2Pseudomonas aeruginosa Also known as burkholderia aeruginosa.Other species of pseudomonas are1. Pseudomonas cepacia2. Pseudomonas maltophilia3. Pseudomonas pseudomallei
3Properties: 1. Pseudomonas is a gram negative rod with polar flagella 2. It is strict or obligate aerobe unlike themembers of enterobacteriacea.Therefore it gets its energy throughaerobic processes and not throughfermentation.3. It is lactose non fermenter
54. Oxidase positive because contains high levels of cytochrome oxidase. 5. It can grow even in tap water with little amount of nutrients.6. It can survive and multiply over a wide temperature range (20 to 42C) in almost any environment, including one with a high salt content.
6P. aeruginosa and cepacia have strong ability to withstand the disinfectants. This property also makes them commonest nosocomial organism.8. Pseudomonas produces two pigments.a. Pyocanin. It gives a blue colour to the pus inwounds.b. Pyoverdin.( Flourescein). A yellow green pigmentwhich flouresces under ultraviolet light.
7Epidemiology: In lab these pigments impart agar a blue green colour P. aerugenosa synthesizes both pigments while others produce only pyoverdin.Epidemiology:The primary habitat of P. aeruginosa is the environment, chiefly found in soil and water.Also found in 10% people as normal flora of colon.
9Infections have resulted from the growth of Pseudomonas in medications, contact lens solutions, and even in some disinfectants.It is responsible for 10-20% nosocomial infections.Commonest cause of hospital acquired gram negative pneumonia.
10Pathogenesis: It mainly causes Pneumonia. UTI. Sepsis in immunocompromized patientsInfections in burnt tissues.Pathogenecity is based on multiple virulence factors.1. Endotoxins. Produce sepsis and septic shock.2. Exotoxins. Two main exotoxins.
11a. Exotoxin Ab. Exotoxin S or Exoenzyme SExotoxin A is the best known. It produces tissuenecrosis. Impairs protein synthesis of the cells.Exoenzyme S is produced by bacteria mainly in burnttissues. It acts by damaging cytoskeleton.P. aeruginosa strains that posses type III secretion system are more virulent.
12Type III secretion systems work through pumps in the bacterial walls Type III secretion systems work through pumps in the bacterial walls. ExoS is transported through this system.
133. Enzymes: Two enzymesElastase.Alkaline Protease are important.They are toxic to tissues and facilitate the invasion of organism into the blood stream.Others include lecithinase and phospholipases.They appear to act together to break down lipids and lecithin.
14Clinical findings: It can cause infection any where in body but commonly it causes 1. UTI2. Pneumonia3. Infection in burn wounds.When disseminates it causes.4. Sepsis5. Necrotic skin lesions called eccthymagangrenosum.
156. Also causes endocarditis in patients on I.V drugs use. 7. Severe external otitis ( malignant otittis externa) and folliculitis in persons using bath tubs and swimming pools.8. Sever osteochondritis of foot9. Corneal infections in contact lens users
16Lab diagnosis: 1. Gram staining. 2. Inoculation of nutrient agar 3. Inoculation of selective medium like Macconkey’s agar or EBM4. Alkaline reaction on TSI agar5. Oxidase test is positive6. Fruity or grape like aroma
17P. aeruginosa isolates may produce three types of colony. 1. Natural isolates from soil or water produce a small, rough colony.2. Clinical samples produce a colony with fried-egg appearance.