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Diagnostic Reagents

DRYSPOT E. COLI SEROCHECK

Oxoid Dryspot E. coli Serocheck kits are individual agglutinating latexes available, one for each of the following non-O157 serotype – O26, O91, O103, O111, O128 and O145.

Introduction
Enterohaemorrhagic Escherichia coli belong to a number of O antigen serotypes. Serotype O157 is the most significant in human disease1,2,3 and these strains are often verocytotoxin producers. However a number of non-O157 serotypes have been shown to produce verocytotoxin. Infection with verocytotoxin (VT) producing strains is associated with a range of symptoms from nonbloody diarrhoea, fever and vomiting, to cases of haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS).

Transmission of these organisms occurs primarily through the consumption of contaminated foods. The major foods implicated in outbreaks include cheese made from unpasteurised milk, raw vegetables, undercooked ground beefburgers and fermented meats4,5.

Each Oxoid Dryspot E. coli Serocheck kit can be used for the detection and identification of one of 6 non-O157 serotypes–O26, O91, O103, O111, O128 and O145. These are among the serotypes most commonly associated with verocytotoxin production. All these components are combined together in the Oxoid Dryspot E. coli Seroscreen (DR0300) test.

Strains for testing should be grown on Enterohaemolysin6 or MacConkey Agar and should have typical non-O157 E. coli appearance. When insufficient material is available for testing, a nonselective purity plate should be prepared. The tests are not intended for direct testing of faecal specimens.

Principle of the Tests
Each Dryspot E. coli Serocheck Test uses antibody-sensitised blue latex particles dried onto cards. The latex will agglutinate in the presence of specific E. coli cell wall antigens to form visible clumps. The test provides a fast and simple screening procedure for common non-O157 serogroups which may produce verocytotoxin. Positive and negative controls are presented as dried spots on strips of 5 tear-off, single use card sticks.These latex agglutination tests do not indicate the presence or absence of verocytotoxin. Production of verocytotoxin may be confirmed with the Oxoid VTEC-RPLA (TD0960) or VTEC Screen Kit (TD0965†)

†Product is not a stock item. Please contact your local customer services administrator for details.


Kits and their components

DR0310 Serocheck O26
DR0320
Serocheck O91
DR0330 Serocheck O103
DR0340 Serocheck O111
DR0350 Serocheck O128
DR0360 Serocheck O145

Each kit contains the following components:

Test Cards−1 pouches each containing 5 cards and a moisture absorbent sachet. There are 3 test and 3 control reaction areas on each test card – 15 tests in total. Blue latex particles sensitised with specific rabbit antibody reactive with the relevant serogroup of E. coli (as indicated on test card) dried onto cards (test reaction area). Blue latex particles sensitised with non-reactive rabbit globulin (control reaction area).
Positive Control Sticks (5 sticks-pink spots)−pink-dyed, inactivated antigenic extract of the relevant
E. coli
Negative Control Strips (5 sticks-green spots)−green-dyed, inactivated antigenic extract of
E. coli O116
Phosphate Buffered Saline (PBS)−pH 7.3 (± 0.1); contains 0.095% sodium azide as a preservative
Mixing Paddles
Plastic Pouch Clips
−for storage of opened pouch
Instruction Leaflet

Materials required but not provided:

Sterile microbiological loops
Laboratory disinfectant, e.g. sodium hypochlorite solution >1.3% w/v

Storage and Opening
The kits should be stored between 2-25ºC. If stored in a cold environment, allow pouches to reach room temperature before opening to prevent condensation of moisture on the cards. The Dryspot reagents will deteriorate and may give false results if they are allowed to absorb moisture. Once opened, remove the number of cards required for immediate testing (testing within the next 10 minutes) and re-seal the pouch immediately by clamping the open end of the bag between the two halves of the plastic clip provided.The Control Sticks are also provided in a moisture-impermeable pouch. Ensure that the same techniques are used to avoid moisture damage. The kit should not be used after the expiry date printed on the carton.

References
1. Willshaw, G. A. Scotland, S. M., Smith, H. and Rowe, B. (1992).
J. Infect. Dis. 166: 797-802.
2. Goldwater, P. N. and Bettelheim, K. A. (1998).
J. Med. Microbiol. 47: 1039-1045.
3. Griffin, P. M. and Tauxe, R. V. (1991).
Epidem. Rev. 13: 60-88
4. Acheson, D. W. K. and Jaeger, J. L. (1999).
Clin. Micro. Newsletter. 21: 183-187.
5. Nataro, J. P. and Kaper, J. B. (1998). Clin. Micro. Rev. 11: 142-201.

6. Bettelheim, K. A. (1998).
J. Med. Microbiol. 47: 1037-1038.

 
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