Infectious Agents Flashcards
what is an infectious agent?
organism capable of producing infectious disease
types of infectious agents?
bacteria viruses protozoa fungi parasites - endo/ecto
bacteria shapes?
SINGLE CELLES
Bacilli - rods
- vibrio - curved rods
Cocci - spheres
- diplococci - spherical pairs
- streptococci - spherical chain
- staphylococci - spherical clusters
spirilla - spirals with rigid cell wall
spirochaete - spiral with flexible cell wall
main components of bacteria?
capsule
- protection (eg from WBCs)
- allow for sticking (eg to resp tract walls)
pilus
- spikes
- protection and sticking
flagella
- allow for movement
cell wall
- provide strength and structure
plasma membrane
- semi-permeable membrane
cytoplasm
- what organelles are within
ribosomes
- for protein synthesis
nucleoid
- 1 single chromosome
- no nucleus
plasmids
- extra piece of DNA
- can be assed on
- contain learned information
gram stains?
gram positive bacteria
- purple
- thick cell wall - absorbed more die
gram negative bacteria
- pink/red
- thin cell wall - less absorption
- but have double player of plasma membrane
- so better resistance
bacterial replication?
binary fission
- duplication of chromosome
- divide into two identical cells
conjugation
- passing on of plasmids
- pilus binds to receptor site of receiver
- plasmid replicates and passes through pilus
optimal conditions for bacteria?
water
essential nutrients
correct pH - usually 7.4
correct temperature - optimum is body temp
optimal conditions for bacteria?
water match human conditions
essential nutrients
correct pH - usually 7.4
correct temperature - optimum is body temp
correct gaseous environment
- obligate aerobes - must have oxygen
- obligate anaerobes - can’t have oxygen
- facultative anaerobes - doesn’t matter
- microaerophiles - oxygen percentage less than atmospheric air
bacteria spore function?
occur when conditions are not met - enables survival
process
- chromosome replicates
- septum forms
- produces a forespore within the mother cell
- spore coat forms around the forespore
- released by rupture of patent cell
most common with bracillus species often found in soil extremely resistant - can survive be dormant for years - then will germinate and replicate
sterilisation is only way t destroy them
bacteria toxigenicity?
toxin = poisonous substances that damage host cells
exotoxins
- released into the surrounding environment
- eg circulatory system
- can be destroyed by some chemicals and heat
- toxoids (inactive exotoxins) stimulate antitoxins (vaccines)
endotoxins
- released when bacteria die and disintegrate
- part of their cell wall
- responsible for non-specific reactions (eg fever)
- can cause endotoxicc shock (type of distributive shock)
bacilli examples?
contagious equine metritis (-ve)
tetanus (+ve)
anthrax (+ve)
contagious equine metritis (CEM)?
inflammation in the uterus and vaginal tract
passed from stallion to mare
uterine contains mucopurulent exudate
- drains from vulva
straw colour fluid within cranial vagina
tetanus?
toxins within the nervous system
- eventually travels to brain
commonly caused by spores from soil or each other
causes muscle spasms and still gait top of tail sticks out worried expression rigid ears prolapsed third eyelid flared nostrils
anthrax?
toxins enter thrugh wounds or ingestion
can be released or travel anywhere in body
in CSF affecting nervous system
or skin causing blister
clocci examples?
strangles
MRSA
strangles?
caused by direct contact
effects lymph nodes at head - causes abscesses can place pressure on the respiratory tract can burst and/or spread around body - can be fatal
MRSA?
lives healthily on human skin
- uncontrolled growth when immunocompromised
can enter wounds
- release toxins
- cause a necrotic wound
spirals examples?
leptospirosis (-ve) lymes disease (-ve)
leptospirosis?
zoonotic
from rats and dirty water
cause liver and kidney failure
lymes disease?
zoonotic
from ticks
affect nervous system
what is a virus?
obligate intracellular parasites
must invade host in order to replicate and survive
main components of a virus?
is composed of two parts
- nucleic acid (DNA or RNA)
- capsid - protein coat
can be enveloped or non-enveloped
- envelope made of plasma membrane from host
- protects
- may have protein spikes that help enter host cell
virus replication?
virus attaches to a suitable receptor cell
virus penetrates cell membrane and injects nucleic acid into cell
viral nucleic acid replicates using host cellular machinery
new viral nucleic acids are packaged into viral particles and released from the cell
- the host cell will be destroyed in the process
virus incubation?
once a host cell has been infected there is a lag time before symptoms are seen
- called incubation period
clinical signs are seen once a large number of particles infect a large number of cells
virus examples?
rabies (RNA) enveloped
parvovirus (DNA) - non-enveloped
equine herpes virus (DNA) - enveloped
rabies?
Aggression rabies
- foaming from mouth
- passed on by bites
paralytic rabies
- paralysed
not in UK
attacks nervous system
can be fatal
parvovirus?
attacks GI system
replicates in GI cells
- destroys them
- so can’t take in nutrients
- causes extreme diarrhoea
equine herpes virus?
5 strains
attack many areas
- respiration system
- nervous system
- reproduction system
what is a protozoa?
the lowest form of animal life
- unicellular organisms
- move, intake nutrients, dispose of products
reproduce via binary fission
attack many ways/areas
- so many different side effects
- attacks different body systems
