Evaluation of media and test kits for the detection and isolation of escherichia coli o157 from cattle faeces
Evaluation of media and test kits for the detection and isolation of
Escherichia coli O157 from cattle faeces
A.V. Tutenel, L. De Zutter and J. Van Hoof
Department of Veterinary Food Inspection and Public Health, Faculty of Veterinary Medicine,
RUG, Salisburylaan 133, B-9840, Belgium
Presented at the symposium: ”Escherichia coli: friend and foe” at the University of York (UK),
13th - 16th of July 1999.
Four strains of enterohemorrhagic E. coli O157:H7 (one reference strain, one human strain, one strain from meat and one strain from carcasses) were used to inoculate feces from cattle. Each strain was added to 25 g of sample at a level of 5 to 14 cfu. Three selective enrichment media were used: (1) buffered peptone water (BPw), (2) modified tryptone soya broth with 1% novobiocine (mTSB-n) and (3) mTSB-n followed by cefixime-tellurite MacConkey (CT-MAC). Five different test kits were applied to these media: (1) Dynabeads® anti E. coli O157 (Dynal); (2) Captive® O157 (Lab M); (3) Vidas® E. coli O157 ECO (Biomérieux); (4) Vidas® E. coli O157 ICE (Biomérieux) and (5) Transia Plate® E. coli O157 (Diffchamb). These kits were tested after 6 h and/or 24 h of incubation. Plating on CT-SMAC plates occurred direct and after using the kits 1, 2 and 5.
This study showed that isolation of E. coli O157 was very good by using the Dynal Dynabeads® after 6h of incubation in BPw by 37°C. For Captive®, the results depended on the strain tested. The Transia Plate® O157 was very useful for the detection of E. coli after 22h incubation. Successful confirmation was only obtained using an immunomagnetic separation after incubation in BPw and CT-MAC. Vidas® ECO yielded less positive results than the test kits 1, 2 and 5. With Vidas® ICE, not all Vidas® ECO positive samples could be confirmed.
O157:H7 is a foodborne pathogen and can cause haemorrhagic colitis, haemolytic uraemic syndrome and thrombocytopaenia.
Most outbreaks are associated with the consumption of raw meat and raw meat products. It is believed that cattle is the main reservoir for this pathogen.
Since the first outbreak of E. coli
O157:H7 in America in 1982, lots of different isolation and detection kits and enrichment media are developed.
Isolation and detection can occur by: (1) chromogenic and/or fluorogenic media, (2) biochemical test kits, (3) electrical, (4) ELISA, (5) immunochromatography, (6) immuno-capture, (7) latex agglutination, (8) nucleic acid hybridization probe, and (9) PCR
The aim of this work was to compare different detection and isolation media and test kits for the isolation of E. coli
O157:H7 from faeces of cattle.
The different isolation and detection kits
used in this recourse are:
(1) Dynabeads® anti E. coli
O157 (Dynal); (2) Captive® O157 (Lab M); (3) Vidas® E. coli
O157 ECO (Biomérieux); (4) Vidas® E. coli
O157 ICE (Biomérieux) and (5) Transia Plate® E. coli
O157 (Diffchamb). These kits were tested after 6 h and/or 24 h of incubation.
We used four different E. coli O157 strains
to test the different kits: (1) LMG 15068, a
reference strain isolated from hamburgers; (2) VUB EH1, the first strain isolated from
human; (3) B032, isolated from carcasses; (4) 17762/1, isolated from minced beef.
t occurred in (1) BPw, (2) mTSBn and (3) CT-Mac.
Everything was streaked
onto CT-SMAC plates.
Materials and Methods
(1) Incubation in BPw
25 g faeces 225 mL BPw 10 µL E. coli strain (103/mL) 0,5 h warm water
(2) Incubation in mTSBn
Four different strains were tested on five different faeces samples.
(A) after 6 h incubation
! all positive samples were found back using Dynabeads
! less positive samples were found back using mTSBn
(B) after 22 h incubation
! enrichment in BPw: Captive gave a 100% result
! enrichment in mTSBn: Transia Plate gave a 100% result
! enrichment in CT-Mac: Transia plate gave a 100% result
! less positive results yielded with Vidas
(1) immediate streaking gave never a 100% result
(2) after 6 h incubation, using BPw as enrichment broth gives a 100 %
(3) after 22 h incubation, using mTSBn as enrichment broth gives a
(4) successful isolation of E. coli
after the Transia Plate was only
(5) Vidas ECO yielded less positive results comparing with the other
(6) Vidas ICE could not confirm all Vidas ECO positive samples
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