Causes and Spread of Infection
ESSEX HEALTH PROTECTION UNIT
Part of the
INFECTION CONTROL GUIDELINES
CARE HOMES
Issued January 2004
Revised April 2006 and December 2007
2
ESSEX HEALTH PROTECTION UNIT
INFECTION CONTROL GUIDELINES
FOR CARE HOMES
SECTION B – INFECTION, ITS CAUSES AND SPREAD
1. The Causes of Infection
An understanding of commonly encountered mi cro-organisms is essential for good infection control practice. Micro-organism s that cause disease are referred to as pathogenic organisms. They ma y be classified as follows:
Bacteria
are minute organisms about one-thousandth to five-thous andth of a millimetre in diameter. They are susceptible to a greater or lesser ext ent to antibiotics.
Viruses
are much smaller than bacteria and although they may survive outside the body for a time they can only grow inside cells of the body. Viruses are not susceptible to antibiotics, but there are a few anti-viral drugs available which are active against a limited number of viruses.
Pathogenic Fungi can be either moulds or yeasts
. For example, a mould which causes infections in humans is
Trichophtyon rubrum which is one cause of ringworm and it may also infect nails. A common yeast infection is thrush caused by
Candida
albicans
.
Protozoa are microscopic organisms, but larger than bacteria. Free-living and non- pathogenic protozoa include amoebae and paramecium. Ex amples of medical importance include:
Giardia lamblia which can cause an ent eritis (symptoms of diarrhoea). Parasites
Worms
are not always microscopic in size but pathogenic worms do cause infection and some can spread from person to pers on. Examples include: threadworm and tapeworm. Ectoparasites
i.e. headlice and scabies.
Prions
are infectious protein particles. Ex ample: the prion causing (New) Variant
Creutzfeldt-Jakob Disease (vCJD).
3
2. The Spread of Infection
One feature that distinguishes infection from
all
Part of the
INFECTION CONTROL GUIDELINES
CARE HOMES
Issued January 2004
Revised April 2006 and December 2007
2
ESSEX HEALTH PROTECTION UNIT
INFECTION CONTROL GUIDELINES
FOR CARE HOMES
SECTION B – INFECTION, ITS CAUSES AND SPREAD
1. The Causes of Infection
An understanding of commonly encountered mi cro-organisms is essential for good infection control practice. Micro-organism s that cause disease are referred to as pathogenic organisms. They ma y be classified as follows:
Bacteria
are minute organisms about one-thousandth to five-thous andth of a millimetre in diameter. They are susceptible to a greater or lesser ext ent to antibiotics.
Viruses
are much smaller than bacteria and although they may survive outside the body for a time they can only grow inside cells of the body. Viruses are not susceptible to antibiotics, but there are a few anti-viral drugs available which are active against a limited number of viruses.
Pathogenic Fungi can be either moulds or yeasts
. For example, a mould which causes infections in humans is
Trichophtyon rubrum which is one cause of ringworm and it may also infect nails. A common yeast infection is thrush caused by
Candida
albicans
.
Protozoa are microscopic organisms, but larger than bacteria. Free-living and non- pathogenic protozoa include amoebae and paramecium. Ex amples of medical importance include:
Giardia lamblia which can cause an ent eritis (symptoms of diarrhoea). Parasites
Worms
are not always microscopic in size but pathogenic worms do cause infection and some can spread from person to pers on. Examples include: threadworm and tapeworm. Ectoparasites
i.e. headlice and scabies.
Prions
are infectious protein particles. Ex ample: the prion causing (New) Variant
Creutzfeldt-Jakob Disease (vCJD).
3
2. The Spread of Infection
One feature that distinguishes infection from
all