RESUMEN
Of the study was to type Serraria marcescens responsible for nosocnmial outbreaks in an intensive care unit in Stax-Tunisia. The relatedness between S. marcescens isolates was studied by Pulsed field get electrophoresis [PFGE]. We included 56 strains of Serratia marcescens isolated from patients hospitatized in the intensive care unit during 2003 and 2004. Seven epidemiological unrelated strains of Serratia marcescens were also tested. Samples from environment and hands of the nursing and medical staff were collected and cultured to identify the source of contanirnation. All strains showed a wild type of antimicrobial susceptibility. PEGE typing revealed that three different clones were present. None of the cultures taken from hands of unit staff and from environmental samples yielded positive results for S. snarcescens. We have confirmed the presence of three consecutive outbreaks caused by rhree genetically unrelated bacterial clones of Serraria marcescens in the intensive care unit ward. These outbreaks are closely related to the frequent use of colistin and the lack of measures of hygiene in this ward