Positive Blood Culture Broths Research Articles

Blood-rsCDM: a new rapid and simplified carbapenemase detection method for detecting carbapenemases in Enterobacterales directly from positive blood cultures

ObjectiveWe aim to validate and evaluate a new rapid and simplified method, called Blood-rsCDM, for the detection and characterization of carbapenemase using 3-aminophenylboronic acid (APBA) and ethylenediaminetetraacetic acid (EDTA) β-lactamase inhibitors from positive blood cultures.MethodWe utilized a panel of 172 Enterobacterales strains, including blaKPC (77), blaNDM (48), blaIMP (9), blaVIM (2), blaOXA-181 (2), blaKPC and blaNDM (6), as well as 28 carbapenem-susceptible Enterobacterales isolates, to assess the performance of Blood-rsCDM and the EDTA-carbapenem inactivation method (eCIM). Carbapenemase class was determined using specific inhibitors at 4 h and 6 h by Blood-rsCDM.ResultsBlood-rsCDM exhibited a sensitivity of 97.9% at both time points, with a specificity of 100%, regardless of the culture duration. The sensitivity of eCIM was 94.4%, with a specificity of 100%. Blood-rsCDM accurately characterized KPC-producing isolates as 77/77, metallo-β-lactamases (MBLs) as 58/59, and KPC and NDM carbapenemases as 6/6 at 4 h. There was no difference in results between the 4 h and 6 h time points. However, Blood-rsCDM could not differentiate OXA-181-producing strains. For eCIM, the characterization numbers for KPC-, OXA-181-, and MBLs-producing strains were 77/77, 2/2, and 57/59, respectively, but it failed to detect the coproduction of KPC and NDM isolates.ConclusionBlood-rsCDM accurately discriminates carbapenemase within 4 h and is capable of directly differentiating multi-enzyme (KPC and NDM) presence from positive blood culture broths. Therefore, Blood-rsCDM represents a rapid, simple, easy-to-read, and accurate tool that can be utilized in resource-limited settings.

QMAC-dRAST for direct testing of antibiotic susceptibility in positive blood-culture broth: a comparison with the BD Phoenix® system and the disc diffusion method.

QMAC-dRAST for direct testing of antibiotic susceptibility in positive blood-culture broth: a comparison with the BD Phoenix® system and the disc diffusion method.

Assessing the effectiveness of direct susceptibility testing from positive blood culture broth using the VITEK-2 system

Assessing the effectiveness of direct susceptibility testing from positive blood culture broth using the VITEK-2 system

Evaluation of Direct Antimicrobial Susceptibility Testing of Gram-Negative Bacilli and Staphylococcus aureus from Positive Pediatric Blood Culture Bottles Using BD Phoenix M50.

Bloodstream infections (BSIs) are life-threatening infections for which a timely initiation of appropriate antimicrobial therapy is critical. Antibiotic susceptibility testing (AST) directly performed on positive blood culture broths can help initiate targeted antibiotic therapy sooner than the standard AST performed on colonies isolated on solid media after overnight incubation. Faster antimicrobial susceptibility testing (AST) results can improve clinical outcomes, and reduce broad-spectrum antimicrobial consumption and healthcare-associated costs in sepsis. In this study, we evaluated the accuracy of a direct AST inoculation method on the BD Phoenix M50 system using serum separator tubes to harvest bacteria from positive pediatric blood culture bottles. Direct AST was performed on 132 monomicrobial pediatric blood culture bottles that were positive for Enterobacterales (65; 49.2%), Staphylococcus aureus (46; 34.8%), and non-fermenting Gram-negative bacilli (21; 16%). Overall, the categorical and essential agreements between the direct method and standard method were 99.6% and 99.8%, respectively. Very major, major, and minor error rates were 0.1%, 0.09%, and 0.20% respectively. Direct AST performed on pediatric blood culture bottles using BD Phoenix M50 can quickly provide accurate susceptibility information to guide antimicrobial therapy in patients with BSI.

Evaluation of the QMAC-dRAST System Version 2.5 for Rapid Antimicrobial Susceptibility Testing of Gram-Negative Bacteria From Positive Blood Culture Broth and Subcultured Colony Isolates.

