Klebsiella Pneumoniae: An Explanation of the Bacteria

Klebsiella is a genus, named after a German microbiologist Edwin Klebs (1834 to 1913), of a rod shaped, gram negative, oxidase negative, non-motile bacteria with a prominent polysaccharide based capsule. It belongs to Enterobacteriaceae family.

You will find two types of antigens on the surface of the Klebsiella’s cell, capsular polysaccharide (K antigen) and lipopolysaccharide (O antigen); both have a major role in contributing to pathogenicity.

Phagocytosis by polymorphonuclear granulocytes and the bactericidal result of serum influence the host defense against bacterial invasion which is mainly mediated by complement proteins.

According to preclinical studies, neutrophil myeloperoxidase and lipopolysaccharide-binding protein plays a vital role in host defense against K pneumonia infection. To mediate oxidative inactivation of Elastase, an enzyme involved in the pathogenesis of different tissue destroying infections, neutrophil myeloperoxidase plays an important part.

Bacteria devise so many means to defeat the host immune system because of the polysaccharide capsule. Its layer provides protection from phagocytosis by polymorphonuclear granulocytes and avoids bacterial death from bactericidal serum factors.

Klebsiella is found everywhere in the nature and is commonly reside in the skin, gastroinytestinal tract or pharynx, sterile wounds and urine of the humans.

Two members of the genus called K pneumoniae cause most human infections and K oxytoca and they are prominent in the mammalian mucosal surfaces. The major causes of pathogenic infections are the hands of hospital staff and the gastrointestinal tract of the patients.

Klebsiella generally attacks the middle or old aged people suffering from diabetes or alcoholism and the infection usually begins to start in lungs causing severe damage.

Another prominent infection caused by Klebsiella is nosocomial infection, which normally affects the biliary tract, urinary tract and lower respiratory tract or surgical wound areas. The major reasons for this infection are urinary catheters, use of antibiotics, pollution of respiratory support equipment and invasive apparatus. There are two other rare infections which are caused by Klebsiella, i.e. ozena and rhinoscleroma.

It has been seen that the usage of antibiotics in hospitals paves the way for Klebsiella which results in the appearance of multidrug strains. These strains have the ability to spread quickly and are very powerful.

There are certain other factors that contribute in spreading the infection, which are weak health status, venous catheter, indwelling catheter and feeding tube. However, it has become a matter of major debate in many hospitals on the use of such species along with other antibiotics, which are responsible of transferring plasmids to other organisms.

K pneumonia and neonatal septicemia are common all over the globe but K rhinoscleromatis is not very common worldwide. It is rare in United States as well. Some cases of this infection have been seen in Latin America, Central Africa, Eastern Europe and Southern Asia.

As far as mortality rate is concerned for K pneumonia, it has a mortality rate of 50% in case of antimicrobial therapy, while for people with bacteremia and alcoholism; the mortality rate for K pneumonia is 100%.

Article by Tauqeer ul Hassan

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