Impact of Rapid Pathogen Identification From Blood Cultures (RABbIT) (RABbIT)

Impact of Rapid Pathogen Identification From Blood Cultures (RABbIT - Rapid Blood Culture Intervention Trial)

Septic shock carries high mortality, which may be exacerbated by inappropriate initial therapy. Inappropriate therapy may result from unanticipated antimicrobial resistance. Conversely, positive blood cultures may result from contamination, leading to unnecessary therapy and procedures and possibly prolonged hospitalization. Clinicians may also resort to broad spectrum antimicrobials and be hesitant to de-escalate while awaiting susceptibility results. The investigators hypothesize that rapid identification of pathogens and antimicrobial resistance will ameliorate the above problems and improve time to optimal therapy, avoid unnecessary therapy and ultimately improve patient outcomes. While there are a number of in-vitro and uncontrolled clinical studies, there is a paucity of well-designed clinical trials objectively examining the real-world clinical and health-economic impact of such technology. To date only one randomised trial has been performed in the US (ClinicalTrials.gov NCT01898208), at a setting with low endemic rates of antimicrobial resistance. This is a companion study to NCT01898208. The investigators aim to study the clinical impact and cost-effectiveness of a strategy for rapid pathogen and resistance detection in a setting with a moderate to high levels of antimicrobial resistance.

Hypothesis: Rapid pathogen identification from blood cultures, including early identification of resistance (via specific genetic markers or phenotypic tests), will allow timelier initiation of appropriate antibiotic therapy and improved patient outcomes Rapid organism identification from blood cultures will allow timelier initiation of effective and optimal antibiotic therapy; minimizing the use of unnecessary antibiotics, including combination therapy Devices to be studied for this proposed study: BCID panel (Biofire Diagnostics Inc., bioMerieux) : The BCID panel is an FDA-approved nucleic acid amplification test (based on nested polymerase chain reaction) which detects Gram positive, Gram negative, the major Candida species and antimicrobial resistance markers (mecA for methicillin resistance, van A/B for vancomycin resistance, blaKPC for Klebsiella pneumoniae carbapenemase (KPC)) directly from positive blood cultures in < 1 - 1.5 hours Rosco Diagnostica extended-spectrum beta-lactamase (ESBL) and carbapenemase screen kit (Rosco Diagnostica): These kits are CE-marked (Approved in the European Union) rapid chromogenic tests for ESBL/ carbapenemase detection from both blood cultures and cultured bacterial colonies.

Standard Tan Tock Seng Hospital (TTSH) practices (bacterial culture and susceptibility testing) AND FilmArray Blood Culture ID (BCID) Panel test AND Rosco Diagnostica ESBL and carbapenemase screen will be performed. The Interventions to be administered are the rapid diagnostic tests: FilmArray Blood Culture ID (BCID) Panel test AND Rosco Diagnostica ESBL and carbapenemase screen. Subjects will be recruited 8am-3pm daily, weekdays only. Results of the BCID and Rosco test will be communicated to the managing physicians by phone in real-time.

Standard Tan Tock Seng Hospital (TTSH) practices (bacterial culture and susceptibility testing) will be used. FilmArray BCID and Rosco Diagnostica ESBL and carbapenemase screen will NOT be performed. Subjects will be recruited 8am-3pm daily, weekdays only.

The BCID panel is an FDA-approved nucleic acid amplification test (based on nested polymerase chain reaction) which detects Gram positive, Gram negative, the major Candida species and antimicrobial resistance markers (mecA for methicillin resistance, van A/B for vancomycin resistance, blaKPC for KPC carbapenemase) directly from positive blood cultures in < 1 - 1.5 hours

These kits are CE-marked (Approved in the European Union) rapid chromogenic tests for extended-spectrum beta-lactamase / carbapenemase detection from both blood cultures and cultured bacterial colonies.

An effective antibiotic is defined as an antibiotic regimen to which the bacterial/fungal isolate is susceptible (or predicted to be susceptible for Candida, per speciation).An optimal antibiotic is defined as an antibiotic regimen to which the bacterial/fungal isolate is susceptible/predicted to be susceptible, which is the most narrow spectrum and targeted, as recommended by institutional guidelines. This will be considered as the time from the positive Gram stain to first effective and the first optimal antibiotic.

