Growing role of community-acquired MRSA infections in the United States: a 10-year trend of replacement and expansion

Abstract number: O483

Mera R.M., Suaya J., Madsen H.A., Hogea C.S., Lu E., Acosta C.

Objectives: To describe the role of Community-Acquired (CA) MRSA in inpatient and outpatient staphylococcus aureus infections over a 10 year period in the US.

Methods: The study used the TSN Network® surveillance database (Eurofins Medinet) for the period 1998 to 2007. The database contains information on isolate source, setting (ambulatory or hospital), geographic region, and demographic characteristics such as gender and age. Identical CLSI breakpoints were used for all the time points. CA-MRSA phenotype was defined by a resistance profile that includes the absence of gentamicin/cotrimoxazole resistance, and the absence of ciprofloxacin/ clindamycin/ erythromycin co-resistance. Using multivariate logistic regression, we computed adjusted phenotype prevalences and odds ratios (OR) with 95% confidence intervals (CI).

Results: The study consisted of 824,307 S. aureus isolates. MRSA prevalence continuously increased over the 10 year period from 32.7% in 1998 to 53.8% in 2007 (OR 2.4, 95% CI 2.3–2.5). CA-MRSA represented an increasing proportion of MRSA from 22.3% in 1998 to 66.1% in 2007 (OR 6.7, 95% CI 6.5–6.9). Changes in CA-MRSA prevalence were observed for all age-groups, isolate sources, inpatient or outpatient settings, and across all geographic regions of the US. However, a comparatively larger statistically significant temporal increase of CA-MRSA occurred in children and young adults as compared to the elderly, and in abscess and wound isolates when compared to blood and sputum. By 2007, 81.5% of all MRSA isolates were categorized as CA-MRSA among children, while CA-MRSA represented 48.9% of MRSA isolates from the elderly. In 2007, out of all MRSA, CA-MRSA represented 85.7% of all abscess, 75.4% of wound, 43.6% of blood and 30.4% of sputum isolates, as well as 84.5% of outpatient and 40.8% of inpatient isolates.

Conclusion: In the study period, MRSA isolates have become a growing proportion of all S. aureus isolates. The majority of the growth of MRSA share of S. aureus infections is explained by CA-MRSA, which has not only proportionally expanded but also replaced HA-MRSA. These changes occurred principally among abscess and wound isolates, children and young adults, but with a lesser degree also among other isolate sources and age groups. Four out of five isolates in the outpatient setting now possess the CA-MRSA phenotype. These findings may have preventive and therapeutic implications in the management of S. aureus infections.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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