TABLE 1.
Pathogen and patient characteristics stratified by agr function
| Characteristic | No. (%) of infections with characteristic (unless indicated otherwise) |
P value | ||
|---|---|---|---|---|
| Strains with functional agr (n = 633 [77.8% of infections]) | Strains with dysfunctional agr (n = 181 [22.2% of infections]) | All strains (n = 814) | ||
| Pathogen characteristics | ||||
| Methicillin resistance | 372 (58.8) | 116 (64.1) | 488 (60.0) | 0.20 |
| agr groupa | <0.01 | |||
| I | 363 (58.3) | 60 (34.1) | 423 (52.0) | |
| II | 221 (35.4) | 79 (44.9) | 300 (36.8) | |
| III | 36 (5.8) | 35 (19.9) | 71 (8.7) | |
| IV | 3 (0.5) | 2 (1.1) | 5 (0.6) | |
| Vancomycin MIC (μg/ml) | <0.01 | |||
| 0.5 | 1 (0.2) | 3 (1.7) | 4 (0.5) | |
| 0.75 | 18 (2.8) | 14 (7.7) | 32 (3.9) | |
| 1 | 113 (17.8) | 45 (24.9) | 158 (19.4) | |
| 1.5 | 339 (53.6) | 89 (49.2) | 427 (52.5) | |
| 2 | 149 (23.5) | 24 (13.3) | 173 (21.3) | |
| >2 | 13 (2.1) | 6 (3.3) | 19 (2.3) | |
| hVISA phenotype | 27 (4.3) | 8 (4.4) | 35 (4.3) | 0.93 |
| Hospital-onset infection | 223 (35.2) | 72 (39.8) | 295 (36.2) | 0.26 |
| USA300 clone | 171 (27.0) | 19 (10.5) | 190 (23.3) | <0.01 |
| spa type motif MDMGMK | 156 (24.6) | 78 (43.1) | 234 (28.8) | <0.01 |
| Yr of isolation | 0.01 | |||
| 2003 | 158 (25.0) | 51 (28.2) | 209 (25.7) | |
| 2004 | 147 (23.2) | 57 (31.5) | 204 (25.1) | |
| 2005 | 151 (23.8) | 34 (18.8) | 185 (22.7) | |
| 2006 | 117 (18.5) | 33 (18.2) | 150 (18.4) | |
| 2007b | 60 (9.5) | 6 (3.3) | 66 (8.1) | |
| Patient characteristics | ||||
| Age (yr) (mean ± SD) | 48 ± 16 | 52 ± 17 | 49 ± 16 | <0.01 |
| Female sex | 240 (37.9) | 70 (38.7) | 310 (38.1) | 0.85 |
| Admitted to ICU prior to culture collection | 186 (29.4) | 61 (33.7) | 247 (30.3) | 0.27 |
| Endocarditis | 110 (17.4) | 28 (15.5) | 138 (17.0) | 0.55 |
| Median (IQR) severity-of-illness score | 16 (8-28) | 19 (11-28) | 17 (9-28) | 0.08 |
| Median (IQR) chronic disease score | 1.0 (0-2.1) | 1.0 (1.0-2.2) | 1.0 (0-2.1) | 0.14 |
| Received vancomycin on index admission | 540 (85.3) | 160 (88.4) | 700 (86.0) | 0.29 |
| Receipt of antibiotics during previous yr | 263 (41.6) | 75 (41.4) | 338 (41.5) | 0.98 |
| Injection drug use | 219 (34.6) | 32 (17.7) | 251 (30.8) | <0.01 |
| Presence of central venous catheter before culture collection | 322 (63.0) | 114 (50.9) | 436 (53.6) | <0.01 |
a
Fifteen isolates were unable to be typed for agr group.
b
Only the first 6 months of 2007 were assessed.