Rapid antimicrobial susceptibility testing (AST) for bloodstream infections (BSIs) facilitates the optimization of antimicrobial therapy, preventing antimicrobial resistance and improving patient outcomes. QMAC-dRAST (QuantaMatrix Inc., Korea) is a rapid AST platform based on microfluidic chip technology that performs AST directly using positive blood culture broth (PBCB). This study evaluated the performance of QMAC-dRAST for Gram-negative bacteria using PBCB and subcultured colony isolates, comparing it with that of VITEK 2 (bioMérieux, France) using broth microdilution (BMD) as the reference method. We included 141 Gram-negative blood culture isolates from patients with BSI and 12 carbapenemase-producing clinical isolates of Enterobacterales spiked into blood culture bottles. QMAC-dRAST performance was evaluated using PBCB and colony isolates, whereas VITEK 2 and BMD were tested only on colony isolates. For PBCB, QMAC-dRAST achieved 92.1% categorical agreement (CA), 95.3% essential agreement (EA), with 1.8% very major errors (VMEs), 3.5% major errors (MEs), and 5.2% minor errors (mEs). With colony isolates, it exhibited 92.5% CA and 95.1% EA, with 2.0% VMEs, 3.2% MEs, and 4.8% mEs. VITEK 2 showed 94.1% CA and 96.0% EA, with 4.3% VMEs, 0.4% MEs, and 4.3% mEs. QMAC-dRAST yielded elevated error rates for specific antimicrobial agents, with high VMEs for carbapenems and aminoglycosides. The median time to result for QMAC-dRAST was 5.9 h for PBCB samples and 6.1 h for subcultured colony isolates. The QMAC-dRAST system demonstrated considerable strengths and comparable performance to the VITEK 2 system; however, challenges were discerned with specific antimicrobial agents, underlining a necessity for improvement.

A study on direct antimicrobial susceptibility testing of positive blood culture broth using BacT/Alert 3D microbial identification system in a tertiary care hospital

A study on direct antimicrobial susceptibility testing of positive blood culture broth using BacT/Alert 3D microbial identification system in a tertiary care hospital

Rapid diagnostic work-up of Streptococcus dysgalactiae endophthalmitis by a novel culture processing system

The diagnosis of infective endophthalmitis is supported by microbiological work-up. Rapid work-up is critical to confirm clinical suspicion and appropriate antimicrobial therapy. We report the novel use of an automated liquid culture processing system (FAST system, Qvella, ON, Canada) in a vitreous fluid culture. A 59-year-old patient with post-operative endophthalmitis presented with acute right eye pain and blurred vision. Vitreous fluid collected for microbiology culture was of limited quantity and only inoculated to thioglycolate broth. The broth recovered beta-haemolytic, group G Streptococcus dysgalactiae susceptible to penicillin and vancomycin. Experimental application of the FAST system to purify the organism from broth culture yielded the same identification and susceptibility test results but 1 day sooner. Despite prompt treatment with appropriate antibiotics, including vancomycin and ceftazidime, disease progressed rapidly and required enucleation to achieve a stable therapeutic outcome. Use of automated processing of monomicrobial broth cultures has thus far focused on positive blood culture broths, but could potentially include other liquid-based cultures such as for sterile body fluids of critical nature.

Customized molecular diagnostics of bacterial bloodstream infections for carbapenem resistance: A convenient and affordable approach

ABSTRACT The acute crisis of carbapenem resistance impedes the empirical use of carbapenems in medical emergencies, especially, bloodstream infections. Carbapenemase-producing carbapenem-resistant organisms (CP-CROs) attribute high case-fatality, necessitating rapid diagnostics to initiate early targeted antibiotics. Expensive diagnostics are the major driver of antibiotic misuse, neglecting evidence-based treatment in India. One in-house molecular diagnostics assay was customized for rapid detection of CP-CROs using positive blood-culture (BC) broths at a low-cost. The assay was validated using a known-set of isolates and evaluated on positive BC broths. DNA was extracted from positive BC broths using a modified alkali-wash/heat-lysis method. One end-point multiplex-PCR was customized targeting five carbapenemases (KPC, NDM, VIM, OXA-48-, and OXA-23-type) with 16S-rDNA as internal extraction control. Carbapenem resistance due to other carbapenemases, efflux-pump activity, and loss of porins was not under the scope of the assay. Promising analytical performances (sensitivity and specificity, >90%; kappa = 0.87), encouraged to assess diagnostic value, qualified the assay for the WHO minimal requirements (both≥95%) for a multiplex-PCR. Higher LR+ (>10) and lower LR− (<0.1) indicate a good diagnostic tool for ruling in or ruling out CRO bloodstream infections. Inclusion of OXA-23-type improved assay positivity. Multiple carbapenemases were detected in>30% of samples. Good concordance was found (kappa = 0.91) with twenty-six discrepant results. The results were available in 3 hours. The running cost of the assay was US$10 per sample. Fast and reliable detection of carbapenemase(s) allows clinicians and infection-control practitioners to execute early-directed therapy and containment measures. This convenient approach facilitates implementing the assay in resource-limited healthcare settings.

