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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, also known as K. pneumoniae subspecies pneumoniae, rhinoscleromatis, and ozaenae.
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. See Escherichia, Pneumonia
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.
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. See Endotoxin
Klebsiella rhinoscleromatis 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. Klebsiella ozaenae is one cause of chronic rhinitis (ozena), a destructive atrophy of the nasal mucosa, and is infrequently isolated from urinary tract infections and bacteremia. See Medical bacteriology
a genus of capsular nonsporiferous bacteria, the typical representative of which is Klebsiella pneumoniae, or Friedländer’s bacillus, a rodlike (0.3–0.5 × 5 microns) organism that occurs singly or in pairs and is nonmotile, gram-negative, and forms a mucous capsule.
Klebsiella pneumoniae grows well on ordinary nutrient media. On solid media it forms round, convex, shiny, mucoid colonies. It ferments glucose, saccharose, and lactose, forming acid and gas; it does not liquefy gelatin; it sours but does not curdle milk; it does not form either hydrogen sulfide or indole; and it reduces nitrates. Klebsiella pneumoniae is a facultative aerobe. Its optimal growth temperature is 37°C. It inhabits the nasal, oral, and intestinal mucosae of healthy persons, but it is conditionally pathogenic and may produce pneumonia in man. Other Klebsiella produce rhinoscleroma and ozena. Klebsiella cause klebsielloses in many farm animals.
A. A. IMSHENETSKII