Implementation of a Rapid Phenotypic Susceptibility Platform for Gram-Negative Bloodstream Infections with Paired Antimicrobial Stewardship Intervention: Is the Juice Worth the Squeeze?

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.

Getting Up to Speed: Rapid Pathogen and Antimicrobial Resistance Diagnostics in Sepsis

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Time to receive effective therapy is a primary determinant of mortality in patients with sepsis. Blood culture is the reference standard for the microbiological diagnosis of bloodstream infections, despite its low sensitivity and prolonged time to receive a pathogen detection. In recent years, rapid tests for pathogen identification, antimicrobial susceptibility, and sepsis identification have emerged, both culture-based and culture-independent methods. This rapid narrative review presents currently commercially available approved diagnostic molecular technologies in bloodstream infections, including their clinical performance and impact on patient outcome, when available. Peer-reviewed publications relevant to the topic were searched through PubMed, and manufacturer websites of commercially available assays identified were also consulted as further sources of information. We have reviewed data about the following technologies for pathogen identification: fluorescence in situ hybridization with peptide nucleic acid probes (Accelerate PhenoTM), microarray-based assay (Verigene®), multiplex polymerase chain reaction (cobas® eplex, BioFire® FilmArray®, Molecular Mouse, Unyvero BCU SystemTM), matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (Rapid MBT Sepsityper®), T2 magnetic resonance (T2Bacteria Panel), and metagenomics-based assays (Karius©, DISQVER®, Day Zero Diagnostics). Technologies for antimicrobial susceptibility testing included the following: Alfed 60 ASTTM, VITEK® REVEALTM, dRASTTM, ASTar®, Fastinov®, QuickMIC®, ResistellTM, and LifeScale. Characteristics, microbiological performance, and issues of each method are described, as well as their clinical performance, when available.

Impact of Gram-Negative Rod Bacteremia Rapid Diagnostic Testing and Real-Time Clinical Pharmacist Intervention

Background: The optimal method for implementing rapid diagnostic testing (RDT) into clinical practice has not been determined for gram-negative rod (GNR) bacteremia. At our institution, RDT was implemented in conjunction with real-time notification of results to decentralized clinical pharmacists. Objective: To determine the impact of RDT result notification plus real-time clinical pharmacist review on the management of GNR bacteremia. Methods: This retrospective, matched cohort study included patients with a positive blood culture for a GNR on the BIOFIRE® Blood Culture Identification 2 panel from September 2020 to August 2021 (historical) and October 2021 to September 2022 (interventional). Exclusion criteria were polymicrobial bacteremia, discrepant RDT results from traditional culture, 24-hour mortality, and comfort care or not admitted at the time of RDT result. Patients were matched based on age, pathogen, and resistance. The primary endpoint was time from Gram stain to appropriate antibiotic therapy. Results: This study consisted of 240 patients (n = 120 historical, n = 120 interventional). Escherichia coli was isolated in 71% of patients with extended-spectrum beta-lactamase-producing organisms isolated in 8%. There was no difference in median time to appropriate therapy (0 vs 0 hours, P = 0.28). There was a statistically significant decrease in time to first organism-directed change in therapy (40 vs 11 hours; P < 0.01). Length of stay, days of anti-pseudomonal therapy, and inpatient mortality did not differ between groups. Conclusion: Implementation of RDT plus real-time clinical pharmacist review did not significantly decrease time to appropriate therapy in patients with GNR bacteremia but significantly reduced time to organism-directed antibiotic changes.

