R-Biopharm Improves Detection of Colonies on RIDA®COUNT Staph aureus!

The principle behind the RIDA®COUNT test cards is generally based on cultivating micro-organisms using standard nutrients combined with a specific chromogenic detection system.

During the growth phase, micro-organisms will form typical colonies whilst the presence of specific enzymes will change the originally colourless substrate to produce a distinctively coloured colony.

All of the different products of the RIDA® COUNT line are suitable for the detection of micro-organisms deriving from food or feed, contact samples, as well as membrane filtration and air sampling systems.

Unprocessed food and feed are known to possess enzymes similar to specific bacterial enzymes. These enzymes originate from the plant or meat cells, which are present in food or feed and have been found to cause problems within the sample analyses with RIDA®COUNT Staph. aureus.

The presence of these food enzymes can interfere with reading the test cards by producing a background colouration making the typical colonies difficult to distinguish. The detection of the typical blue-green coloured colonies of Staphylococcus aureus becomes more difficult as the background coloration increases.

This problem has now been solved as changes have been made to the chromogenic system of RIDA®COUNT Staph aureus, which also crucially improves the detection of S. aureus colonies. On the new RIDA®COUNT Staph aureus (R1005) test card, positive colonies are clearly distinguished from the background compared to the old product formulation.

S.aureus now appear as black colonies surrounded by a blue halo which develops after 24 to 48 hours incubation at 35 °C. As a result of the reduction of the blue colouring chromogen the incidence of a background effect has been reduced to a point that the new improved test card can now be used without restrictions for analysis of any kinds of food and feed.