Captive™ is a range of antibody coated paramagnetic particles for the specific ImmunoMagneticSeparation of microorganisms.

This technology consists of microscopic paramagnetic particles. The beads have a magnetite core and a “ceramic” zirconium oxide coating. The beads are manufactured by high speed blending process and typically cover a size diameter range of 1-4 µm, with a 2.5 µm average size.

Purified antibodies to surface components of the target microorganism are covalently coupled to the bead. With careful antibody selection, a highly specific separation system for microorganisms is produced.

The pre-coated beads are designed for the IMS of target bacteria from enrichment cultures. A sample is taken form a filter stomacher bag and incubated with the Captive™ beads for 30 minutes. The bead/microoragnism complexes are then removed from the sample by placing the sample in a magnetic concentrator device. This separates them form the background organisms and interfering materials. The complexes are then washed using a PBS/Teen 20 wash buffer to remove non-specifically bound material. The beads can then be plated out onto the appropriate selective agar media and incubated as described.

The IMS technique will increase the sensitivity of the methodology and, in most circumstances, results can be achieved 24 hours earlier than standard protocols.

These products can also serve as a capture system for rapid detection systems.

Special Notes on IMS Techniques.
There are important factores that affect the performance of IMS techniques. Thorough mixing of the particles and sample allied with efficient recovery of the beads from the sample matrix is paramount to the success of this technique. Care must be taken not to aspirate the sample vigorously as this can result in the loss of captured target organisms. Certain sample types (e.g. very fatty, particulate and viscous samples) can interfere with bead recovery. To counter-act this interference, samples can also be diluted in PBS-Tween e.g. 1:2-1:4, reducing the effect of the matrix and allowing more efficient bead recovery. Alternatively with problem samples, after the initial magnetic separation the incomplete removal of the sample (i.e. remove 800 µl) and continuation of the wash protocol as described can minimise bead losses.

Captivate™ E.coli

Captive™O157 are magnetisable particles coated with specific antibody intended for the isolation of E.coli O157:H7 from food, animal feeds, beverages, pharmaceutical or environmental samples. The particles help to concentrate O157:H7 cells in mixed culture reducing the probability of missing low numbers or overgrowth of O157:H7 colonies by competing flora. In fact, immunomagnetic separation is now regarded as the gold standard method for isolation of E.coli O157:H7 from food and environmental samples.

E.coli O157:H7 is the primary serovar associated with food borne gastrointestinal infection, resulting in self-limiting diarrhoea, that can lead to serious disease conditions such as haemorrhagic colitis, haemolytic uraemic syndrome and thrombotic thrombcocytopaenic purpura (TTP).

The organism itself is associated with raw meats and unpasteurised milk, probably due to the implication of farm animals and particularly cattle as carriers of E.coli O157:H7. Large outbreaks have been recorded in the United States from consumption of unpasteurised apple juice (apple cider) possibly as a result of using apples which have fallen to the ground where the potential for contamination with the organism exists.

Also available


Captivate™ Salmonella
This product is designed to capture and concentrate the common serotypes of Salmonella involved in human and animal disease from enriched samples. The particles are coated with affinity purified plyclonal antibody directed towards, common somatic and flagellar antigens. This gives an excellent high avidity broad spectrum IMS reagent fro the capture of salmonellas. Due to the large variation in Salmonella serotypes and antigen expression there is naturally strain dependent variation in the capture efficiency.