Evaluation of a sterile, filter-based, in-house method for rapid direct bacterial identification and antimicrobial susceptibility testing using positive blood culture.

This study aimed to assess the performance of our in-house method for rapid direct bacterial identification (ID) and antimicrobial susceptibility testing (AST) using a positive blood culture (BC) broth. For Gram-negative bacteria, 4mL of BC broth was aspirated and passed through a Sartorius Minisart syringe filter with a pore size of 5µm. The filtrate was then centrifuged and washed. A small volume of the pellet was used for ID, using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and for AST, using automated broth microdilution. For Gram-positive cocci, 4mL of BC broth was passed through the Minisart syringe filter. Then, 4mL of sterile distilled water was injected in the direction opposite to that of the filtration to collect the bacterial residue trapped in the filter. Compared with the conventional method performed with pure colonies on agar plates, 94.0% (234/249) were correctly identified using the in-house method, with rates of 91.4% (127/139) and 97.3% (107/110) for Gram-positive and Gram-negative isolates, respectively. Of 234 correctly identified isolates, 230 were assessed by AST. Categorical agreement and essential agreement were 93.3% and 94.5%, respectively, with a minor error rate of 3.8%, a major error rate of 3.4%, and a very major error rate of 1.6%. Our in-house preparation method showed good performance in rapid direct ID and AST using positive BC broths compared to the conventional method. This simple method can shorten the conventional turnaround time for ID and AST by at least 1day, potentially contributing to better patient management.

Correction to: QMAC-dRAST for the direct testing of antibiotic susceptibility for Enterobacterales in positive blood-culture broth: a comparison of the performances with the MicroScan system and direct disc diffusion testing methods

Correction to: QMAC-dRAST for the direct testing of antibiotic susceptibility for Enterobacterales in positive blood-culture broth: a comparison of the performances with the MicroScan system and direct disc diffusion testing methods

QMAC-dRAST for the direct testing of antibiotic susceptibility for Enterobacterales in positive blood-culture broth: a comparison of the performances with the MicroScan system and direct disc diffusion testing methods.

To evaluate the performances of the QMAC-dRAST GN (Gram-negative) kit for rapid antimicrobial sensitivity testing (AST) and two other methods, directly on positive blood-culture broth (PBCB), by comparison with a reference method: the MicroScan method based on broth microdilution on colonies isolated on PBCB subculture. In total, 156 samples were collected prospectively from blood cultures positive for a Gram-negative rod. Each sample was tested with four AST techniques: (i) the QMAC dRAST GN kit, (ii) the disc diffusion (DD) method, (iii) the MicroScan method applied directly to PBCB; and (iv) MicroScan with isolates from PBCB subculture, as a reference. For 124 PBCB containing Enterobacterales, overall essential agreement (EA) and categorical agreement (CA) between the QMAC-dRAST on PBCB and the reference reached 95.7% and 93.5%, respectively. There were 3.0% very major errors (VME), 4.0% major errors (ME) and 2.8% minor errors (mE). A comparison of MicroScan on PBCB and the reference yielded 98.8% EA, 98.5% CA, and rates of 0.6% VME, 0.9% ME and 0.7% mE. The DD method on PBCB gave a CA of 95.8% and rates of 1.7% for VME, 2.0% for ME and 1.9% for mE. Results were obtained more rapidly for QMAC-dRAST (median of 6 h 37 min versus 18 h for the MicroScan and DD methods on PBCB). The QMAC-dRAST system provided rapid results well correlated with the reference method on PBCB containing Enterobacterales. Given the shorter time-to-results, the QMAC-dRAST system constitutes a fast and reliable alternative to conventional AST methods.

