Toxin Testing - PCR

PCR-based testing of: E. coli for stx1*, stx2*, eaeA*, hlyA*; E.coli (if stx negative) for LT, ST, CNF1, CNF2, Eagg, Einv, CDT I, CDT II, CDT III, subAB.

Isolate from urine, stool, blood, environmental, food, other.

Isolate provided on culture medium.

Send as growth on culture medium or in transport medium. Organisms should be sent as cultures.

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

Gastroenteritis, septicemia, infection, other.

Completed Enteric Diseases Program requisition form.

*This test is accredited.

stx1, stx2 - shigatoxins (toxins secreted into extracellular milieu); cause mild-bloody diarrhea, can lead to HUS; stx-2 typically associated with more severe disease.

eaeA – intimin (outer membrane protein); intimate adhesion of STEC/EHEC and EPEC to enterocytes is mediated in part by eae, resulting in formation of an attaching and effacing (A/E) lesion on the surface of the intestinal cells.

hlyA – hemolysin; hylA encodes Enterohemolysin (Ehx), a pore-forming toxin that lyses erythrocytes, Ehx is cytotoxic to endothelial cells and may contribute to development of HUS.

LT - heat-labile enterotoxin; generally LT-1 is more important in human illness, but LT-II has been isolated from human cases of ETEC diarrhea.

ST - heat-stable enterotoxin; found solely or with LT; more frequently found in severe human disease than LT-only isolates; causes watery diarrhea.

CNF (1, 2) - Cytotoxic Necrotizing Factors; associated mainly with extraintestinal pathogenic strains causing UTIs and meningitis; associated with septicemia and/or diarrhea.

Eagg – aggregative adherence factor – indicative of EAEC (do not secrete LT or ST but adhere to epithelial cells in a stacked brick pattern); associated with acute and persistent diarrhea.

Einv – invasive factor – indicative of EIEC (cause watery diarrhea and dysentery).

CDT (I, II, III) - cytolethal distending toxins; isolated from patients with GI or UTIs, and sepsis. suggested link to diarrhea and bloody diarrhea.

subAB - Subtilase cytotoxin; cuases hemorrahing in the small intestine and a disease similar to HUS including renal damage, hemolytic anemia, thrombocytopenia, organ damage: liver, spleen, brain and has been reported to cause leukocytosis.

PCR-based identification of genes encoding toxins and virulence factors based on the following references and Standard Operating Procedures.

7 calendar days (unless prior notification that the sample is urgent)

1. Paton, A.W. and Paton, J. C. 1997. Detection and Characterization of Shiga Toxigenic Escherichia coli by using Multiplex PCR Assays for stx1, stx2, eaeA, Enterohemorrhagic E. coli hlyA, rfb0111, and rfb0157. J. of Clin. Micro. 36: 598- 602.
2. Pierard, D., Muyldermans, G., Moriau, L., Stevens, D., and Lauwers, S. 1998. Identification of New Verocytotoxin Type 2 Variant B-Subunit Genes in Human and Animal Escherichia coli Isolates. J. Clin. Microbiol. Nov;36(11):3317-3322.