490. An Outbreak Investigation: Methicillin-sensitive Staphylococcus aureus (MSSA) surgical site infection after spinal surgery
Session: Poster Session: Hospital-acquired and Transplant Infections
Friday, October 30, 2009: 12:00 AM
Room: Poster Hall A
Introduction: Staphylococcus aureus has been implicated in outbreaks in the health care setting, some being linked to a colonized health care worker (HCW). Surgical site infections after elective spinal surgery are uncommon. We recently noted an increase in the number of spinal wound infections due to MSSA in our institution. We describe the investigation of this outbreak.
Methods: We reviewed all microbiological data on all patients who underwent spinal surgery between June 2007 and December 2008. We assessed infection prevention practices and conducted a case-control study. A case was defined as an MSSA-infected surgical site occurring within 30 days of the operation. Patients’ demographic, operative report, hospital stay, and microbiological data were reviewed.
Results: In the 18-month period studied, 12 patients developed MSSA spinal wound infection. Isolates were not available for molecular typing; however, all shared the same antibiotic susceptibility pattern, distinctly different from that of the usually circulating hospital strains of S. aureus. Compared with the control group, patients were more likely to be women and to have diabetes (odds ratio, 4). The risk of infection was much higher when a specific HCW was present during surgery (odds ratio, 3.86); the outbreak subsided without any specific intervention when the HCW resigned; no further cases of MSSA surgical-site infection occurred in the ensuing 5 months.
Discussion: Outbreaks of nosocomial infections with common pathogens and a small number of cases are often not recognized early. By the time of the investigation, the isolates are often no longer available for molecular typing. We speculate that the described cluster of infections was linked to a HCW who was an MSSA carrier. Our investigation triggered implementation of more vigorous infection prevention measures among surgical teams, resulted in a better collaborative relationship between the infection prevention and surgical teams, and re-emphasized that more resources need to be allocated to infection prevention to enable early detection and thus early termination of outbreaks.
Dong Lee, MD, Division of Infectious Diseases & HIV Medicine, Drexel University College of Medicine, Philadelphia, PA, Ole Vielemeyer, MD, Division of Infectious Diseases and HIV Medicine, Drexel University College of Medicine, Philadelphia, PA and  D. H. Lee, None..
O. Vielemeyer, None.