisation with Gramnegative bacteria. Prevalence of colonisation increased with length of ICU stay. The probability of 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). 47% of colonisations were due to multiresistant strains. Higher APACHE II-scores and MV were associated with a higher prevalence of colonisation (p<0.01). 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.