Pseudomonas basics


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Pseudomonas basics


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Dr.T.V.Rao MD 1 Dr.T.V.Rao MD Pseudomonas


Pseudomonas Dr.T.V.Rao MD 2 A large group of aerobic, non sporing gram negative bacteria motile by polar flagella Found I nature water, soil, other moist environments Some of them are pathogenic to plants Creation of new genera such as Burkholderia. Stenotrophomnonas

General Characteristics:

Widely distributed in soil and water Gram negative rods Aerobic Motile Produce water-soluble pigments Opportunistic pathogens General Characteristics Dr.T.V.Rao MD 3


Morphology Dr.T.V.Rao MD 4 They are slender gram negative bacillus, 1.5 – 3 microbes x 0.5 microns Monoflgellar ? Non capsulated but many strains have mucoid slime layer Isolates from Cystic fibrosis patients have abundance of extracellular polysaccharides composed of alginate polymers Escape the defence mechanisms by loose capsule in which micro colonies of bacillus are enmeshed and protected from host defences.

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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 o C.

Cultural Characters:

Cultural Characters Dr.T.V.Rao MD 6 Obligate aerobe, but grow anaerobically if nitrate is available Growth occurs at wide range of temperatures 6-42 c the optimum being 37 c Growth on ordinary media producing large opaque irregular colonies with distinctive musty mawkish or earthy smell. Iridescent patches with metallic sheen are seen in cultures on nutrient agar. In broth forms dense turbidity with surface pellicle.

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Motile (by single or multiple polar flagella) gram-negative rods Obligate (strict) aerobes (most strains) Oxidase (usually) and catalase positive Nonfermentative chemoheterotrophic respiratory metabolism Minimal nutritional reqts.; Many organic compounds used as C and N sources, but only a few carbohydrates by oxidative metabolism Glucose used oxidatively Lactose negative on MacConkey’s agar Characteristics of Pseudomonas aeruginosa Dr.T.V.Rao MD 7

Pigment Production :

Pigment Production Dr.T.V.Rao MD 8 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

Biochemical reactions:

Biochemical reactions Dr.T.V.Rao MD 9 Oxidative and Non fermentative Glucose is utilized oxidatively Indole, MR and VP and H2 S tests are negative Catalase, Oxidase, and Arginine tests are positive

Typing and Importance:

Typing and Importance Dr.T.V.Rao MD 10 Important cause of Hospital Infections Important for epidemiological purpose Serotyping Bacteriocins typing Pyocyanin Aeruginosin typing Restriction endonuclease typing with pulsed gel electrophoresis


Resistance Dr.T.V.Rao MD 11 Killed at 55 o c in on 1 hour High resistance to chemical agents Resistance to quaternary ammonium compounds.Chlorxylenol Resistant to Hexchlorophenes Grows also in antiseptic bottles Dettol as cetrimide as selective medium Sensitive to acids silver salts, beta glutaraldehyde

What antibiotics to use:

What antibiotics to use Dr.T.V.Rao MD 12 Aminoglycosides Gentamycin, Amikacin, Cephalosporins Cefotaxime. Ceftazidime. Ofloxacin, Piperacillin, ticarcillin Local application, colistin, polymyxin


Pathogenicity Dr.T.V.Rao MD 13 Blue pus Causing the nosocomial infection Suppurative otitis Localised and generalised infections Urinary tract infection after catheterization Iatrogenic meningitis Post tracheostomy pulmonary infections

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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 ).

PowerPoint Presentation:

P. aeruginosa Antigenic structure, enzymes, and toxins Pili and nonpilus adhesins. Capsule (alginate, glycocalyx): seen in cultures from patients with cystic fibrosis. LPS- endotoxin, multiple immunotypes. Pyocyanin: catalyzes production of toxic forms of oxygen that cause tissue damage. It also induces IL-8 production. Pyoverdin: a siderophore. Proteases Serine protease, metalloprotease and alkaline protease cause tissue damage and help bacteria spread . Phospholipase C: a hemolysin Exotoxin A: causes tissue necrosis and is lethal for animals (disrupts protein synthesis); immunosuppressive. Exoenzyme S and T: cytotoxic to host cells. Pathogenesis

Pathogenesis and Immunity :

Pathogenesis and Immunity Dr.T.V.Rao MD 16 P. aeruginosa can infect almost any external site or organ. P. aeruginosa is invasive and toxigenic. It attaches to and colonizes the mucous membrane or skin, invade locally, and produces systemic diseases and septicemia. P. aeruginosa is resistant to many antibiotics. It becomes dominant when more susceptible bacteria of the normal flora are suppressed.

