The Clinical Impact of Cobas® Eplex Blood Culture Panels for the Diagnosis of Bacteremia and Fungemia

Bloodstream infections (BSIs) impose a considerable burden on patients and healthcare systems due to the need for hospital admission, extended stays, additional diagnostic tests and specific treatments. Receiving inappropriate empirical antibiotic therapy can increase the risk of renal and hepatic toxicity, antibiotic resistance, opportunistic infections and mortality. Therefore, early identification of the causative pathogens and their resistance patterns is of utmost importance.

The gold standard for diagnosis of BSIs is through blood cultures. To detect bacteremia or fungemia, blood from patients is collected and incubated in blood culture bottles. When using conventional culture methods, a positive blood bottle is investigated using direct microscopic investigation, gram-staining, inoculation of selective and non-selective agars, MALDI-TOF identification, rapid antimicrobial susceptibility testing (AST) and standardized AST methods. These methods require several (manual) steps and days of turn-around-time. Following the collection of a blood culture, time to result depends on several factors such as the time needed for transporting the blood bottles and loading in the incubator, the growth rate of bacteria or fungi as well as the time to obtain the identification and AST result.

Rapid diagnostic tests to improve the time to appropriate antimicrobial therapy have been developed. Most tests involve organism identification and genotypic resistance profiles. Rapid molecular diagnostic testing, such as multiplex PCR methods, enable early identification of bacteria or fungi and their antimicrobial resistance genes (results within less than 2 hours after initiation of the test). This helps minimize the time needed to initiate effective antimicrobial therapy. Commercial diagnostic systems to accelerate the identification and detection of antibiotic resistance genes of causative pathogens in BSI have been developed. Examples include Cepheid® GeneXpert, BioFire® FilmArray®TM, and Roche eplex®. The system used in this study, the eplex system, is a random access multiplex PCR platform combining extraction of nucleic acids and rapid RT-PCR. Three Blood Culture Identification (BCID) panels are used to identify the disease-causing organisms: Gram-positive panel, Gram-negative panel and Fungal Pathogen panel. These panels are designed to detect 56 different organisms covering 95% of pathogens commonly associated with BSIs and 10 common antibiotic resistance genes.

The objective of this study is to assess the impact of rapid molecular testing on positive blood cultures with the cobas® eplex system (Roche) on antibiotic therapy and patient outcome.

In this study, we prospectively evaluate the performance of the eplex system for pathogen identification and detection of resistance markers compared to routine SOC for bloodstream infections. The potential impact of the eplex on time to optimization (inititiation, discontinuation, escalation or de-escalation) of antimicrobial therapy and patient outcome will be evaluated.

In summary, Finally, this study will evaluate the potential benefits of implementing CE-IVD registered syndromic diagnostic testing of bloodstream infections.

Inclusion criteria

• Patients with onset of BSI at the emergency department or general wards
• Patients hospitalized from blood draw (at least 24h)
• For pediatric patient only BSI episodes caused by gram-negative organisms

Exclusion criteria

• Patients deceased at the time of the positive blood culture
• Patients in comfort care or with an estimated survival before sepsis of less than one month
• Patients with positive blood culture bottles within the past 14 days
• Patients for which the blood bottles are highly suspected of contaminants (bacterial species belonging to potential skin commensals or known environmental contaminants) and in the absence of any other site of infections.