The Bacillaceae are gram-positive bacteria in the Bacillales group. A well-known pathogen from this family is Bacillus anthracis, the causative agent of anthrax.
What are Bacillaceae?
Bacillaceae is a family within the bacterial species. They belong to the order Bacilliales. There are more than 50 different genera known within the Bacillaceae family. Among them are for example Amphibacillus, Lentibacillus or Saccharococcus. However, the best-known subgroup is the genus Bacillus, which includes pathogens such as Bacillus anthracis, Bacillus cereus or Bacillus stearothermophilus. The Bacillaceae are gram-positive, long rod bacteria. Accordingly, they can be stained blue in the Gram stain. Unlike the Gram-negative bacteria, they have only a thick outer peptidoglycan layer of murein and no additional cell membrane on their outer surface. Many representatives of the Bacillaceae belong to the aerobic spore-forming group. When sufficient oxygen is present, the bacteria form spores. These enable the bacteria to survive even under unfavorable conditions. This makes the bacteria more resistant to environmental influences. In their spore form, the Bacillaceae can even survive in 70% alcohol.
Occurrence, distribution, and characteristics
Bacillaceae are obligate aerobes. This means that they can only exist under oxygen-rich conditions, and they also reproduce only when enough oxygen is available. Bacillaceae live primarily in humus-rich soil. However, the bacteria are also found in water, in dust, in the air and in the intestinal tract of animals and humans. Thus, they make up a large part of the so-called normal flora. Normal flora refers to the totality of all microorganisms living in or on the body of a living being. The transmission of pathogens usually occurs through direct contact. For example, the bacterium Bacillus anthracis is transmitted through ingestion of contaminated meat. However, ingestion is also possible through inhalation of infected spores or particles. The anthrax pathogen can still multiply in the carcass or pass into the spore stage even after the death of the infected animals. Therefore, animals infected with Bacillus anthracis must be incinerated. Otherwise, other animals could become infected. In the case of the pathogen Bacillus subtilis, infection also occurs through direct contact. In most cases, people become infected by eating contaminated food. Similar to the pathogen Bacillus anthracis, infection is also possible through [[inspiration|inhalation|| of infected spores or particles.
Diseases and symptoms
Bacillaceae can be apathogenic, facultative pathogenic, or obligate pathogenic to humans. Apathogenic bacteria such as Bacillus sporothermodurans are not dangerous to humans. Facultative pathogens such as Bacillus subtilis cause disease primarily in people with suppressed immune systems. Obligate pathogens can cause infections even in people who are actually healthy. Bacillus subtilis belongs to the facultative pathogens. In rare cases, the bacterium can cause non-specific food poisoning. Enzymes in the pathogen that convert proteins contained in food to biogenic amines are responsible for this. This leads to the typical symptoms of vomiting and diarrhea. In case of food poisoning by Bacillus subtilis, penicillins are used for treatment. However, the disease is usually self-limiting, so in most cases no medication is given. The situation is different with Bacillus anthracis, the causative agent of anthrax. Anthrax occurs rather rarely in northern Europe and in North America. It usually affects people who are in close contact with animals. In Europe, sheep and cows in particular are carriers of anthrax. Farmers and veterinarians, for example, are therefore at risk. Clinically, anthrax can be divided into three forms: Intestinal anthrax, cutaneous anthrax, and pulmonary anthrax. The most common course is cutaneous anthrax. After infection, an itchy papule develops on the skin. The surrounding skin is swollen. In the course, this papule decays and a black necrosis forms in the center. In addition, blisters appear around the papule. These are also called pustulae malignae. In intestinal anthrax, a severe gastrointestinal inflammation develops with mucous, later also bloody diarrhea.Massive multiplication of Bacillus anthracis in the intestine results in ulcers and disintegration of the lymph nodes in the abdomen. The most severe form of progression is pulmonary anthrax. The infection begins with flu-like symptoms. Subsequently, a rapidly progressing pneumonia with severe respiratory distress and fever develops very quickly. Exposure to the bacterial toxins also inflames the mediastinum. The prognosis is unfavorable even with very early treatment. The disease is often lethal. The other forms of the disease can also be fatal due to blood poisoning (sepsis) or damage to the organs. Anthrax is treated with antibiotics administered orally or intravenously. The pathogen Bacillus cereus occurs primarily in raw rice and survives cooking. Especially if the rice is kept warm or reheated, the bacteria multiply rapidly. Bacillus cereus forms two different toxins. The emetic toxin (cereulide, vomiting toxin) causes vomiting and nausea after one to six hours. Rarely, affected individuals also suffer from diarrhea and abdominal cramps. The diarrhea toxin causes watery diarrhea 8 to 17 hours after ingestion of the contaminated food. These usually subside after one day at the latest.
