Table 2.
Comparison of baseline characteristics and clinical outcomes of patients with methicillin-susceptible S. aureus bacteremia who received empiric combination therapy with β-lactam plus vancomycin or empiric β-lactam monotherapy
| Patient characteristics | β-lactam plus vancomycina (n = 88) | β-lactam monotherapya (n = 43) | p value |
|---|---|---|---|
| Age (mean ± standard deviation in years) | 50.5 ± 16.4 | 58.9 ± 16.6 | 0.006 |
| Males | 53 (60.2) | 30 (69.8) | 0.34 |
| Community-onset | 74 (84.1) | 31 (72.1) | 0.16 |
| Hospital-onset | 14 (15.9) | 12 (27.9) | 0.16 |
| HIV infection | 9 (10.2) | 2 (4.7) | 0.34 |
| Hepatitis C infection | 19 (21.6) | 10 (23.3) | 0.83 |
| Immunocompromised | 8 (9.1) | 6 (14.0) | 0.39 |
| Alcohol or illicit drug abuse | 29 (33.0) | 12 (27.9) | 0.69 |
| Intravenous drug use | 21 (23.9) | 8 (18.6) | 0.65 |
| Charlson comorbidity index (median with IQR) | 2 (1–4) | 3 (1–5) | 0.07 |
| Pitt bacteremia score (median with IQR) | 1 (0–2) | 0 (0–1) | 0.01 |
| Infectious diseases consultation | 71 (80.7) | 27 (62.8) | 0.03 |
| Source of bacteremia | |||
| Central or peripheral line | 12 (13.6) | 8 (18.6) | 0.45 |
| Skin and soft tissue | 20 (22.7) | 11 (25.6) | 0.83 |
| Intravenous drug use | 16 (18.2) | 5 (11.6) | 0.45 |
| Bone or joint infection | 10 (11.4) | 8 (18.6) | 0.29 |
| Lung | 2 (2.3) | 2 (4.7) | 0.60 |
| Other | 9 (10.2) | 3 (7.0) | 0.75 |
| Unknown | 19 (21.6) | 6 (14.0) | 0.35 |
| Infective endocarditis | 19 (21.6) | 5 (11.6) | 0.23 |
| Metastatic complications | 33 (37.5) | 7 (16.3) | 0.02 |
| Surgical source control | 22 (25) | 11 (25.6) | 1.00 |
| Recurrent infection at 6 months | 2 (2.3) | 2 (4.7) | 0.60 |
| Empiric antimicrobials | |||
| Daptomycin | 0 | 2 (4.7) | 0.11 |
| Linezolid | 1 (1.1) | 1 (2.3) | 0.55 |
| Cloxacillin or cefazolin | 88 (100) | 43 (100) | 1.00 |
| 3rd generation cephalosporin | 35 (39.8) | 5 (11.6) | 0.001 |
| Piperacillin–tazobactam | 30 (34.1) | 3 (7.0) | <0.001 |
| Ticarcillin–clavulanic acid | 2 (2.3) | 1 (2.3) | 1.00 |
| Carbapenem | 1 (1.1) | 1 (2.3) | 0.55 |
| Otherb | 27 (30.7) | 20 (46.5) | 0.08 |
| Blood culture time to positivity (median hours with IQR) | 20 (16.0–24.0) | 20.7 (18–27.3) | 0.07 |
| Duration of empiric therapy (median hours with IQR) | 54.1 (43.0–71.7) | 51.7 (38–64.5) | 0.18 |
| Duration of definitive therapy (median days with IQR) | 38 (16–43) | 23 (12–40) | 0.08 |
| Time to receipt of empiric therapy (median hours with IQR) | 1.91 (0–6.17) | 3.42 (0.58–17.2) | 0.19 |
| Time to receipt of β-lactam (median hours with IQR) | 2.88 (0.21–15.1) | 3.42 (0.58–17.2) | 0.87 |
| Time to receipt of cloxacillin or cefazolin (median hours with IQR) | 23.1 (13.0–31.7) | 6.5 (1.5–22.1) | 0.001 |
| Primary outcome | |||
| 28-day mortality | 5 (5.7) | 2 (4.7) | 1.00 |
| Secondary outcomes | |||
| 90-day mortality | 10 (11.4) | 4 (9.3) | 1.00 |
| Duration of bacteremia (median hours with IQR)c | 71.4 (50.3–126.9) | 68.5 (36.4–115.8) | 0.35 |
| ≥3 days | 41 (46.6) | 17 (39.5) | 0.46 |
| Hospital length of stay (median days with IQR)d | 22 (12–44) | 14 (10–22.8) | 0.02 |
IQR interquartile range
aVariables are displayed as counts and percentages in parentheses unless otherwise specified
bOther antimicrobials used during empiric and definitive therapy included rifampin, aminoglycosides, fluoroquinolones, macrolides, trimethoprim-sulfamethoxazole, and clindamycin
c6 and 9 patients from the β-lactam plus vancomycin and β-lactam monotherapy subgroup respectively were excluded from the analysis due to lack of follow-up blood cultures
d9 and 3 patients from the β-lactam plus vancomycin and β-lactam monotherapy subgroup respectively were excluded from the analysis due to death during hospital admission