Endemicity, molecular diversity and colonisation routes of Pseudomonas aeruginosa in intensive care units

Objective: We carried out a prospective study to evaluate the endemicity of Pseudomonas aeruginosa in intensive care units (ICUs). Pulsed-field gel el ectrophoresis (PFGE) was used to determine the genotypes of P. aeruginosa i solates. This allowed us to determine the importance of cross-colonisation and the colonisation routes of P. aeruginosa. Design: We screened epidemiological specimens (rectal swab, nose swab and t racheal aspiration) and routine clinical cultures from patients admitted to ICUs during a 2-year period, from 1st January, 1998, to 31st December, 199 9. Setting: The study was carried out in four separate adult ICUs located in t he Franche-Comte region of France. These four units admitted a total of 1,5 00 patients per year. Results: A total of 1686 specimens were collected from 473 patients; 122 of these patients were positive on admission, 351 became positive during hosp italisation. The overall incidence of P aeruginosa was 15.7 cases per 100 p atients and 15.1 cases per 1000 days of hospitalisation. Of 184 patients wi th at least one ICU-acquired positive clinical culture, 104 had been previo usly identified as carriers by a similar genotype. Typing of 208 non-replic ate isolates revealed 101 major DNA patterns. Approximately 50 % of P. aeru ginosa carriage or colonisation/infection was acquired via cross-transmissi on; the other cases probably originated from endogenous sources. Conclusion: Cross-colonisation seems to play an important role in the gener al spread of P. aeruginosa in ICUs.