From bottle to bedside: Implementation considerations and antimicrobial stewardship considerations for bloodstream infection rapid diagnostic testing

Antimicrobial stewardship (AMS) programs have been quick to adopt novel molecular rapid diagnostic technologies (mRDTs) for bloodstream infections (BSIs) to improve antimicrobial management. As such, most of the literature demonstrating the clinical and economic benefits of mRDTs for BSI is in the presence of active AMS intervention. Leveraging mRDTs to improve antimicrobial therapy for BSI is increasingly integral to AMS program activities. This narrative review discusses available and future mRDTs, the relationship between the clinical microbiology laboratory and AMS programs, and practical considerations for optimizing the use of these tools within a health system. Antimicrobial stewardship programs must work closely with their clinical microbiology laboratories to ensure that mRDTs are used to their fullest benefit while remaining cognizant of their limitations. As more mRDT instruments and panels become available and AMS programs continue to expand, future efforts must consider the expansion beyond traditional settings of large academic medical centers and how combinations of tools can further improve patient care.

Rapid Diagnostic Test Value and Implementation in Antimicrobial Stewardship Across Low-to-Middle and High-Income Countries: A Mixed-Methods Review

Despite technological advancements in infectious disease rapid diagnostic tests (RDTs) and use to direct therapy at the per-patient level, RDT utilisation in antimicrobial stewardship programmes (ASPs) is variable across low-to-middle income and high-income countries. Key insights from a panel of seven infectious disease experts from Colombia, Japan, Nigeria, Thailand, the UK, and the USA, combined with evidence from a literature review, were used to assess the value of RDTs in ASPs. From this, a value framework is proposed which aims to define the benefits of RDT use in ASPs, separate from per-patient benefits. Expert insights highlight that, to realise the value of RDTs within ASPs, effective implementation is key; actionable advice for choosing an RDT is proposed. Experts advocate the inclusion of RDTs in the World Health Organization Model List of essential in vitro diagnostics and in iterative development of national action plans.

Implementing Alfred60AST in a clinical lab: Clinical impact on the management of septic patients and financial analysis

INTRODUCTION

Sepsis is an important cause of morbidity and mortality. An accelerated microbiology diagnosis is crucial in order to reduce the time to initiate targeted antibiotic therapy. The Alfred60AST system is able to provide phenotypic Antimicrobial Susceptibility Testing (AST) results within hours. This study has two objectives: assess the clinical impact of this technology and determine its cost-effectiveness.

METHODS

During a ten-week period, all new enterobacterial or enterococcal bloodstream infection was analyzed with the Alfred60AST system, in parallel with routine methods. Its impact on the clinician's therapeutic strategy was studied. In order to assess the financial and practical aspects of the method, an analysis of the extracosts and a survey of the technical staff were conducted.

RESULTS

Fifty-three cases of bacteriemia were included. For the Enterobacteriaceae bacteriemias, a clinical impact was shown in 18.9% of the cases (e.g, treatment modification). The financial analysis highlighted an increase in costs (+38% for Enterobacteriaceae, +50% for Enterococci), compared to the theoretical costs reported by the firm, due to the workflow and the volumes of samples used. Finally, results of the technical staff survey were favorable in terms of ease of use of the system.

CONCLUSION

In addition to its ease of use, the Alfred60AST system is able to provide an AST in a record time. This study shows a real interest of the technique in the therapeutic management of patients with enterobacterial sepsis. However, its routine implementation requires an increase of the analyzed volumes as well as a 24/7 organization of the laboratory in order to be profitable.

Impact of phenotypic rapid diagnostic assay on duration of empiric antibiotics for gram-negative bacteremia

Objective

Rapid diagnostic tests (RDTs) are increasingly being implemented as antimicrobial stewardship tools to facilitate antibiotic modification and reduce complications related to their overutilization. We measured the clinical impact of a phenotypic RDT with antimicrobial stewardship (AMS) in the setting of gram-negative bacteremia.

Setting and participants

In this single-center retrospective cohort study, we evaluated adult patients with gram-negative bacteremia who received at least 72 hours of an antibiotic.

Methods

The primary outcome was the duration of empiric antibiotic therapy for gram-negative bacteremia. Secondary outcomes included time-to-directed therapy, proportion of modifications, hospital length of stay (LOS), and subsequent infection with a multidrug-resistant organism (MDRO) or C. difficile infection (CDI).

