Pseudomonas for MBBS students

1. Pseudomonas
Dr Kamlesh Patel
MBBS MD DCP
Asst Prof, Microbiology, SAIMS
Founder director, www.jaailab.com

2. Pseudomonas
• Aerobic,
• Non spore 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 by Pseudomonas
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

5. Greenish pus

6. Pseudomonas Keratitis and
Corneal Ulceration
Pseudomonas can invade
intact cornea
Malignant Otitis Externa
Mind the word malignant

7. Nosocomial infections
• Fourth most 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
• It is 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
Virulence Factors (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
• Gram Stain:??
• Motility:??

13. Culture and Sensitivity
Growth requirements:
• 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 green phenazine 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

15. Pyocyanin
Pyoverdin

16. Biochemical reaction
• Lactose Non 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 resistance to 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
• Pseudomonas aeruginosa 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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