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Pseudomonaceae

Medical Microbiology. Pseudomonaceae. BIOL 533 Lecture 13. General Aspects. Ecology Found throughout the environment Very simple nutritional requirements Not usually in normal flora unless hospitalized or immunocompromised. General Aspects. Virulence

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Pseudomonaceae

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  1. Medical Microbiology Pseudomonaceae BIOL 533 Lecture 13

  2. General Aspects • Ecology • Found throughout the environment • Very simple nutritional requirements • Not usually in normal flora unless hospitalized or immunocompromised

  3. General Aspects • Virulence • Possess number of structural factors and toxins • Resistant to most common antibiotics • Surprising that they do not constitute problem in general population

  4. Microbial Physiology and Structure • Morphology • Straight or slightly curved Gram— bacterial • Polar flagella; motile • Some strains appear mucoid due to polysaccharide capsule • Some produce diffusible pigments • Pyocyanin (blue), fluorescin (yellow), pyorubin (red-brown)

  5. Microbial Physiology and Structure • Physiology • Carbohydrate fermentation • Use only few CHO using oxidative pathways • Glucose, ribose, gluconate • Oxygen is terminal electron acceptor • Presence of cytochrome oxidase • Distinguishes from Enterobacteriaceae • Anarobic growth can occur by using mitrate as terminal acceptor

  6. Virulence Factors • Adhesins: pili and nonpilus adhesins • Production of neuraminidase enhances adherence • Alginate (mucoid layer): Protects against phagocytosis and facilitates adherence to host cells

  7. Virulence Factors • Elastase: cause damage to blood vessel walls, resulting in hemorrhagic lesions (ecthyma gangrenosum) • Associated with disseminated Pseudomonas infections • Pyocyanin: mediates tissue damage through toxic oxygen radicals

  8. Toxins • Exotoxin A: mechaism like diphtheria toxin, but much milder • Two toxins are structurally and immunologically different • Exoenzyme S: also ADP-ribosyltrnasferase, but heat stabile • Found in 33.3% clinical isolates

  9. Clinical Syndromes of Pseudomonas aeruginosa • Bacteremia • Common in patients with neutropenia, diabetes mellitus, extensive burns, a hematologic malignancies • Originate from infections of lower respiratory tract, urinary tract, skin, and soft tissue • Associated symptoms: minority of patients have ecthyma gangrenosum

  10. Clinical Syndromes of Pseudomonas aeruginosa • Endocarditis • Observed primarily in drug abusers • Source is contaminated drug equipment • Anatomy of heart affected • Tricuspid valve: chronic and more favorable prognosis • Aortic or mitral valve: acute and frequently fatal

  11. Clinical Syndromes of Pseudomonas aeruginosa • Pulmonary infections • Range from colonization to severe necrotizing bronchopneumonia • Colonization seen in patients with cystic fibrosis, other chronic lung diseases, and neutropenia

  12. Clinical Syndromes of Pseudomonas aeruginosa • Ear infections • Swimmer’s ear: can be managed with topical antibiotics and drying agents • Malignant external otitis: more virulent; can invade underlying tissues and cause death • Surgical and antimicrobial intervention required

  13. Clinical Syndromes of Pseudomonas aeruginosa • Burn infections—severe burns • Colonization of wound followed by local vascular damage and tissue necrosis • Leading to bacteremia • Predisposition • Moist tissue surface and absence of neutrophils • Topical creams and wound management has had only limited success

  14. Clinical Syndromes of Pseudomonas aeruginosa • Other infections • Localized in gastrointestinal and urinary tracts • Eye and central nervous system • Musculoskeletal system

  15. Clinical Syndromes of Pseudomonas aeruginosa • Prerequisites for infection • Presence of organism in moist reservoir • Circumvention or absence of host defenses • Cutaneous trauma • Elimination of normal flora • Neutropenia

  16. Laboratory Diagnosis • Grow on most common laboratory media • Identification • Morphology • Colony size and hemolysis: flat colony with spreading border • Pigmentation: green • Odor: sweet, grape-like • Oxidase+

  17. Treatment • Resistant to large number of antibiotics • Problems: • Production of -lactamase • Aminoglycosides ineffective in acidic environment of abscess • Successful treatment • Combination of -lactum antibiotic and amioglycoside

  18. Prevention • Possibly impossible in hospital environment • Prevent inappropriate use of broad-spectrum antibiotics

  19. Lecture 13 • Questions? • Comments? • Assignments...

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