Program Schedule

Characteristics of USA500/Iberian Methicillin-Resistant Staphylococcus aureus (MRSA) Invasive Disease

Session: Poster Abstract Session: MRSA and VRE
Thursday, October 9, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Background: Describe the clinical and epidemiologic characteristics of invasive USA500/Iberian MRSA infections and compare to USA300 and USA100 invasive disease.

Methods: Population-based surveillance for invasive MRSA disease was conducted in the 8-county metropolitan Atlanta area from 1-1-2005 to 12-31-2011 through the Active Bacterial Core surveillance program of the Georgia Emerging Infections Program.  Isolates were typed by pulse-field gel electrophoresis (PFGE) and/or screened for SCCmec (SM) types II and IV and categorized as non-USA300 with SM IV, USA300, USA100 or other.  SM IV isolates were subtyped and spa typed; clonal complex (CC) was inferred by spa type.  CC8, non-USA300 that were SM IV but not IVa, were classified as USA500/Iberian.  Medical records were reviewed.

Results: Among a total of 2,006 invasive MRSA infections, 36% were due to USA300, 31% USA 100, 27% (540/2,006) USA500/Iberian, and 7% other.  Most invasive USA500/Iberian cases (99%) were bacteremias.  Clinical syndromes included:  bacteremia without focus (38%), central line-associated bloodstream infection (24%), pneumonia/empyema (12%), skin and soft tissue (9%), urinary tract (9%), bone or joint infections (7%), and endocarditis (3%).  Most were healthcare-associated community-onset (72%), in men (63%) of black race (73%); 24% were in persons with HIV/AIDS.  Trimethoprim-sulfamethoxazole resistance was high (97%).  In-hospital mortality was 21% (110/532) for USA500/Iberian, compared to 21% (126/608) for USA100 and 14% (98/712) for USA300.  On multivariable analysis, invasive USA500/Iberian infections had similar risk of in-hospital mortality as USA300 (aOR 1.34; 95% CI 0.96 – 1.87) and USA100 (aOR 0.97; 95% CI 0.70 – 1.35).

Conclusion: USA500/Iberian MRSA was a common cause of invasive disease in Atlanta.  The association with healthcare exposure, HIV/AIDS and trimethoprim-sulfamethoxazole resistance was strong.  In-hospital mortality for invasive USA500/Iberian MRSA infections was similar to USA100 and USA300 after adjusting for confounders.

Andre G. Melendez, MD1, Sarah W. Satola, PhD1,2, Emily K. Crispell, BS1,2 and Monica M. Farley, MD1,2, (1)Emory University School of Medicine, Atlanta, GA, (2)Georgia Emerging Infections Program, Atlanta Veterans Affairs Medical Center, Decatur, GA


A. G. Melendez, None

S. W. Satola, None

E. K. Crispell, None

M. M. Farley, None

See more of: MRSA and VRE
See more of: Poster Abstract Session

Findings in the abstracts are embargoed until 12:01 a.m. EDT, Oct. 8th with the exception of research findings presented at the IDWeek press conferences.

Sponsoring Societies:

© 2014, All Rights Reserved.

Follow IDWeek