Evaluating Rapid Diagnostics for Bloodstream Infections Without Stewardship Involvement

Previous research has shown that using a rapid diagnostic test for bloodstream infections can improve clinical outcomes, specifically when accompanied by antimicrobial stewardship interventions for gram-positive bloodstream infections. However, there is little available data on outcomes of gram-negative bloodstream infections in the absence of antimicrobial stewardship involvement.

Now, a team of investigators from the University of Maryland School of Pharmacy and School of Medicine have conducted a retrospective, quasi-experimental study of patients with gram-negative bloodstream infections, the findings of which were presented in a poster session at the Making a Difference in Infectious Diseases 2019 (MAD-ID) annual meeting.

Verigene Blood Culture Gram-Negative (VBC-GN) is a rapid diagnostic that can detect key gram-negatives, as well as resistance within hours. For the study, the investigators followed patients with VBC-GN target-gram negative bloodstream infections between December 2014 and September 2015 for pre-implementation information and between October 2015 and May 2015 for post-implementation data.

A total of 547 patients met inclusion criteria and were included in the study, 238 participants were identified as pre-implementation and the remaining 309 were sorted into the post-implementation group. According to the investigators the 2 groups had similar baseline characteristics. Among all participants, the median age was 58 years and 62% of participants were male. The most commonly observed infections were E coli (38%) and urinary (31%) and intra-abdominal (22%).

In an exclusive interview at MAD-ID, Contagion® spoke with the presenter of the poster Kimberly Claeys, PharmD, an assistant professor of pharmacy practice at Maryland School of Pharmacy.

The investigators indicate that the appropriateness of antibiotics in the study were determined based on the final susceptibility results. It is also noted that “optimal antibiotics were not overly broad, accounted for resistance, source of infection, and other infecting organisms.”

The study team also reports that categorical variables were compared using Chi-squared/Fisher’s exact and continuous variables with Mann-Whitney U, with time to event analyzed through Kaplan Meier survival analysis.

Results indicate that post-implementation patients had higher rates of previous Extended-spectrum beta-lactamases (3.8% versus 8.1%, p= 0.048). Appropriate therapy was achieved in 99% of patients with time to appropriate therapy similar in both groups (2.7 [IQR 1.5 — 3.9] versus 4.2 [IQR 2.5 – 5.8] hours, p = 0.408).

Optimal therapy was reported to be achieved in 66% of the pre-implementation population versus 79% post-implementation, p < 0.001, with time to optimal therapy significantly shorter in the post-implementation group (47 [IQR 5.3 — 61.2] versus 24 [IQR12 – 49], p = 0.018).

Time to de-escalation was noted as similar in both groups (62 [IQR 48 — 84] versus 64 [IQR 25.8 – 89.2], p = 0.572). Time to escalation was significantly shorter post-implementation (50.7 [IQR 18.1 – 65.3] versus 20.6 [IQR 14.9 –30.2], p < 0.001). Additionally, the median hospital and post-bloodstream duration of stay, in days, were similar (16.9 [IQR 6.4 – 32.3] versus 15.9 [7.8 – 29.4], p = 0.738), (9.5 [IQR 5.1 – 18.8] versus 9.8 [IQR 5.4 – 19.6], p = 0.509), respectively. Inpatient mortality was 15%, in each group, as well.

“Implementation of VBC-GN without active antimicrobial stewardship intervention was shown to improve time to optimal therapy, which was primarily driven by decreased time to antibiotic escalation,” the authors conclude, noting that stewardship intervention could further improve the time through optimal de-escalation.

Claeys also told Contagion® that there will be 3 phases of this research and the third stage will include stewardship involvement. Claeys also noted that this research was funded by MAD-ID.

The poster “Impact of Verigene Blood Culture Gram-negative without Active Stewardship Intervention,” was presented on Thursday, May 9, 2019 at MAD-ID 2019 in Orlando, Florida.