Community-associated methicillin-resistant Staphylococcus aureus, Minnesota, 2000-2003

Area of Science:

• Infectious Diseases
• Microbiology
• Public Health

Background:

• Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a growing public health concern.
• Distinguishing CA-MRSA skin and soft tissue infections (SSTIs) from invasive disease is crucial for effective management.
• Understanding risk factors and isolate characteristics associated with invasive CA-MRSA disease is essential.

Purpose of the Study:

• To compare the characteristics of patients with CA-MRSA SSTIs and invasive CA-MRSA disease.
• To identify risk factors and microbial features differentiating invasive CA-MRSA from SSTIs.
• To inform surveillance and clinical strategies for CA-MRSA infections.

Main Methods:

• Retrospective analysis of CA-MRSA cases in Minnesota (2000-2003).
• Comparison of patient demographics, risk factors, and isolate antimicrobial susceptibility between SSTI and invasive disease groups.
• Pulsed-field gel electrophoresis (PFGE) subtyping to differentiate healthcare-associated and community-associated MRSA strains.

Main Results:

• A total of 586 SSTI patients and 65 invasive disease patients were identified.
• Patients with invasive disease were more likely to be smokers, have a history of immunosuppressive therapy, emphysema, or injection drug use.
• Invasive disease isolates showed decreased susceptibility to ciprofloxacin and clindamycin and were more likely to be healthcare-associated subtypes.

Conclusions:

• Invasive CA-MRSA disease is associated with specific patient risk factors and distinct isolate characteristics.
• Healthcare exposures may contribute to invasive CA-MRSA infections, even within the CA-MRSA definition.
• Continued surveillance is necessary to accurately characterize and combat CA-MRSA infections.