LabDx improves stool culture methodologies
TECHNICAL UPDATE
TEST NAME: Enteric Pathogen Panel, Stool
Order Code: EPP
Specimen Requirement: Stool in Cary-Blair
Para-Pak C&S (Orange Top) to fill line
TEST NAME: Enteric Pathogen Panel 2, Stool
Order Code: EPP2
Specimen Requirement: 1. Stool in Cary-Blair
Para-Pak C&S (Orange Top) to fill line; and 2. Frozen or
refrigerated raw stool in sterile container
LabDx is pleased to announce that effective February 14, 2011, testing for Campylobacter and Shiga toxin producing E. coli, in stool, will be performed using an Immunochromatography methodology. With this change in methodology, our existing stool culture order code, CXSSC, will be replaced with order code EPP, Enteric Pathogen Panel, Stool which includes the following:
| ORDER CODE | TESTS PERFORMED | CPT CODE |
|---|---|---|
| EPP | * Salmonella and Shigella Culture | 87045 |
| * Campylobacter Antigen | 87899 | |
| * Shiga Toxin 1 | 87899 | |
| * Shiga Toxin 2 | 87899-59 | |
| * Shiga Toxin Broth Enhancement | 87015 |
To facilitate the ordering process, we have set up an additional panel to include all analytes listed in the Enteric Pathogen Panel, Stool with the addition of C. difficile antigen and toxins. The test name for this panel is Enteric Pathogen Panel 2, Stool (EPP2):
| ORDER CODE | TESTS PERFORMED | CPT CODE |
|---|---|---|
| EPP2 | * Salmonella and Shigella Culture | 87045 |
| * Campylobacter Antigen | 87899 | |
| * Shiga Toxin 1 | 87899 | |
| * Shiga Toxin 2 | 87899-59 | |
| * Shiga Toxin Broth Enhancement | 87015 | |
| * C. difficile Antigen | 87449 | |
| * C. difficile Toxins A/B | 87324 |
The primary benefits provided by Immunochromatography versus traditional culture methods for Campylobacter and Shiga toxin producing serotypes of E. coli are as follows:
CAMPYLOBACTER
Eliminates Concerns of Organism Viability
Campylobacter is fragile and difficult to grow in culture. However, the antigen remains present for detection which increases the ability to detect the organism by Immunochromatography versus traditional culture methods. “Stool culture techniques lack sensitivity as Campylobacter are fastidious microaerophillic organisms that, when exposed to oxygen or other stress, may enter a non-culturable state.” 1
Antibiotics in Culture Media can Suppress Growth
The utilization of an Immunochromatography detection test reduces the potential negative growth impact of inhibitory antibiotics in culture media specific for Campylobacter. 2,3,4
Rapid Results
The Campylobacter Immunochromatography test takes significantly less time to perform. Culture for Campylobacter can take 48-72 hours.
SHIGA TOXIN PRODUCING E.COLI
An Increase in non-O157 Shiga toxin-producing E. coli
Enterohemorrhagic (Shiga toxin-producing) E. coli, EHEC, has been recognized as an important cause of hemorrhagic diarrhea and hemolytic uremic syndrome. Although E. coli 0157:H7 has been documented as the most common serotype, it has become increasingly apparent that other serotypes are capable of causing the same disease. 5 A recent regional outbreak of Shiga toxin-producing E. coli due to contaminated lettuce was caused by E. coli O145, an emerging bacterial pathogen that can produce the same illness as E. coli O157.
More Accurate than Conventional Culture Methods
Conventional culture methods using MacConkey with Sorbitol (SMAC) have a demonstrated sensitivity of 50%. Therefore, SMAC plates miss 50% of Shiga toxin-producing E. coli infections caused by 0157, and all cases due to non-0157. 6
Detection of Both Shiga toxin 1 and Shiga toxin 2
One virulence trait of all EHEC strains is their ability to produce toxins. The two toxins produced are Shiga toxin 1 and Shiga toxin 2, and a single strain may produce either toxin, or both toxins. Studies have shown that the use of a Shiga toxin assay has led to increases of 20% to 59% in detection of EHEC infections. 7 Thus, routine screening of all stools for the presence of Shiga toxin-producing E. coli reflects the true prevalence of EHEC infection.
1 www.fda.gov/CVM/Documents/RRASec2.pdf, pages 2-5.
2 Nachamkin, I. “Campylobacter and Acrobacter – Chapter 57”. Manual of Clinical Microbiology, 8th Edition, Volume 1. pg. 905.
3 Goosens, H. et al. “Modified selective medium for isolation of Campylobacter spp from feces: comparison with Preston medium, a blood-free medium and filtration system”. Journal of Clinical Microbiology. 24:840-843.
4 Ng, L.K., et al. “Characterization of freshly isolated Campylobacter coli strains and suitability of selective media for their growth”. Journal of Clinical Microbiology. 26:518-523.
5 P. Gavin and R. Thomson, Diagnosis of Enterohemmorhagic Escherichia coli Infection by Detection of Shiga Toxins, Clinical Microbiology Newsletter, April 1, 2004, Vol.26, No.7, pp.49-54
6 C. Thorpe, Shiga Toxin-Producing Escherichia coli Infection, Clinical Infectious Diseases, April 15, 2004, Vol.38, pp. 1298-1303
7 P. Gavin and R. Thomson, Diagnosis of Enterohemmorhagic Escherichia coli Infection by Detection of Shiga Toxins, Clinical Microbiology Newsletter, April 1, 2004, Vol.26, No.7, pp.49-54