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 Gram-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 Gram-negative 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 Gram-negative bacteria. These patients should be cared with the optimal precautions in the prevention of colonisation and infection.