Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving antigen-antibody binding – specific binding protein...
Reexamination Certificate
1999-11-19
2004-04-27
Nguyen, Bao-Thuy L. (Department: 1641)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving antigen-antibody binding, specific binding protein...
C435S007370, C435S007940, C435S028000, C435S287800, C435S030000, C436S518000, C436S526000, C436S536000, C436S538000, C436S161000, C436S810000
Reexamination Certificate
active
06727073
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of immunochromatographic assays. More particularly, the present invention relates to a method for detecting enteric pathogens in fecal specimens. More particularly yet, the present invention relates to a method for detecting the presence of one or more specific enteric pathogens from the simultaneous assay for several enteric pathogens. Most particularly, the present invention relates to a method for detecting the presence or absence of several enteric pathogens and concurrently applying one or more general tests for an inflammatory condition of the intestines.
2. Description of Prior Art
Enteric pathogens can cause severe illness in people and affect a large number of people within a short period of time. The U.S. Centers for Disease Control estimates that there are five million cases of foodborne illnesses per year in the United States with up to 5,000 deaths.
Campylobacter jejuni
and Salmonella are the leading causes of foodborne illnesses;
E. coli
O157 is less frequent, but is significant in disease control because this strain of
E. coli
, the most noted of the enterohemorrhagic
E. coli
bacteria, causes the majority of severe disease from
E. coli
and is also a cause of large epidemics. Other strains of
E. coli
, such as O111, have also been implicated in foodborne outbreaks. Although the number of illnesses from
E. coli
O157 is low relative to the numbers of cases of
Campylobacter jejuni
or Salmonella, this
E. coli
pathogen is significant because the rate of mortality is much higher and the treatment significantly different. Some antibiotics can have a detrimental effect on patient health if the patient is suffering from an illness caused by an enterohemorrhagic
E. coli
that has not been diagnosed. For this reason, before prescribing antibiotics for a patient apparently suffering from an illness caused by a pathogen, it is important to determine whether
E. coli
bacteria is the cause in order to avoid prescribing medication detrimental to the health of the patient. Rapid determination of the cause of the illness is thus a critical factor in providing the timely and proper care of the ill. Moreover, it is critical to determine the possible sources of contamination as quickly as possible in order to take appropriate steps to eliminate them.
A method to rapidly screen patients for enteric illnesses would greatly increase the ability of medical personnel to accurately diagnose the cause of the illness and provide appropriate treatment, thus accelerating the rate of patient recovery. Furthermore, a method for rapid screening for enteric pathogens also has great economic value because it can focus valuable resources. For example, rapid screening can be used to rule out certain pathogens as a cause of illness before making the decision to use the more costly methods of culturing a specimen for a pathogen that cannot be readily detected by a rapid screening device. Use of a method for rapidly screening patients for enteric illnesses that can be performed reliably by unskilled persons is also a more cost-effective use of personnel resources than the use of a method that requires the attention of skilled personnel.
Enteric pathogens are not the only cause of diarrhea. Other causes include food sensitivities, allergic reactions, side effects from medication, and psychosomatic factors. The treatment for diarrhea resulting from such non-pathogenic factors is very different than the anti-microbial treatment of pathogenic diarrhea. A screening method that would give an indication of whether the cause of the diarrhea is infectious or non-infectious, inflammatory or non-inflammatory would provide valuable diagnostic information to a treating physician. A common response to enteric pathogens is an inflammation of the intestines. In contrast, an inflammatory condition of the intestines is generally lacking when the cause of the diarrhea is non-infectious or non-immune. Thus, it is very useful to assay for a marker that is associated with intestinal inflammation and that is absent or present only in very low concentrations in the absence of such inflammation. The detection of such a general marker is useful, for example, in a situation in which none of the specific pathogens assayed for appears to be present. The knowledge that the “inflammation” marker is present then will lead to a continued search for the pathogen causing the inflammation, and will also provide additional causes for symptoms such as inflammatory bowel disease. Thus, a method that not only tests for multiple enteric pathogens simultaneously, but also tests for an inflammatory condition of the intestines would provide the physician with additional valuable diagnostic information. Furthermore, a method that would also test for a bacterial, viral, or protozoan cause of enteric disease would provide further valuable diagnostic information in the situation where none of the specific pathogens being assayed for appears to be present.
The immunoassay technique, which relies on the specific binding action between an antigen or a hapten and a corresponding antibody, has proven to be a reliable method for determining the presence (or absence) of a pathogen in a specimen. A class of devices known as immunochromatographic test (ICT) devices uses the immunoassay technique in combination with a label that is conjugated with the antibody and is now commonly used for rapid, reliable field tests to determine the presence or absence of a particular analyte. The label, when attached to antibody/antigen molecules that are then amassed together in a specific, restricted area, becomes readily detectable by the naked human eye, or by a scanning device, depending on the type of label used. In general, the label can be a particle of latex, gold, or carbon, a radioactive particle, a magnetic particle, or have other physical or chemical properties that allow it to be fixed or attracted to a certain defined area. ICT devices that use the sandwich technique are particularly easy to use. With this technique, labeled antibody that binds with the specific antigen to be assayed is mixed with the sample that is suspected of containing the specific antigen. If the antigen is present in the sample, the labeled antibody binds with the antigen to form a label-antibody-antigen complex. A second antibody that is immovably fixed at a test zone and that also binds with the specific antigen binds the label-antibody-antigen complex at the test zone. A positive result is made visible by the accumulation of the label at the test zone. Such devices are economical and can be used by unskilled workers. Thus, a method that uses such an ICT device to determine, in a single assay, the presence or absence of multiple enteric pathogens, in particular, multiple enteric pathogens, plus a general marker for an inflammatory condition of the intestines would provide valuable diagnostic information to a treating physician.
Several types of such ICT devices are known. Most are the “dipstick” type in which a test strip is encased in a hollow housing with a bibulous pad extending from one end. This pad is dipped into the liquid sample and draws the liquid by capillary (“wicking”) action up onto a section of the test strip that contains a labeled antibody, i.e., a label conjugated to an antibody that will specifically bind with the antigen being assayed. The labeled antibody moves with the liquid that is being drawn by the capillary action further along the test strip and, if the specific antigen to which the antibody binds is present in the liquid sample, the labeled antibody will bind with the antigen, forming a labeled antibody-antigen complex. This complex continues to flow with the liquid along the test strip. Downstream from the area containing the conjugated antibody is a test zone. This test zone is typically a nitrocellulose pad into which a second binding partner, an antibody that binds to the same antigen as the labeled antibody, but to a second epitope of the
Moore Norman
Tarr Phillip I.
Binax, Inc.
Nguyen Bao-Thuy L.
Sears Mary Helen
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