Table 3.
Risk factors for nosocomial S. aureus infection in nasal S. aureus carriers and nasal S. aureus non-carriers among surgical inpatients (n = 325).
| Variable |
S. aureus Carriers (n = 62) |
S. aureus Non-Carriers (n = 263) |
p-Value a | Relative Prevalence (99% CI) | ||
|---|---|---|---|---|---|---|
| n | n with Infection (% Carriers) | n | n with Infection (% Non-Carriers) | |||
| Nosocomial S. aureus infection | 62 | 27 (43.5) | 263 | 20 (7.6) | 0.0001 | 5.73 (2.93-11.13) |
| MRSA | 12 | 3 (25.0) | 313 | 4 (1.3) | 0.0001MH | 19.56 (3.18-120.2) |
| Hospitalized ≤ 12 months | 15 | 7 (46.6) | 53 | 7 (13.2) | 0.002MH | 3.53 (1.12-11.2) |
| Antibiotic therapy ≤ 12 months | 6 | 4 (66.6) | 11 | 4 (36.36) | 0.122MH | 1.83 (0.51-6.51) |
| Intravenous device ≤ 12 months | 12 | 5 (41.6) | 27 | 3 (11.1) | 0.015MH | 3.75 (0.71-19.63) |
| Surgery ≤ 12 months | 9 | 3 (33.3) | 24 | 5 (20.8) | 0.231MH | 1.60 (0.33-7.84) |
| LOS (This study) ≤ 3days | 3 | 1 (33.3) | 28 | 0 (0.0) | 0.096F | Undefined |
| LOS ≤ 2 weeks | 14 | 3 (21.4) | 83 | 5 (6.0) | 0.026MH | 3.55 (0.63-20.02) |
| LOS ≤ 4 weeks | 12 | 7 (58.3) | 60 | 6 (10.0) | 0.0001MH | 5.83 (1.79-18.97) |
| LOS ≤ 8 weeks | 19 | 8 (42.1) | 50 | 3 (6.0) | 0.0001MH | 7.02 (1.42-34.75) |
| LOS ≤ 12 weeks | 8 | 5 (62.5) | 25 | 4 (16.0) | 0.005MH | 3.91 (0.98-15.45) |
| LOS > 12 weeks | 6 | 3 (50.0) | 17 | 2 (11.7) | 0.088F | 4.25 (0.57-31.66) |
| Antibiotic use (this study) | 58 | 26 (44.8) | 207 | 20 (9.6) | 0.0001 | 4.64 (2.38-9.01) |
| Intravenous device (˃24 h) | 24 | 9 (37.5) | 64 | 4 (6.3) | 0.0001MH | 6.00 (1.45-24.82) |
| Urinary catheter (˃24 h) | 2 | 1 (50.0) | 8 | 0 (0.0) | 0.200F | Undefined |
| Hemodialysis | 1 | 0 (0.0) | 0 | 0 | - | Undefined |
| Surgery (this study) | 53 | 22 (41.5) | 184 | 15 (8.2) | 0.0001 | 5.09 (2.37-10.92) |
| Emergency | 12 | 9 (75.0) | 21 | 2 (9.5) | 0.0001MH | 7.87 (1.32-46.93) |
| Elective | 41 | 13 (31.7) | 163 | 13 (7.9) | 0.0001 | 3.98 (1.61-9.82) |
| ≥ 2 surgeries (This study) | 29 | 16 (55.2) | 61 | 10 (16.4) | 0.0001 | 3.37 (1.42-7.95) |
| Comorbidities | 49 | 24 (48.9) | 176 | 20 (11.4) | 0.0001 | 4.31 (2.23-8.34) |
| Bone disease. | 17 | 5 (29.4) | 55 | 4 (7.3) | 0.008MH | 4.04 (0.84-19.5) |
| Skin and soft-tissue disease | 7 | 3 (42.8) | 28 | 4 (14.3) | 0.047MH | 3.00 (0.58-15.45) |
| Bone, skin and soft-tissue disease | 19 | 13 (68.4) | 38 | 9 (23.7) | 0.001MH | 2.89 (1.23-6.76) |
| Cardiovascular disease | 2 | 2 (100) | 17 | 2 (11.7) | 0.035F | 8.50 (1.54-47.04) |
| Pulmonary disease | 1 | 0 (0.0) | 4 | 2 (50.0) | 0.600F | 2.0 (0.55-7.25) |
| Genitourinary disease | 1 | 0 (0.0) | 15 | 1 (6.6) | 0.125F | 15.0 (1.25-180.6) |
| Neurological disease | 0 | 0 (0.0) | 8 | 2 (25.0) | - | Undefined |
| Diabetes mellitus | 1 | 1 (100) | 8 | 1 (12.5) | 0.222F | 8.00 (0.72-89.03) |
| Total number of patient-days | 2,529 | 1,441 (56.9) | 8,763 | 996 (11.4) | 0.0001 | 5.01 (4.58-5.48) |
a Uncorrected chi-square p-values were derived (p ≤ 0.01). For uniform reporting of p-values, and for continuity corrections (cell frequencies ≤ 10), Mantel–Haenszel-corrected chi-square p-values superseded crude uncorrected chi-square p-values, Fisher exact p-values were derived for cell frequencies ≤ 2. All p-values are one-tailed. Degree of freedom = 1. Dashed lines indicate any row or column total = 0, for which no statistical- or p-values are derivable. Undefined risk ratios are indicated. MRSA—methicillin-resistant S. aureus, F—Fisher exact p-value, MH—Mantel–Haenszel, LOS—length of stay.