bacteria as pathogens Flashcards
what happens if bacteria get into the blood
they can be carried all around system and cause systemic infection
different ways bacteria make people ill
some because of how they invade and destroy host tissues
-most through toxins they make as by product of their metabolism
-toxins may incapacitate whole organism or just immune system
how can toxins be classified
endotoxins
exotoxins
chemical structure of endotoxins
lipopolysaccharides
where do endotoxins come from
come from outer layer of cell wall of gram negative bacteria
what acts as toxin in endotoxins
lipid part of polysaccharide that acts as toxin while polysaccharide stimulates immune system
infection area of endotoxins
they effect around site of infection by the bacteria
pathogenic effects of endotoxins
-fever
-vomiting
-diarrhoea
examples of endotoxins
salmonella spp
-E.coli
how do antibiotics release more endotoxins
when they destroy bacterial cells by lysis of cell wall endotoxins can be released because of lipopolysaccharide component of cell wall
diseases caused by salmonella bacteria
salmonellosis gasreoenteritis
how do salmonella bacteria act in diseases
invade lining of intestine and endotoxins cause inflammation
-cells no longer absorb water so faeces become liquid
-gut then goes into spasms of peristalsis that result in diarrhoea
how is salmonella spread
by ingestion of good and water contaminated with infected faeces
who do antibiotics work for when treating bacterial infections
young people
old people
people with compromised immune system
what do antibiotics do to most people when taken to treat bacterial infections
just reduce symptoms allowing person to fell better but act as carrier for longer
best way to deal with diseases caused by salmonella spp
avoid them by cooking meat all the way
-washing hands after dealing with raw meat
-wash hands after using toilet
-avoid drinking contaminated water
s typhi
strain of salmonella spp that causes typhoid
features of exotoxins
usually soluble proteins
-produced and releases into body by bacteria as they metabolise and reproduce in cells of their host
how are exotoxins produced
by gram negative and positive
effect of exotoxins on infection
effect can be more widespread than endotoxins as they act at sites distances from the infecting bacteria
specific effects of exotoxins
-some damage cell membranes causing cell breakdown or internal bleeding
-some act as competitive inhibitors to neurotransmitters
-others directly poison cells
example of deadly exotoxin caused disease
clostridium botulinum
-produces botulinum toxins
-most toxic natural substance known
-1mg of pure toxin could kill a million guinea pigs
example of exotoxin strains
staphylococcus
-one third of us carry at some of then in normal skin and gut flora
how to STP cause disease
if they get inside body tissues
-if normal skin flora is changed
-if the person has a compromised immune system due to another disease
-treatments such as chemo
