Expanded Surveillance in the Acute Care Setting in an Investigation of an Outbreak of Serratia Liquefaciens Bloodstream Infections at an Outpatient Hemodialysis Facility

BACKGROUND: In April 2013, the facility manager from an outpatient hemodialysis facility (Facility A) in Tennessee reported an outbreak of 4 Serratia liquefaciens blood stream infections (BSI) among 8 patients dialysed through central-venous catheter (CVC) at Facility A in February and March 2013.  An additional S. liquefaciens case was identified in a patient dialysed through an arteriovenous graft catheter between the first report of the outbreak and the site visit to Facility A from the Tennessee Department of Health (TDH). 

METHODS: TDH conducted an on-site investigation of Facility A on separate days to observe injection practice procedures, dialysis procedures, and product preparation.  An environmental assessment, including the collection of environmental and product samples, was completed.  A cohort study was conducted on all procedures on patients with CVCs in the four week period of the original 4 infections to determine potential exposure sources.  Expanded surveillance was conducted for additional S. liquefaciens cases in other facilities, including the main acute care hospital in the region.

RESULTS: All environmental and product samples were negative, except for a single non-Serratia colony from the dialysate of one machine. A potential association was observed for procedures completed on Mondays [relative risk (RR): 10.5 0.6, 185.3)], especially procedures involving two staff members on Mondays [RR: 17.0 (1.0, 298.4)].  We observed  fresh paint on walls and a strong scent of bleach during both site visits. Case finding efforts identified 3 additional S. liquefaciens positive blood cultures collected at an acute care hospital among patients receiving dialysis at Facility A that had not been previously reported to the dialysis facility.  All three were identified prior to the date range of the original BSI cluster reported by the facility manager. Discussion with the hospital infection preventionist indicated prior knowledge of an increase in cases from patients receiving hemodialysis at Facility A. 

CONCLUSIONS: The outbreak investigation highlights the importance of timely outbreak notification and response, as changes to staff procedures and the facility environment prior to TDH’s involvement in the investigation limited the ability to detect the underlying source of S. liquefaciens in the clinic.  Improvement in communication between the acute care hospital, the outpatient dialysis center and the health department may have allowed for earlier identification of an increase in S. liquefaciens BSIs.  Outbreak investigations in the outpatient setting can also be enhanced by increased surveillance in the acute care setting.