Rapid antimicrobial susceptibility testing on positive blood cultures through an innovative light scattering technology: performances and turnaround time evaluation

Abstract

BackgroundA bacteremia diagnosis with speeded-up identification and antimicrobial susceptibility testing (AST) is mandatory to adjust empirical broad-spectrum antibiotherapy and avoid the emergence of multi-resistant bacteria. Alfred 60AST (Alifax, Polverara, PD, Italy) is an innovative automated system based on light scattering measurements allowing direct AST from positive blood cultures with rapid results. In this study we aimed to evaluate the system’s performances and turnaround time (TAT) compared to routine AST.MethodsThe study was conducted during 2 non-consecutive 3-month periods at the microbiology laboratory of the Cliniques universitaires Saint-Luc. All blood cultures detected positive in the 0 AM–10 AM time frame with a pure Gram-positive cocci or Gram-negative bacilli stain were included for Alfred 60AST testing. Two customized EUCAST antibiotic panels were set up composed of 1) a “Gram-negative” panel including cefuroxime, ceftazidime Enterobacteriaceae, piperacillin-tazobactam Enterobacteriaceae, ciprofloxacine, and ceftazidime Pseudomonas 2) a “Gram-positive” panel including cefoxitin Staphylococcus aureus, cefoxitin coagulase-negative (CNS) Staphylococci and ampicillin Enterococci. Categorical agreement (CA), very major errors (VME), major errors (ME), minor errors (mE) and TAT to Alfred 60AST results were calculated in comparison with AST results obtained from direct testing on positive blood cultures with the Phoenix system (Becton Dickinson, Franklin Lakes, NJ, USA).ResultsFive hundred seventy and one hundred nine antibiotics were evaluated on respectively 166 Gram-negative bacilli and 109 Gram-positive cocci included in the studied population. During the first study period regarding Gram-negative strains a CA of 89.5% was obtained with a high rate of VME (19 and 15.4% respectively) for cefuroxime and piperacillin-tazobactam Enterobacteriaceae. Considering this, Alifax reviewed these antibiotics’ formulations improving Gram-negative bacilli total CA to 92.2% with no VME during the second study period. For Gram-positive cocci, total CA was 88.1% with 2.3% VME, 13.8% ME (mainly cefoxitin CNS) and 12% mE rates both study periods combined. Median TAT to AST results was 5 h with Alfred versus 12 h34 with Phoenix.ConclusionThe Alfred 60AST system shows correct yet improvable microbiological performances and a major TAT reduction compared to direct automated AST testing. Clinical studies measuring the impact of the approach on antibiotic management of patients with bacteremia are recommended.

Time to positive culture can differentiate post‐neurosurgical coagulase‐negativeStaphylococciother thanS epidermidismeningitis from contamination: A case‐control observational study

“…CoNS play an important role in nosocomial infections and are frequently associated with bacteremia bloodstream infections, 12 surgical site infections, catheter‐related infections 13 and it is widely present in hospitals and clinical environments. It has been reported that this type of bacteria is the most common cause of nosocomial bloodstream infections 14 .…”

Validation of Rapid Antimicrobial Susceptibility Testing directly from blood cultures using WASPLab®, including Colibrí™ and Radian® in-Line Carousel

“…Especially, pathogens growing in blood cultures (BC) are of paramount importance. Bacteremia is a condition that can lead to severe complications, such as sepsis or septic shock, with high mortality rates [1][2][3]. It has been shown that early initiation of effective antibiotic therapy is an important prognostic factor in the management of bacteremia [4].…”

Rapid Antimicrobial Susceptibility Testing on Clinical Urine Samples by Video-Based Object Scattering Intensity Detection

“…This indirect assessment of bacterial growth and cell concentration requires pure sample inoculation and time for the cells in suspension to reach appropriate density levels . With the improvement of the light source and optical configurations, other light scattering methods were developed to increase the detection limit. − However, the methods collect the total scattered light from the sample, including background noises from vial defects, wall contamination, and surface reflection, and still require enrichment and substantial cell growth, thus a longer sample-to-answer time. To minimize sample pre-processing time, we introduced a low magnification solution that incorporates forward-scattering imaging with dark-field illumination, direct real sample detection, and an efficient background removal algorithm, thereby employing rapid AST based on object scattering intensity (Figure ).…”