Table 3.
Antibiotic Utilization Among All Study Subjects in the First 96 Hours Following Enrollment
| Outcome | Control | Rapid Multiplex PCR | Rapid Multiplex PCR + Stewardship | P Value Comparing 3 Groups |
|---|---|---|---|---|
| Duration of therapya, h | ||||
| Vancomycin | ||||
| All patients (n = 357) | 44 (22–72) | 42 (21–93) | 42 (19–90) | .92 |
| Organisms not requiring vancomycinb (n = 169) | 8.2 (0–26) | 0 (0–16) | 0 (0–3)c | .032 |
| Vancomycin-susceptible enterococci (n = 32) | 20 (1–59) | 70 (48–88)c | 82 (40–96)c | .037 |
| Methicillin-susceptible Staphylococcus aureus (n = 42) | 23 (20–53) | 11 (0–26) | 8 (0–44) | .2 |
| Nafcillin, oxacillin, or cefazolin (n = 50) | 42 (24–57) | 71 (51–79)c | 85 (42–92)c | .035 |
| Piperacillin-tazobactam (n = 214) | 56 (39–82) | 44 (27–74)c | 45 (19–78)c | .012 |
| Cefepime (n = 181) | 55 (28–96) | 71 (43–96) | 58 (32–96) | .56 |
| Antibiotic modifications | ||||
| Time to first appropriate de-escalationd (n = 344) | 34 (21–55) | 38 (22–66) | 21 (7–37)c,e | <.0001 |
| Time to first appropriate escalationf (n = 122) | 24 (3–67) | 6 (2–36) | 5 (2–22)c | .04 |
| Time to administration of active antibiotics (n = 123)g | 11 (2–51) | 6 (2–31) | 4 (2–20) | .55 |
| Contaminated blood cultures not treated or treated for <24 h, No. (%)h | 47 (75) | 49 (89)c | 57 (92)c | .015 |
Data are presented as median (IQR) unless otherwise specified.
Abbreviations: IQR, interquartile range; PCR, polymerase chain reaction.
a Duration of therapy (hours) was calculated as the difference between the date and time of the antibiotic start order (or Gram stain–positive blood culture, if antibiotics were started prior to the positive culture result) and the date and time of the antibiotic stop order, for subjects who received the specified antibiotics, according to the organisms identified and study group. Shorter duration of broad-spectrum antibiotics, longer duration of narrow-spectrum antibiotics, faster antibiotic escalation or de-escalation, and less treatment of contaminants were considered favorable outcomes.
b Organisms not requiring vancomycin included monomicrobial cultures with methicillin-susceptible Staphylococcus aureus; groups A, B, C, or G streptococci; Streptococcus anginosus species group; or gram-negative or fungal organisms.
c Statistically significant compared to control group.
d From positive Gram stain to 96 hours after enrollment. De-escalation included discontinuation of 1 or more antibiotics and/or switching from a broad- to a narrow-spectrum antibiotic.
e Statistically significant comparison between the 2 intervention groups.
f From positive Gram stain to 96 hours after enrollment. Escalation included initiation of 1 or more antibiotics and/or switching from a narrow- to a broad-spectrum antibiotic.
g From positive Gram stain to start of active antibiotic among patients not on active therapy at enrollment; excludes patients with contaminated blood cultures.
h Contaminated blood cultures were defined as growth of organisms such as coagulase-negative staphylococci from a single blood culture set when ≥2 blood culture sets were collected, except among subjects suspected to have true bacteremia associated with central venous catheters or devices.