Lecture 8.docx

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Department
Medical Laboratory Science
Course
MELS223
Professor
Jenny Rhodes
Semester
Spring

Description
MELS223 Lecture 8 8/1/2013 4:09:00 PM Environment as a source of infectious microorganisms Environmental pathogens  Microorgansm that spends substantial part of life cycle outside human hosts but when introduced to humans cause disease with measurable frequency..  Microbes that can survive in the environment for a long period at ambient temperature while remaining infectious – Brooks  Native soil or water organisms – opportunistic infections in a susceptible host  Animal/human pathogens or normal microbiota – may or may not replicate, often obligate parasites Air = fungi Water= most will cause gastrointestinal infection Fomites = surfaces. Potential source of infectious organisms Pseudomonas aeruginosa  Facultative anaerobe, gram negative rods o Single polar flagellum o Oxidative metabolism- non fermentative o Will grow on anything pretty much o Nutritionally and metabolically diverse o Easy to identify clinically – characteristic fruity odour o Produces pigments- colonies coloured o Grows at 42 degrees.  Found in soil, water, plants, animals  Can be found as part of normal microbiota – gut, skin (50% of us)  Really important organism in hospital acquired infection  Antimicrobial resistance high  Significant mortality- opportunistic pathogen  Treating difficult  Can get through cuts on skin – tube down cilia, immune deficiently.  CF can’t remove mucous which get colonized by this organism  Broad spectrum antibiotics (gram positive and negative both affected) – over growth occurs due to this Virulence factors  Biofilms! – 1000x more resistant  Alginate (slime) / polysaccharide (capsule) o EPS – glue that holds biofilm together  Immune evasion – physical barrier against phagocytes, complement, antibodies  Once colony made, metabolic pathways slows down- antimicrobials difficult to work on Motility – flagella, chemotaxis for respiratory mucous Adhesions through fimbrae, LPS, slime, capsule Invasins – Elastase – destruction of elastin-containing tissues  Blood vessels, lung tissue, skin Protease – break down immunoglobulins, complement factors  Inactivation TNF and INF Haemolysins – lecithinase , phospholipase  Breaks down phospholipid bilayer causing tissue destruction Pyocyanin (pigment)  Impairs ciliary function  Apoptosis of neutrophils  Impaired release of IL-8/immunoglobins Toxins  LPS – lipopolysaccharise = endotoxin o Structural component gram negative cell wall o PAMP via PRR (TLR4) o Activates inflammation  Exotoxin A o Similar in structure and function to diptheria toxin o Inhibits protein synthesis – inactivates G protein EF-2 (elongation factor)  Causes cell death! o Results in deermatonecrosis in burn wounds, corneal damage in ocular infections, damage in pulmonary infections Diagnosis : pigment production  Pyocyanin – ‘blue pus’  Pyoverdin (fluorescein) Growth as 42 degrees Fruity odour Oxidase positive Mucoid Beta hemolysis Treatment of pseudomonas  Multi drug resistant  Multiple drug resistance mechanism o Efflux pumps o Beta- lactamases (penicillin)
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