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Pseudomonas aeruginosa [autosaved]
Pseudomonas are aerobic, non-spore forming, gram-negative bacilli that can cause opportunistic infections in humans and other hosts. Pseudomonas aeruginosa is a common cause of nosocomial infections and can infect the urinary tract, lungs, blood, and other sites. It is resistant to many antibiotics but can be treated with combinations including gentamicin and carbenicillin. Pseudomonas produces pigments like pyocyanin and pyoverdin and secretes toxins and enzymes that contribute to its virulence and ability to infect compromised hosts like burn patients.
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Pseudomonas aeruginosa [autosaved]
- 1. Pseudomonas Dr Kamlesh Patel MBBSMD DCP Asst Prof, Microbiology, SAIMS Founder director, www.jaailab.com
- 2. Pseudomonas • Aerobic, • Nonspore forming • Gram negative bacilli • Causing opportunistic infections in human, animals, plants and insects. • Common species responsible for human infections are: – Pseudomonas aeruginosa, – Burkholderia – Stenotropomonas
- 3. Pseudomonas aeruginosa • Aerobic,GNB • Size 1.5- 3 microns x 1.5microns. • Motile by polar Flagella. • Found In nature water, soil, other moist Environments • Common cause of nosocomial infections
- 4. Infections caused byPseudomonas Localised and generalised infections •Greenish pus •Suppurative otitis externa (Malignant Otitis Externa) •Infantile diarrhoea •Disabling eye Infections (Survive with minimal nutrients) Nosocomial infection •Urinary tract infection after catheterization •Iatrogenic meningitis •Post tracheostomy Pulmonary infections •Septicaemia •Endocarditis •Ecthyma gangrenous •VAP Special Concern of Pseudomonas infection in: •Cystic fibrosis patients •Burn patients •Hospitalised patients
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- 6. Pseudomonas Keratitis and CornealUlceration Pseudomonas can invade intact cornea Malignant Otitis Externa Mind the word malignant
- 7. Nosocomial infections • Fourthmost common isolated nosocomial pathogen. • Patient-to-patient spread or • Direct patient contact with: – Environmental reservoirs (ex. Flowers, water, other inert material) – Disinfectants – Respiratory equipment, – Food, – Sinks, taps
- 8. Ecthyma Gangrenosum • Itis a well circumscribed cutaneous lesion. • A type of of severe, invasive infection by Pseudomonas aeruginosa. • Usually seen in: – Immunocompromised and – Burn patients and – Other critically ill patients
- 9. Structure and Virulence VirulenceFactors (structural components) • “Alginate” • Adherence proteins and “pili • Lipopolysaccharide (LPS) • Pyocyanin Virulence Factors (toxins and enzymes): • Exotoxin A • Exoenzyme S • Endotoxins • Phospholipase C • Elastase and Alkaline Protease
- 10. Mechanism of pathogenesis Adhesion –Pile, flagella and fimbriae Invasion – Extracellular enzymes and toxins (proteases, elastase, phospholipases, Exotoxin A) Dissemination – Leukocidin, inhibits neutrophils und leukocytes Protection – Capsule (Alginate): Mucoid strain specially causes infection in Cystic fibrosis patients.
- 11. Diagnosis • Samples: – Urine –Pus – Sputum – Implant – Swab • Like any other infections by bacteria the modes of diagnosis are same: 1. Microscopy: Gram stain, Motility. 2. Culture and Sensitivity (C/S). 3. Serological evaluation of toxins and enzymes or antigens. 4. Molecular diagnosis.
- 12. 1. Microscopy • GramStain:?? • Motility:??
- 13. Culture and Sensitivity Growthrequirements: • Obligate aerobe, Wide range of temperature 5°c- 42°c, optimum 37°c • Can grow anywhere even in antiseptic solutions. (Hence, no special requirements) Cultural characteristics 1. Nutrient Agar (Ordinary media) • Large, opaque, irregular, with distinctive colonies with metallic sheen and sweetish aromatic smell (odour) with a greenish blue color. 2. Blood agar • beta hemolysis. 3. MacConkey agar • Pale coloured colony (Lactose non-fermenter) Identification of P. aeruginosa is usually based on oxidase test and its colonial morphology: b-hemolysis, the presence of characteristic pigments and sweet odor with oxidase positive.
- 14. Pigments Pyocyanin – Bluish greenphenazine pigment – Soluble in chloroform and water – Only produced by P aeruginosa Pyoverdin(fluorescein) – It is a greenish yellow pigment – Insoluble in chloroform but soluble in water – Produced by many other species (ex. P aeruginosa and P putida) Pyorubin – Reddish brown pigment – Insoluble in chloroform but soluble in water pyomelanin – Brown to black pigment – Production is uncommon
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- 16. Biochemical reaction • LactoseNon fermenter (pale colonies on Mac) • Oxidative: Positive • Catalase: Positive • Glucose is utilized oxidatively (*TSI) • IMVpC: ?? • Urease ?? • Triple Sugar Iron (TSI): ?? • Nitrate reduction: positive
- 17. Sensitivity • High resistanceto chemical agents like: – Quaternary ammonium compounds.Chlor-xylenol – Resistant to Hexachlorophenes – Hence, can grow in antiseptic bottles • Sensitive to acids silver salts, beta glutaraldehyde
- 18. Antibiotic Sensitivity • Pseudomonasaeruginosa a resistant pathogen – resistant to many commonly used antibiotics. – List of antipseudomonal antibiotics – Although many strains are susceptible to gentamicin, tobramycin, colistin, and amikacin, resistant forms have developed. – The combination of gentamicin and carbenicillin is frequently used to treat severe Pseudomonas infections.
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