Klebsiella

Klebsiella
A genus of gram-negative, nonmotile bacteria. Characteristic large mucoid colonies are due to production of a large amount of capsular material. Species of Klebsiella are commonly found in soil and water, on plants, and in animals and humans. Harmless strains of Klebsiella are beneficial because they fix nitrogen in soil. Pathogenic species include K. pneumoniae, K. rhinoscleromatis, and K. ozaenae.
Klebsiella may produce E. coli-like enterotoxins and cause acute gastroenteritis in infants and young children. Enteric illnesses due to Klebsiella are more predominant where populations are more crowded and conditions less sanitary. Other virulence factors of Klebsiella include a relatively high ability to survive and multiply outside the host in a variety of environments, and its relatively simple growth requirements.
K. pneumoniae is present in the respiratory tract and feces of about 5% of normal individuals. It causes a small proportion (about 1%) of bacterial pneumonias. K. pneumoniae can produce extensive hemorrhagic necrotizing consolidation of the lung. It occasionally produces urinary tract infection and bacteremia with focal lesions in debilitated patients. Other enterics also may produce pneumonia. K. pneumoniae and Klebsiella oxytoca cause hospital-acquired infections ( nosocomial infections) .
Klebsiella pneumoniae is the second most frequently isolated colon-related bacterium in clinical laboratories. The carbohydrate-containing capsule of Klebsiella promotes virulence by protecting the encased bacteria from ingestion by leukocytes; nonencapsulated variants of Klebsiella do not cause disease. Capsular types 1 and 2 cause pneumonia; types 8, 9, 10, and 24 are commonly associated with urinary tract infections.
Klebsiella accounts for a large percentage of hospital-acquired infections, mostly skin infections (in immunocompromised burn patients), bacteremia, and urinary tract infections. It is also the most common contaminant of intravenous fluids such as glucose solutions and other medical devices.
Two other klebsiellae are associated with inflammatory conditions of the upper respiratory tract: Klebsiella ozaenae has been isolated from the nasal mucosa in ozena, a fetid, progressive atrophy of mucous membranes and it is one cause of chronic rhinitis (ozena), a destructive atrophy of the nasal mucosa, and is infrequently isolated from urinary tract infections and bacteremia
and Klebsiella rhinoscleromatis from rhinoscleroma, a destructive granuloma of the nose and pharynx. It is causes rhinoscleroma, a chronic destructive granulomatous disease of the upper respiratory tract that is most common in eastern Europe, central Africa, and tropical South America.
Members of the Klebsiella genus typically express 2 types of antigens on their cell surface. The first, O antigen is a component of the lipopolysaccharide (LPS), of which 9 varieties exist. The second is K antigen, a capsular polysaccharide with more than 80 varieties. Both contribute to pathogenicity and form the basis for serogrouping.