Serratia marcescens outbreak associated with extrinsic contamination of 1% chlorxylenol soap

Infect Control Hosp Epidemiol. 1997 Oct;18(10):704-9. doi: 10.1086/647516.


Objectives: To determine risk factors for Serratia marcescens infection or colonization, and to identify the source of the pathogen and factors facilitating its persistence in a neonatal intensive-care unit (NICU) during an outbreak.

Design: Retrospective case-control study; review of NICU infection control policies, soap use, and handwashing practices among healthcare workers (HCWs); and selected environmental cultures.

Setting: A university-affiliated tertiary-care hospital NICU.

Patients: All NICU infants with at least one positive culture for S marcescens during August 1994 to October 1995. Infants who did not develop S marcescens infection or colonization were selected randomly as controls.

Results: Thirty-two patients met the case definition. On multivariate analysis, independent risk factors for S marcescens infection or colonization were having very low birth weight (< 1,500 g), a patent ductus arteriosus, a mother with chorioamnionitis, or exposure to a single HCW. During January to July 1995, NICU HCWs carried their own bottles of 1% chlorxylenol soap, which often were left standing inverted in the NICU sink and work areas. Cultures of 16 (31%) of 52 samples of soap and 1 (8%) of 13 sinks yielded S marcescens. The 16 samples of soap all came from opened 4-oz bottles carried by HCWs. DNA banding patterns of case infant, HCW soap bottle, and sink isolates were identical.

Conclusions: Extrinsically contaminated soap contributed to an outbreak of S marcescens infection. Very-low-birth-weight infants with multiple invasive procedures and exposures to certain HCWs were at greatest risk of S marcescens infection or colonization.

MeSH terms

  • Anti-Infective Agents, Local*
  • Case-Control Studies
  • Contact Tracing
  • Cross Infection / transmission*
  • Disease Outbreaks*
  • Female
  • Housekeeping, Hospital
  • Humans
  • Infant, Newborn
  • Intensive Care Units, Neonatal*
  • Male
  • Retrospective Studies
  • Risk Factors
  • Serratia Infections / transmission*
  • Serratia marcescens*
  • Soaps*
  • Xylenes*


  • Anti-Infective Agents, Local
  • Soaps
  • Xylenes
  • chloroxylenol