Comparative analysis of conventional and direct antimicrobial susceptibility testing of blood cultures in a tertiary care cancer hospital: the way forward

ABSTRACT Bloodstream infections (BSI) are associated with high mortality rates, especially in immunocompromised patients. Identifying pathogens early and selecting appropriate antimicrobials to treat BSI is integral in reducing the mortality rate. There is a need to reduce the turnaround time (TAT) of pathogen identification as well as to accelerate the antimicrobial susceptibility testing (AST) of blood cultures, which can be achieved by following relevant identification methods and performing the direct AST (DAST) by the disk diffusion method. In this study, blood samples were collected from patients with suspected bacteremia/septicemia, and aseptic precautions were taken to prevent contamination. Samples containing gram-negative bacilli (GNB) were then analyzed by DAST and conventional AST (CAST). We tested 118 GNB-positive isolates in total to compare the results of DAST and CAST. DAST and CAST showed good categorical agreement (CA) for various groups of microorganisms: 98.9% and 99.6% for Enterobacterales and Pseudomonas spp., respectively. Early detection of pathogens in blood along with the determination of their antibiotic susceptibility patterns is a need of the hour. By performing DAST on positive blood culture broth, clinical teams can obtain the information necessary for switching from empirical therapy to definitive treatment one day faster. This rapid identification of the pathogen, along with corresponding AST results, will help clinicians to accelerate targeted antimicrobial therapy for critical patients and, thus, reduce mortality and morbidity rates in patients with bloodstream infections.

Reporting of Antimicrobial Resistance from Blood Cultures, an Antibacterial Resistance Leadership Group Survey Summary: Resistance Marker Reporting Practices from Positive Blood Cultures.

We assessed how laboratories use and handle reporting of results of rapid diagnostics performed on positive blood culture broths, with a focus on antimicrobial resistance (AMR) markers. A survey assembled by the Antibacterial Resistance Leadership Group Diagnostics Committee was circulated from December 2020 to May 2021. The survey was sent to local hospitals, shared on the ClinMicroNet and Division C listservs, and included in a College of American Pathologists proficiency testing survey. Ninety-six laboratories of various sizes across the United States (95%) and outside of the United States (5%) participated. Of the laboratories that had at least 1 rapid diagnostic in place (94%), significant heterogeneity in methods used and reporting practices was found across community (52%) and academic (40%) laboratories serving hospitals of various sizes. Respondents had implemented 1 to 6 different panels/platforms for a total of 31 permutations. Methods of reporting rapid organism identification and AMR results varied from listing all targets as "detected"/"not detected" (16-22%) without interpretive guidance, to interpreting results (23-42%), or providing therapeutic guidance comments to patient-facing healthcare teams (3-17%). Current approaches to reporting molecular AMR test results from positive blood culture vary significantly across clinical laboratories. Providing interpretative comments with therapeutic guidance alongside results reported may assist clinicians who are not well-versed in genetic mechanisms of AMR. However, this is currently not being done in all clinical laboratories. Standardized strategies for AMR gene result reporting are needed.

Optimized Method for Bacterial Nucleic Acid Extraction from Positive Blood Culture Broth for Whole-Genome Sequencing, Resistance Phenotype Prediction, and Downstream Molecular Applications.

The application of direct metagenomic sequencing from positive blood culture broth may solve the challenges of sequencing from low-bacterial-load blood samples in patients with sepsis. Forty prospectively collected blood culture broth samples growing Gram-negative bacteria were extracted using commercially available kits to achieve high-quality DNA. Species identification via metagenomic sequencing and susceptibility prediction via a machine-learning algorithm (AREScloud) were compared to conventional methods and other rapid diagnostic platforms (Accelerate Pheno and blood culture identification [BCID] panel). A two-kit method (using MolYsis Basic and Qiagen DNeasy UltraClean kits) resulted in optimal extractions. Taxonomic profiling by direct metagenomic sequencing matched conventional identification in 38/40 (95%) samples. In two polymicrobial samples, a second organism was missed by sequencing. Prediction models were able to accurately infer susceptibility profiles for 6 common pathogens against 17 antibiotics, with an overall categorical agreement (CA) of 95% (increasing to >95% for 5/6 of the most common pathogens, if Klebsiella oxytoca was excluded). The performance of whole-genome sequencing (WGS)-antimicrobial susceptibility testing (AST) was suboptimal for uncommon pathogens (e.g., Elizabethkingia) and some β-lactamase inhibitor antibiotics (e.g., ticarcillin-clavulanate). The time to pathogen identification was the fastest with BCID (1 h from blood culture positivity). Accelerate Pheno provided a susceptibility result in approximately 8 h. Illumina-based direct sequencing methods provided results in time frames similar to those of conventional culture-based methods. Direct metagenomic sequencing from blood cultures for pathogen detection and susceptibility prediction is feasible. Additional work is required to optimize algorithms for uncommon species and complex resistance genotypes as well as to streamline methods to provide more rapid results.

