Pseudomonas Dr. Dalia M. Mohsen Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

General Characteristics Widely distributed in soil and water Gram negative rods Aerobic Motile Produce water-soluble pigments Opportunistic pathogens Dr. Dalia M. mohsen

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 . Dr. Dalia M. mohsen

P. aeruginosa Forms 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. Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

Characteristics of Pseudomonas aeruginosa Motile (by single or multiple polar flagella) gram-negative rods Obligate (strict) aerobes (most strains) Oxidase (usually) and catalase positive Nonfermentative chemoheterotrophic respiratory metabolism Dr. Dalia M. mohsen

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 Dr. Dalia M. mohsen

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 Dr. Dalia M. mohsen

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 Dr. Dalia M. mohsen

What antibiotics to use Aminoglycosides Gentamycin, Amikacin, Cephalosporins Cefotaxime. Ceftazidime. Ofloxacin, Piperacillin, ticarcillin Local application, colistin, polymyxin Dr. Dalia M. mohsen

Pathogenicity Blue pus Causing the nosocomial infection Suppurative otitis Localised and generalised infections Urinary tract infection after catheterization Dr. Dalia M. mohsen

P. aeruginosa Pathogenesis 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). Dr. Dalia M. mohsen

Infection of Equipment's Respirators Endotracheal tubes Can be Infected All equipment's to be sterilized Dr. Dalia M. mohsen

Toxins and enzymes in pseudomonas 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 Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

Identification with Chromagar 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. Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

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. Dr. Dalia M. mohsen

Thank You Dr. Dalia M. mohsen