DR. DALIA M. MOHSEN 1

Dr. Dalia M. Mohsen

PSEUDOMONAS

DR. DALIA M. MOHSEN 2

PSEUDOMONAS• A large group of aerobic, non sporing gram

negative bacteria motile by polar flagella• Found in water, soil, other moist environments

• Some of them are pathogenic to plants.

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- Widely distributed in soil and water

- Gram negative rods- Aerobic- Motile- Produce water-soluble

pigments• Opportunistic pathogens

GENERAL CHARACTERISTICS

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MORPHOLOGY• They are slender gram negative bacillus, 1.5 – 3 microbes x 0.5

microns

• Monoflgellar ?

• Non capsulated but many strains have mucoid slime layer

• Escape the defence mechanisms by loose capsule .

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P. aeruginosaForms round colonies with a fluorescent greenish color, sweet odor, and b-hemolysis.

Pyocyanin- nonfluorescent bluish pigment;

pyoverdin- fluorescent greenish pigment;

pyorubin, and pyomelanin

Some strains have a prominent capsule (alginate).

Identification of P. aeruginosa is usually based on oxidase test

and its colonial morphology: b-hemolysis, the presence of

characteristic pigments and sweet odor, and growth at 42 oC.

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CULTURAL CHARACTERS• Obligate aerobe, but grow anaerobically if nitrate is

available

• Growth occurs at wide range of temperatures 6-42 c the optimum being 37 c

• patches with metallic sheen are seen in cultures on nutrient agar.

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Motile (by single or multiple polar flagella) gram-negative rods

Obligate (strict) aerobes (most strains)Oxidase (usually) and catalase

positiveNonfermentative chemoheterotrophic

respiratory metabolism

Characteristics of Pseudomonas aeruginosa

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PIGMENT PRODUCTION Some strains produce diffusible pigments: • Pyocyanin (blue); fluorescein (yellow);

pyorubin (red) P. aeruginosa produces characteristic

grape-like odor and blue-green pus & colonies

Broad antibiotic resistance

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BIOCHEMICAL REACTIONS• Oxidative and Non fermentative• Glucose is utilized oxidatively• Indole, MR and VP and H2S tests are

negative• Catalase, Oxidase, and Arginine tests

are positive

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TYPING AND IMPORTANCE• Important cause of Hospital Infections

• Important for epidemiological purpose

• Serotyping

• Bacteriocins typing

• Pyocyanin

• Aeruginosin typing

• Restriction endonuclease typing with pulsed gel electrophoresis

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WHAT ANTIBIOTICS TO USE• Aminoglycosides• Gentamycin, Amikacin, Cephalosporins • Cefotaxime. Ceftazidime. Ofloxacin,• Piperacillin, ticarcillin• Local application, colistin, polymyxin

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PATHOGENICITY• Blue pus

• Causing the nosocomial infection

• Suppurative otitis

• Localised and generalised infections

• Urinary tract infection after catheterization

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P. aeruginosaPathogenesis and Immunity

This organism is widely distributed in nature and is commonly present in moist environments in hospitals. It is pathogenic only when introduced into areas devoid of normal defenses, e.g.,

1. Disruption of mucous membrane and skin.

2. Usage of intravenous or urinary catheters.

3. Neutropenia (as in cancer therapy).

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• Respirators• Endotracheal

tubes• Can be Infected • All equipment's to

be sterilized

INFECTION OF EQUIPMENT'S

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• 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

TOXINS AND ENZYMES IN PSEUDOMONAS

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PSEUDOMONAS PROMINENT HOSPITAL ACQUIRED INFECTIONS

It causes urinary tract infections,• respiratory system infections,

• dermatitis, soft tissue infections, bacteraemia,

• bone and joint infections,

• gastrointestinal infections

• variety of systemic infections, particularly in patients with severe burns and in cancer and AIDS patients who immunosuppressed.

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DIAGNOSIS OF P.AEROGINOSA INFECTION

Diagnosis of P,aeroginosa infection depends Isolation and laboratory identification of the bacterium.

(blood agar or eosin-methylthionine blue agar). Inability to ferment lactose, a positive oxidase reaction,

its fruity odour, and its ability to grow at 42°C. Fluorescence under ultraviolet light. Fluorescence is

also used to suggest the presence of P. aeruginosa in wounds.

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Pseudomonas sp. develop as blue-green coloured colonies, clearly visible under normal lighting conditions.

Other bacterial species are inhibited or give colourless colonies. Pseudomonas aeruginosa, Pseudomonas fluorescens, all give typical blue-green colony colouration and can be studied directly by serotyping or biochemical methods.

IDENTIFICATION WITH CHROMAGAR

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TREATING PSEUDOMONAS INFECTIONS

Combined antibiotic therapy is generally required to avoid resistance that develops rapidly when single drugs are employed.

Avoid using inappropriate broad-spectrum antibiotics, which can suppress the normal flora and permit overgrowth of resistant pseudomonads.

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PSEUDOMONAS AERUGINOSA A RESISTANT PATHOGEN

• Pseudomonas aeruginosa is frequently resistant to many commonly used 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. Several types of vaccines are being tested, but none is currently available for general use.

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P. aeruginosa

Prevention and Control

Pseudomonas spp. normally inhabit soil, water, and vegetation and can be isolated from the skin, throat, and stool of healthy persons.

Spread is mainly via contaminated sterile equipment's and cross-contamination of patients by medical personnel.

High risk population: patients receiving broad-spectrum antibiotics, with

leukemia, burns, cystic fibrosis, and immunosuppression. Methods for control of infection are similar to those for other nosocomial pathogens. Special attention should be paid to sinks, water baths, showers, hot tubs, and other wet areas.

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Thank You