Introduction: Serratia marcescens is a serious death-causing factor especially for premature and low birth weighted neonates, and has become an important cause of nosocomial infection over the last years. It is a motile, non-sporulating gram-negative bacillus classified in the family enterobacteriacea. This group of bacteria affect on immune system mainly in newborns.

 In this report, we describe the course of the outbreak we had experienced and the measures taken to control it.

Materials & Methods: All of the medical records and other associated variables of patients suffered from serratia marcescens infection were studied. .  Also certain procedures including cell cultures of medical equipments, water supply, sanitation of medical personels and patients, were done to find sources of the outbreak in neonatal ward (Kermanshah – Iran). 

Results: 565 hospitalized patients from September 2000 till March 2001 was studied.33 patients showed positive infection results with Serration Marcescens and confirmed using blood culture (68.8%), in cerebro-spinal fluid culture (23.2%) and both methods (6.8). 13 out of 33 (39.4%) patients have died. Finally it was found that the source of infection could derive from hospital water supply since after taking preventive steps such as controlling consumed water no cases were found with Serration marcescens.

Conclusion: This study showed that outbreak of serratia marcescens would lead to serious in the newborn infants.  Marcessence infection in newborn wards is difficult to manage and may temporarily need closure of units to new admissions and care should be exercised to control the spread.

Awareness of the danger for the presence of this organism in a newborn unit and controlling its spread will be necessary to prevent life threatening infection in the high risk newborn in the future.