Macrorestriction analysis of Pseudomonas aeruginosa in colonized burn patients

The colonization of hospitalized patients by Pseudomonas aeruginosa at an intensive care unit for burn victims was studied over a one-year period. A total of 231 isolates from 12 patients were analyzed by macrorestriction analysis. The results revealed that most patients were infected with only one to three different strains. In several patients Pseudomonas aeruginosa isolates of the same clonal lineage exhibited considerable differences in their macrorestriction fragment pattern. Digestion with further restriction enzymes, however, allowed differentiation between clonal variants due to a high genetic drift and superinfection with a different Pseudomonas aeruginosa strain. Isolates of the same clonal lineage could be isolated from several patients as well as from the patients' environment. Notably, Pseudomonas aeruginosa could be isolated from sedimentation plates. Thus, patients may have been extensively cross-infected on the ward. These data underline the importance of strict infection control measures and of regular surveillance for Pseudomonas aeruginosa by an appropriate typing method, i.e. one that can differentiate strains with high genomic variability.