Systematic Bacteriology II Flashcards
What is pathogenesis?
Parasitic life cycle - adhere/colonise and invade
evade host defenses
multiply/complete life cycle
exit host (leaving it damaged)
What is virulence?
The capacity of a microbe to cause damage to the host
What is an endogenous micro-organism?
Already present within the body
What is an exogenous micro-organism?
Not already present within the body
What is a pathogen?
A harmful organism that produces a pathology
What is a commensal?
An organism that is part of the normal flora - usually mutualistic and endogenous
What is an opportunistic pathogen?
An organism that causes infection when a change in natural immunity arises (eg an immunocompromised human)
What is a contaminant?
An organism that is growing in a culture by accident
What are prions?
Infectious proteins. nvCJD and BSE (in cattle)
What is the most common type of fungal infection?
Candida spp. (yeast budding) - causes skin infection to candidaemia. can be brought on by changes in the natural flora
What is the biggest protozoan disease in humans?
Malaria caused by the plasmodium (mosquito as vectors)
What are some of the gram -ve prokaryotic pathogens?
Neisseria spp and Escherichia spp
What are some of the gram +ve prokaryotic pathogens?
Streptococcus spp, staphylococcus spp, enterococcus spp, and clostridium
What are 2 diseases caused by neisseria?
Bacterial meningitis (neisseria meningitids) and gonorrhoea (neisseria gonorrhoeae)
What gram -ve bacteria is associated with the GI tract?
Gut commensal coliforms (E. coli, klebsiella spp., enterobacter spp., and proteus spp. Significant gut pathogens (salmonella spp etc)
What are coliforms?
Species of gram -ve bacilli that look like E. coli on gram film. Grow best aerobically (can also grow anaerobically). Many are commensal
How do you differentiate coliforms?
Biochemical reactions, and the antigenic structure of the cell wall (O or H antigens)
How do coliforms cause infection?
When they get into a normally sterile site
What is the 1st line antibiotic used for treatment of coliform infections?
Gentamicin
What does the O antigen have the ability to do?
Stimulate the immune system
What is the mechanism of fever?
Antigen or LPS interact with microphages, which release cytokines into the blood stream. Cytokines travel to the anterior hypothalamus (also stimulate the adverse effects of sepsis) and prostoglandin E is released which increased body’s thermal set point. Body now thinks its cold and shivers (for heat conservation) causing fever = increased survival
What is fever (temp)?
> 38c
What is the mechanism of sepsis?
Small blood vessels begin to leak and lose fluid into tissue. Low blood oxygen volume requires increases heart rate. Lower oxygen perfusion means blood supply to essential organs in shut down (blood goes to brain). Blood clotting system is activated causing blood clotting (in tiny blood vessels) which uses up all clotting factors (increases haemorrhage risk)
What is alpha-haemolysis?
Partial haemolysis (enzymes that denature haemoglobin inside RBC - goes green)
