Clinical and Financial Impact of Rapid Antimicrobial Susceptibility Testing in Blood Cultures

Evaluating the impact of rapid antimicrobial susceptibility testing for bloodstream infections: a review of actionability, antibiotic use and patient outcome metrics

Antimicrobial susceptibility testing (AST) is a core function of the clinical microbiology laboratory and is critical to the management of patients with bloodstream infections (BSIs) to facilitate optimal antibiotic therapy selection. Recent technological advances have resulted in several rapid methods for determining susceptibility direct from positive blood culture that can provide turnaround times in under 8 h, which is considerably shorter than conventional culture-based methods. As diagnostic results do not directly produce a medical intervention, actionability is a primary determinant of the effect these technologies have on antibiotic use and ultimately patient outcomes. Randomized controlled trials and observational studies consistently show that rapid AST significantly reduces time to results and improves antimicrobial therapy for patients with BSI across various methods, patient populations and organisms. To date, the clinical impact of rapid AST has been demonstrated in some observational studies, but randomized controlled trials have not been sufficiently powered to validate many of these findings. This article reviews various metrics that have been described in the literature to measure the impact of rapid AST on actionability, antibiotic exposure and patient outcomes, as well as highlighting how implementation and workflow processes can affect these metrics.

Combination of a Rapid Diagnostic Assay and Antimicrobial Stewardship Intervention for Gram-Negative Bacteremia

Background

Traditional blood cultures for gram-negative bacteremia can take up to 72 hours or more to return results, prolonging the duration of empiric broad-spectrum intravenous antibiotics. The Accelerate Pheno system provides rapid identification and susceptibilities for blood cultures in gram-negative bacteremia. Current data on its clinical utility are mixed overall, so the system requires further research.

Methods

A multicenter, retrospective quasi-experimental study was conducted comparing the Accelerate Pheno rapid diagnostic system with antimicrobial stewardship intervention and traditional blood cultures alone.

Results

A total of 264 patients with blood cultures with gram-negative bacteria growth were included in the final analysis (102 pre-intervention, 162 post-intervention). The antimicrobial stewardship team made 364 recommendations in 152/162 (93.8%) patients in the post group. Duration of intravenous therapy was shorter (P < .001) for the post-intervention group (median, 4.0 days) compared with the pre-intervention group (median, 7.5 days). Hospital length of stay was also shorter (P < .001) for the post-intervention group (median, 5.1 days) compared with the pre-intervention group (median, 7.0 days). Readmission rates within 30 days were reduced (P = .042) post-intervention (13.0%) compared with pre-intervention (22.6%). In the post-intervention group, a larger proportion of patients were transitioned to oral therapy at any point (126/162, 77.8%) compared with pre-intervention (62/102, 60.8%; P < .001).

Conclusions

These results suggest that the Accelerate Pheno system, with active review and intervention by a multidisciplinary antimicrobial stewardship team, is a useful tool in improving both patient-centric and antimicrobial stewardship outcomes.

Clinical impacts of the rapid diagnostic method on positive blood cultures

OBJECTIVE

This study aimed to evaluate the impact of short-term incubation (STI) protocol on clinical outcomes of bloodstream infection (BSI) patients.

METHODS

A total of 1363 positive blood culture records from January 2019 to December 2021 were included. The main clinical outcomes included pathogen identification turnaround time (TAT), antimicrobial susceptibility testing (AST) TAT, and length of total hospital stay.

RESULTS

The TAT of pathogen identification and AST significantly decreased after implementing the STI protocol (2.2 vs 1.4 days and 3.4 vs 2.5 days, respectively, with P < .001 for both). Moreover, for patients with Gram-negative bacteria (GNB)-infected BSIs, the length of total hospital stay decreased from 31.9 days to 27.1 days, indicating that these patients could be discharged 5 days earlier after implementing the STI protocol (P < .01).

CONCLUSION

The protocol led to a significant reduction in TAT and improved clinical outcomes, particularly for GNB organisms. The findings suggest that the STI protocol can improve patient outcomes and hospital resource utilization in the management of BSIs.

Antimicrobial susceptibility testing: An updated primer for clinicians in the era of antimicrobial resistance: Insights from the Society of Infectious Diseases Pharmacists

Antimicrobial susceptibility testing (AST) is a critical function of the clinical microbiology laboratory and is essential for optimizing care of patients with infectious diseases, monitoring antimicrobial resistance (AMR) trends, and informing public health initiatives. Several methods are available for performing AST including broth microdilution, agar dilution, and disk diffusion. Technological advances such as the development of commercial automated susceptibility testing platforms and the advent of rapid diagnostic tests have improved the rapidity, robustness, and clinical application of AST. Numerous accrediting and regulatory agencies are involved in the process of AST and setting and revising breakpoints, including the U.S. Food and Drug Administration and the Clinical and Laboratory Standards Institute. Challenges to optimizing AST include the emergence of new resistance mechanisms, the development of new antimicrobial agents, and generation of new data requiring updates and revisions to established methods and breakpoints. Together, the challenges in AST methods and their interpretation create important opportunities for well-informed clinicians to improve patient outcomes and provide value to antimicrobial stewardship programs, especially in the setting of rapidly changing and increasing AMR. Addressing AST challenges will involve continued development of new technologies along with collaboration between clinicians and the laboratory to facilitate optimal antimicrobial use, combat the increasing burden of AMR, and inform the development of novel antimicrobials. This updated primer serves to reinforce important principles of AST, and to provide guidance on their implementation and optimization.

The Accelerate Pheno™ System-A New Tool in Microbiological Diagnostics of Bloodstream Infections: A Pilot Study from Poland

The aim of this study was to evaluate the usefulness of the Accelerate Pheno™ system (APS) (Accelerate Diagnostics, Denver, CO, USA) for rapid laboratory diagnosis of bloodstream infections. The study included 45 positive blood samples obtained from patients hospitalized in University Hospital No. 1 in Bydgoszcz, Poland. In 40 (88.9%) blood samples, the APS was capable of identification of at least one microorganism at the genus or species level and in 38 (84.4%) of them additionally assessed antimicrobial susceptibility. The time of identification and the time to result of antimicrobial susceptibility ranged from 1:32 to 1:42 and 5:02 to 5:36 h, respectively. Six positive blood samples revealed a poly-microbial culture. In these cases, only one out of two or three microorganisms was detected by the APS, and the system assessed antimicrobial susceptibility only for them. For 78.6% positive blood samples, agreement on identification compared to mass spectrometry was found. For all but one sample, a 96-100% compliance of the resistance category was achieved when comparing the antimicrobial susceptibility testing results to conventional methods. Using the APS, the total time to report was reduced from 13:34 to even 63:47 h compared to the standard microbiological laboratory workflow. The APS is a very useful system, especially for the rapid assessment of antimicrobial susceptibility of bacteria directly from positive blood samples, offering the greatest potential for microbiology laboratories operating around the clock.