Table 3.
Risk factors for methicillin-resistant S. aureus among isolates positive for S. aureus, Kaiser Permanente of Northern California, 2006–2009
| Patient characteristic | OR (CI) of MRSA vs. MSSA among S. aureus isolates (n = 74,333)a |
|---|---|
| Sex | |
| Female | 1.05 (1.02, 1.08) |
| Male | Reference |
| Age (yr) | |
| Under 5 | 1.02 (0.96, 1.09) |
| 5 to <18 | 0.84 (0.79, 0.88) |
| 18 to <50 | 1.20 (1.15, 1.26) |
| 50 to <65 | 0.97 (0.92, 1.02) |
| 65+ | Reference |
| Race/ethnicity | |
| Asian | 0.69 (0.65, 0.73) |
| African-American | 1.73 (1.64, 1.82) |
| Hispanic | 1.11 (1.06, 1.16) |
| Other/unknown | 1.10 (1.05, 1.15) |
| White | Reference |
| Census block income quintile | |
| Unknown | 1.38 (1.29, 1.47) |
| 1st (lowest income) | 1.54 (1.46, 1.62) |
| 2nd | 1.39 (1.32, 1.46) |
| 3rd | 1.25 (1.19, 1.31) |
| 4th | 1.14 (1.09, 1.20) |
| 5th (highest income) | Reference |
| Onset type | |
| Health care associated, hospital onset | 1.58 (1.46, 1.70) |
| Health care associated, community onset | 0.96 (0.92, 1.00) |
| Community associated | Reference |
a
Odds ratios were estimated using a multivariate logistic regression. The analytic data set had a record for each S. aureus isolate. The dependent variable was whether or not the isolate was methicillin resistant, and the independent variables were gender, age, race/ethnicity, income quintile based on census block, and onset type. Reference, reference group for other odds ratios within a characteristic.