[Molecular study of a false outbreak of ticarcillin-resistant Pseudomonas aeruginosa infections in a clinical hematology department].

Molecular methods for bacterial strain typing are becoming available outside teaching hospitals and large structures. Although it seems reasonable to use conventional markers, most notably the serotype, whenever possible, the limitations of these methods are particularly conspicuous with P. aeruginosa. Combined use of several methods such as quantitative antibiotic susceptibility testing and serotype determination has proved adequate for characterizing P. aeruginosa strains in some cases. In the case of the outbreak reported herein, this approach failed to provide high quality epidemiological data. In contrast, pulsed field gel electrophoresis ruled out epidemic spread of a P. aeruginosa strain in the clinical hematology department.