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The bacterial genus Pseudomonas includes plant pathogenic bacteria such as P. syringae (various patovars), the human pathogen P. aeruginosa, and some species that are known to cause problems in dairy products. However, the actions of this group of bacteria are mainly considered as beneficial or neutral to man. In recent times, members of the Pseudomonas have been used as biocontrol agents.

Pseudomonas aeruginosa

Found in the soil, sweage and water. Some are commensals in the intestine, others cause urinary tract infection, wound infection and otitis media. The organism is highly resistant to antibiotics and causes chronic infections specially in debiliated, old and hospitalized patients with low defence mechanisms.


Gram negative motile bacilli.

Cultural characteristics

They are aerobes that grow on nutrient agar leading to greenish discoloration of the medium due to its diffusible exopigment which consists of pyocyanin (blue green) and fluorescein (yellow).

Biochemical characteristics

Oxidase positive and does not ferment any sugar.

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