Klebsiella pneumoniae is one of the hospital germs. Thus, the bacterium mainly harms people who are already in poor health.
What is Klebsiella pneumoniae?
Klebsiella pneumoniae is a gram-negative human pathogenic rod-shaped bacterium that belongs to the genus Klebsiella. The bacterium belongs to the fast lactose fermenters and is oxidase-negative. It belongs to the Enterobacteriaceae family. Normally, Klebsiella pneumoniae does not have a dangerous effect on humans. However, if a person’s immune system is weakened or if an acute infection is present, the microorganism also shows itself as a pathogen. This primarily results in diseases of the upper respiratory tract, such as pneumonia. In addition to humans, animals can also be affected by Klebsiella pneumoniae. The genus Klebsiella was named after the German physician Edwin Klebs (1834-1913). The first description of Klebsiella pneumoniae was in 1883 by the German microbiologist Carl Friedländer (1847-1887). Friedländer found that the germ was causative of a rare form of pneumonia, which was named Friedländer’s pneumonia. The name for Klebsiella pneumoniae at the time was Diplococcus. Furthermore, the pathogens were also called Friedländer bacteria. In the following years, scientists divided the bacterial species into three subspecies: Klebsiella pneumoniae, Klebsiella ozaenae and Klebsiella rhinoscleromatis. Klebsiella rhinoscleromatis causes rhinoscleroma, which is a granulomatous inflammation of the nasal mucosa. However, pneumonia is also possible due to complications.
Occurrence, distribution, and characteristics
Klebsiella pneumoniae is normally found in the intestines of humans and animals, where it belongs to the intestinal flora. There, the bacterium does not cause disease and is considered harmless. In about one third of the population, Klebsiella pneumoniae is present in the body without causing disease. In addition to the intestine, the oral mucosa is also frequently populated by the bacterial species. All Klebsiella species are considered chemoorganotrophic. Thus, they break down organic matter to obtain energy. In addition, Klebsiella pneumoniae is facultatively anaerobic. If the bacteria have sufficient oxygen, oxidative energy metabolism occurs. In this process, organic matter is oxidized to carbon dioxide (CO2) and water in the absence of oxygen. Under anoxic conditions, 2,3-butanediol fermentation is used to obtain energy. The end products are mainly CO2, the alcohol 2,3-butanediol, and some acids. Klebsiella pneumoniae has the shape of a rod. Spores are not formed by the microorganism. In addition, the bacterium does not have flagella, so it remains immobile. Instead, Klebsiella pneumoniae is equipped with fimbriae (fringes or tassels). A typical feature of the Klebsiella bacterium is an extensive capsule. This causes a thick layer of slime on crops such as an agricultural plate. If aerobic conditions prevail, rapid and pronounced growth occurs. In order to detect and differentiate Klebsiella pneumoniae, a bacterial culture is normally established. This can be done in a liquid culture or on a solid selective culture medium, such as a MacConkey agar. Differentiation of Klebsiella pneumoniae is important against other enterobacteria that are similar to the germ. However, bacterial culture is considered a relatively uncertain method of detection. In serological detection, the bacterium is identified by capsular antigens. Other detection options include a so-called variegated series, which consists of test tubes containing multiple culture media, in which differences in metabolic performance can be detected.
Diseases and ailments
Klebsiella pneumoniae becomes a health hazard only under certain conditions. Therefore, the bacterium belongs to the facultative pathogenic germs. In most cases, it causes nosocomial infections. Klebsiella pneumoniae is responsible for about 10 percent of all Klebsiella infections. People with a weakened immune system are considered to be particularly at risk of contracting the disease. The same applies to newborn babies, as they do not yet have a sufficient immune defense.Since infections with Klebsiella pneumoniae usually occur in hospitals, the bacterium is also one of the hospital germs. There is also resistance to antibiotics. Klebsiella pneumoniae is insensitive to the commonly used antibiotics. Even the reserve drug carbapenem is sometimes used in vain. In recent years, the number of infections with carbapenem-resistant pathogens (CRE), such as Klebsiella pneumoniae, has increased significantly, resulting in several deaths. However, since there is no obligation to report CRE infections in Germany, no exact figures are available. In other regions such as the USA or the Middle East, Klebsiella bacteria have also been widespread for some time and cause life-threatening pneumonia. The fact that there are hardly any therapeutic options available to medicine when carpapanems are no longer effective against pneumonia caused by Klebsiella pneumoniae is considered particularly problematic. The only effective remedy left then is the antibiotic colistin, which, however, can damage nerves and kidneys. There are no other effective antibiotics as yet. The bacterium is also naturally immune to numerous penicillins. Apart from Friedländer’s pneumonia, in which the two upper lobes of the lungs become inflamed, Klebsiella pneumoniae can cause other diseases. These include infections of the urinary tract, meningitis, and life-threatening blood poisoning (sepsis). Sometimes the germ is also spread by air conditioning systems. Other conceivable diseases caused by Klebsiella pneumoniae include sinusitis, pleurisy, lung abscess, bronchitis, otitis media, cholecystitis, cholangitis, osteomyelitis, and endocarditis.
