String Test (Entero-Test)
The Entero-test is a new type of antibiotic test that detects enteric pathogens such as E. coli, Salmonella, Shigella, Campylobacter, Yersinia Pneumoniae and others. The Entero-test is used to screen patients with diarrhea or other gastrointestinal symptoms for possible infection with these organisms.
In the past, Entero-tests were not widely available because they are expensive and require specialized equipment. However, recent advances in technology have made it easier to perform these tests. Also, the Entero-test is much less invasive than traditional culture methods which can cause discomfort and pain.
The Entero-test is performed using a swab soaked in alcohol and placed into your mouth. A small amount of liquid is then drawn from your stomach through the swab. If the liquid comes back positive for one of these organisms, it means that you may have been infected with one of them.
How Does the Entero-test Work?
A sample of stool is taken from a patient’s mouth and placed into a tube called an enteroscope. Then, a thin stream of fluid flows out through the tube. A few drops of this liquid are placed on a special culture (such as blood agar, thiosulfate citrate bile sucrose yeast extract (TCBY) or xylose lysine desoxycholate agar (XLD) plates) to check for the presence of enteric pathogens.
The Entero-test is very accurate in detecting many common causes of diarrhea and other gastrointestinal distress. It can reliably detect Salmonella, Shigella, E. coli and Campylobacter species in less than an hour. It is also very useful for identifying patients with bloody diarrhea who may have a more serious illness such as amebiasis or giardiasis.
Who Should Use the Entero-test?
If you have been suffering from diarrhea or other gastrointestinal distress for more than a few days, it is best to get the Entero-test performed. If you have had contact with anyone with similar symptoms and/or if you have recently visited a foreign country, it is also a good idea to get the test done.
The Entero-test can help identify the common causes of diarrhea, which can help direct treatment. It is less useful in diagnosing less common enteric pathogens and does not reliably detect viruses, fungi or parasites.
What are Common Causes of Diarrhea?
The most common causes of diarrhea are bacterial infections. Viral infections are less common and parasites cause even less diarrhea. However, any of these pathogens can be serious if left untreated.
Bacterial Infections: Bacterial infections usually cause liquid stools containing high amounts of mucus. Bloody stools typically mean that the patient has a more serious illness such as amebiasis or giardiasis. The most common causes of bacterial infections are Salmonella, Campylobacter, Shigella and Escherichia coli (E. coli).
Viral Infections: Viral infections can cause either bloody or non-bloody diarrhea. Viral infections rarely cause serious dehydration unless the patient is suffering from an immunodeficiency disease. Some of the more common viral causes of diarrhea include rotavirus, adenovirus, enteric calicivirus and norovirus (often called “stomach flu”).
Parasitic Infections: Parasites are less common causes of diarrhea. The most common parasites in North America are tapeworms and pinworms (usually seen in children).
Detection of Food Poisoning
If you think that your illness is the result of a food-borne bacteria such as Salmonella, E. coli or Campylobacter, it is important to get a stool culture to identify which one. This will help the physician prescribe the correct antibiotic treatment. A stool culture can also detect C.
difficile, a cause of infectious diarrhea that is commonly treated with antibiotics.
How is the Entero-test Performed?
The Entero-test is very easy to perform. No needles are involved and stools can be tested while still in the body (this is called an “OAT” or “Onsite” test). The technician takes a sample of your stool using a sterile swab and places it in a special solution. The solution is then sent to the lab for analysis. It usually takes less than a day to get results.
What are the Benefits of the Entero-test?
The Entero-test can detect amoebas, giardia and other parasites that cause diarrhea. It is also useful for identifying E. coli 0157:H7, a common cause of infectious diarrhea that requires immediate medical treatment. It can also quickly identify C. difficile, a dangerous cause of infectious diarrhea that is becoming more common in hospitals and nursing homes.
Most importantly, the test can distinguish between patients who have diarrhea with an infectious cause and those who do not. This allows doctors to treat patients with antibiotics immediately and stop those who do not need them from being overmedicated with unnecessary drugs.
What are the Potential Problems of the Entero-test?