Results

The duration of empiric antibiotics decreased in the RDT+AMS group (4 days vs 2 days; P < .01). Time to directed therapy decreased from 75.0 to 27.9 hours (P < .01).

Conclusions

The clinical outcomes of LOS, MDRO, and CDI were reduced. The phenotypic RDT demonstrated an improvement in stewardship measures and clinical outcomes.

A Baker's Dozen of Top Antimicrobial Stewardship Intervention Publications for Hospitalized Patients in 2021

Keeping abreast of the antimicrobial stewardship-related articles published each year is challenging. The Southeastern Research Group Endeavor (SERGE-45) identified antimicrobial stewardship-related, peer-reviewed literature that detailed an "actionable" intervention among hospitalized populations during 2021. The top 13 publications were selected using a modified Delphi technique. These manuscripts were reviewed to highlight "actionable" interventions used by antimicrobial stewardship programs in hospitalized populations to capture potentially effective strategies for local implementation.

Empirical antibiotic therapy for difficult-to-treat Gram-negative infections: when, how, and how long?

PURPOSE OF REVIEW

To discuss empirical therapy for severe infections due to Gram-negative bacteria with difficult-to-treat resistance (GNB-DTR) in current clinical practice, focusing in particular on the positioning of novel therapeutic agents and rapid diagnostic tests.

RECENT FINDINGS

The current era of novel agents active against GNB-DTR and showing differential activity against specific determinants of resistance is an unprecedented scenario, in which the clinical reasoning leading to the choice of the empirical therapy for treating severe GNB-DTR infections is becoming more complex, but it also allows for enhanced treatment precision.

SUMMARY

Novel agents should be used in line with antimicrobial stewardship principles, aimed at reducing selective pressure for antimicrobial resistance. However, this does not mean that they should not be used. Indeed, excesses in restrictive uses may be unethical by precluding access to the most effective and less toxic treatments for patients with severe GNB-DTR infections. Given these premises (the 'how'), empirical treatment with novel agents should be considered in all patients with risk factors for GNB-DTR and severe clinical presentation of acute infection (the 'when'). Furthermore, empirical novel agents should preferably be continued only for a few hours, until de-escalation, modification, or confirmation (as targeted therapy) is made possible by the results of rapid diagnostic tests (the 'how long').

Evaluation of the Performance and Clinical Impact of a Rapid Phenotypic Susceptibility Testing Method Directly from Positive Blood Culture at a Pediatric Hospital

Bloodstream infection poses a significant medical emergency that necessitates timely administration of appropriate antibiotics. Standard laboratory workup for antimicrobial susceptibility testing (AST) involves subculture of organisms from positive blood bottles followed by testing using broth microdilution; however, this process can take several days. The Accelerate Pheno Blood Culture panel (Pheno) provides rapid phenotypic testing of selected Gram-negative organisms directly from positive blood cultures. This has the potential to shorten the AST process to several hours and impact time to antimicrobial optimization and subsequent clinical outcomes; however, these metrics have not been assessed in pediatric populations. We retrospectively compared two patient cohorts with blood cultures positive for on-panel Gram-negative organisms: 82 cases tested by conventional AST methods, and 80 cases postintervention at our pediatric hospital. Susceptibility testing from the Pheno yielded 91.5% categorical agreement with a broth microdilution-based reference method with 7.4% minor error, 1.1% major error, and 0.1% very major error rates. The median time from blood culture positivity to AST decreased from 20.0 h to 9.7 h (P < 0.001), leading to an overall decrease in time from blood culture positivity to change in therapy from 36.0 h to 25.0 h (P < 0.001). There was no observed change in length of stay or 30-day mortality. Median duration on meropenem decreased from 64.8 h to 31.6 h (P = 0.04). We conclude the Pheno had accurate performance and that implementation allowed for faster AST reporting, improved time to optimal therapy, and decreased duration on meropenem in children.

