Bacterial Separation and Concentration from Complex Sample Matrices: A Review

Abstract

The use of many rapid detection technologies could be expanded if the bacteria were separated, concentrated, and purified from the sample matrix before detection. Specific advantages of bacterial concentration might include facilitating the detection of multiple bacterial strains; removal of matrix-associated assay inhibitors; and provision of adequate sample size reduction to allow for the use of representative food sample sizes and/or small media volumes. Furthermore, bacterial concentration could aid in improving sampling techniques needed to detect low levels of pathogens or sporadic contamination, which may perhaps reduce or even eliminate the need for cultural enrichment prior to detection. Although bacterial concentration methods such as centrifugation, filtration, and immunomagnetic separation have been reported for food systems, none of these is ideal and in many cases a technique optimized for one food system or microorganism is not readily adaptable to others. Indeed, the separation and subsequent concentration of bacterial cells from a food sample during sample preparation continues to be a stumbling block in the advancement of molecular methods for the detection of foodborne pathogens. The purpose of this review is to provide a detailed understanding of the science, possibilities, and limitations of separating and concentrating bacterial cells from the food matrix in an effort to further improve our ability to harness molecular methods for the rapid detection of foodborne pathogens.

Landscape phage probes for Salmonella typhimurium

“…For example, widespread use of PCR in environmental microbiology has been limited by high sample volumes compared to miniscule amplification reaction volumes and uncontrolled organic impurities and environmental inhabitants inhibiting enzymatic reactions (Lantz et al, 2000). Thus, the uses of many rapid detection techniques could be expanded if the pathogens were separated, concentrated, and purified from the sample matrix before detection reactions (Benoit and Donahue, 2003;Stevens and Jaykus, 2004). However, existing filters and absorbents are not specific and accumulate biological agents in a complex mixture with environmental inhabitants and pollutants.…”

Enzymatic Digestion for Improved Bacteria Separation from Leafy Green Vegetables

“…Despite the advances in the development of the rapid detection of foodborne bacteria, there remain significant challenges for the improvement of the separation step. Without the ability to physically separate and concentrate the bacteria from the food matrix, many of these new detection techniques cannot be put into practice (6,39,49). Additionally, possible inhibitors, particulates, and competing chemistries can make conducting rapid and sensitive pathogen detection in food matrix difficult.…”

“…Currently the food and agricultural industries rely mostly on standard microbiological methods to detect the presence of bacteria (53). However, the complexity of foods makes the sample preparation difficult and raises the possibility of false negative results (39,49). Another obstacle to pathogen separation is that bacterial cells can form relatively strong attachments to the surface and interior of the food which also makes separation from the matrix much more complex (16).…”

Measuring and modeling continuous quality distributions of soil organic matter

“…Separating into eight or more densities is a very tedious procedure and a potentially more powerful approach is to use density gradient centrifugation (DGC). DGC has not been widely used for this purpose, but is being applied routinely for separating microorganisms from soil or other media (Lindahl and Bakken, 1995;Stevens and Jaykus, 2004). After centrifugation in a density gradient a density distribution of particles will have settled in the gradient and samples can be taken out at different positions for determination of C content and isotope ratios.…”