Transmission

The transmission of bacteria can take place in three different ways: Either through direct contact (body contact, food or infected objects), via the air through a so-called droplet infection (for example through sneezing or coughing) or via body fluids such as blood, semen or vaginal secretion.

Medical benefit

In medicine, knowledge of bacteria and their properties is of utmost importance, as they play a major role in both the state of health and the disease. Some bacteria are essential to human life. For example, there are bacteria found in the large intestine, which make an important contribution to normal digestion and the human defence system.

Almost 99% of the bacteria found in the human body live in the intestine, which shows their importance at this point. It is estimated that there are about 1014 bacteria in the human intestine. There is also a large number of bacteria in the entrance to the female vagina, which prevents pathogens from entering through this body orifice.

Various bacteria also live in the mouth and throat area and on our skin, but they do not harm humans and ensure that no potentially disease-causing bacteria can spread there. On the other hand, there is also a myriad of bacteria that are responsible for the most diverse and sometimes life-threatening diseases. For example, bacteria cause inflammation of practically all organs (cystitis, pneumonia, periosteitis, etc.

), can infect wounds or even trigger blood poisoning (sepsis). Once an infection with a bacterium has taken place, there are now a large number of means to fight it. These are summarised under the heading of antibiotics, of which there are now apparently infinite numbers.

The best known and still one of the most effective antibiotics is penicillin, which was developed in 1945. The various antibiotics attack the bacteria at different sites, for example at their cell wall or at their protein biosynthesis. One of today’s problems is the frequent and sometimes too generous use of antibiotics, which makes bacteria increasingly resistant to these agents, which means that they can no longer be killed by them.

Occurrence

The stomach is a part of the digestive tract. As a hollow organ, the stomach can temporarily store the food it takes in and begins to break it up with its strong muscle layer. The stomach also produces an acidic gastric juice with which the food is mixed and further broken down.

This acid gastric juice prevents bacteria in the stomach from surviving and therefore offers protection against infections. In principle, therefore, no growth of bacteria is possible in the stomach. However, one particular bacterium, the so-called Helicobacter pylori, is an exception.

This is a small rod-shaped bacterium which, because it is equipped with certain substances, can neutralise the acidic gastric juice and thus colonise the stomach lining and survive in the stomach. Colonisation of the stomach with Helicbacter pylori is not uncommon. In Germany, every fourth adult carries the bacterium.

Thus, infection with Helicobacter pylori is one of the most common bacterial infections. SymptomsA patient with a Helicobacter pylori infection is often free of symptoms for years. In the long term, however, the stomach lining can become very irritated, as this is where the bacterium settles down and continues to multiply.

The continuous irritation can lead to an inflammation of the stomach lining, a so-called gastritis. Typical symptoms of such an inflammation of the gastric mucosa are pain in the upper abdomen, as well as a feeling of pressure or fullness in the upper abdomen. In addition, nausea, vomiting and loss of appetite can occur.

If the inflammation of the stomach lining continues, the risk of developing a stomach ulcer increases. Furthermore, an infection with Helicobacter pylori promotes the development of stomach cancer. In order to prevent the development of an inflammation of the stomach lining, any suspicion of a Helicobacter pylori infection should be clarified in detail.

DiagnosisThe bacterium can be detected directly by taking a sample from the patient’s stomach lining. In addition, various tests in the patient’s blood, stool and exhaled air can provide indications of an infection with the bacterium in the stomach. TherapyThe aim of the treatment of Helicobacter pylori infection is the complete elimination of the bacterium in the stomach.

This is done with a combination of two antibiotic preparations and a drug that inhibits the production of acid gastric juice, a so-called acid blocker. The treatment of the bacterium in the stomach is therefore also called triple therapy. This triple therapy is the most common form of therapy and is successful in about 70 percent of cases.

The intestine is an important part of the digestive tract. In addition to digestion, the intestine plays a role in the water balance. It also produces various cells that are important for the human immune system.

In adults, the intestine is around eight metres long and is more or less heavily colonised by bacteria over its entire length. The entirety of these bacteria in the intestine is called intestinal flora. The colonisation of the intestine with bacteria begins during birth and increases with increasing age.

The intestinal flora of an adult is then characterised by a multitude of different types of bacteria. These bacteria in the intestine are of great importance to humans because they protect the intestine from other bacteria that cause illness. In addition, the bacteria in the intestine support the digestion of food components, stimulate intestinal activity, supply the intestine with vitamins and energy and have an influence on the immune system.

However, if the intestinal flora is altered, in the sense of over- or under-population with intestinal bacteria, complaints can occur. Symptoms These complaints generally manifest themselves as abdominal pain, food intolerance, flatulence and diarrhoea. Diagnosis Whether a change in the intestinal flora is present can be determined with the help of a stool sample.