Impact of a laboratory developed phenotypic rapid susceptibility test directly from positive blood cultures on time to narrowest effective therapy in patients with Gram-negative bacteremia: a prospective randomized trial

Background

Antimicrobial susceptibility testing (AST) is often needed prior to antimicrobial optimization for patients with gram-negative bloodstream infections (GN-BSIs). Rapid AST (rAST) in combination with antimicrobial stewardship (AS) may decrease time to administration of narrower antibiotics.

Methods

This was a prospective, nonblinded, randomized trial evaluating the impact of a phenotypic rAST method vs conventional AST (cAST) in hospitalized patients with GN-BSI and source control. The primary outcome was time to narrowest effective therapy.

Results

Two hundred seventy-four patients were randomized and 205 underwent analysis (97 cAST, 108 rAST). Median (interquartile range [IQR]) time to susceptibility results was 23 hours shorter in the rAST group (cAST: 62 [59–67] hours vs rAST: 39 [IQR, 35–46] hours; P < .001). Median (IQR) time to narrowest effective therapy was similar between groups (cAST: 73 [44–138] hours vs rAST: 64 [42–92] hours; P = .10). Median (IQR) time to narrowest effective therapy was significantly shorter in a prespecified subgroup of patients not initially on narrowest therapy and during AS working hours (cAST: 93 [56–154] hours vs rAST: 62 [43–164] hours; P = .004). Significant decreases were observed in median (IQR) time to oral therapy (cAST: 126 [76–209] hours vs rAST: 91 [66–154] hours; P = .02) and median (IQR) length of hospital stay (cAST: 7 [4–13] days vs rAST: 5 [4–8] days; P = .04).

Conclusions

In patients with GN-BSI, rAST did not significantly decrease time to narrowest effective therapy but did decrease time to oral antibiotics and length of hospital stay. Rapid AST using existing microbiology platforms has potential to optimize patient outcomes.

Susceptibility Testing by Volatile Organic Compound Detection Direct from Positive Blood Cultures: A Proof-of-Principle Laboratory Study

Background: Bacteria produce volatile organic compounds (VOCs) during growth, which can be detected by colorimetric sensor arrays (CSAs). The SpecifAST® system (Specific Diagnostics) employs this technique to enable antibiotic susceptibility testing (AST) directly from blood cultures without prior subculture of isolates. The aim of this study was to compare the SpecifAST® AST results and analysis time to the VITEK®2 (bioMérieux) system. Methods: In a 12-month single site prospective study, remnants of clinical positive monomicrobial blood cultures were combined with a series of antibiotic concentrations. Volatile emission was monitored at 37 °C via CSAs. Minimal Inhibitory Concentrations (MICs) of seven antimicrobial agents for Enterobacterales, Staphylococcus, and Enterococcus spp. were compared to VITEK®2 AST results. MICs were interpreted according to EUCAST clinical breakpoints. Performance was assessed by calculating agreement and discrepancy rates. Results: In total, 96 positive blood cultures containing Enterobacterales, Staphylococcus, and Enterococcus spp. were tested (269 bug–drug combinations). The categorical agreement of the SpecifAST® system compared to the VITEK®2 system was 100% and 91% for Gram-negatives and Gram-positives, respectively. Errors among Gram-positives were from coagulase-negative staphylococci. Overall results were available in 3.1 h (±0.9 h) after growth detection without the need for subculture steps. Conclusion: The AST results based on VOC detection are promising and warrant further evaluation in studies with a larger sample of bacterial species and antimicrobials.

Impact of rapid susceptibility testing on antimicrobial therapy and clinical outcomes in Gram-negative bloodstream infections

Background

Rapid antimicrobial susceptibility testing (rAST) has the potential to improve care of bloodstream infections.

Objectives

The aim of this service evaluation was to assess the impact of rAST on antimicrobial therapy and clinical outcomes in patients with Gram-negative bloodstream infection.

