Table 2.
Risk Factors for Methicillin-Resistant Staphylococcus aureus USA300 Bloodstream Infections
| Variable | USA300 Infections Among Patients With Variable Present, No. (%) | USA300 Infections Among Patients With Variable Absent, No. (%) | Relative Risk (95% CI) | P Value* |
|---|---|---|---|---|
| Hospital-onset | 64/182 (35) | 240/367 (65) | 0.5 (.4–.7) | <.001 |
| Community-associated | 115/160 (72) | 189/389 (49) | 1.5 (1.3–1.7) | <.001 |
| Healthcare-associated community-onset | 125/207 (60) | 179/342 (52) | 1.2 (1.0–1.3) | .066 |
| Hospitalization | 111/190 (58) | 14/17 (82) | 0.7 (.6–.9) | .053 |
| Hemodialysis | 29/54 (54) | 96/153 (63) | 0.9 (.6–1.1) | .24 |
| Prior surgery | 42/62 (68) | 83/145 (57) | 1.2 (.9–1.5) | .157 |
| Central venous catheter | 29/56 (52) | 96/151 (64) | 0.8 (.6–1.1) | .123 |
| Age (years) | ||||
| 5–17 | 8/13 (62) | 296/536 (55) | 1.1 (.7–1.7) | .65 |
| 18–29 | 38/58 (66) | 266/491 (54) | 1.2 (1.0–1.5) | .100 |
| 30–39 | 52/85 (61) | 252/464 (54) | 1.1 (.9–1.4) | .24 |
| 40–49 | 83/146 (57) | 221/403 (55) | 1.0 (.9–1.2) | .68 |
| 50–59 | 89/161 (55) | 215/388 (55) | 1.0 (.8–1.2) | .98 |
| ≥60 | 34/86 (40) | 270/463 (58) | 0.7 (.5–.9) | .001 |
| Race | ||||
| White | 144/242 (60) | 157/293 (54) | 1.1 (1.0–1.2) | .169 |
| Black | 104/169 (62) | 197/366 (54) | 1.1 (1.0–1.3) | .095 |
| Hispanic | 33/72 (46) | 268/463 (58) | 0.8 (.6–1.0) | .055 |
| Other | 20/52 (38) | 281/483 (58) | 0.7 (.5–.9) | .007 |
| Male sex | 220/398 (55) | 84/151 (56) | 1.0 (.8–1.2) | .94 |
| IVDU | 164/261 (63) | 133/278 (48) | 1.3 (1.1–1.5) | .001 |
| Homeless/marginally housed | 168/274 (61) | 127/258 (49) | 1.2 (1.1–1.5) | .005 |
| Alcohol abuse | 86/158 (54) | 207/377 (55) | 1.0 (.8–1.2) | .92 |
| Diabetes | 245/429 (57) | 59/119 (50) | 1.2 (.9–1.4) | .144 |
| Renal insufficiency | 82/147 (56) | 222/402 (55) | 1.0 (.9–1.2) | .91 |
| Congestive heart failure | 39/79 (49) | 265/470 (56) | 0.9 (.7–1.1) | .25 |
| HCV infection | 170/278 (61) | 134/271 (49) | 1.2 (1.1–1.4) | .006 |
| COPD | 22/43 (51) | 279/499 (56) | 0.9 (.7–1.2) | .55 |
| Immunosuppressive therapy | 8/21 (38) | 294/526 (56) | 0.7 (.4–1.2) | .108 |
| HIV infection | 69/101 (68) | 208/410 (51) | 1.3 (1.1–1.6) | .002 |
| <0.35 × 109 CD4+ cells/L | 49/73 (67) | 13/17 (76) | 0.9 (.6–1.2) | .45 |
| SSTI in past 12 months | 96/145 (66) | 208/404 (51) | 1.3 (1.1–1.5) | .002 |
| Antibiotic use in past 30 daysa | 61/151 (40) | 243/398 (61) | 0.7 (.5–.8) | <.001 |
| BSI diagnosis in ED | 182/264 (69) | 122/285 (43) | 1.6 (1.4–1.9) | <.001 |
*Numbers in boldface indicate statistical significance (P <.05).
Abbreviations: BSI, bloodstream infection; CI, confidence interval; COPD, chronic obstructive pulmonary disease; ED, emergency department; HCV, hepatitis C virus; HIV, human immunodeficiency virus; IVDU, intravenous drug use; MRSA, methicillin-resistant Staphylococcus aureus; SSTI, skin and soft tissue infection.
aOnly agents usually active on MRSA were collected. Data were missing for 13 (2.4%) on race, 10 (1.8%) on IVDU, 17 (3.1%) on homeless/marginally housed status, 13 (2.4%) on alcohol abuse, and 37 (6.7%) on HIV infection. Of the 101 patients with HIV infection, 11 (11%) had missing data on CD4 count in the preceding 6 months.