Pseudomonas aeruginosa produces a number of pigments which diffuse into surrounding medium and they are of following types:
It is a bluish -green phenazine pigment soluble in water and chloroform.
P. aeruginosa only produces this pigment, therefore this is a diagnostic property of this bacterium.
This pigment is a greenish yellow soluble in water but insoluble in chloroform.
other species can also produce this pigment.
This pigment is a reddish brown that is soluble in water and insoluble in chloroform.
It is a brown to black pigment.
It is chemically unrelated to melanin and its production is uncommon.
Above picture is showing pigment produced by Pseudomonas aeruginosa i.e. pyocyanin and pyorubin left to right respectively on nutrient agar.
Scientific classification
Domain: Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Pseudomonadales
Family: Pseudomonadaceae
Genus: Pseudomonas
Species: Pseudomonas aeruginosa
There are 6 different types of Pseudomonas aeruginosa colonies may be observed-
Type 1. Large and leafy
2. smooth, circular and coliform type Type
3. Rough Type
4. rogose Type
5. Mucoid due to exopolysaccharide as shown above image and
Type 6. Dwarf and smallest
Pseudomonas aeruginosa are widely distributed in soil and water, Gram negative rods-,aerobic, motile, produce water-soluble pigments and opportunistic pathogens.
They are slender gram negative bacillus, 1.5 – 3µm x 0.5 µm and active motile due to having a polar flagellum. Non sporing, non- capsulated but many strains have mucoid slime layer. Isolates from Cystic fibrosis patients have abundance of extracellular polysaccharides composed of alginate polymers. They escape the defence mechanisms by loose capsule in which micro colonies of bacillus are enmeshed and protected from host defence. They forms round colonies with a fluorescent greenish color, sweet odor, and hemolysis. Pyocyanin- nonfluorescent bluish pigment; pyoverdin- fluorescent greenish pigment; pyorubin (reddish brown pigment), and pyomelanin (brown to black pigment). Some strains have a prominent capsule (alginate).
They are obligate aerobe, but grow anaerobically if nitrate is available. Growth occurs at wide range of temperatures 6 to 42°C the optimum being 37 °C. Growth on ordinary media producing large opaque irregular colonies with distinctive musty mawkish or earthy smell. Iridescent patches with metallic sheen are seen in cultures on nutrient agar. In broth forms dense turbidity with surface pellicle. Many organic compounds used as carbon and nitrogen sources, but only a few carbohydrates by oxidative metabolism . Glucose used oxidatively and lactose negative on MacConkey’s agar.
Some strains produce diffusible pigments like Pyocyanin (blue), pyoverdin or fluorescein ( greenish yellow), pyorubin (reddish brown) and pyomelanin ( brown to black).
They are oxidative and non- fermentative. Glucose is utilized oxidatively. Indole, Methyl Red (MR) and Voges-Proskauer (VP) and hydrogen sulphide (H2S) tests are negative. Catalase, oxidase, and arginine tests are positive.
Toxic extracellular products in culture filtrates, exotoxin A and S. Exotoxin A acts as NADase resembling Diphtheria toxin. Proteases, elastatese hemolysins and enterotoxin, Slime layer and Biofilms
Important cause of Hospital Infections and important for epidemiological purpose. Serotyping, bacteriocins typing, pyocyanin, restriction endonuclease typing with pulse field gel electrophoresis
They are Killed at 55°C in 1 hour. High resistance to chemical agents. Resistance to quaternary ammonium compounds like chlorxylenol, resistant to hexchlorophenes. They also grow in antiseptic bottles like dettol as cetrimide as selective medium. and sensitive to acids silver salts, beta glutaraldehyde.
They cause blue pus, causing the nosocomial infection, suppurative otitis, localised and generalised infections, Urinary tract infection (UTI) after catheterization,iIatrogenic meningitis, post tracheostomy pulmonary infections etc.
This organism is widely distributed in nature and is commonly present in moist hospitals. It is pathogenic only when introduced into areas devoid of normal defenses, e.g. disruption of mucous membrane and skin, usage of intravenous or urinary catheters, neutropenia (as in cancer therapy). Antigenic structure, proteasesenzymes, and toxins Serine protease, Pili and nonpilus adhesins. metalloprotease and alkaline Capsule (alginate, glycocalyx): protease cause tissue seen in cultures from patients damage and help bacteriawith cystic fibrosis. spreadLPS- endotoxin, multiple phospholipase C: a hemolysinimmunotypes. Exotoxin A: causes tissue Pyocyanin: catalyzes necrosis and is lethal for animals production of toxic forms of (disrupts protein synthesis); oxygen that cause tissue immunosuppressive damage. It also induces IL-8production. Pyoverdin: a Exoenzyme S and T: cytotoxic to siderophore host cells.
This bacterium is of particular concern to individuals with cystic fibrosis who are highly susceptible to Pseudomonas lung infections. It is also of grave concern to cancer and burn patients as well as those people who are immuno-compromised. The case fatality rate for individuals infected with this approaches 50%.
Diagnosis of P. aeroginosa infection depends upon isolation and laboratory identification of the bacterium. It grows well on most laboratory media and commonly is isolated on blood agar or eosin-methylthionine blue agar. It is identified on the basis of its Gram morphology, inability to ferment lactose, a positive oxidase reaction, its fruity odour, and its ability to grow at 42°C. Fluorescence under ultraviolet light is helpful in early identification of P. aeruginosa colonies. Fluorescence is also used to suggest the presence of P. aeruginosa in wounds.
Following antimicrobial agents are useful to get rid of this microorganism and they are gentamycin, amikacin, Cephalosporin, cefotaxime, Ceftazidime, Ofloxacin, Piperacillin, ticarcillin, Piperacillin tazobactum, meropenem, imipenem, tobramycin, colistin B and polymyxin. For local application colistin and polymyxin are also recommended.