Lecture 8.docx

11 Pages
Unlock Document

Medical Laboratory Science
Jenny Rhodes

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)
More Less

Related notes for MELS223

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.