Time taken for implementation of appropriate infection control measures (isolation precautions) as appropriate for pathogen detected

This included all adverse events that occurred within 2 weeks following enrollment and were documented in the medical record.

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. Shorter duration of broad spectrum antibiotics and longer duration of narrow-spectrum antibiotics were considered favorable outcomes.

These will be calculated based on actual billable patient costs (without government subventions/subsidies) following 7 days after the positive blood culture episode and for the duration of hospitalization, up to an estimated 24 weeks.

These will be calculated based on actual billable laboratory costs (without government subventions/subsidies) following 7 days after the positive blood culture episode and for the duration of hospitalization, up to an estimated 24 weeks.

These will be calculated based on actual billable antimicrobial costs (without government subventions/subsidies) following 7 days after the positive blood culture episode and for the duration of hospitalization, up to an estimated 24 weeks.

Incremental cost-effectiveness ratios will be determined by dividing the difference between the average costs of treating a patient in the after phase (C1) and the average cost in the before phase (C0) by the difference between average health outcomes (QALYs) gained in the after phase (O1) and those gained in the before phase (O0). The incremental cost-effectiveness ratio is calculated by the following equation: (C1 - C0)/(O1 - O0). Incremental cost-effectiveness ratios using quality adjusted/sepsis adjusted life years gained as the health outcome of interest will then be determined, based on the method of Jones et al Crit Care Med. 2011 June ; 39(6): 1306-1312.

Up to 1 year after enrolment and using a 'modeled horizon' based on sepsis-adjusted life expectancies

An effective antibiotic is defined as an antibiotic regimen to which the bacterial/fungal isolate is susceptible (or predicted to be susceptible for Candida, per speciation).An optimal antibiotic is defined as an antibiotic regimen to which the bacterial/fungal isolate is susceptible/predicted to be susceptible, which is the most narrow spectrum and targeted, as recommended by institutional guidelines. This will be considered in the 96-hour time frame from the positive Gram stain.

De-escalation included discontinuation of 1 or more antibiotics and/or switching from a broad- to a narrow spectrum antibiotic. Escalation included initiation of 1 or more antibiotics and/or switching from a narrow- to a broad-spectrum antibiotic

Contaminated blood cultures were defined as growth of organisms such as coagulase-negative staphylococci from a single blood culture set when greater than or equal to 2 blood culture sets were collected, except among subjects suspected to have true bacteremia associated with central venous catheters or devices.

Multidrug-resistant organisms included vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, extended-spectrum cephalosporin-resistant Enterobacteriaceae, and Pseudomonas aeruginosa and Acinetobacter species resistant to greater than or equal to 3 antibiotic classes.

Inclusion Criteria: Age > 21 years and above to 103 years Blood culture flagged positive on automated instrument, with Gram positive, Gram negative bacteria or Yeast on Gram staining (including polymicrobial blood cultures) Ability to provide informed consent or ability to obtain informed consent from legal guardian/representative (verbal and written) Exclusion Criteria: Patients whose blood cultures turn positive, but have no organism seen on Gram stain. Patients who have been previously enrolled. Patients who withdraw their consent (verbal or written). Patients with any positive blood culture in the preceding 7 days.

Ong SWX, Hon PY, Wee SSH, Chia JWZ, Mendis S, Izharuddin E, Lin RJ, Chia PY, Sim RCS, Chen MI, Chow A, Yoong J, Lye DC, Teng CB, Tambyah PA, Banerjee R, Patel R, De PP, Vasoo S. Accuracy of a Rapid Multiplex Polymerase Chain Reaction Plus a Chromogenic Phenotypic Test Algorithm for Detection of Extended-Spectrum beta-Lactamase and Carbapenemase-Producing Gram-Negative Bacilli in Positive Blood Culture Bottles. Clin Infect Dis. 2022 May 30;74(10):1850-1854. doi: 10.1093/cid/ciab848.