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مساعدة في البحث عن بكتريا السيدوموناس

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    لكم الشكر

  • #2
    The Pseudomonads
    * Definition: gram negative rod, motile (polar flagellum), aerobic,
    catalase positive, oxidase positive, oxidizes sugars, pigment
    may be produced, non-sporing, non-capsulated.
    * Habitat: @ Free living in water, sewage, soil, air
    @ Intestine of man and animals
    @ Plant pathogen
    @ Skin of man and animals.

    Classification of Pseudomonads
    • Fluorescent group: Ps. aeruginosa (most common human
    pathogen), Ps. putida, Ps. fluorescens
    • Pseudomallei group: Ps. pseudomallei
    • Maltophilia group: Ps. maltophilia
    • Diminuta group: Ps. diminuta
    • Other pseudomonads: Ps. cepacia, Ps. stutzeri, Ps. mallei,
    Ps. pickettii "

    Pseudomonas aeruginosa
    • Stool carrier rate: 5% in healthy individuals
    • 50% among hospital patients.
    • Pigment production: two water-soluble pigments:
    1. Bluish pigment: pyocyanin
    2. Greenish fluorescent pigment: fluorescin.
    • Function: lethal to bacteria but not to humans.
    * Toxins and enzymes production:
    1. Exotoxin: leukocidin
    2. Enzymes: phospholipase C, proteases (exotoxin A),
    3. Exopolysaccharide : inhibits phagocytosis and adhesion of phagocytes to bacteria.

    Exotoxin A of Ps. aeruginosa
    • Lethal to mice, monkeys, cell cultures, dogs and cats (LD50 less than 1 μg).
    • It acts by inhibiting protein synthesis as follows:
    1. First it cleaves the nicotinamide moiety from NAD.
    2. Second it catalyses the transfer of the resulting ADP-ribose to form a covalent bond with the elongation factor 2 (EF-2)
    3. EF-2 becomes inactivated and so ribosome will not move to next codon, and hence protein synthesis stops.
    • Other enzymes produced:
    1. Elastase: digests elastin in the arterial walls; and inactivates some complement components.
    2. Collagenase : hydrolyses collagen
    3. Exoenzyme-S: hydrolyses NAD and helps Pseudomonas to spread in the blood.

    Ps. aeruginosa Infections
    • Skin infections: burn, wounds, pressure sores, ulcers.
    • Urinary infections: catheterization
    • Respiratory infections: among cystic fibrosis and immuno- suppressed patients.
    • Otitis externa
    • Hospital-acquired eye infections.
    • Septicaemia: among poor health patients
    * Factors predisposing to infection:
    • Mechanical procedures: catheterization, lumbar puncture
    • Debilitated health
    • Long-term antibiotic therapy among burn or cystic fibrosis patients.

    Epidemiology
    • Sources of infection: clinical cases, healthy carriers
    • Modes of spread of infection:
    1. Endogenous: Patient is a carrier leading to UTI, wound infections
    2. Exogenous: From an external source. More common among infants
    • Epidemics: In maternity units, paediatric wards, burn wards
    • Multiplication in hospitals:
    1. Human intestines of patients and hospital staff
    2. Sinks, wards, eye drops, disinfectants, antiseptics.
    3. Wet medical equipment, e.g: tracheostomy tubes
    4. Dust contamination
    5. Water taps, bed-pans, urine bottles.
    • Control measures:
    1. Isolation of hospital patients
    2. Use of sterile instruments and dressings
    3. Hospital utensils are to be cleaned under high temperatures.

    Laboratory Diagnosis¬
    • Specimens collected: pus, urine, sputum, blood, effusions
    • Microscopy: gram negative, motile rods
    • Culture:
    1. Blood agar, nutrient agar, Mc Conkey agar, cetrimide agar, iron agar (aerobic)
    2. Pigment: Blue pyocyanin or green fluorescin, or none (4%)
    3. Characteristic smell due to aminoacetophenone production
    4. Blood agar: large flat, haemolytic colonies
    • Biochemical reactions: oxidase positive, catalase positive, indole negative, citrate positive, acid from sugars by oxidation (no fermentation)
    • Typing:
    1. serological typing: 12 serotypes depending on somatic antigen
    2. Pyocine typing: 37 pyocine types
    3. Phage typing: very broad, not employed.

    Other Pseudomonads
    • Ps. cepacia:
    1. More associated with burn and cystic fibrosis infections
    2. Resistant to most antibiotics.
    • Ps. pseudomallei:
    1. Naturally found in rice fields, river banks mud, stagnant water
    2. Infects cattle, pigs and man (melioidosis).
    3. Melioidosis disease more common in rice growing areas in Asia and Far East.
    4. In melioidosis abscesses form in lungs, spleen, liver, joints, skin, subcutaneous tissues.
    5. Other symptoms of melioidosis: diarrhoea, vomiting, fever, skin rash, septicaemia.
    • Ps. mallei: causes glanders in horses, seldom infects humans
    • Ps. fluorescens and Ps. putida: contaminate blood in blood banks.
    اجازة 10ايام وراجع للغربه الله يعين

    انا احبكم

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    • #3
      Assalamu alaikom

      salam....I did my master degree on pseudomonas and i am doing doctorate also on pseudomonas aeruginosa..so if u specify about what u r looking..maybe i can help you


      elza3eem82
      راح إجمع الغيمات... وأعطيهم مواعيد
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      قلتلن إن بيافا... مخبايتها ستي

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