Most common Gram negative organism in cystic fibrosis?
Correct Answer: Pseudomonas
Description: ANSWER: (A) PseudomonasREF: Jawetz Microbiology, 24th Ed Ch. 17P aeruginosa is a cause of community acquired pneumonia in patients with bronchiectasis or cystic fibrosis.Cultures from patients with cystic fibrosis often yield P aeruginosa organisms that form mucoid colonies as a result of overproduction of alginate, an exopolysaccharide. In cystic fibrosis patients, the exopolysaccharide appears to provide the matrix for the organisms to live in a biofilm.P aeruginosa is an obligate aerobe that grows readily on many types of culture media, sometimes producing a sweet or grape-like or com taco-like odor. P aeruginosa forms smooth round colonies with a fluorescent greenish color. Many strains of P aeruginosa also produce the fluorescent pigment pyoverdin, which gives a greenish color to the agar. It often produces the nonfluorescent bluish pigment pyocyanin, which diffuses into the agar. Some strains produce the dark red pigment pyorubin or the black pigment pyomelanin.P aeruginosa is pathogenic only when introduced into areas devoid of normal defenses, eg, when mucous membranes and skin are disrupted by direct tissue damage; when intravenous or urinary catheters are used; or when neutropenia is present, as in cancer chemotherapy. The bacterium attaches to and colonizes the mucous membranes or skin, invades locally, and produces systemic disease.P aeruginosa produces infection of wounds and bums, giving rise to blue-green pus; meningitis, when introduced by lumbar puncture; and urinary tract infection, when introduced by catheters and instruments or in irrigating solutions.
Category:
Microbiology
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