Tuesday, August 23, 2011

Klebsiella species

Klebsiella are Gram-negative straight rods about 1-2 µm long and 0.5-0.8 µm wide, with parallel or bulging sides and rounded or slightly pointed ends. The cells are either in pairs end to end or are arranged singly. They are characteristically non-motile and capsulate. This results in the precipitation of complex inorganic salts and flourishing of some bacterial spp. (Clegg and Sebghatti, 2002).

Nosocomial Klebsiella infections are caused mainly by K. pneumoniae, the medically most important species of the genus. To a much leeser degree, K. oxytoca has been isolated from human clinical specimens. It is estimated that Klebsiella species cause 8% of all nosocomial bacterial infections in the United States and in Europe. No great geographical variations in frequency have been noted (Podschun and Ullmann, 1998).

Klebsiella spp. are the second frequently isolated pathogen from different types of nosocomial infections. Klebsiella spp. Are preceded by
E. coli in case of urinary tract infection. On the other types (surgical wound,
pneumonia and septicemia) they are preceded by Staphylococcus aureus
(Lee and Bishop, 1997).

The Gram-negative bacteria of the genera Klebsiella, Enterobacter, and Serratia are important opportunistic pathogens, commonly isolated from
urinary tract infections, nosocomial pneumonia, surgical wounds, and blood
stream infections, mostly in intensive care unit patients. The majority of the
strains involved are highly resistant to an increasing number of antibiotics, as shown by the emergence of several extended spectrum β-lactamases in Klebsiella species nosocomial isolates (Livrelli et al., 1996).

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