Pseudomonas aeruginosa infections

• opportunistic pathogen

  • colonises more than 50% of healthy humans
  • will infect any tissue given the opportunity
  • all sorts of wounds, especially burn wounds
  • immunocompromised people
  • people with cystic fibrosis
  • patients under assisted ventilation
  • most common bacterium associated with nosocomial infections
• pseudomonas aeruginosa

  • isolated cultures smell nice, like grapes and almonds
  • the almond smell is due to the production of hydrogen cyanide
• cyanide

  respiratory poison, attaches to the iron in cytochrome c oxidase, preventing the transport of electrons to oxygen
• HQNO

  respiratory poison, binds to and inhibits complex III, preventing the transport of electrons to cytochrome C
• pseudomonas aeruginoase - intrinsic resistance

  • low outer membrane permeability
  • multidrug efflux pumps that expel antibiotics out of the cell
  • production of antibiotic-inactivating enzymes
• pseudomonas aeruginosa - acquired resistance

  achieved by either horizontal transfer of resistance genes or mutational changes
• pseudomonas aeruginosa - adaptive resistance

  • formation of biofilm in the lungs of infected patients
  • serves as a diffusion barrier to limit antibiotics access to the dormant cells that are able to survive antibiotic attack
• genome

  • relatively large, circular chromosome
  • some clinical isolates carry plasmids
  • about 10% of the genes have a regulatory function
  • high adaptability, enormous metabolic capacity, can grow in soil and in lungs
  • antibiotics used to treat infections are losing efficiency due to emergence of resistance