lecture 8 Flashcards
microbes and diseases vaccinations
disproving the spontaneous generation (1864)
Pasteur disprove the spontaneous generation theory
he took a non-sterile liquids and poured it into a flask
the neck of the flask was drawn out in the flame
the liquid sterilized by heating
the liquid was cooled slowly and dust and microorganisms were trapped in the bend of the tube
the liquid remained sterile for many years
when he tipped the flask so that the microorganisms get into contact with the sterile liquid, he realised that the microorganism started growing in the liquid
so he proved that microorganisms cannot create themselves and it’s gave him the idea that microbes can spread
Koch’s postulates (1884)
koch discovered what causes the diseases and his postulates are still used to define the organisms that cause diseases
he took a healthy mouse and a deceased infected mouse
cells extracted from the healthy animal did not cause a disease in another animal
but the cells from the pure culture of the infected animal caused a disease in the healthy animal
give examples of physical chemical and anatomical barriers to infections (11)
- eyes. lysozyme in tears dissolves cell walls
- airways. normal flora compete with pathogens
- nose. removal of particles by rapid passage of air over cilia
- airway. mucus cilia lining of the trachea suspend
- blood. proteins inhibit microbial growth
- lungs. mucus and phagocytes prevent colonisation
- stomach. acidity inhibits microbial growth
- small intestine. rapid pH change inhibit microbial growth
- large intestine. normal flora compete with pathogens
- urinary tract. flushing of urinary tract prevents colonisation
- skin. physical barrier that produces antimicrobial fatty acids and it’s normal flora inhibits pathogen colonization
the human microbiome
it’s a concept for suggested by Joshua ledeberg
the microbiome is the ecological community of commensal, symbiotic and pathogenic microorganisms that literally share our bodyspace
the Human microbiome Project was funded to assess the microbiome in 250 volunteers
benefits and diseases of the human microbiome
BENEFITS
it shields our body tissues against the invasion of bad bugs
it produces vitamins by bacteria
it is implicated and yet not proven in a range of conditions obesity type 1 diabetes Crohn's disease irritable bowel syndrome colon cancer
virulence factors
virulence is determined by many factors that aid in:
the adhesion to cells in the entry into cells
antiphagocytic activity
immune system evasion
production of toxins
anything that allows the bacterial cell to avoid being detected to stick to a cell which produce toxins counts as a virulence factor
conventional virulence factors are bacterial toxins, adhesins, cell surface carbohydrates and capsules, secreted hydrolytic enzymes, LPS
other factors also indirectly contribute to virulence like: secretion machineries (push the bacteria and toxins to the surface or out of the cell) siderophores (proteins that bacteria produce to send out into the environment and pick up things like iron) catalases (counteract the effect of phagocytes when they are trying to destroy cells) genetic regulators (switch these things on and off)
genetic elements encoding virulence factors
virulence maybe plasmid or phage encoded
in chromosomes they may occur clustered in so called pathogenicity Islands where it encodes 6 gene products for example
some genetic elements are the results of horizontal gene transfer
other genetic elements can aid in horizontal gene transfer from one strain to another
major staphylococcus aureus virulence factors
adherence antiphagocytosis exoenzyme iron uptake secretion system toxins
define MRSA
methicillin-resistant staphylococcus aureus
there are limited options of antibiotic chemotherapy left due to multiple antibiotic resistance
now VRSA isolates have been isolated
emerging new bacterial pathogens
new means not previously been known as pathogens
this includes bacteria with the wide environmental distribution that can cause infections in the immunocompromised
such opportunistic pathogens are increasingly important in causing outbreaks in hospitals
define tetanus
tetanus neurotoxin leads to over activity of motor neurones causing muscle spasms
it’s a toxin based infection damage and vaccine targets the toxin rather than the cell
read the other slides
…………………. if u have time
