Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving viable micro-organism
Patent
1998-10-14
2000-12-26
Marschel, Ardin H.
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving viable micro-organism
435 737, 435 18, 435208, C12Q 110, C12Q 134, G01N 33569, C12N 938
Patent
active
061657433
DESCRIPTION:
BRIEF SUMMARY
This is the U.S. national stage entry of PCT application No. PCT/FR97/00656 under 35 U.S.C .sctn. 371, filed Apr. 14, 1997.
The present invention relates to a novel medium for isolating and identifying E. coli O157 and/or O11 bacteria, and to a process for revealing them.
Enterohemorrhagic Escherichia coli (EHEC), in particular the serotype O157, has been the cause of most of the cases of food poisoning in the United States, Canada and Europe. In North America, beef (in particular raw beef), beef-based products and unprocessed milk have been involved in these epidemics.
The virulence characteristics of this microorganism, which are identical to those of enteropathogenic E. coli and verotoxinogenic E. coli make this microorganism a major public health problem, since it causes hemorrhagic colitis characterized by sanguinolent diarrhea, and these symptoms may develop into very serious renal complications (hemolytic uremic syndrome).
In recent years, studies have thus been directed toward the rapid detection of EHEC strains in food products (FDA, 8th edition, 1995--Bolton et al., 1995), and more particularly toward specific detection of the serotype O157.
The isolation media of the prior art are: medium, and examination of all the gram-negative and sorbitol-negative bacteria, inhibition of the growth of the desired E. coli O157 can be obtained, allows elimination of the bacterial colonies containing a .beta.-glucuronidase (essentially typical E. coli).
Most of the strains of Escherichia coli O157 isolated from epidemics do not ferment sorbitol in 24 hours, have no .beta.-glucuronidase activity and do not grow at 45.5.degree. C. Thus, many methods for screening for EHEC strains in clinical or food samples use sorbitol MacConkey agar (SMAC) as primary isolation medium.
The suspected sorbitol-negative colonies are then confirmed as Escherichia coli O157 by biochemical and serological tests.
Among the other media most commonly used, mention is made of: potassium tellurite) which make it more selective, since these compounds inhibit many bacteria which do not ferment sorbitol, such as Proteus spp., Morganella morganii, Providencia spp., Hafnia alvei, etc. A study carried out in 1993 showed that close to 400 strains of EHEC E. coli O157, all of which were cultured on CT-SMAC medium, allowed sorbitol-negative colonies to be revealed. revealing sorbitol-negative, rhamnose-negative colonies. sorbitol-negative, .beta.-glucuronidase-negative colonies. sorbitol-negative, .beta.-glucuronidase-negative colonies. thiosulfate, for revealing sorbitol-negative, MUG-negative and H.sub.2 S-negative colonies.
The variants of SMAC medium, which to begin with is a relatively unselective medium, were prepared by adding inhibitors, which contribute toward increasing the sensitivity of isolation of E. coli O157 by eliminating the associated flora.
However, the current detection techniques have major drawbacks, as regards both the sensitivity and the specificity, since E. coli O157 is present in low amount in food samples, compared with the other microorganisms present, and compared with other species such as E. hermanii which has the same phenotypes on the current media.
The present invention provides a solution to this problem since it provides better specificity and selectivity than those of the media of the prior art, since the addition to a colorless medium of chromogen which detects the .beta.-galactosidase enzyme allows the strains of serogroup O157 and often those of serogroup O11 to be detected rapidly and easily. Highly concentrated colorations are obtained, the color of which depends on the chromophoric part of the chromogen chosen, these colorations being localized in the colonies and allowing easy revelation.
The present invention thus relates to a novel culture medium for revealing enterohemorrhagic E. coli bacteria, in particular of the serotypes O157 and/or O11, which comprises, besides a culture medium for E. coli, a chromogenic compound which is a substrate for the .alpha.-galactosidase enzyme.
In order to increase the
REFERENCES:
patent: 3562113 (1971-02-01), Kawamura et al.
patent: 4923804 (1990-05-01), Ley et al.
patent: 5210022 (1993-05-01), Roth et al.
patent: 5821066 (1998-10-01), Pyle et al.
Todd et al. Rapid Hydrophobic Grid Membrane Filter-Enzyme-Labeled Antibody Procedure for Identification and Enumeration of Escherichia Coli 0157 in Foods. Appl. Environ. Microbiol. 54, pp. 2536-2540, (Oct. 1988).
Doyle et al. Isolation of Escherichia Coli 0157:H7 From Retail Fresh Meats and Poultry. Appl. Environ. Microbiol. 53, pp. 2394-2396, (Oct. 1987).
Ogdon et al. An Evaluation of Fluorogonic and Chromogenic Assays for the Direct Enumeration of Escherichia Coli. Lett. Appl. Microbiol. 13, pp. 212-215, (1991), No Month Found.
Frampton et al. J. Food Protection 51(5), pp. 402-404, (May 1988).
X-a-Gal Medium; 1993 American Society of Brewing Chemists, Inc. pp. 185-187, (1993), No Month Found.
Derwent abstract XP 002020743, AN 92-110005 C14! PN JP4051900 A 920220, abstract only. (Feb. 1992).
Marschel Ardin H.
Moran Marjorie A.
LandOfFree
Culture medium for revealing enterohemorrhagic E. coli bacteria does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Culture medium for revealing enterohemorrhagic E. coli bacteria , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Culture medium for revealing enterohemorrhagic E. coli bacteria will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-993345