Diplococci are bacteria that are visible as paired spheres under the microscope. They belong to the streptococcus family and can cause various diseases in humans.
What are diplococci?
Diplococci are a form of cocci. Cocci, in turn, are spherical bacteria that can be completely round or egg-shaped. Cocci are recognized in medical terminology by the suffix “coccus.” For example, there are the bacteria Enterococcus, Streptococcus or Staphylococcus. If cocci do not separate after a cell division, different organizational patterns can arise. Thus, a distinction can be made between parcel cocci, streptococci, chain cocci, staphylococci and diplococci. While streptococci are stored in chains, diplococci lie together in pairs. Depending on the classification, diplococci are also counted as streptococci. This is explained by the fact that paired diplococci are a chain with two links. Diplococci include, for example, pneumococci, meningococci, and the bacteria Neisseria gonorrhoeae and Neiserria meningitidis (meningococci). These pathogens can cause disease in humans. However, there are also so-called apathogenic diplococci. Apathogenic bacteria have no disease value for humans. The individual cocci can be distinguished by their staining behavior in the Gram stain. Thus, there are both Gram-positive and Gram-negative diplococci. While the pathogen Streptococcus pneumoniae (pneumococcus) belongs to the Gram-positive diplococci, Neisseria are Gram-negative diplococci.
Occurrence, distribution, and characteristics
The various diplococci have different distributions. The pathogen reservoir for the bacterium Neisseria gonorrhoeae is humans. The pathogen is transmitted via sexual intercourse or during childbirth. Neisseria meningitidis live intracellularly and preferentially colonize the pharynx-nasal cavity in humans. In about 10 percent of the European population, the pathogen is found in this area. The bacteria can be transmitted from person to person via droplet infection. Kissing is therefore a possible source of infection. Meningococci have small appendages, also called pili, with which they can adhere to the mucous membrane of the nasopharynx for weeks or months. When the immune system is weakened, they multiply, invade the mucous membranes and enter the blood. Pneumococci also feel at home in the mucous membranes of the nose and throat. Although they can be passed from person to person by droplet infection, infections are usually caused endogenously. This means that pneumococcal infections usually develop from bacteria already present in the body. Carriers and vectors of pneumococcus are primarily children one or two years of age. While adults are hardly carriers of the bacteria, colonization increases again with age. In people over 65 years of age, quite a lot of pneumococci are again found in the body.
Diseases and symptoms
Colonization with pneumococci is usually asymptomatic. Eventually, the infestation manifests itself by a mild infection. However, the pathogens weaken the immune system, increasing the likelihood of additional viral infections. However, especially in old age and with a weak immune system, the bacteria can spread in the body. The result is inflammation of the middle ear, sinuses, lungs or meninges. Penumococci are classic pathogens of lobar pneumonia. This is accompanied by fever, pain and difficulty breathing. Ulcus serpens corneae, an ulcer of the cornea in the eye, can also be caused by the pathogens. If the bacterium spreads in the blood, a life-threatening sepsis develops. The bacterium Neisseria meningitidis is the causative agent of bacterial meningitis (meningitis). It develops preferentially in children, adolescents, the elderly and immunosuppressed patients. The leading symptom of meningitis is a very severe headache. These are often accompanied by neck stiffness. Neck stiffness is also known as meningismus in medical terminology. Other symptoms of diplococcal meningitis include photophobia and sensitivity to sound. The classic triad of meningitis consists of meningismus, high fever, and impaired consciousness. However, this characteristic triad is seen in only 45 percent of patients.The bacterium Neisseria gonorrhoeae causes the disease gonorrhea. In colloquial language, this infectious disease is also known as gonorrhea. In men, infection with gonococci can lead to inflammation of the prostate. This prostatitis is manifested by pain during urination, frequent urination with a small amount of urine, blood in the urine, pain during defecation, pain during ejaculation, and a feeling of tightness in the perineal area. Depending on the severity of the inflammation, acute urinary retention may occur, in which patients are unable to urinate. In addition to the prostate, the epididymis is also often affected by the inflammation. Inflammation of the epididymis is called epididymitis. It leads to severe and painful enlargement of the epididymis. When infected with Neisseria gonorrhoeae, a woman develops pelvic and fallopian tube inflammation. Inflammation of the fallopian tubes, also called salpingitis, is manifested by abdominal pain. These increase both during urination and ovulation. Depending on the severity of the inflammation, fever and vaginal discharge may also occur. In newborns who become infected during birth, purulent inflammation of the conjunctiva may occur. This is also known as ophthalmia neonatorum. To prevent this unpleasant condition, which can lead to blindness, mothers with gonococcal infection receive prophylactic medication to protect the baby during birth.