Speed and safety of mass spectrometry for identification of Burkholderia pseudomallei directly from spiked blood cultures

Burkholderia pseudomallei is a bipolar Gram-negative bacillus and the causative agent of melioidosis; an infectious disease which commonly presents with bacteraemia. Data regarding direct from blood culture identification of B. pseudomallei using the Vitek mass spectrometer (MS) are limited. The authors aim to assess the safety and sensitivity of the Vitek MS for identification of B. pseudomallei from spiked positive blood culture samples. Safety was assessed by determining the ability of the standard MS α-cyano-4-hydroxycinnamic acid (CHCA) matrix solution to inactivate B. pseudomallei. Organism identification using the manufacturer's blood culture extraction method was compared to an in-house technique. Additionally, identification following abbreviated agar incubation of blood culture broth was performed. All 70 MS target spots were inactivated by the matrix solution. The manufacturer's blood culture extraction method identified 0/26 (0%) B. pseudomallei samples. An in-house method using the spun deposit from blood culture broth samples identified 38/38 (100%) B. pseudomallei samples. MS analysis of a blood culture broth drop on Chocolate agar following a 6 h incubation identified 30/32 (94%) samples. Decreased time to diagnosis of melioidosis bacteraemia is likely to improve patient outcomes. This study adds to the literature with regards to the utility of MALDI-TOF MS identification of B. pseudomallei both directly from positive blood culture broth and a subsequent 6 h plate incubation. The use of a standard matrix solution inactivates the organism, and use of the spun deposit from a positive blood culture broth is most effective for early identification of B. pseudomallei.

Parallel Validation of the NG-Test Carba 5 and the Xpert Carba-R for Detection and Characterization of Carbapenem-Resistant Enterobacterales Causing Bloodstream Infections

The rapid detection and characterization of carbapenemases in isolates of Enterobacterales are crucial for precise antibiotic administration and infection control. This article reports the findings from a parallel evaluation of the NG-Test Carba 5 (NG Biotech, Guipry, France) and Xpert Carba-R (Cepheid, Sunnyvale, CA) assays in the detection and differentiation of five carbapenemases [imipenem-resistant phenotype (IMP), Klebsiella pneumoniae carbapenemase, New Delhi metallo-β-lactamase (NDM), oxacillin-hydrolyzing β-lactamase (OXA)-48-like, and Verona integron-encoded metallo-β-lactamase] or the genes that encode them. A total of 122 isolates recovered from blood cultures and 106 positive blood culture broth (BCB) specimens, including 134 Klebsiella pneumoniae, 54 Escherichia coli, 27 Enterobacter cloacae, 8 Klebsiella oxytoca, 2 Klebsiella aerogenes, and 3 Citrobacter freundii, were collected from two tertiary hospitals (Xi'an, China). Using PCR sequencing techniques, 89 isolates and 29 BCB specimens were determined to be Enterobacterales harboring carbapenem-resistance genes. In comparison to the PCR sequencing results, the specificities with both the NG-Test Carba 5 and Xpert Carba-R assays were 100%; the sensitivities were 92.1% and 100%, respectively, for recovered isolates and 79.3% and 100% for BCB specimens. The NG-Test Carba 5 missed eight NDM, four OXA-48-like, and one IMP β-lactamases in specimens containing two or three carbapenemase types. In summary, the NG-Test Carba 5 assay may yield false-negative results if isolates or BCB specimens contain two or three carbapenemases.

The Genotype-to-Phenotype Dilemma: How Should Laboratories Approach Discordant Susceptibility Results?

