Neisseria are bacteria belonging to the group of gram-negative bacteria. They belong to the Neisseriaceae family.
What are Neisseria?
Neisseria bacteria are so-called proteobacteria. They form a separate group within the Neisseriaceae and belong to the Gram-negative bacteria. Gram-negative bacteria appear red in the Gram stain. In contrast to Gram-positive bacteria, they do not have a cell wall, but are only coated with a thin layer of murein. The distinction between gram-positive and gram-negative is crucial for choosing the right antibiotic. The group of bacteria was discovered by bacteriologist Albert Neisser. He was the first bacterium in the group to discover the gonorrhea pathogen, Neisseria gonorrhoeaea. Neisseria exist as diplococci. Cocci are spherical bacteria. Diplococci are stored in pairs. Among the many different species of Neisseria are four that are pathological to humans: Neisseria gonorrhoeae, Neisseria flavescens, Neisseria meningitidis, and Neisseria sicca.
Occurrence, distribution, and characteristics
Neisseria gonorrhoeae, the causative agent of gonorrhea (gonorrhea), is distributed worldwide. Gonorrhea is one of the most common sexually transmitted infections (STIs), with more than 100 million cases worldwide each year. The disease predominantly affects people between 15 and 25 years of age. In Germany, about 14 out of every 100,000 inhabitants contract the disease every year. Humans are the only known pathogen reservoir for Neisseria gonorrhoeae. Transmission occurs only through direct mucosal contact. This occurs, for example, during sexual intercourse or during the birth process. Neisseria gonorrhoeae feels particularly at home in the cells of the female and male urethra, in the uterine canal, in the rectum and in the conjunctiva of the eye. The causative agent of purulent meningitis, Neisseria meningitidis, is also found worldwide. The bacteria are also known as meningococci. Humans are also the only host for Neisseria meningitidis. Outside the body, the pathogens die quickly. Thus, very close contact is required for infection. Transmission usually occurs through nasopharyngeal secretions. Thus, the pathogen is transmitted when sneezing, kissing, or coughing on someone. Meningococci can attach to the mucous membranes in the nasopharynx with small pili and remain there for weeks or months. When the immune system is weakened, the bacteria multiply, penetrate the mucous membranes and enter the brain through the blood. There they can cause meningitis. Blood poisoning caused by the pathogens is feared. Neisseria flavescens and Neisseria sicca both live in the mucous membranes of the upper respiratory tract. It is not yet clear what role they play as pathogens. Neisseria flavescens appears in many different inflammations. Neisseria sicca appears to be involved in meningitis.
Diseases and conditions
Infection with Neisseria gonorrhoeae results in the development of gonorrhea, colloquially known as gonorrhea. It is one of the sexually transmitted diseases. The incubation period is two to three days. In individual cases, however, a week may pass. Five percent of infected persons do not develop any symptoms. In particular, these symptomless carriers of the disease play a decisive role in the spread of gonorrhea. In men, the disease is usually manifested by inflammation of the urethra (urethritis). There is itching and purulent discharge. The inflammation makes urination painful (alguria). Without treatment, the inflammation of the urethra lasts for two months. In rare cases, the epididymis or prostate may also become inflamed. Infertility may also develop. In women, the first symptoms appear after about ten days. In addition to inflammation of the urethra, there is usually also inflammation of the cervix. Both inflammations cause a purulent discharge. Rarely, the vaginal mucosa or Bartholin’s glands are also inflamed. The uterus and fallopian tubes can become stuck due to the infection, which can lead to infertility. Gonococcal infection of the eyes is very rare in adults. However, gonoblennorrhea can develop in newborns who have contracted it from their mothers. Gonoblennorrhea is a purulent conjunctivitis that can lead to blindness.To prevent this, children are given antibacterial eye drops after birth (Credé prophylaxis). Meningococci (Neisseria meningitidis) can cause meningitis. The disease can be mild and heal spontaneously or take a highly acute course with a fatal outcome. The disease begins with high fever, vomiting, chills, and convulsions. A characteristic symptom of meningitis is neck stiffness. Opisthotonus is also commonly observed. Opisthotonus is a spasm of the back muscles that results in hyperextension of the trunk and legs. Infants are also noticeable for apathy or restlessness. They refuse food and are sensitive to touch and light. A feared complication of meningococcal meningitis is Waterhouse-Friderichsen syndrome. As they decay, meningococci release endotoxins. This process results in activation of the coagulation system with massive thrombus formation in the blood vessels. Due to the thrombotic occlusion of the vessels, the peripheral areas are not supplied with sufficient blood. In addition, clotting depletes the clotting factors in the blood. This leads to severe bleeding into the skin, mucous membranes and internal organs. The adrenal cortex is particularly severely affected. It can be completely destroyed, resulting in an acute deficiency of the hormone cortisol. Without a direct start of therapy, almost 100 percent of patients die.
