485. Molecular Characterization of Nosocomial Transmission of Methicillin Resistant Staphylococcus aureus in a Veterans Affairs Medical Center (VAMC)
Session: Poster Session: Hospital-acquired and Transplant Infections
Friday, October 30, 2009: 12:00 AM
Room: Poster Hall A
Background: Since 2001, a dramatic increase in MRSA has been observed in the United States, mostly related to emergence of the USA300 clone in the community and subsequently in hospitals. As part of the VA MRSA initiative at the Durham VAMC, we screen all patients for MRSA nasal colonization on admission, on transfer within the hospital, and at discharge. To determine the contribution of USA 300 strains to spread of MRSA in our patient population, we genotyped admission and hospital acquired transmission (HAT) isolates.
Methods: From April 2008 to March 2009, we screened 6451(94%) admissions. We tested for MRSA colonization on admission and transfer by PCR, GeneXpert® (Cepheid, Sunnyvale, CA) and discharge using BBL CHROMagar (BD, Sparks, MD). We prospectively identified HAT as a patient negative by PCR nasal screening on admission, but positive on transfer or discharge from the hospital. We performed pulsed-field gel electrophoresis (PFGE) to characterize the isolates according to USA typing scheme (100 - 800), if similarity was 80% or greater.
Results: From 1075 (17%) patients colonized on admission, we randomly selected 109 (10%) isolates for genotyping. Admission PFGE types were as follows: 24(35%) USA 100; 9(13%) USA 200; 32(47%) USA 300; 1(1%) USA 400; 2(3%) USA 500. Another 41 (37%) could not be assigned. Of 84 (1.3%) confirmed HAT (transfer and discharge), we genotyped 40 (49%), 11(39%) USA100; 7(25%) USA 200; 10(36%) USA 300; 12 (30%) had <80% similarity on PFGE.
Discussion: At our institution, a high percentage of admissions (17%) are colonized with MRSA. Preliminary results indicate that USA 300 strain account for a significant percentage of strains found in our hospital, on admission (47%) and HAT (36%). The distribution of HAT strain types is consistent with those on admission.
Kyle Breitschwerdt, BS1, Sara Hoffman, BSN2, Daphne Jones, BS3, Maria Joyce, MD2, Brad Nicholson, PhD2, Lawrence Park, PhD4, Susan Wilkins, BS, MDiv2, Christopher Woods, MD, MPH and  K. T. Breitschwerdt, None..
D. C. Jones, None..
L. P. Park, None. 
B. P. Nicholson,
Roche Role(s): Research Relationship.
C. W. Woods,
Roche Role(s): Consultant, Research Relationship, Received: Research Support, Consulting Fee.
Biomerieux Role(s): Consultant, Research Relationship, Received: Research Support, Consulting Fee.
S. O. Hoffman, None..
S. B. Wilkins, None..
M. J. Joyce, None., (1)Durham Va Medical Center, Durham NC, NC, (2)Durham Va Medical Center, Durham, NC, (3)Durham VAMC, (4)Duke University Medical Center, Durham, NC