EHEC

EHEC: description

The abbreviation EHEC stands for enterohaemorrhagic Escherichia coli. These are certain bacterial strains of the bacterial species Escherichia coli (E.coli). The EHEC bacteria are sometimes mistakenly referred to as EHEC virus.

Occurrence and frequency

EHEC diseases occur all over the world. Infants under the age of five are most commonly affected, but all age groups may experience EHEC infection. In 2013, according to the Robert Koch Institute (RKI), 30 percent of all EHEC cases in Germany affected children under the age of five. In total, 1621 cases were reported to the RKI in the same year. In two patients, the consequences of EHEC infection resulted in death. According to the Robert Koch Institute, the fact that the number of reported new cases of EHEC in 2013 was the second highest (highest: EHEC 2011) is most likely due to the increased attention of patients and doctors after the EHEC epidemic in 2011 in Germany and others countries.

EHEC epidemic 2011

The year 2011 is a special case. There were more reports of EHEC outbreaks. A hitherto unknown EHEC strain triggered extremely serious illnesses in early May 2011, especially in adult women in northern Germany. In some cases, the severe complication of EHEC infection, HUS (hemolytic uremic syndrome), was reported in those affected. A total of 4,908 EHEC infections were reported, more than five times as many cases as in 2010 (according to RKI: 918). While nearly 50 percent of the cases in the previous years were mainly infants, in 2011 this age group accounted for only 14 percent of all EHEC infections. 21 cases ended fatally.

EHEC: symptoms

Especially in adults EHEC is often without signs. There are usually no other EHEC symptoms. The bacteria are excreted after one to three weeks through the bowel movement and can be transferred to other people in poor hygiene. If complaints occur during the EHEC infection, the patient is usually sick. They complain of watery diarrhea, have abdominal cramps and vomit. In rare cases, mild fever is one of the EHEC symptoms. In rare cases, EHEC infection is very severe. The following symptoms may occur:

Severe bowel inflammation (hemorrhagic colitis)

In 10 to 20 percent of EHEC infections, a serious disease develops. Older people, infants, and immunocompromised individuals are particularly likely to be affected. EHEC bacteria cause severe intestinal inflammation. The patients have very painful abdominal cramps and bloody diarrhea. There may be a fever. Doctors speak in this disease of the hemorrhagic colitis, which translates to bleeding intestinal inflammation means.

Anemia and renal weakness (hemolytic uremic syndrome)

In the context of an EHEC infection can also dangerous hemolytic uremic syndrome (HUS) occur: The EHEC toxins are the cause of red blood cells (hemolysis) and lead to anemia (anemia). The patients therefore feel limp and are strikingly pale. In addition, the bacterial toxins damage the blood vessel walls and the platelets (thrombocytes). This leads to a strong bleeding tendency.

Consequently, it comes to bleeding, which can be seen in the skin as pinhead-sized punctate hemorrhages (“petechiae”). In addition, the kidneys and thus the fluid excretion are no longer working properly. As a result, the affected persons store water on the legs (edema). The kidneys may fail completely (acute kidney failure). The detoxification of the blood is consequently limited. It can lead to states of confusion or seizures.

EHEC: causes and risk factors

EHEC infections are caused by specific strains of the bacterium Escherichia coli (E.coli). Millions of E. coli bacteria belong to the normal intestinal flora of humans and animals. There they fulfill important tasks: they break down indigestible nutrients and repel pathogens. However, EHEC are strains of these bacteria that can make humans sick. Mistakenly, they are sometimes referred to as EHEC, even though they are bacteria.

Contagion with EHEC

EHEC bacteria normally occur in the gut of ruminants such as cattle, sheep or goats. They are excreted in the droppings. Contamination is usually via food that is contaminated with manure (liquid animal manure used to fertilize fields). In small children, direct contact with the animals also carries the risk of illness.

The risk of EHEC infection is also increased when consuming certain foods, such as unpasteurized milk or raw meat. In the summer of 2011, there were frequent EHEC cases. The exact source of infection could not be found out. However, researchers speculate that raw green leafy vegetables such as sprouts or spinach were responsible for the outbreaks.

EHEC can also be transferred via contaminated water, for example when drinking or bathing in it. To infect with EHEC, only a very small number (about 100) of bacteria is needed. This is why transmission from person to person is more common than with other diseases. Again, the pathogens are found in the bowel movement and go through smear infection and poor hygiene on the next person. The duration between infection and the first symptoms of illness (EHEC incubation period) is two to ten, but usually three to four days.

Why are EHEC dangerous to humans?

