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Diagnostic Reagents

DRYSPOT E. COLI O157 TEST KIT

Code: DR0120

The Oxoid Dryspot E. coli O157 test is a latex agglutination test for the identification of Escherichia coli serogroup O157.

Principle of the Test.
Enterohaemorrhagic Escherichia coli belong to a number of O serogroups with O157 being most significant in human disease.
The potentially verocytotoxin (VT) producing strains are associated with a range of symptoms from non - bloody diarrhoea, fever and vomiting to cases of haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS).
The Dryspot E. coli O157 latex test will demonstrate by agglutination
Escherichia strains possessing the O157 serogroup antigen. The test is best used in conjunction with Sorbitol MacConkey Agar (Oxoid CM0813) The majority of Escherichia O157: H7 strains do not ferment sorbitol and therefore give colourless colonies on this medium. The majority of non O157 Escherichia isolates do ferment sorbitol and give characteristic pink colonies
Sorbitol MacConkey Agar should be used as the primary screen. Non-sorbitol fermenting colonies can then be tested with the latex reagents, to determine whether the isolate belongs to the O157 serogroup and therefore is a potential VT-producing strain.
Production of verotoxin may be confirmed with the Oxoid VTEC-RPLA kit TD0960.

Components of the kit
DR0121.
Dryspot E. coli O157 Test Reagent Cards Blue latex particles coated with antibody specifically reactive with the Escherichia O157 serogroup antigen. 4 pouches each containing 10 cards and a moisture absorbent sachet. There are 3 test and 3 control reaction areas on each card -120 tests in total.
DR0122. Positive control strips (10 Sticks - pink spots) Pink-dyed inactivated antigenic extract of Escherichia O157.
DR0123. Negative control strips (10 sticks - green spots) Green-dyed inactivated antigenic extract of Escherichia 0116.
Instruction leaflet.

Materials required but not provided.
Saline (0.9% NaCl prepared using distilled or deionised water)
Microbiological loop and bunsen burner.
A suitable laboratory disinfectant.
A timer.

Storage and Opening.
This kit must 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 dry reagents will deteriorate and 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.
The kit should not be used after the expiry date printed on the carton.

References
l. Borczyk A., Lior H. and Ciebin B.(1987) False positive identifications of Escherichia coli O157 in foods. Int. J. Food. Microbiol. 4. 347 - 349.
2. Konowalchuk, J., Speirs, J. and Stavric, S. (1977) Vero Response to a Cytotoxin of Escherichia coli. Vero Infect.Immun.18.775-779.
3. Scotland S., Day N. and Rowe B. (1980) Production of a Cytotoxin Affecting Vero Cells by strains of Escherichia coli belonging to Traditional Enteropathogenic Serogroups. FEMS. Microbiol. Lett, 7.15-17.
4. Centres for Disease Control. (1982). Isolation of E. coli O157 : H 7 from Sporadic Cases of Hemorrhagic colitis United States. Morbid. Mortal. Wkly. 31. 580-585.
5. Karmali, M., Still, B. et al. (1983), Sporadic cases of Haemolytic - Uraemic Syndrome Associated with Faecal Cytotoxin and Cytotoxin - Producing Escherichia coli in stools. Lancet i, 619-620.
6. Johnson, W., Lior, H. and Bezanson, (1983), Cytotoxic Escherichia coli O157 : H7 Associated with Haemorrhagic colitis in Canada. Lancet i.76.
7. March S., and Ratnam (1986). Sorbitol - MacConkey Medium for Detection of Escherichia coli O157 : H7 Associated with Hemorrhagic Colitis. J. Clin. Microbiol. 23. 869-872.
8. Krishnan, C., Fitzgerald. et al. (1987), Laboratory Investigation of Outbreak of Haemorrhagic Colitis caused by Escherichia coli O157 : H7. J. Clin. Microbiol. 25.1043-1047.
9. Chapman, P.A. (1989). Evaluation of Commercial Latex Slide test for Identifying Escherichia coli O157. J. Clin. Pathol. 42. 1109-1110.
10. Westerman, R.B., Yongsheng, H. et al.(1997). Production and Charecterisation of Monoclonal Antibodies Specific for the Lipopolysaccharide of Escherichia coli 0157. J. Clin. Microbiol. 35. 679-684.

 
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