The Entero-test occasionally gives false-positives and false-negatives. This means that on rare occasions it will test positive when no infection is present and on other occasions it will fail to detect an infection. Physicians should not rely upon a single test result to make a diagnosis. For this reason, a positive Entero-test should be followed up with a second test called a C. difficile toxin assay.
Entero-test Limitations: The Entero-test should never be used as a stand-alone diagnostic tool to make a final diagnosis. It can only be used to rule in or rule out infectious diarrhea as a possible cause of acute diarrhea.
What is the C. difficile
Toxin A and B assay?
The C. difficile toxin A and B assay is a more specific test for C. difficile. The test involves sending a stool sample to a reference lab where it is grown in culture dishes. The resulting cultured bacteria are then tested for the presence of CDTF toxin A and B using a standardized lab procedure.
How Effective is the Test?
This test is excellent at detecting the presence of C. difficile. It has a sensitivity that approaches 100% and a specificity of about 98%. The problem is that about 2% of the population may naturally carry C. difificile in their intestines without ever getting sick (this is called “carrier state”). So in some cases it will falsely appear that someone has CDIF if they are a carrier. Of course it will also correctly identify anyone who does have CDIF so it is still a very useful test.
How is the C. difficile
Toxin A and B assay Performed?
The stool sample is sent to a reference lab where it is cultured in special sterile dishes and tested for the presence of CDT toxins. It usually takes about 3 days to get results.
What are the Benefits of the C. difficile
Toxin A and B assay?
The C. difficile toxin A and B assay is very accurate at detecting the presence of C. difificile. It will reliably identify anyone who has this infection and will reliably rule out anyone who does not have it.
What are the Potential Problems of the C. difficile
Toxin A and B assay?
The C. difficile toxin A and B assay does have one major limitation: it does not distinguish between a true C. difificile infection and a carrier state. This is important because carriers do not need any treatment and will get better on their own (usually in a few weeks). In fact, unnecessary use of antibiotics for C. difificile can lead to resistant bacteria developing, which is an important emerging problem in hospitals.
How Often Should the C. difficile
Toxin A and B assay be used?
The C. difificile toxin A and B assay should be used any time symptoms of CDIF are present.
A physician should not use the Entero-test alone to make a final diagnosis because of its limitations. It is only meant to rule in or rule out that a patient has infectious diarrhea as a possible cause of acute diarrhea. It is strongly recommended that the test be followed up with a C. difificile toxin A and B assay to confirm the result.
Is There Anything Else I Should Know?
Both of these tests are offered by most major clinical laboratories. If your physician sends a stool sample to be tested for either of these illnesses, just make sure he or she is sending it to a lab that does both Entero-tests and C.
Sources & references used in this article:
Use of a Non-invasive Test (Entero-test) in the Detection of Helicobacter pylori in Children in an Endemic Area in Colombia by RN Arboleda, BG Schneider, LE Bravo… – Journal of pediatric …, 2013 – ncbi.nlm.nih.gov
Use of Entero‐Test, a simple approach for non‐invasive clinical evaluation of the biliary disposition of drugs by WJ Guiney, C Beaumont, SR Thomas… – British journal of …, 2011 – Wiley Online Library
Use of the entero-test, a novel approach for the noninvasive capture of biliary metabolites in dogs by WJ Guiney, C Beaumont, SR Thomas – Drug metabolism and disposition, 2010 – ASPET
Routine in vitro cultivation of Giardia lamblia by using the string test. by SH Korman, E Hais, DT Spira – Journal of clinical microbiology, 1990 – Am Soc Microbiol
The clinical utility of string-PCR test in diagnosing Helicobacter pylori infection. by SW Wang, FJ Yu, YC Lo, YC Yang, MT Wu… – Hepato …, 2003 – europepmc.org
Evaluation of the string test for the detection of Helicobacter pylori by RWL Leong, CC Lee, TKW Ling… – World Journal of …, 2003 – ncbi.nlm.nih.gov
Collection of duodenal bile in infants and children by the string test by P Rosenthal – Journal of pediatric gastroenterology and nutrition, 1985 – journals.lww.com
Evaluation of the peroral string test in the diagnosis of canine giardiasis by EJ Hall, HC Rutgers, RM Batt – Journal of Small Animal …, 1988 – Wiley Online Library