Traditional culture-based methods for identification and antimicrobial susceptibility testing (AST) of bacteria take 2 to 3 days on average. Syndromic molecular diagnostic panels have revolutionized clinical microbiology laboratories as they can simultaneously identify an organism and detect some of the most significant antimicrobial resistance (AMR) genes directly from positive blood culture broth or from various specimen types (e.g., whole blood, cerebrospinal fluid, and respiratory specimens). The presence or absence of an AMR marker associated with a particular organism can be used to predict the phenotypic AST results to more rapidly guide therapy. Numerous studies have shown that genotypic susceptibility predictions by syndromic panels can improve patient outcomes. However, an important limitation of AMR marker detection to predict phenotype is the potential discrepancies that may arise upon performing phenotypic AST of the recovered organism in culture. The focus of this minireview is to address how clinical laboratories should interpret rapid molecular results from commercial platforms in relation to phenotypic AST. Stepwise approaches and solutions are provided to resolve discordant results between genotypic and phenotypic susceptibility results.

A rapid and inexpensive protocol to screen for third generation cephalosporin-resistant and non-fermenting Gram-negative rods directly in positive blood cultures

Third generation cephalosporins are frequently used in the first-line treatment of Gram-negative rod (GNR) bacteremia but are unsuitable in the case of extended-spectrum-beta-lactamase-producing Enterobacterales (ESBL-E) or non-fermenting GNR infections. The aim of this study was to develop and evaluate a simple and rapid two-test protocol involving oxidase and β-Lacta tests performed directly on positive blood culture broth as a preliminary screen for non-fermenting or third generation cephalosporins-resistant GNR. The diagnostic performance of this approach was evaluated on 294 bottles for the oxidase test and 267 bottles for the β-Lacta Test. The sensitivity and specificity of the oxidase test were respectively 93.1% and 100%, and the sensitivity of the β-Lacta Test for ESBL-E was 100% and the specificity 99.5%. This simple protocol, which can be implemented in all laboratories and performed in only 20 min, may be a valuable tool to optimize first-line antibiotic therapy for bacteremia.

In-house method for direct bacterial identification in positive blood culture broths using microfiltration, bead beating, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Rapid identification of bacterial pathogens facilitates earlier optimization of antibiotic treatment and reduces morbidity and mortality in sepsis patients. The aim of this research was to design an in-house chemical-free method for direct bacterial identification in positive blood culture (BC) broths and to compare the performance of this method with that of the commercial Sepsityper® kit. The overall species identification rates for the in-house and Sepsityper methods were 88.4% and 85.8%, respectively (n = 190). Among 146 facultative anaerobes, 92.5% and 95.9% were identified to the species level using the in-house and Sepsityper methods, respectively. For 32 anaerobic bacteria, the in-house method showed a higher species identification rate (75.0%) than the Sepsityper method (53.1%). The in-house method correctly identified more Bacteroides species (100.0%) than the Sepsityper method (18.2%). Our novel in-house method and the Sepsityper method showed a high accuracy for direct bacterial identification in positive BC broths using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Impact of Rapid Antimicrobial Susceptibility Testing in Gram-Negative Rod Bacteremia: a Quasi-experimental Study.

Clinical justification for rapid antimicrobial susceptibility testing (AST) in Gram-negative rod (GNR) bacteremia is compelling; however, evidence supporting its value is sparse. We investigated the impact of rapid AST on clinical and antimicrobial stewardship outcomes in real-world practice. We performed a before-and-after quasi-experimental study from February 2018 to July 2019 at a tertiary hospital of the 24-h/day, 7-day/week implementation of the direct Vitek 2 AST method from positive blood culture broth for GNR bacteremia with electronic isolate-specific de-escalation comments and daytime antibiotic stewardship program (ASP) intervention. The primary outcome was time to appropriate antibiotic escalation or de-escalation, and secondary outcomes included time to oral antibiotic stepdown, hospital length of stay (LOS), all-cause 30-day mortality, 7-day incidence of acute kidney injury (AKI), and 30-day incidence of Clostridioides difficile infection (CDI). A total of 671 GNR isolates were included from 643 adult patients. Among patients for whom antibiotic change occurred after rapid AST result, rapid AST was associated with a trend in decreased time to escalation or de-escalation (hazard ratio, 1.22; 95% confidence interval [CI], 0.99 to 1.51; P = 0.06), with median times of 52.3 versus 42.2 h. Secondary outcomes were similar in both groups and include median time to oral antibiotic stepdown, LOS, all-cause mortality, and incidence of AKI and CDI. Rapid AST led to improved stewardship measures but did not impact clinical patient outcomes. These results highlight that multiple variables in addition to the timing of the AST result contribute to clinical outcome and that further intervention may be required to clinically justify rapid AST implementation.