The so-called H2-breath test can also give indications of a malpopulation of the intestine. Causes Damage to the healthy intestinal flora can occur, for example, if a patient has to take antibiotics because of another disease. As an undesirable side effect, the patient’s intestinal flora is also damaged so that the bacteria causing the disease can spread more easily.

This can lead to diarrhoea. In chronic intestinal inflammations, such as ulcerative colitis or Crohn’s disease, it is assumed that the intestine is not only genetically impaired and affected by environmental factors, but also incorrectly colonised with bacteria. Therapy The treatment depends on the underlying disease or on the cause of the intestinal colonisation and includes measures such as simple drug administration or even surgery.

If bacteria spread from a local focus of disease into the bloodstream, sepsis occurs. Colloquially, this is called blood poisoning. In sepsis, bacteria enter the bloodstream throughout the body and can potentially damage any organ.

CausesNormally, the human immune system is able to fight invading bacteria and to contain the further growth of the bacteria. In some cases, however, the immune system’s function is limited or the pathogens are simply too aggressive, causing the defence mechanisms to fail. The body is unable to limit the infection to its point of origin and the pathogens can spread via the bloodstream.

DiagnosisWhether pathogens have entered the bloodstream can be determined by means of a blood culture. In this examination, blood is taken from the patient and transferred to various culture media. The growth of the bacteria is then observed.

Depending on the culture medium on which the bacteria then grow, it can be determined which bacteria are present in the blood. This allows for a more targeted treatment. Furthermore, the blood can be examined for so-called inflammation parameters.

These include, for example, the number of white blood cells or blood sedimentation rate. However, these are unspecific and only give an indication of whether an infection is present or not. SymptomsThe focus of the disease can be located in different parts of the body and thus cause a wide variety of symptoms.

If the infection spreads into the bloodstream, symptoms such as fever, chills, increased heart and respiratory rate, a drop in blood pressure, lack of oxygen, and brain damage can occur. Those affected are seriously ill. TherapyIf the bacteria have spread in the blood and sepsis is present, the affected patients are treated in an intensive care unit, as the function of the organs can deteriorate at any time. This is a potentially life-threatening situation.

Early administration of infusions with fluid and early treatment with antibiotics are crucial for the course of the disease. Depending on the extent of organ damage, artificial respiration and artificial nutrition may also be necessary. The prognosis is poor.

Despite therapy, about 30 to 50 percent of those affected still die of organ failure. Urine is produced in the kidneys and excreted via the urinary tract. It consists of over 95 percent water.

Urine also contains substances such as uric acid, urea, salts and dyes. Normally there are no bacteria in urine. However, if there are bacteria in the urine, this can indicate infections of the kidneys and the urinary tract, especially if the patient reports additional symptoms and the number of bacteria in the urine is high.

When urinating, however, the urine comes into contact with the skin, on which bacteria are found in everyone. So it is possible that bacteria can get into the urine even in healthy people. The mere presence of bacteria in the urine therefore does not prove a urinary tract infection.

Causes A urinary tract infection occurs when bacteria (more rarely viruses) enter the bladder via the urethra, causing the surrounding tissue to become inflamed. An inflammation of the bladder develops. The pathogens can rise up to the kidneys and cause an inflammation of the renal pelvis.

In the worst case, a urinary tract infection can spread to the bloodstream and blood poisoning can develop. Women are more often affected by a urinary tract infection than men because the urethra of women is much shorter and bacteria therefore have to travel a much shorter distance. Congenital malformations of the urinary tract and changes in the hormone balance can also promote the development of a urinary tract infection.

Diagnosis To find out whether there is an infection of the kidneys or the urinary tract, the urine is examined. The urine is examined for the number of bacteria as well as for a substance that bacteria produce, called nitrite. A number of more than 100,000 bacteria per millilitre is a sure sign of infection.

On the other hand, the presence of proteins, red and white blood cells is determined in the urine. If proteins and white blood cells are present, this indicates kidney involvement. In most cases, the urine is examined with the help of urine test strips and, if necessary, the urine is examined under a microscope.

A thorough interview with the patient must also be carried out. Symptoms Typical symptoms of a urinary tract infection are pain and burning sensation when urinating, as well as a frequent urge to urinate. Fever and flank pain indicate that the kidney is also affected.

In some cases, however, patients have no symptoms at all. Therapy Various measures can be considered for the treatment of a urinary tract infection. Care should be taken to ensure a sufficient fluid intake and to avoid cooling of the abdomen. In addition, antibiotics such as Cotrimoxazole can be used to kill the bacteria. Prophylaxis The risk of urinary tract infections can be significantly reduced by simple hygiene measures.