Methods

A prospective service evaluation was conducted from March 2018 to December 2018. A rAST system (Alfred 60AST) was run Monday–Friday before midday and results were communicated to clinicians on the same day as positive blood culture, with subsequent conventional AST performed. Times to antibiotic therapy and clinical outcomes were compared between rAST and conventional AST.

Results

One hundred and ninety-one patients with Gram-negative bacteraemia were included (93 in the rapid group and 98 in the conventional group). Aminoglycoside combination therapy was stopped earlier in the rapid group [32 h (0–795) versus 54 h (4–216), P = 0.002]. The median time to optimal antibiotic based on AST results was significantly shorter than that in the conventional group [50 h (10–339) versus 69.5 h (20–872), P = 0.034]. In the subgroup of patients on ineffective empirical antibiotic, time to effective antibiotic was shorter in the rapid group [39.5 h (32–97) versus 57 h (49–83), P = 0.036]. No differences were found in 28 day mortality or length of stay.

Conclusions

Rapid susceptibility testing resulted in faster discontinuation of aminoglycosides and a shorter time to starting effective and optimal antibiotic when compared with conventional AST results. rAST has potential clinical benefits and points to the need for larger future studies in areas of high antibiotic resistance.

New evidence for managing Gram-negative bloodstream infections

PURPOSE OF REVIEW

Gram-negative bloodstream infections (GNBSI) are common and carry considerable mortality. Treatment is complicated by increasing antimicrobial resistance, posing a challenge for timely appropriate antibiotics and limiting the choices of effective definitive therapy. The present review aims to summarize recent studies addressing the management of GNBSI.

RECENT FINDINGS

New rapid diagnostic tests (RDT) for pathogen identification and antibiotic susceptibility are associated with improved antimicrobial stewardship and reduced length of stay. No mortality benefit or patient-related outcomes are reported. Data regarding the use of new beta-lactam beta-lactamase inhibitors (BLBLIs) for treating multidrug resistance Gram-negative bacteria is supportive, though questions regarding combinations, optimal dosing, mode of administration, and resistance emergence remain to be clarified. Current data regarding cefiderocol necessitates further studies in order to support its use in GNBSI. Shortened (≤7 days) duration of therapy and early oral step down for GNBSI are supported by the literature. The role of repeated blood cultures should be further defined.

SUMMARY

RDTs should be implemented to improve antibiotic stewardship. Clinical implications on patient-related outcomes should be evaluated. New BLBLIs show promise in the treatment of GNBSI. Additional data are needed regarding the use of cefiderocol. Antibiotic therapy should be shortened and early oral step down should be considered.

Clinical characteristics, appropriateness of empiric antibiotic therapy, and outcome of Pseudomonas aeruginosa bacteremia across multiple community hospitals

There is relatively little contemporary information regarding clinical characteristics of patients with Pseudomonas aeruginosa bacteremia (PAB) in the community hospital setting. This was a retrospective, observational cohort study examining the clinical characteristics of patients with PAB across several community hospitals in the USA with a focus on the appropriateness of initial empirical therapy and impact on patient outcomes. Cases of PAB occurring between 2016 and 2019 were pulled from 8 community medical centers. Patients were classified as having either positive or negative outcome at hospital discharge. Several variables including receipt of active empiric therapy (AET) and the time to receiving AET were collected. Variables with a p value of < 0.05 in univariate analyses were included in a multivariable logistic regression model. Two hundred and eleven episodes of PAB were included in the analysis. AET was given to 81.5% of patients and there was no difference in regard to outcome (p = 0.62). There was no difference in the median time to AET in patients with a positive or negative outcome (p = 0.53). After controlling for other variables, age, Pitt bacteremia score ≥ 4, and septic shock were independently associated with a negative outcome. A high proportion of patients received timely, active antimicrobial therapy for PAB and time to AET did not have a significant impact on patient outcome.