Relationship of social and medical factors to other antimicrobial resistance among methicilin-resistant Staphylococcus aureus strains

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of healthcare- and community-acquired infections. The emergence and spread of MRSA strains resistant to commonly prescribed antibiotics has made successful treatment conditional on having detailed knowledge of the antimicrobial susceptibility profile. Medical factors such as a history of hospitalization or previous MRSA infections affect patients' risk of developing an MRSA infection. Prior work in social epidemiology suggests that social factors likely influence which patients may contract resistant strains. We developed a theoretical framework in which the type of MRSA strain mediates the effect of individual and community level social factors such as gender, age, race, and residence location on the phenotype of antibiotic resistance. Using data on 633 cases from Ohio hospitals, we performed logistic regression to identify social and medical factors significantly associated with having a resistant MRSA strain (p≤0.10). Patients age ≥60 years and patients living in an urban environment have increased odds of having a resistant MRSA strain (OR=3.10, 95% CI=1.54-6.24 and OR=1.63, 95% CI=0.96-2.77, respectively). After adjusting for medical risk factors associated with having a resistant strain, patient age ≥60 years (OR=2.33 95% CI=1.12-4.84), but not urban residence (OR=1.20, CI=0.70-2.09), is significantly associated with odds of having a resistant MRSA strain. In conclusion, prevention and treatment efforts targeting resistant MRSA strains should focus on populations of older adults and those with medical risk factors.