EHEC form toxins, called shigatoxins (Stx), which ultimately trigger EHEC symptoms. To date, researchers have discovered numerous subgroups (serotypes) of EHEC. These can cause a variety of symptoms in humans, ranging from mild gastrointestinal complaints to severe intestinal inflammation. The EHEC serotype O157: H7 is most frequently found worldwide (O and H stand for special surface structures of the respective E. coli strain). The serotypes O103 and O26 follow.

Mode of action of EHEC toxins

The formed shiga toxins, also called verotoxins, bind to human cells, especially to the blood vessel walls of humans. There they block the building of important proteins and the affected cells die down. In addition, some EHEC strains can “spatter” harmful proteins into body cells. Through this mechanism, the pathogens can also attach tightly to cells of the intestine.

There are two main skin groups of toxic Shigatoxinen, Shigatoxin 1 (Stx1) and Shigatoxin 2 (Stx2). The Stx1 group mainly causes diarrhea. EHEC, which form Stx2, mainly cause severe diseases such as hemolytic uremic syndrome (HUS). This also explains why EHEC caused such a severe epidemic in Germany in 2011. Because the newly discovered EHEC serotype O104: H4 forms both Shiga toxins 1 and 2. This makes this strain particularly aggressive.

EHEC: diagnosis and examination

In case of diarrhea, the person has bowel movements more than three times a day. The chair is unformed and has a high water content (> 75 percent) – so it is liquid. In most cases, the high amount of fluid also increases the amount of bowel movements (> 250 grams a day). If a patient presents with this condition in a practice, the doctor will perform some examinations regardless of age. The right contact person for suspected EHEC infection is first the family doctor. In case of severe symptoms (severe diarrhea, poor general condition), a hospital with an infection department should be visited directly.

Anamnesis and physical examination

First, the medical professional asks a few questions (anamnesis) in order to be able to uncover possible additional EHEC signs: How often do you have a bowel movement? How is the chair shaped? Is blood added to the stool? Equally crucial are questions about fever, abdominal pain and urine frequency or appearance. Blood in the urine is a potential indication of damaged kidneys.

The doctor will also ask about possible risk factors. This attempts to track down a source of infection with EHEC. Invented contact with animals on a farm? Were unwashed vegetables or raw meat eaten? Did you have contact with people with diarrhea, for example at work?

Another important information is also the profession of the person concerned. If he works with food, it may explain and curb the spread of EHEC infections. It also takes into account which medications are taken. Above all, the excessive use of laxatives (laxatives) can lead to severe diarrhea and feign infection.

During physical examination, the doctor looks for signs of kidney failure or kidney damage such as edema or blood in the urine. If the patient feels weak and is unusually pale, this may be an indication of anemia. The skin is also thoroughly examined by the physician. Smaller bleedings (petechiae) indicate a disturbed blood coagulation.

If bloody diarrhea is accompanied by signs of impaired kidney function, poor blood clotting or anemia, the patient is immediately hospitalized and isolated from other patients. There are then further investigations.

Examination of stool samples

There are a number of causes for diarrhea. With a stool sample, the doctor can try to find the cause. In EHEC patients usually suffer from diarrhea without blood, but otherwise show no health restrictions. However, in a stool sample, EHEC can sometimes detect hidden (fecal occult) blood in the stool.

In certain situations, the doctor will arrange for a special chair examination on EHEC. According to the valid EHEC 2011 guidelines of the German Society of General Medicine, this applies if

• the patient has diarrhea and blood is visible in the stool
• the patient works directly with food
• the person affected had contact with HUS patients
• Children suffer from kidney weakness

Blood and urine tests

When examining the blood, particular attention is paid to those values ​​which speak for an EHEC-induced hemolytic uremic syndrome (HUS). This is especially the number of red blood cells and platelets. Both the red blood cells and the platelets can be significantly reduced as they are destroyed by the toxins of the EHEC.

Altered renal values ​​in the blood (for example, creatinine) indicate a possible impairment of the kidney by the EHEC infection. In addition, the inflammatory parameters (white blood cells, C-reactive protein) are determined in the blood. However, elevated levels of inflammation only indicate an infection; they are not proof of EHEC. When examining the urine (with so-called urinary sting), doctors pay attention primarily to hidden blood and proteins. These can be detected in a functional disorder of the kidneys.

Proof of EHEC toxins

Most important in case of suspected EHEC infection is the investigation of whether the bacteria have the toxin production (toxin production) genes necessary (toxin detection), and whether they actually form the toxins (toxin detection). The detection of the toxin genes takes place with a PCR examination (polymerase chain reaction) of stool material. For toxin detection, the E. coli obtained from the patient material are first multiplied in culture. In this culture, the Shiga toxins can be detected with a so-called ELISA (Enzyme Linked Immunosorbent Assay).

