title: On-chip acoustophoretic isolation of microflora including S. typhimurium from raw chicken, beef and blood samples.
abstract: Pathogen analysis in food samples routinely involves lengthy growth-based pre-enrichment and selective enrichment of food matrices to increase the ratio of pathogen to background flora. Similarly, for blood culture analysis, pathogens must be isolated and enriched from a large excess of blood cells to allow further analysis. Conventional techniques of centrifugation and filtration are cumbersome, suffer from low sample throughput, are not readily amenable to automation and carry a risk of damaging biological samples. We report on-chip acoustophoresis as a pre-analytical technique for the resolution of total microbial flora from food and blood samples. The resulting 'clarified' sample is expected to increase the performance of downstream systems for the specific detection of the pathogens. A microfluidic chip with three inlets, a central separation channel and three outlets was utilized. Samples were introduced through the side inlets, and buffer solution through the central inlet. Upon ultrasound actuation, large debris particles (10-100 μm) from meat samples were continuously partitioned into the central buffer channel, leaving the 'clarified' outer sample streams containing both, the pathogenic cells and the background flora (ca. 1 μm) to be collected over a 30 min operation cycle before further analysis. The system was successfully tested with Salmonella typhimurium-spiked (ca. 10(3)CFU mL(-1)) samples of chicken and minced beef, demonstrating a high level of the pathogen recovery (60-90%). When applied to S. typhimurium contaminated blood samples (10(7)CFU mL(-1)), acoustophoresis resulted in a high depletion (99.8%) of the red blood cells (RBC) which partitioned in the buffer stream, whilst sufficient numbers of the viable S. typhimurium remained in the outer channels for further analysis. These results indicate that the technology may provide a generic approach for pre-analytical sample preparation prior to integrated and automated downstream detection of bacterial pathogens.
authors.affiliation: Department of Chemistry, University of Hull, Hull HU6 7RX, UK.
authors.forename: Bongkot
authors.initials: B
authors.lastname: Ngamsom
authors.affiliation: Department of Chemistry, University of Hull, Hull HU6 7RX, UK.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Lopez-Martinez
authors.affiliation: bioMérieux Innovation, Chemin de I'Orme, Marcy I'Etoile, 69280, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Raymond
authors.affiliation: bioMérieux Innovation/Technology Research Lab, Grenoble 38024, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Broyer
authors.affiliation: bioMérieux Innovation, Chemin de I'Orme, Marcy I'Etoile, 69280, France.
authors.forename: Pradip
authors.initials: P
authors.lastname: Patel
authors.affiliation: Department of Chemistry, University of Hull, Hull HU6 7RX, UK.
authors.forename: Nicole
authors.initials: N
authors.lastname: Pamme
mesh_terms: D000818:Animals; D001769:Blood / Q000382:microbiology*; D002417:Cattle; D002645:Chickens; D005506:Food Contamination / Q000032:analysis; D006801:Humans; D008460:Meat / Q000382:microbiology*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D016133:Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000235:genetics / Q000302:isolation & purification*
keywords: Acoustophoresis; Microbial flora resolution; Salmonella typhimurium; Sample preparation