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Most infections are
communicable ­ capable
of spreading from one
person to another.
A living organism that
transmits infection from
one host to another.
Can occur through a break in the skin. INGESTION
This transmission might be via an Many pathogens that cause gut
injury from contaminated medical diseases are transmitted by
instruments or shared needles, e.g. contaminated food or drink. The risk
hepatitis B. of infection is greatest from raw
How food, e.g. diarrhoea.
DIRECT CONTACT transmitted Many droplets are from your
Important in the spread of respiratory tract. These droplets are
disease in small children. Many full of pathogens if you have an
sexual diseases are spread by infection. When the pathogens are
direct contact of the genital inhaled by another person the
organs, e.g. impetigo. pathogens enter their respiratory
tract and a new infection is set up, e.
g. influenza.
Inanimate objects that carry
pathogens from one host to
another, e.g. hospital towels.…read more

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The contents of bacterial
cells are usually hypertonic
, so water moves in by
The skin
It is an impenetrable layer toughened by
keratin, a fibrous structural protein.
It forms a physical barrier between the
pathogen-laden environment and the
delicate, blood-rich tissues beneath the skin.
Sebum contains chemicals that inhibit the
growth of microorganisms.…read more

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Mucus contains lysozymes ­ enzymes capable of
destroying microbial cell walls.
They are very effective against Gram-positive
bacteria, breaking down the cross-linkages in the
peptidoglycans in the bacterial cell wall.
Cilia move mucus in the reproductive tracts.
Lysozymes are also present
in tears, to keep the eyes
moist and protect them from
the entry of pathogens.…read more

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The natural flora compete
both for nutrients and space
with any microorganisms
that manage to get through
the stomach.
The gut
Polypeptides in the salivary glands destroy
bacteria while others slow down bacterial
Stomach acid (pH 2) destroys the majority of
ingested microorganisms.…read more

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Can be caused by infection of the gut, toxins,
bad smells, pregnancy and tumours.…read more


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