RESUMEN
Background: Stenotrophomonas maltophilia is a non-fermentative gram-negativebacillus which is widely recognised as an important nosocomial pathogen causing pneumonia,blood-stream, wound and urinary tract infections, particularly in immunosuppressed patients. Theaim of this study was to evaluate a nosocomial outbreak of by S. maltophilia in an intensive careunit of a tertiary hospital and evaluate unexpected multiclonality.Methods: A total of 11 isolates from respiratory cultures in intensive care unit of a 24 bedtertiary hospital obtained over a one months period and one isolate obtained from the nebuliserduring environmental screening were investigated. The bacteria were identified by Phoenix 100system. The clonal relatedness was evaluated by PFGE and semi-automated repetitive sequencebasedPCR. Genotyping tests were repeated for 10 serial subcultures.Results: PFGE and DiversiLab yielded 10 genotypic profiles for 12 isolates. Four to eightdifferent genotypes were observed from 10 subcultures of the same isolate.Conclusion: We conclude that, high genetic diversity and supposed multiclonalappearance of the outbreak isolates may be due to changing profiles during subcultures mostprobably depending on hypermutation.