487. MRSA Surgical Site Infections - What Is the Role of SCCmec Type IV Community-Associated Strains?
Session: Poster Session: Hospital-acquired and Transplant Infections
Friday, October 30, 2009: 12:00 AM
Room: Poster Hall A
Background: Hospital-acquired MRSA (HA-MRSA) is a common cause of surgical site infections (SSIs). Rising numbers of infections are being seen in the general population due to community associated (CA)-MRSA strains, distinguishable by the unique methicillin resistance locus SCCmec type IV. We hypothesized that CA-MRSA would emerge as a cause of SSIs in patients undergoing spinal fusion at our institution.
Methods: We performed a retrospective, observational study of MRSA SSIs in patients who underwent spinal fusions between 2005 and 2008. We previously found an excellent correlation between SCCmec type IV and clindamycin susceptibility (S) (confirmed by a double-disk diffusion test) among local isolates. Therefore, clindamycin S was used as a surrogate marker to identify CA-MRSA isolates. A detailed chart review was performed to compare CA-MRSA and HA-MRSA cases.
Results: 58 cases of MRSA spinal fusion SSIs were identified out of 5749 procedures (1%). 14 patients had trauma and 9 had spinal tumors; 17 had prior spinal surgery. 10 patients had associated MRSA bacteremia. 13 MRSA isolates (22%) were clindamycin S consistent with SCCmec IV strains. There were no significant differences in patient characteristics or outcomes, but there was a trend toward shorter time to infection in clindamycin S cases compared to clindamycin resistant cases (mean 17.4 vs 35.1 days). Although the number of MRSA SSIs did not significantly change during the study period, the proportion of infections due to clindamycin S isolates increased from 0% in 2005 to 34.3% in 2007-2008. Logistic regression confirmed that the relative frequency of clindamycin S MRSA was associated with year (p =0.025); the odds ratio was 2.11 (95% CI 1.09 -4.58) per year.
Conclusions: There was a significant increase in the relative frequency of spinal fusion SSIs caused by CA-MRSA strains from 2005 -2008. These data support the need to identify patients colonized with CA-MRSA and re-evaluate SSI prevention strategies.
Phyllis Flomenberg, MD, James Harrop, MD2, Donald Jungkind, PhD2, Mitchell Maltenfort, PhD2, Dionissios Neofytos, MD2, Shilpa Rao, MD2, Gustavo Vasquez, MD2 and  G. A. Vasquez, None..
S. B. Rao, None..
D. Neofytos, None..
M. Maltenfort, None..
J. Harrop, None..
D. Jungkind, None..
P. Flomenberg, None., (1)Thomas Jefferson University, Philadelphia, PA