Submitted to: Carbohydrate Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2003
Publication Date: 1/2/2004
Citation: IRWIN, P.L., GEHRING, A.G., TU, S., CHEN, C. BLOCKING NON-SPECIFIC ADSORPTION OF NATIVE FOOD-BORNE MICROORGANISMS BY IMMUNO-MAGNETIC BEADS WITH IOTA-CARRAGEENAN. CARBOHYDRATE RESEARCH. 2004. V. 339(3) pg. 613-621 Interpretive Summary: The contamination of foods with pathogenic bacteria (e.g., Salmonella or E. coli O157:H7) may lead to substantial food poisoning epidemics. In order to sensitively detect food poisoning bacteria certain isolation methods, such as the well-known immuno-magnetic bead (IMB) technique for separating and concentrating these bacteria, have been developed. Unfortunately, the level of pathogenic bacteria in foods is very low relative to the concentration of benign bacteria. Thus, IMB methods for extracting pathogenic bacteria from foods also capture some of the good bacteria thereby limiting the functionality of these methods. In this report we describe a new blocking buffer which appears to inhibit the non-specific binding of certain benign bacteria to IMBs. This information is useful to microbiologists in the detection of pathogenic bacteria from foods using IMBs protocols.
Technical Abstract: We have observed and modeled the partitioning characteristics of anti-Salmonella and anti-Escherichia coli O157 immuno-magnetic beads (IMB) with respect to the adsorption of several non-target food-borne organisms both with and without an assortment of well-known blocking agents (i.e., casein). We found several common food-borne organisms which strongly interacted with both types of IMB even in the presence of casein. However, when a native K12-like E. coli isolate was tested for binding in the presence of iota-carrageenan (0.03-0.05%), there was an average decline of ca. 90% in the equilibrium capture efficiency. Varying the iota-carrageenan concentration (0 to 0.05%) resulted in greatly diminished binding between 0 and 0.02% which then leveled off at ca. 0.03% whereupon the equilibrium capture efficiency was ca. 0.05 (DeltaG = 11 ± 2 kJ per mole) from a control (buffer only) value of ca. 0.69 (DeltaG = -19 ± 3 kJ per mole). The iota-carrageenan blocking effect is apparently related to this polysaccharide¿s anionic lattice inasmuch as the effect was nearly reversed in a lower ionic strength phosphate buffer (20 mM) in the presence of NaCl.