Pseudomonas aeruginosa: Introduction, Identification Features, Keynotes, and Pseudomonas Footages

Introduction of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a widely distributed environment like in soil and water, Gram-negative rods, aerobic, motile due to having a polar flagellum, non-sporing, non- capsulated but many strains have mucoid slime layer, produce water-soluble pigments and opportunistic pathogens of size 1.5 – 3µm x 0.5 µm. An isolate of Cystic fibrosis patients has an abundance of extracellular polysaccharides composed of alginate polymers and it escapes the defense mechanisms by loose capsules in which microcolonies of the bacillus are enmeshed and protected from host defense. It forms round colonies with fluorescent greenish color, sweet odor, and hemolysis on blood agar. Pyocyanin (non-fluorescent bluish pigment); pyoverdin (fluorescent greenish pigment); pyorubin (reddish-brown pigment), and pyomelanin (brown to black pigment). Some strains have a prominent capsule (alginate) and it is the etiological agent of blue pus formation, nosocomial infection, suppurative otitis, localized and generalized infections, Urinary tract infection (UTI) after catheterization, iatrogenic meningitis and post tracheostomy pulmonary infections.

Biochemical Reactions of Pseudomonas aeruginosa

Basic Features	Properties
1. Gram Staining	Gram-Negative Rods (GNRs)
2. Spore	Non-Sporing
3. Capsule	Variable
4. Motility	Motile (unipolar)
5. Pigment	Positive Blue (pyocyanin) Yellow-green (pyoveridin) Red (pyorubin) and Brown (pyomelanin)
6. Growth in potassium cyanide (KCN) medium	Positive
7. Catalase test	Positive
8. Oxidase test	Positive
9. Nitrate reduction test	Positive
10. MR (Methyl Red) test	Negative
11. VP (Voges- Proskauer) assay	Negative
12. OF (Oxidative-Fermentative) test	Oxidative (obligate aerobes)
13. Gas	Negative
14. H2S production	Negative
15. Indole formation	Negative
16. Urease/ urea hydrolysis test	Variable
17. Citrate/citrate utilization	Positive
18. DNase test	Negative
19. Glucose fermentation	Negative
20. Maltose fermentation	Negative
21. Lactose fermentation	Negative
22. Sucrose fermentation	Negative
23. Xylose fermentation	Negative
24. Mannitol fermentation	Negative
25. Acetate Utilization	Positive
26. ONPG (β-galactosidase)	Negative
27. Phenylalanine Deaminase (PDA)/PPA Test	Negative
28. Lipase test	Positive
29. Esculin Hydrolysis test	Negative
30. Lysine Decarboxylase Test	Negative
31. Ornithine Decarboxylase Test	Negative
32. Arginine Dihydrolase Test	Positive
33. Gelatin Hydrolysis	Positive
34. Cetrimide Test	Positive
35. Lecithinase	Negative

Keynotes on Pseudomonas

• There are 6 different types of Pseudomonas aeruginosa colonies that may be observed are-

Type	Colony Morphology
1	Large and leafy
2	Smooth, circular, and coliform type
3	Rough type
4	Rogose type
5	Mucoid due to exopolysaccharide
6	Dwarf and smallest

• It also grows in antiseptic bottles like dettol as cetrimide as a selective medium and sensitive to acids silver salts, beta glutaraldehyde.
• The people who are on ventilators, using the medical devices (catheters) with wounds from surgery or burns are more prone the Pseudomonas infections.

Pseudomonas Footages

Pseudomonas aeruginosa typical colony morphology on MacConkey agar

Pseudomonas aeruginosa biochemical tests in TSI, SIM, Urea and Citrate agar Demonstration

Pseudomonas aeruginosa growth on thioglycollate broth showing pellicle formation of growth on aerobic surface

Gram-negative rods or bacilli of Pseudomonas aeruginosa in Gram staining of culture

Oxidase test of Pseudomonas aeruginosa positive demonstration

Antibiotic Susceptibility Testing (AST) Pattern of Pseudomonas aeruginosa

Pseudomonas aeruginosa and Klebsiella pneumoniae colony morphology on MacConkey agar plate

Mucoid strain of P. aeruginosa growth on MacConkey agar

Pyoverdin pigment of Pseudomonas aaeruginosa strain on nutreint agar plate

Pyocyanin and pyorubin pigments of Pseudomonas aeruginosa strains on nutrient agar plate

Non-lactose fermenter (NLF) colony of Pseudomonas aeruginosa on MacConkey agar of clinical specimen pus culture

Pseudomonas aeruginosa growth on blood agar of pus culture

UTI Due to Pseudomonas Infection

Pseudomonas aeruginosa Antibiogram

Further Reading

1.  Textbook of Diagnostic Microbiology. Editors: Connie R. Mahon, Donald G. Lehman & George Manuselis, 3rd edition2007, Publisher Elsevier.
2. Cowan & Steel’s Manual for identification of Medical Bacteria. Editors: G.I. Barron & R.K. Felthani, 3rd ed 1993, Publisher Cambridge University Press.
3. https://www.himedialabs.com/TD/M936.pdf
4. Bailey & Scott’s Diagnostic Microbiology. Editors: Bettey A. Forbes, Daniel F. Sahm & Alice S. Weissfeld, 12th ed 2007, Publisher Elsevier.
5. Clinical Microbiology Procedure Handbook Vol. I & II, Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
6. Colour Atlas and Textbook of Diagnostic Microbiology. Editors: Koneman E.W., Allen D.D., Dowell V.R. Jr, and Sommers H.M.
7. Jawetz, Melnick and Adelberg’s Medical Microbiology. Editors: Geo. F. Brook, Janet S. Butel & Stephen A. Morse, 21st ed 1998, Publisher Appleton & Lance, Co Stamford Connecticut.
8. Mackie and Mc Cartney Practical Medical Microbiology. Editors: J.G. Colle, A.G. Fraser, B.P. Marmion, A. Simmous, 4th ed, Publisher Churchill Living Stone, New York, Melborne, Sans Franscisco 1996.