EHEC: treatment

Although EHEC is bacteria (there is no EHEC virus!), Antibiotic treatment is currently not recommended, as such treatment may prolong bacterial excretion and cause increased toxin release of the bacteria. However, recent research indicates that high-dose antibiotic therapy may be beneficial. However, this must be checked by further studies. In addition, diarrhea should not be treated with diarrheal medications such as loperamide, as these also interfere with excretion of the pathogens with the stool.

EHEC therapy is therefore usually purely symptomatic. Which measures are necessary depends on the severity of the disease. As a rule, a liquid and salt replacement is necessary: ​​The patients lose over the diarrhea salts (electrolytes) such as potassium and sodium. For example, these play an important role in the function of the heart, nerves and muscles.

Even a disturbed kidney function affects the electrolyte levels in the body. Therefore, electrolyte losses are compensated by infusions, tablets or electrolyte powder. The same applies to the fluid balance of the patients, as the patients also lose excess water through diarrhea.

Treatment of HU syndrome

Since the complication of hemolytic uremic syndrome (HUS) can reach life-threatening levels, a purely symptomatic treatment is not sufficient. The weakened kidney function is stimulated with special drugs (diuretics). If the kidneys fail completely, a renal replacement procedure such as dialysis (“blood washing”) is necessary. By dialysis, the blood is cleaned of waste. Optionally, the blood plasma of the patient, similar to a dialysis, cleaned with the so-called plasma apheresis.

In addition, there are other treatment measures, but for their effectiveness and tolerability, there are so far no long-term studies. In the medical journal “The New England Journal of Medicine” was presented in 2011, a study in which, among other things, German experts were involved. According to the results of the study, the treatment of HUS by EHEC with a special active substance called eculizumab promises success. With annual costs of around € 400,000, it is one of the most expensive medicines ever, and its use is only possible in specialized treatment centers.

EHEC: Disease course and prognosis

As a rule, a simple EHEC infection heals without consequences. However, complications such as bleeding intestinal inflammation or haemolytic uremic syndrome (HUS) can have long-term consequences: About 50 percent of children who contract a HUS then permanently need renal replacement therapy (dialysis) due to permanent kidney damage. Up to 40 percent develop hypertension and chronic kidney failure in the ten to fifteen years after HUS. In the epidemic in 2011, the death rate was about one percent. Considering previous studies, this rate is about two percent. It is elevated in a complex hemolytic uremic syndrome in which about four percent of people die.

EHEC: Prevention

The Robert Koch Institute has issued some recommendations to protect itself and its environment from EHEC infection. These recommendations are aimed primarily at infants, elderly, immune-compromised and pregnant women:

Be careful of direct animal contact

This applies, for example, in a petting zoo. Be careful not to put your hands in the mouth after contact with the animal. Avoid simultaneous eating and drinking. Clean your hands thoroughly with warm water and soap.

Store your food well chilled

This is especially true perishable food. Because EHEC bacteria multiply best at a temperature of 37 ° Celsius.

Wash your fruit thoroughly and peel it if necessary

EHEC can be on vegetables and fruits when animal manure has been used as fertilizer.

Do not eat vegetables or peel vegetables

As with the preparation of meat, attention should be paid to heating the food to at least 70 ° Celsius over ten minutes.

Do not eat raw animal products

Avoid eating raw or under-cooked meat. The same applies to raw milk and products made from it. Only in well-heated animal products are EHEC and its toxins harmless.

Make sure you have a clean cooking environment

Thoroughly clean dishes, cutlery, work surfaces, towels, and chopping boards after preparing raw food. Thus, the EHEC bacteria can not be transferred to the next prepared food.

Wash your hands thoroughly with hot water and soap

This is especially true after using the toilet, after working with raw foods and before eating or drinking.

Go to the doctor in time

This is especially true for over several days of persistent diarrhea or if you find the stool blood. Especially in infants and toddlers a doctor should be visited quickly, if it is distributed over the day heaped to diarrhea.

Prevent the spread

To prevent the spread of EHEC, thorough hygiene measures are of enormous importance. This also successfully restricts the transmission from person to person. If patients are hospitalized in a hospital, they are cared for there in isolation. Only when the EHEC bacteria are no longer detectable after three stool samples, the isolation is lifted. Infected persons working in community facilities such as schools may not work there as long as they leave EHEC. The same applies to working people who work with food. Since infections are already reportable on suspicion, an attempt is made to detect and contain EHEC spread early.