Clinical Presentations:

Septicaemia Endocarditis Ecthyma gangrenous Infantile diarrhoea Shanghai fever Disabling eye infections Survive with minimal nutrients Clinical Presentations Dr.T.V.Rao MD 17


WHO IS MORE SUSCEPTIBLE TO INFECTION Dr.T.V.Rao MD 18 This bacterium is of particular concern to individuals with cystic fibrosis who are highly susceptible to pseudomonas lung infections. Pseudomonas aeruginosa is also of grave concern to cancer and burn patients as well as those people who are immunocompromised. The case fatality rate for individuals infected with Pseudomonas aeruginosa approaches 50 percent.

Pseudomonas and Cystic fibrosis:

Pseudomonas aeruginosa is the most frequently encountered lung pathogen in patients with cystic fibrosis (CF). Following initial, often intermittent, episodes of infection, it becomes a permanently established component of the chronically infected lung in more than 80% of patients and confers an adverse prognosis Pseudomonas and Cystic fibrosis Dr.T.V.Rao MD 19

Infection of Equipment's:

Respirators Endotracheal tubes Can be Infected All equipment's to be sterilized Infection of Equipment's Dr.T.V.Rao MD 20

Pseudomonas and urinary tract infections:

Pseudomonas and urinary tract infections Dr.T.V.Rao MD 21 Pseudomonal UTIs are usually hospital-acquired and are associated with catheterization, instrumentation, and surgery. These infections can involve the urinary tract through an ascending infection or through bacteriuic spread. In addition, these infections are a frequent source of bacteraemia. No specific characteristics distinguish this type of infection from other forms of UTI.

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 Toxins and enzymes in pseudomonas Dr.T.V.Rao MD 22

Pseudomonas aeruginosa an important opportunistic pathogen:

Pseudomonas aeruginosa an important opportunistic pathogen Dr.T.V.Rao MD 23 Pseudomonas aeruginosa is an opportunistic pathogen, meaning that it exploits some break in the host defences to initiate an infection. In fact, Pseudomonas aeruginosa is the epitome of an opportunistic pathogen of humans. The bacterium almost never infects uncompromised tissues, yet there is hardly any tissue that it cannot infect if the tissue defences are compromised in some manner

P.aeroginosa is an opportunistic pathogen:

P.aeroginosa is an opportunistic pathogen Dr.T.V.Rao MD 24 P,aeroginosa is an opportunistic pathogen. It rarely causes disease in healthy persons. In most cases of infection, the integrity of a physical barrier to infection (eg, skin, mucous membrane) is lost or an underlying immune deficiency (eg, neutropenia, immunosuppression) is present. Adding to its pathogenicity, this bacterium has minimal nutritional requirements and can tolerate a wide variety of physical conditions

Pseudomonas prominent hospital acquired infections:

Pseudomonas prominent hospital acquired infections Dr.T.V.Rao MD 25 It causes urinary tract infections, respiratory system infections, dermatitis, soft tissue infections, bacteraemia, bone and joint infections, gastrointestinal infections and a variety of systemic infections, particularly in patients with severe burns and in cancer and AIDS patients who are immunosuppressed.

Diagnosis of P.aeroginosa infection :

Diagnosis of P.aeroginosa infection Dr.T.V.Rao MD 26 Diagnosis of P,aeroginosa infection depends upon isolation and laboratory identification of the bacterium. It grows well on most laboratory media and commonly is isolated on blood agar or eosin-methylthionine blue agar. It is identified on the basis of its Gram morphology, inability to ferment lactose, a positive oxidase reaction, its fruity odour, and its ability to grow at 42°C. Fluorescence under ultraviolet light is helpful in early identification of P.s aeruginosa colonies. Fluorescence is also used to suggest the presence of P. aeruginosa in wounds.

Identification with Chromagar:

Pseudomonas sp. develop as easily distinguishable blue-green coloured colonies, clearly visible under normal lighting conditions. Other bacterial species are inhibited or give colourless colonies. Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida and Pseudomonas fragilis all give typical blue-green colony colouration and can be studied directly by serotyping or biochemical methods. Identification with Chromagar Dr.T.V.Rao MD 27

Laboratory identification of Diagnosis of P.aeroginosa infections :

Laboratory identification of Diagnosis of P.aeroginosa infections Dr.T.V.Rao MD 28 Diagnosis of P. aeruginosa infection depends upon isolation and laboratory identification of the bacterium. It grows well on most laboratory media and commonly is isolated on blood agar or eosin-methylthionine blue agar. It is identified on the basis of its Gram morphology, inability to ferment lactose, a positive oxidase reaction, its fruity odour, and its ability to grow at 42° C. Fluorescence under ultraviolet light is helpful in early identification of P. aeruginosa colonies and may also help identify its presence in wounds.

Treating pseudomonas infections:

Treating pseudomonas infections Dr.T.V.Rao MD 29 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.

Pseudomonas aeruginosa a resistant pathogen :

Pseudomonas aeruginosa a resistant pathogen Dr.T.V.Rao MD 30 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.

PowerPoint Presentation:

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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Dr.T.V.Rao MD 32 Programme created by Dr.T.V.Rao MD for Medical and Paramedical Students Email

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